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Proceedings of the 4th Scientific Workshop for the Mackenzie GEWEX Study

[MAGS]

held at the Delta Hotel

Montréal, Québec 16-18 November, 1998

Participants of the 4th GEWEX/MAGS Workshop, 16-18 November, 1998

Proceedings of the 4th Scientific Workshop for the Mackenzie GEWEX Study

[MAGS]

held at the Delta Hotel,

Montréal, Québec 16-18 November, 1998

Technical Editor: G.S. Strong

GEWEX/MAGS Secretariat/Coordinator National Hydrology Research Centre

11 Innovation Boulevard Saskatoon, SK Canada S7N 3H5

e-mail correspondence to: [email protected]

Editorial Assistant: Y.ML. Wilkinson

Box 311, Vanscoy, SK S0L 3J0 e-mail: [email protected]

ISSN: 1480-5308 March, 1999

mailto:[email protected]


Proceedings 4th MAGS Workshop November, 1998

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ACKNOWLEDGEMENTS

The Mackenzie GEWEX Study [MAGS] is funded by the Natural Sciences and Engineering Research Council [NSERC] of Canada and by Environment Canada. Funding for these workshop proceedings was provided by NSERC and the Atmospheric Environment Service of Environment Canada.

GEWEX/MAGS Web Site

These proceedings are also available on the MAGS web site at:

http://www.tor.ec.gc.ca/GEWEX/MAGS.html

printed by Apex Graphics

Saskatoon, Saskatchewan March, 1999



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TABLE OF CONTENTS

Acknowledgements......................................................................................................................................ii GEWEX/MAGS Web Site ..........................................................................................................................ii Workshop Participants .............................................................................................................................. iv Workshop Agenda....................................................................................................................................... v A. INTRODUCTION ................................................................................................................................1 MAGS Objectives...................................................................................................................................2 Workshop Objectives..............................................................................................................................2

B. PRESENTATIONS - Extended Abstracts..........................................................................................3

1. Atmospheric Moisture (and Energy) Budget Studies.......................................................................4 2. Land Surface Process Studies ........................................................................................................32 3. Remote Sensing Studies .................................................................................................................80 4. Modelling Studies ........................................................................................................................107 5. MAGS Support and Operational Inputs .......................................................................................143 6. Invited Presentations ....................................................................................................................158

C. SESSION SUMMARIES..................................................................................................................179 D. GENERAL DISCUSSIONS - Reports from Working Groups.....................................................191

1. Progress and Future Prospects of the MAGS Research Basins....................................................192 2. The 1994-95 Water Year Study ...................................................................................................195 3. CAGES Data and Analysis ..........................................................................................................196 4. Post MAGS – Where do we go from here? .................................................................................198

E. FINAL DISCUSSION ......................................................................................................................201 Statements on the Status of MAGS ....................................................................................................202 Workshop Concluding Remarks .........................................................................................................203 REGISTERED PARTICIPANTS..........................................................................................................205

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Proceedings 4th M

AGS W

orkshop Novem

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Participants of the 4th GEWEX/MAGS Workshop, 16-18 November 1998, MontrJal, QuJbec.

Left to right: (Row 1) Murray Mackay, Ric Soulis, Raoul Granger, John Gyakum, Istzar Zawadski, Ron Stewart, Ehrhard Raschke, Bob Crawford, Peter Taylor, Muyin Wang, Paul Louie, Brian Currie, Zuohao Cao; (Row 2) Geoff Strong, Karen Graham, Stephen DJry, Anne Walker, Alan Betts, Brian Wilkinson, Kit Szeto, Vladimir Smirnov, Normand BussiPres, Terry Prowse, John Pomeroy, Bob Kochtubajada, Richard Essery; (Row 3) Ted Whidden, Murray Kroeker, Phil Marsh, Al Pietroniro, Barry Goodison, Hal Ritchie, Bill Schertzer, Dave Hudak, Dennis Lettenmaier, David Whittle, Richard Petrone, Sean Carey, Chris Spence; (Row 4) Peter Schuepp, Richard Hogue, Ekaterina Radeva, Henry Leighton, Ken Snelgrove, Frank Seglenieks, Brian Proctor, Jason Burford, Arvid Silis, Wayne Rouse, Ian Macpherson, Lawrence Martz, Peter Yau.


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Mackenzie GEWEX Study [MAGS]

4th Annual Workshop 16-18 November, 1998

Salon Opus II, Delta Hotel, Montr�al, Qu�bec

AGENDA

Monday, 16 November, AM

A. Introduction Registration 08:30 Welcome, Introductory Remarks (Henry Leighton/Geoff Strong) 09:00 Status of MAGS and CAGES (Ron Stewart/Ric Soulis) 09:10 B. Presentations Each presenter is allocated 15 minutes for presentation and 5 minutes for discussion. An

additional 10-20 minutes of discussion is scheduled at the end of each session. We must adhere to this schedule if we are to accomplish the workshop objectives. Presenters will not have the option of extending their presentations into the time allotted for discussion of their presentations, as the discussions are an important component of the workshop.

1. Atmospheric Moisture and Energy Budgets Chair: Han-Ru Cho 1.1 The Effects of the Mackenzie River on the Canadian Weather and Climate (Cho) 09:25 1.2 Airborne Observations of Surface-Atmosphere Energy Exchange over the 09:45 Northern Mackenzie Basin (Schuepp) 1.3 Atmospheric Moisture Budgets for MAGS (Proctor/Strong/Wang) 10:05 χχχχ Coffee Break 10:25-10:45 1.4 Cyclones and their Role in High Latitude Water Vapour Transport (Gyakum) 10:45 1.5 Low-level Inversions, Precipitation Recycling, and Air-Land Interactions over the 11:05 Mackenzie Basin (Szeto) Invited Presentation - Water Budgets of Seven Sub-basins of the Mackenzie from the 11:25 ECMWF Analysis (Betts) 1.6 High Latitude Atmospheric Moisture Transport (Smirnov) 11:45 Discussion 12:05-12:25 LUNCH 12:25-13:40


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Monday, 16 November, PM 2. Land Surface Process Studies Chair: T.D. Prowse 2.1 Evaporation from Wetlands and Large Lakes (Rouse) 13:40 2.2 Cross-Lake Variation of Evaporation, Radiation, and Physical Limnological 14:00 Processes in Great Slave Lake (Schertzer) 2.3 Biome Scale Representation of Snow Cover Development and Ablation in Boreal 14:20 and Tundra Ecosystems (Pomeroy) 2.4 Hydrologic Processes in Cold Regions (Gray) 14:40 χχχχ Coffee Break 15:00-15:20 2.5 Snowcover Melt and Runoff in Boreal and Tundra Ecosystems (Marsh) 15:20 2.6 Effects of Seasonal Frost and Permafrost on the Hydrology of Subalpine Slopes 15:40 and Drainage Basins (Woo/Martz/Carey) 2.7 Isotopic Tracing of Water-Balance Processes in the Mackenzie Basin (Prowse) 16:20 Discussion 16:40-17:00


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Tuesday, 17 November

Invited Presentation – BALTEX: Recent Advances and Future Problems! 09:00-09:15 (Raschke) 3. Remote Sensing Studies Chair: Anne Walker 3.1 Evapotranspiration and Energy Balance Components from Satellite Data 09:15

(Bussi�res) 3.2 Parameterization of Evaporation/Evapotranspiration (Granger) 09:35 3.3 Surface Radiation Budgets in the Mackenzie River Basin (Leighton) 09:55 3.4 Snow Cover and Lake Ice Determination in the MAGS Region using Passive 10:15 Microwave Satellite and Conventional Data (Walker) χχχχ Coffee Break 10:35-11:00 3.5 Satellite Ranfall Estimates over the Mackenzie Basin (Zawadski) 11:00 3.6 (a) IPIX Radar Activities in Support of CAGES (Currie and Haykin) 11:20 (b) IPIX Radar Observations during CAGES (Hudak) Discussion 11:40-12:00 LUNCH 12:00-13:15

4. Modelling Studies Chair: Peter Taylor 4.1 Hydrological Investigations of a Canadian Shield Basin (Spence) 13:15 4.2 Integrated Hydrologic Modelling for MAGS (Soulis) 13:35 4.3 (a) Hydrologic Response of Lower Mackenzie System in the Discontinuous 13:55 Permafrost/Wetland Zone (Pietroniro) (b) Scaling of Hydrologic Models for MAGS (Pietroniro) 4.4 MAGS RCM, Climate System and Cloud Field Studies (Stewart/Mackay/Cao) 14:15 χχχχ Coffee Break 14:35-15:00 4.5 Developing a Global Numerical Weather Prediction System for the Canadian 15:00 GEWEX Program (Ritchie) 4.6 High Resolution Simulations of Warm and Cold Precipitation Systems over the 15:20 Mackenzie River Basin (Yau) 4.7 GEWEX Northern Boundary-Layer Modelling (Taylor) 15:40 Discussion 16:00-16:20 5. MAGS Support and Operational Inputs Chair: Murray Mackay 5.1 CMC Model Archive and Activities in Support of GEWEX (Hogue) 16:20 5.2 MAGS Data Management (Crawford) 16:45


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Wednesday, 18 November

5. MAGS Support and Operational Inputs (continued) 5.3 (a) CAGES Update (Kochtubajda) 09:00 (b) Radiosonde Operations during CAGES IOP-1 (Strong) 5.4 Preliminary Analysis and Assessment of the CAGES Enhanced Surface 09:20 Observations (Louie) C. Session Summaries

Identification of highlights, gaps, synergy between projects – not a re-presentation of the presentations. (Rapporteurs indicated in parentheses)

1. Atmospheric Moisture and Energy Budget Studies (Szeto) 09:40 2. Land Surface Process Studies (Schertzer) 09:50 3. Remote Sensing Studies (Hudak) 10:00 4. Modelling Studies (Yau) 10:10 5. Support and Operational Inputs (Kochtubajda) 10:20

χχχχ Coffee Break 10:30-10:50 D. General Discussions – Reports from Working Groups

(Rapporteurs indicated in parentheses)

1. Progress and Future Prospects of the MAGS Research Basins 10:50-11:50 Discussion Leader – Pietroniro (Pomeroy)

LUNCH 11:50-13:00 2. The 1994-95 Water Year Study 13:00-14:00 Discussion Leader – Stewart (Granger) 3. CAGES Data and Analysis 14:00-15:00 Discussion Leaders – Strong/Kochtubajda (Crawford) χχχχ Coffee Break 15:00-15:30 4. Post MAGS – Where do we go from here? 15:30-16:30 Discussion Leader – Gyakum (Marsh) E. Final Discussion and Recommendations 1. Workshop Concluding Remarks & Recommendations 16:30-17:00 Stewart/Soulis 2. Statements on the Status of MAGS

COMPLETION OF FORMAL PORTION OF WORKSHOP


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Related Meetings

Science Advisory Panel Tuesday, 17 November - Dinner Meeting Evening – Location TBA Wednesday, 18 November - Meeting 13:00-17:00 – Bach Room, Delta Hotel Management Committee Wednesday, 18 November - Dinner Meeting 16:00 – Faculty Club, McGill University, 3450 McTavish Science Committee Thursday, 19 November and Friday, 20 November 09:00-17:00 – Burnside Hall, Room 719A, McGill University

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Proceedings 4th MAGS Workshop Session 0: November, 1998 Introduction

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INTRODUCTION

Proceedings 4th MAGS Workshop Session 0: November, 1998 Introduction

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MAGS Objectives

The Mackenzie GEWEX Study [MAGS] is a major Canadian contribution to the Global Energy and Water Cycle Experiment [GEWEX]. MAGS is a comprehensive study of the hydrologic cycle and energy fluxes of the Mackenzie River Basin. The Mackenzie River is the largest North American source of fresh water for the Arctic Ocean, and this region has experienced one of the most pronounced warming trends in the world over the last few decades. An improved understanding of this climate system will contribute significantly to coupled atmospheric-hydrologic-land surface models capable of predicting the climate for many decades into the future. Therefore, the objectives of MAGS are to:

1. quantify the hydrologic cycle and energy fluxes of the Mackenzie Basin; 2. accurately model the hydrological cycle and its impact on the atmosphere, land surface, and the

oceans; 3. develop abilities to predict climate change-induced variations in hydrological processes and water

resources; 4. foster development of observational and data management systems that allow us to monitor such

changes.

Workshop Objectives

The fourth MAGS Workshop was held the 16-18 November, 1998 in Montréal, Québec, home to many MAGS researchers. There were more than 75 participants in this workshop. The objectives of the MAGS 4th Annual Workshop were to:

1. collectively present and discuss our research results; 2. assess progress towards the goals of MAGS; 3. develop and review plans for the next year and beyond.

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PRESENTATIONS Extended Abstracts

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Proceedings 4th MAGS Workshop Session 1: November, 1998 Atmospheric Moisture and Energy Budgets

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1.1 The Effects of the Mackenzie River on the Canadian Weather and Climate

Han-Ru Cho Dept. of Physics, University of Toronto, Toronto, Ontario

1. Objectives The effects of rivers and river systems on our climate systems is the central objective of GEWEX. However, the details of these effects are not yet properly understood. The most direct and pronounced test of the effects of the Mackenzie River on Canadian weather and climate is by answering the following question: What happens if the Mackenzie River were not there? However, river systems are basically the product of climate, topographical, and geological conditions. Therefore, to assess the effects of the river by removing the river is to assume the present-day topographic and geological conditions are altered as well. The ultimate goal of this project is to understand the effects of the Mackenzie River on the Canadian weather and climate. To achieve this objective, a number of tools are needed. We shall (1) assemble these tools; (2) make sure these tools represent the present-day climatic conditions accurately; (3) improve these tools if any deficiencies are found. Once steps (1) to (3) are done, we can then (4) remove the Mackenzie River completely in a GCM simulation of the atmospheric system in order to examine the effects of the river on our weather and climate systems. We realize that perfect tools are impossible to obtain. We intend to alternate between step (2) to (3) and (4) so that we won't wait until the tools are perfect before doing the numerical experimentation in step (4). 2. Progress and Collaborations To carry out this project, we need a general circulation model of the atmosphere with an interactive land surface model to model the hydrological processes of the land surface. At the moment we are using the CCM3 developed at NCAR, together with its land surface scheme developed by Gordon B. Bonan. Discussion has started with Norman McFarlane to use the AES GCM version III together with the CLASS model. However, to use the AES GCM it is necessary to use to AES NEC computer. We intend to pursue this as a joint project with the Canadian Climate Center of Victoria. During the past year, we have completed the following sub-projects: (a) the study of intra-seasonal oscillations in precipitation in the atmosphere over North America; a

manuscript has been submitted to the Journal of Geophysical Research; (b) a study was completed on the method often used to calculate the convergence of atmospheric

moisture; (c) a diagnostic study of surface runoff using eight years of NCAR/NCEP Reanalysis data; (d) eight years of simulation using NCAR CCM3 with a model resolution of T21; (e) a comparison of the distributions of the diagnostic runoff rates with the CCM3 simulated runoff

rates. 3. Scientific Results

(a) The intra-seasonal oscillations in precipitation is only second to annual oscillations in terms of the magnitude of climate signals in the mid-latitudes. Two intra-seasonal modes are found in the North American precipitation field, one with a period of 37 days and the other with a periodicity of 24 days. The 24-day oscillation has its peak at the eastern North America, while the 37-day oscillation


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is maximum at the northwest coast of the United States. Both oscillations show significant larger amplitudes during the winter seasons.

(b) A standard method to calculate the horizontal moisture convergence, which has been used by quite

a few authors is by applying the Green's theorem and performing the line integrations of moisture fluxes over a closed area. However, because of mountains, the Green's theorem indicates that the horizontal moisture convergence should be equal to the outer line integrations of horizontal moisture flux, minus the inner line integrations around mountains. This inner line integration is not equal to zero because, even though the component of the moisture flux normal to mountains is zero, the horizontal projections of the tangential component do not usually vanish. In the literature, this inner line integration around the mountains are often ignored (Walsh, et al. 1994, Atmos-Ocean, 32, 733-755).

(c) The atmospheric moisture equations, when integrated throughout the depth of the atmosphere gives:

ΜQ/Μt + div VQ = E - P (1) where Q is the total moisture content of an atmospheric column and VQ is the vertically integrated moisture flux vector. E and P are the surface evaporation rate and the columnar precipitation rate, respectively. When we make similar vertical integration of the land water content, the equation is: ΜW/Μt + div VW = P - E (2) where W is the total water content on the ground and div VW is the total runoff rates. P and E are the same as that in equation (1). When one makes long-term integrations, the storage terms ΜQ/Μt and ΜW/Μt can be ignored. The total runoff rates can be obtained from a long-term integration of the atmospheric observations or models: div VW = - div VQ = P - E (3) An eight-year integration of the runoff rates has been performed using the NCAR/NCEP Reanalysis data. (d) Similarly, an eight-year integration is performed with the CCM3 global circulation model of the

atmosphere using a horizontal resolution T21. This is an atmospheric model and the eight-year average runoff rates at the surface and underground can be determined. A comparison can be made with those obtained from NCAR/NCEP reanalysis results.

(e) Comparisons have been made between the runoff rates determined from the NCAR/NCEP

Reanalysis data and those obtained from CCM3 run with the T21 resolution. In general, we found that the areal integrated runoff rates over the Mackenzie River Basin between the two approaches basically agree with one another. However, when one compares the horizontal distributions of the runoff rates, one finds large differences.

One of the reasons for the discrepancies is due to the effect of topography. In the Land Surface Scheme used in CCM3, the slopes of topography are not included in the calculations. We will look into this problem as the distribution of runoff rates has very large effects on the simulated regional climate.


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4. Summary Comparisons are made over the Mackenzie River Basin between the runoff rates obtained from NCAR/NCEP Reanalysis data and those determined from CCM3 integrations. The runoff rates are then integrated over the area. It shows that, although the areal integrated runoff rate between the two approaches agree, they have very large differences in horizontal distributions of runoff rates. 5. Recent Publications and Presentations Liu, Jinliang and Han-Ru, Cho, 1998. “Effects of big lakes in Mackenzie River Basin on local weather

systems.” Presented at the 8th PSU/NCAR Mesoscale Model Users' Workshop, June 15-17, 1998, Boulder, Colorado. In: Proceedings of the 8th PSU/NCAR Mesoscale Model Users' Workshop, pp. 142-144.

Liu, Jinliang and Han-Ru, Cho, 1996. Verification of Runoff Parameterization using Atmospheric Data Instead of Hydrological Data: Preliminary Results in MRB. Presented at 32nd CMOS Congress, June 1-4, 1996, Halifax, Nova Scotia.

Ye, Hengchun and Han-Ru, Cho, 1999. Understanding the Characteristics of the Intra-seasonal Oscillations in the North American Precipitation Field. Presented at the 11th Conference on Applied Climatology, January 10-15, 1999, Dallas Texas.

Ye, Hengchun and Han-Ru, Cho, n.d. Spatial and temporal characteristics of the intra-seasonal oscillations in the North American precipitation field. J. Geophy. Research. (submitted)

Ye, Hengchun, Han-Ru, Cho, and P.E. Gustafson, 1998. The change of Russian winter snow accumulation during 1936-1983 and its spatial patterns. J. Climate, 11:362-370.

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1.2 Airborne Observations of Surface-Atmosphere Energy Exchange over the Northern Mackenzie Basin

Peter H. Schuepp1, Ian J. MacPherson2, Raymond L. Desjardins3

1Dept. of Natural Resource Sciences, McGill University, Ste-Anne-de-Bellevue, Qu�bec 2Flight Research Laboratory, Institute for Aerospace Studies, NRC, Ottawa, Ontario

3ECOR-Centre, Agriculture and Agri-Food Canada, Ottawa, Ontario 1. Objectives The objectives of this study are based on the following facts:

(a) The Mackenzie Basin is vast, and the spatial representativeness of the few (<5) surface stations capable of measuring the surface-atmosphere exchange of heat and moisture cannot be assumed without independent verification.

(b) Given the sparseness of direct observations, the overall surface-atmosphere exchange over the basin

will be estimated primarily from local climate models and algorithms based on remote sensing observations of surface characteristics, supplemented by standard meteorological data. The validity of such estimates also needs to be independently assessed.

(c) Flux measurements from low-flying aircraft are the only available means for measuring surface-

atmosphere energy exchange at regional scales. Therefore, they are essential for the above mentioned validations (within the constraints of their own reliability). The airborne radiometric observations of the surface, with minimal atmospheric absorption, will also be useful for the calibration of radiation balance models.

As a consequence, our study (based on deployment of the NRC Twin Otter research aircraft) will document radiometric surface properties and fluxes of sensible and latent heat over transects up to 100 km in length, over ecosystems typical for the Northern Mackenzie Basin, and spatial variations over a 16 km x 16 km 'grid site' of mixed forest/tundra in the Inuvik area. Flux measurements will then be related to remotely sensed surface observations and compared to projections of local climate models. 2. Progress and Collaborations Instrument upgrades on the Twin Otter of direct benefit to MAGS: Installation of a new LI-COR CO2/H2O analyzer in the nose of the aircraft, close to the point of gust measurement; temperature sensors added to incident and reflected solar radiometers to allow compensation for temperature changes; McCarthy correction algorithm to improve frequency response of temperature and moisture measurements; second GPS installed (NovAtel) for improved back-up wind measurements. Advances in analysis techniques were tested on the database accumulated in the SGP97 (Southern Great Plains 1997) hydrology experiment in Oklahoma. Flight planning and research licence application: During a site visit (April 27 to May 4, 1998) by the PI and the first co-investigator, logistic aspects of aircraft operation from Inuvik were investigated. Projected flight lines and grid site were tentatively identified, in coordination with the team of P. Marsh, who operates two eddy correlation flux stations in that area, and whose support was essential. Federal and native agencies were contacted concerning potential impact of low-flying aircraft on wildlife harvesting operations, in preparation for submission of the research licence application. The application was submitted on August 5 and a favourable decision by the Environmental Impact Screening Committee has been communicated to us by October 9, although minor aspects regarding timing of operations during periods of waterfowl migration remain to be clarified.


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Land classification, geospatial and statistical analyses: Since we have no MAGS data yet (operations are planned for May/June 1999), we continue to develop relevant analysis techniques based on the BOREAS 1994 and 1996 data. We are currently evaluating three different surface classification schemes (based on observations from Landsat TM and Shuttle Imaging Radar-C data), developed by the terrestrial ecology and remote sensing teams of BOREAS, against video recordings of the surface and airborne maps of radiometric surface properties and energy fluxes over two 16 km x 16 km grid sites. This helps to assess the usefulness of various surface classification schemes in scaling up local and regional flux observations to basin-wide scales. We have also improved our ability (through statistical analysis and spatial correlation of flux maps) to separate effects associated with changes in boundary layer dynamics and radiation field from those attributed to landscape features. Tentative model intercomparisons: The CMC-GEM (Global Environmental Multiscale) predictions of surface-atmosphere exchange of sensible and latent heat for 36 km x 36 km 'target areas' in the BOREAS study area (collaboration with M. Beauchemin, AES-RPN, Dorval, Qu�bec) were compared against area-averaged Twin Otter airborne fluxes over two approximately co-located 16 km x 16 km grid sites, for the 1996 data.

(i) The CMC-GEM predictions for various locations in the Northern Mackenzie Basin (collaboration

with E. Radeva, AES-RPN, Dorval, Qu�bec) were compared against flux observations of sensible heat by the Marsh team (P. Marsh, National Hydrology Research Centre, Environment Canada, Saskatoon, SK) in 1996 and 1997.

3. Scientific Results Refinements of Twin Otter flux observations: In SGP97, aircraft- and tower-based estimates of sensible (H) and latent (LE) heat flux were compared in terms of energy closure (the degree to which estimates of H+LE approach available energy, i.e., net radiation minus ground flux). Results (Figure 1) suggest that the Twin Otter, with the refinements described above and over the relatively flat landscape of SGP97, closed the energy budget to within about 10%, comparing favourably with observations from tower and other flux aircraft. This marked improvement represents the best performance in energy balance closure to date and augurs well for the upcoming MAGS/CAGES campaign. Land classification, geospatial and statistical analysis: This ongoing analysis has so far illustrated the crucial importance of the choice of land surface classification in any effort to link regional energy flux to a spatially heterogeneous and biophysically complex terrestrial surface, and - as a consequence - to the extrapolation from local to regional scales based on remote sensing observations. Having demonstrated the statistical robustness of the flux sampling (and resulting flux maps) in view of boundary layer and radiation dynamics that are expected to be similar to those of the MAGS area, we are in the process of defining criteria for optimum selection of surface classification based on maximum likelihood derived from spatial correspondence between flux and surface maps. Model intercomparisons: The CMC-GEM predictions of areally averaged flux of H and LE over northern boreal forest (Candle Lake and Thompson sites at 53.9 N and 55.9 N, respectively) showed encouraging agreement with averaged flux values from Twin Otter flights over the approximately co-located grids, particularly at the Candle Lake site (Figure 2). Comparison of CMC-GEM predictions of H for 1996 and 1997 at Inuvik, against the tower-based observations of the Marsh team at Havikpak Creek (Inuvik) was impressive in terms of agreement in magnitude and - especially - timing of 'escalation' of H at the beginning of May (Figure 3). The delay in the development of significant LE fluxes at Inuvik will have implications about optimum timing of aircraft deployment.


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Figure 1 Sum of sensible and latent heat fluxes from Twin Otter and Long-EZ aircraft and tower

flux, versus tower net radiation minus soil heat flux.

Figure 2 Seasonal CMC-GEM projection of sensible (H) and latent (LE) heat flux and Twin Otter

grid-averaged fluxes over southern study area sites in BOREAS 1996.


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Figure 3 CMC-GEM projection of sensible (H) and latent (LE) heat flux for the Inuvik area in 1996 and 1997, and 1997 surface flux observations at Havikpak Creek. (Team of P. Marsh)

4. Summary The MAGS project is extremely ambitious in trying to describe the interaction between the terrestrial surface and the atmosphere almost exclusively through model simulations and algorithms based on remote sensing observations. This is dictated largely by the inaccessibility of the terrain. It means, however, that the few direct measurements of heat and moisture exchange at regional scales (i.e., by flux aircraft) must be optimally used to validate model and remote-sensing based predictions, on the basis of which we will have to scale up observations to the basin wide scale. This can only be done (i) if we have confidence that airborne observations can capture the bulk of the available energy flux; (ii) if model predictions (in spite of highly simplified surface descriptions) are close enough to actual observations that they can be expected to serve as an extension of the latter; and, (iii) if we understand what meteorological and remotely sensed radiometric parameters form the most promising predictors for regional flux estimates. Progress to date (as described above) has been significant on all these counts. 5. Recent Publications and Presentations We have no data yet on MAGS, but eight collective papers since 1997 on various aspects of regional energy or gas exchange over a variety of terrains, which deal with expertise relevant to MAGS. Recent conference presentations on relevant topics include: Brown-Mitic, C.M., P.H. Schuepp, R.L. Desjardins, and J.I. MacPherson, 1998. A Spatial Model for

Predicting the Distribution and Intensity of the Sources and Sinks for Heat, CO2 and Water Vapour from BOREAS. Presented at the 23rd Conference on Agriculture and Forest Meteorology, AMS, November 2-7, 1998, Albuquerque, New Mexico.

MacPherson, J.I., R. Dobosy, S.B. Verma, W.P. Kustas, J.H. Prueger, and A. Williams, 1998. Intercomparisons Between Flux Aircraft and Towers in SGP97. Presented at the 23rd Conference on Agriculture and Forest Meteorology, AMS, November 2-7, 1998, Albuquerque, New Mexico.


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Ogunjemiyo, S.O., P.H. Schuepp, M. Beauchemin, R.L. Desjardins, and J.I. MacPherson, 1998. Flux Measurements and Characterization over the Boreal Forest of Canada. Presented at the 23rd Conference on Agriculture and Forest Meteorology, AMS, November 2-7, 1998, Albuquerque, New Mexico.

Schuepp, P.H., S.O. Ogunjemiyo, S.K. Kaharabata, J.I. MacPherson, and R.L. Desjardins, 1998. Low-level Flux Observations over Heterogeneous Terrain in BOREAS. Presented at the 23rd General Assembly, European Geophysical Society, April 20-24, 1998, Nice, Italy.

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1.3 Atmospheric Moisture Budgets for MAGS

Brian A. Proctor1, Geoff Strong2, Muyin Wang3

1Climate Research Branch, Atmospheric Environment Service, Saskatoon, Saskatchewan 2 GEWEX/MAGS Secretariat/Coordinator, NHRC, Saskatoon, Saskatchewan

3Dalhousie University, Halifax, Nova Scotia 1. Objectives The proposed atmospheric moisture budget analysis is directly relevant to the central MAGS objective of understanding and modelling high latitude water and energy cycles. The analysis and evaluation of large-scale atmospheric model output is fundamental to our understanding of the moisture budget at whole and sub-basin scales, and for identifying biases in current atmospheric models. The specific objectives for FY 98-99 are:

1) Extend the analysis of MAGS atmospheric moisture budget to the hydrologic year 1997-98, including the enhanced sounding data from the CAGES period.

2) Validate the atmospheric moisture budget against observed precipitation data, and both measured and modelled discharge for the whole period 1995-1998, where such data are available.

3) Continue assessment of the importance of any diurnal variation in the moisture budget due to local evapotranspiration, and compare results between observed and (GEM) modelled data.

4) Submit at least one journal article on atmospheric moisture budget analyses performed to date. The hydrologic year 1997-1998 is intriguing due to the potential impacts of El Niño. Over southwestern portions of the basin, during the winter accumulation period, only 50-75% of normal precipitation fell (Environment Canada, period November 1, 1997 to February 15, 1998), which has resulted in a reduced snowpack. Therefore, P-E computations under these conditions would be crucial to enhancing our knowledge of the water cycle. Secondly, the addition of this hydrologic year may enable other researchers to have consistent numerical model (GEM) output to use through the period. CAGES 1998 summer data and other data sources (BOREAS) will be processed to refine the results from 1997 radiosonde tests at Fort Smith, and also to compare with GEM model runs with and without the enhanced sounding data. Differences in the diurnal signature of integrated water vapour mass between observed radiosonde data and GEM model data initiated at 1200 and 0000 UTC will be investigated. These results will provide feedback to RPN/CMC, which might help in improving model algorithms. 2. Progress and Collaborations Further progress has been made on objective 3) listed above. An investigation of diurnal moisture budget trends was again performed over a two week period from July 17 to August 1, 1998 at Fort Smith, NWT. Details on the results are listed below. Work on the atmospheric moisture budget for Water Year 97-98 is underway. Preliminary results for the whole basin indicate that evaporation may have exceeded precipitation during the months of May through August, a substantial variation from previous MAGS years. Other progress has been made in attempting to assess the apparent closure error between the residual P-E from the moisture budget when compared to the mean gauged discharge. Results from Soulis et al. (1998) suggest that the storage term is on the order of 10 mm. This reduces the closure error by approximately 10%. In addition, a comparison of the observed integrated water column vapour mass, q , (at rawinsonde locations in and adjacent to the basin) with model (RFE and GEM) was completed for the period October 1994 through September 1998. It was found that on monthly and seasonal bases that the model underestimated observed integrated water column vapour mass at nearly all locations. This error


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was found to be a maximum in the early Summer of 1997 when CMC was having using global model results as a first guess field in the data assimilation cycle for the GEM.

Collaborations:

We planned to validate the atmospheric moisture budget estimates against measured and modelled discharge on a whole basin and principal sub-basin basis. This will require collaboration with Soulis and Pietroniro, in particular. Data have been requested from Soulis and will be obtained following the workshop. Betts (1998) produced estimates of the Moisture Budget using ECMWF output. During the water year 1996-1997, the flux comparisons over the sub-basins discussed below compare quite favourably until the Summer of 1997; at this time, the results diverge. Discussions with Ritchie have indicated that a possible cause of this divergence in results could have been associated with the use of global data set as a first guess field in the data assimilation scheme during the Spring and early Summer of 1997. 3. Scientific Results

Moisture Budgets: Figure 1 shows the computational domain used in moisture budget computations, an area of approximately 2.0 x 106 km2. Previous analyses (in the literature) have used much broader boundaries, forced by coarse radiosonde spacing. The atmospheric moisture budget equation is: <P - E> = - <�q/�t> - <��Q> = R (1) where the difference between precipitation (P) and evapotranspiration (E), <P - E> is computed as a residual in the moisture budget (1), and is assumed to be = R (runoff); <�q/�t> = the local rate of change of q, the vertically-integrated vapour mass, - <��Q> = the moisture flux convergence, Q = qV, the vertically-integrated moisture flux, and the brackets, < > denote time averages. The local change term theoretically includes a storage term, �qs/�t, but in these analyses we assume this term is negligible (for lack of data). Analyses of the 1997-1998 water year are incomplete at this writing. Analyses of 1995-97 data revealed that all components of the atmospheric moisture budget had strong seasonal variations, with weakest convergence occurring in August 1997. Two atmospheric terms dominated the annual budget: the moisture flux convergence yields 0.69 mm/day, or 251 mm/year equivalent for the 1996/97 water year, and 279 mm/year for the 1995/96 water year; values of the local change term were less significant, 10 mm/yr or 0.03 mm/day, only 4% of the moisture flux convergence. As a result, the residual term, P-E = R, accounts for about 241 mm/year, while seasonal variations are similar in magnitude to the moisture flux convergence. This compares to a longer-term 17-year average runoff of 176 mm/year from gauge measurements. The analyses also showed that for the 1995-97 period, the basin was a net moisture sink; that is, more moisture was advected into the basin from the west and southwest than left in the east. However, summer periods can often be linked with net divergence, suggesting that local evapotranspiration may make the basin a temporary moisture source. The atmospheric moisture budget analysis was repeated for the six principal sub-basins of the basin. The local rate of change of vertically-integrated water column vapour mass was found to reach its maximum in June, then tapered off during the summer months. Moisture flux convergence and the P-E term over the Athabasca, Great Slave, and Peace sub-basins (southeastern half of the Mackenzie Basin) followed the same trend as the basin whole, decreasing through the year until August, with a sudden increase in September. The patterns of the northwestern sub-basins are less defined, but the differences may be an artifact of the coarse resolution and location of radiosonde sites and/or of model topography.


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These trends, and the fact that climatologically, precipitation reaches a maximum in the summer months throughout the basin, suggests that evapotranspiration plays a strong role in balancing the moisture budget equation during summer. By September, convergence increases sharply, suggesting that precipitation again begins to dominate over evapotranspiration.

Figure 1 Computation domain for the Mackenzie River Basin based on RFE/GEM 0.5ΕΕΕΕx0.5ΕΕΕΕ

grid. The basin moisture flux boundaries are shown as the heavy lines. The sub-basins are indicated as follows: 1) Athabasca; 2) Peace; 3) Liard; 4) Great Slave; 5) Great Bear; and, 6) Peel.

Diurnal Signature in Atmospheric Moisture: Sequential sounding tests conducted at Fort Smith, NWT during 1997 were repeated in 1998, first, to obtain a more representative sample, and second, to check whether GEM model performance was improved over 1997. We can only report on the first of these issues at this time. Figure 2 is a composite of averaged daily trends of observed precipitable water for the 1997 and 1998 two-week periods at Fort Smith when three-hour sounding releases were conducted. The thick line with solid ovals represents the 27-day average (at each sounding hour) for the two years. This 27-day average effectively filters out most trends caused by transient synoptic features, resulting in an average 2-mm diurnal trend, presumably the result of evapotranspiration over the region represented by the sounding. This rate is consistent with estimates of evapotranspiration from other MAGS studies (e.g., Bussi�res 1998). If only 1200 and 0000 UTC soundings had been available during these periods, the analysis would have suggested an evapotranspiration rate of only 1 mm/day, an under-estimate by 50%. Strong (1997) suggested that the under-estimate of vapour mass increase from evapotranspiration due to using only two synoptic soundings could be as high as 40% for the Canadian prairies. While the Mackenzie Basin experiences a colder climate, long daylight hours during summer (~20 hours) and a ready supply of moisture from extensive wetland areas, could sustain similar evapotranspiration rates. Qualitative support for this is provided by Szeto’s (1998) summer precipitation recycling rates, and by the high frequency of summertime convective cloud processes described by Isaac and Stuart (1997).


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The 1997 forecast trends at 0000 and 1200 UTC (dashed lines) in Figure 2 clearly indicate a problem in the GEM model in terms of reproducing this diurnal signature. GEM forecast data for 1998 have not yet been processed, but it is hoped that recent model improvements will yield a better replication of this feature. This necessitates a further evaluation of GEM Run-0 values of precipitable water.

Figure 2 Average diurnal trend in radiosonde-derived precipitable water for 2-week periods in

1997 (O97-01-13 Aug.) and 1998 (O98-17 July - 01 Aug.) at Fort Smith, NWT. Data were averaged for each sounding hour (12=1200, 24=0000, and 36=1200 UTC). Observed data for individual years are solid lines with open triangles, and the composite 4-week trend (O97-98) is indicated by the thick line with solid ovals, for which the average diurnal trend is 1.9 mm (1200 to 0600 UTC). Dashed lines are GEM Run-0 forecast values for 1997.

Run-0 GEM Model Precipitable Water: Run-0 prognoses (i.e., data initialized by the model) model data soundings from the operational CMC runs of the RFE (October 1994 to February 1997) and the GEM (February 1997 to September 1998) were compared with observed sounding data. These comparisons were made for seven radiosonde locations in and adjacent to the basin, and the nearest grid point available from the models for both 0000 and 1200 UTC. Only radiosondes observed having at least 12 mandatory and significant levels from the surface to 300 mb were included in the analysis. Both observed and model data were interpolated to 10 mb prior to the column being integrated to produce water column vapour mass. The resultant data were then aggregated to monthly and seasonal values for comparison. Results of this analysis are shown for Fort Smith, NWT in Figures 3 and 4. Table 1 shows the seasonal results for the seven stations in and adjacent to the basin. In general, the models underestimate precipitable water at nearly all locations on a monthly and seasonal basis. The principle exception to this is Stony Plain Alberta, where the model overestimated the observed q in 11 of the 15 seasons examined at 1200 UTC and 9 of the 15 seasons examined at 0000 UTC. At other sites, the maximum number of seasons where the bias was positive was 3 for Fort Smith, NWT at 0000 UTC and Inuvik at 1200 UTC. The negative bias in precipitable water reaches a maximum in the summer months of 1997 and is of the

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order of 3 mm/day. When incorporating all locations for all seasons, the underestimation of q is approximately 0.7 mm/day at both 0000 and 1200 UTC. The implications of this bias at this time are not known. Model estimates of P-E determined using atmospheric moisture budget techniques are known to be approximately 40% high when compared to gauged discharge, but the implications of q being too small in the model do not necessarily mean that the budget estimates obtained are also in error. It does, however, point out that comparisons of model data need to be ground-truthed with observations to determine model performance. It is hoped that the CAGES observation periods will yield significant numbers of high resolution soundings to determine whether or not this bias found is a result of a systematic error in the methods applied (i.e., lack of enough significant levels in the soundings), or whether the model is not performing well (possible inaccurate depiction of the boundary layer moisture).

Figure 3 Model bias in integrated water column vapour mass (mm) at Fort Smith NWT for (A)

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Figure 4 Seasonal biases in the integrated water column vapour mass (mm). Modelled and

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Bias in Precipitable Moisture q (mm) Model - Observed 00Z DJF94 MAM95 JJA95 SON95 DJF95 MAM96 JJA96 SON96 DJF96 MAM97 JJA97 SON97 DJF97 MAM98 JJA98 AVG YSM -0.13 -0.95 0.15 -0.43 -0.40 0.13 0.43 -0.74 -0.24 -0.94 -2.52 -1.30 -0.29 -1.21 -0.12 -0.57 WSE -0.02 -0.35 0.62 -0.04 0.10 -0.57 1.35 -2.10 0.57 0.83 -0.46 1.18 0.66 0.47 1.01 0.22 YVQ -0.31 -1.38 -1.67 -0.97 -0.41 -0.66 -0.83 -3.15 -0.31 -1.68 -2.82 -1.08 -0.39 -1.03 -1.85 -1.24 YXS -0.57 -0.59 -1.70 -0.67 -0.73 -1.65 -2.39 -0.81 -0.58 -2.76 -1.43 -0.75 -0.61 -0.73 -1.14 YCB -0.07 0.11 -0.30 -0.12 -0.08 -0.15 -0.62 -0.18 YXY -0.18 -0.11 -1.70 -0.75 -0.36 -0.54 -1.49 -2.02 -0.71 -0.88 -3.15 -1.86 -1.41 -0.27 -0.57 -1.00 YEV -0.26 -0.85 -0.42 -0.14 -0.27 -0.39 -0.29 -2.69 -0.22 -1.48 -2.92 -1.38 -0.22 0.36 0.42 -0.72 AVG -0.16 -0.58 -0.56 -0.59 -0.30 -0.41 -0.44 -2.18 -0.29 -0.79 -2.44 -0.98 -0.24 -0.38 -0.31 -0.66 12Z DJF94 MAM95 JJA95 SON95 DJF95 MAM96 JJA96 SON96 DJF96 MAM97 JJA97 SON97 DJF97 MAM98 JJA98 AVG YSM -0.41 -0.47 -1.40 -0.78 -0.73 -0.41 0.29 0.06 -0.48 -0.55 -2.57 -2.11 -0.46 -1.23 -0.18 -0.76 WSE -0.51 0.22 0.24 -0.13 0.14 0.52 1.29 0.47 0.09 0.27 -0.37 0.75 0.59 -0.24 0.01 0.22 YVQ -0.43 -0.93 -2.49 -2.87 -0.95 -0.94 -0.48 -0.36 -0.35 -1.45 -3.22 -1.91 -0.11 -1.15 -1.54 -1.28 YXS -0.63 -0.58 -1.24 -1.80 -0.61 -1.05 -1.54 -1.00 -0.55 -1.11 -3.12 -2.05 -0.63 -1.23 -1.71 -1.26 YCB 0.05 0.07 -0.35 -0.33 -0.25 -0.52 -0.71 -0.29 YXY -0.27 -0.78 -2.39 -0.96 -0.60 -0.33 -1.39 -0.81 -0.92 -1.37 -3.41 -3.17 -0.66 -0.89 -1.25 -1.28 YEV -0.33 -0.20 0.56 -0.13 -0.20 -0.20 0.13 -0.48 -0.35 -1.18 -3.02 -0.74 0.12 -0.15 -0.32 -0.43 AVG -0.36 -0.38 -1.01 -1.00 -0.46 -0.42 -0.34 -0.35 -0.43 -0.90 -2.62 -1.54 -0.19 -0.82 -0.83 -0.73

Table 1 Integrated water column vapour mass bias (mm). Model observed for 7 stations in and adjacent to the Mackenzie Basin:YSM – Fort Smith, WSE – Stony Plain, YVQ – Norman Wells, YXS – Prince George, YCB – Cambridge Bay, YXY –Whitehorse, and YEV – Inuvik.


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4. Summary A key feature of the 1996-97 atmospheric moisture budget analysis of this study is the ~+40% bias in the moisture budget estimate of P-E (241 mm), compared with the long-term mean gauged discharge of 173 mm based on the 1973-90 water years (Walsh et al. 1994). Possible causes are:

1) a negative bias in basin discharge data, perhaps resulting from spring break-up measurement errors;

2) a significant net annual surface water storage within the basin; 3) the inability of two soundings per day to adequately account for summertime evapotranspiration,

fall evaporation (from open-water), wintertime sublimation (basin moisture sources), and precipitated water (rain and snow);

4) the inability of current operational models to accurately model diurnal atmospheric moisture trends; and,

5) inter-annual variability. Our analyses suggest that 3 and 4 may be most important in this study. Data limitations preclude any actual estimates of these additional terms in our analyses of Figures 3 and 4. However, we are hopeful that CAGES will provide better estimates of discharge (1) together with error estimates, as well as sounding data with improved temporal resolution to shed more light on (3) and (4). Soulis (1998) indicated that the storage term is on the order of 5-15 mm. It is hoped that with improved discharge data, hydrologic models (WatFlood) may elucidate and refine the storage term (2) somewhat. Additionally, a complete moisture budget analysis of the 1997-98 water year (an El Niño winter) should help shed light upon (5). The extension of the moisture budget work to the 1997-98 water year that is currently underway will also yield a larger data set to assess the ability of the GEM model, with a consistent data assimilation scheme for the whole year, to determine the components of the atmospheric moisture budget. Current annual ‘atmospheric’ estimates of P-E are some 40% higher than actual runoff estimates. These results suggest that a minimum of at least one additional sounding per day is required to capture most of the diurnal trend, preferably at 0300 UTC, with additional soundings at 2100 and 0600 UTC if funds permit. The same sounding schedule would be required for all sounding sites within the basin, with additional soundings at some central site (preferably, Fort Simpson) to validate the capture. The argument for these additional soundings is strengthened by a critical need to ground-truth the RFE/GEM model output with and without the additional data in order to provide a base-line for improvements in model parameterization. The composite of sequential soundings conducted at Fort Smith during 1997 and 1998 suggest an average evapotranspiration rate of 2 mm/day, consistent with values from other MAGS’ studies. With only two soundings per day, this would have been underestimated by 50%. It is hoped that the installation of a two channel GPS receiver at Fort Smith (Winter of 1998) will enable MAGS to continuously monitor precipitable water to determine whether or not the diurnal trends indicated in summer studies are realistic. 5. References Bussi�res, K., 1998. Evapotranspiration and energy balance components from satellite data. In: G.S.

Strong and Y.ML. Wilkinson (Eds.), Proceedings 4th Scientific Workshop for the Mackenzie GEWEX Study (MAGS), November 1998, Montr�al, Qu�bec, pp. 108-109. (this volume)

Issac, G.A. and R.A. Stuart 1996. Relationships between cloud type and amount, precipitation, and surface temperature in the Mackenzie River valley - Beaufort Sea area. J. Clim.


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Soulis, R., 1998. Integrated hydrologic modelling for MAGS. In: G.S. Strong and Y.ML. Wilkinson (Eds.), Proceedings 4th Scientific Workshop for the Mackenzie GEWEX Study (MAGS), November 1998, Montr�al, Qu�bec, pp. 139-143. (this volume)

Strong, G.S., 1997. Atmospheric moisture budget estimates of regional evapotranspiration from RES-91. Atmosphere-Ocean, 35:29-63.

Strong, G.S., M. Wang, B.A. Proctor, and A. Barr, 1998. Atmospheric Moisture Budgets over the Mackenzie Basin. Paper presented at 32nd Annual Congress, Canadian Meteorological and Oceanographic Society, June 1998, Halifax, Nova Scotia.

Strong, G.S. and B.A. Proctor, 1998. Diurnal Variations in Atmospheric Moisture during GEWEX/MAGS. Paper presented at the 32nd Annual Congress, Canadian Meteorological and Oceanographic Society, June 1998, Halifax, Nova Scotia.

Szeto, K., 1998. Low-level inversions, precipitation recycling, and air-land interactions over the Mackenzie Basin. In: G.S. Strong and Y.ML. Wilkinson (Eds.), Proceedings 4th Scientific Workshop for the Mackenzie GEWEX Study (MAGS), November 1998, Montr�al, Qu�bec, pp. 30-31. (this volume)

Walsh, J.E., X. Zhou, and M.C. Serreze, 1994. Atmospheric contribution to hydrologic variations in the Arctic. Atmos.-Ocean, 32:733-755.

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1.4 Cyclones and Their Role in High Latitude Water Vapour Transport

John R. Gyakum Dept. of Atmospheric and Oceanic Sciences, McGill University, Montr�al, Qu�bec

1. Scientific Objectives a) To investigate the relationship between low-frequency variability of transient eddy activity in the

North Pacific and precipitation-related anomalies in the Mackenzie River Basin (hereafter MRB) and the Beaufort Sea.

b) To analyse the structure and life cycle of individual cyclonic weather systems responsible for

substantive precipitation in the MRB (p. 76 of NSERC GEWEX proposal). These objectives each contribute to the first MAGS objective of undersanding, quantifying, and modelling the critical components of the water and energy cycles that affect the Mackenzie Basin climate system. 2. Progress Relating to Scientific Objectives a) and b) (during the period 1 December 1997 to the present) a) We have published the article entitled, "Moisture transport diagnosis of a wintertime precipitation event in the Mackenzie River Basin" (Lackmann, Gyakum, and Benoit 1998) in the Monthly Weather Review. b) We have recently had accepted for publication in the Monthly Weather Review, the article entitled, "A numerical case study of secondary marine cyclogenesis sensitivity to initial error and varying physical processes" (Carrera, Gyakum, and Zhang 1999). This research utilizes the Mesoscale Compressible Community (MC2) model to assess the predictability of a case of explosive marine cyclogenesis and provide a better understanding of the large variability in the recent model-intercomparison simulations of the case. Such cases of secondary marine cyclogenesis typically provide the water vapour transports into high-latitude regions such as the Mackenzie Basin. Water vapour budget calculations show the surface moisture flux to be the largest contributor of water vapour to the cyclogenesis region, and remains an important moisture supply throughout its 36-h life cycle. When surface evaporation is not allowed, much less precipitation is produced and the secondary cyclone fails to develop. Thus, we find that local surface evaporation is an important driving mechanism for a process that acts to transport water vapour from the tropics into very high latitudes. c) We have produced moisture budgets for a large spectrum of North Pacific oceanic cyclonic disturbances that are responsible for the water vapour transport into the MRB. We find that surface evaporation, as opposed to the convergence of the moisture transport, is the dominant contributor to the water available to the cyclonic region. Additionally, most of the water vapour made available to the system is used to increase the storage in the system's initial phases. Subsequently, as the cyclone develops, this water vapour is used for precipitation, thereby increasing the cyclone's amplitude. Associated warm anomalies of Sea-Surface Temperature and cold anomalies of lower tropospheric air are consistent, in a bulk aerodynamic sense, with the relatively strong surface fluxes occurring in the cyclogeneses region. A paper documenting these processes is currently being revised for publication in the Monthly Weather Review (Gyakum and Danielson 1999).


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d) A comprehensive synoptic-climatology of heavy precipitation events for the Montr�al area has been developed, following the procedure of Lackmann and Gyakum (1996). We find that preferred large-scale circulation anomalies for cold-season precipitation include a downstream anticyclone whose function is to transport moisture into the Montr�al region from the Gulf of Mexico, and later from the Gulf Stream Current region of the North Atlantic Ocean. A comparison with the results of Lackmann and Gyakum (1996) reveals that preferred circulation anomalies for heavy precipitation events are those which provide the most efficient means of transporting relatively-large quantities of water vapour into the region. Further examination of global-scale water vapour transports from the National Centers for Environmental Prediction (NCEP) reanalysis show that much of the moisture is being transported in an anticyclonic North Atlantic Basin-wide gyre. We speculate that much of the water vapour is evaporated from the tropical regions of the North Atlantic. A paper, based upon the thesis work of Alexandre Fischer concerning this process (Fischer 1997) is being prepared for submission to a refereed journal. e) A comprehensive climatology of global Available Potential Energy (APE) has been produced using the newly-tabulated gridded reanalysis of temperature and geopotential height data from the National Centers for Environmental Prediction. This reanalysis consists of 40 years of data from 1957 through 1996. APE, according to Lorenz (1955), is proportional to the horizontal gradient of temperature. The increase in APE is typically associated with higher latitude regions cooling relative to the warmer lower latitude areas. The decrease in APE is most often associated with a thermally direct circulation (warm air rising relative to the cold air) in cyclogenesis (e.g., Bosart et al. 1996). A very surprising result is that the globally-integrated APE increase is associated with a regional thermal gradient increase that is maximized in the MRB. This result demands that research be concentrated on thermodynamic processes in the MRB, since this region is so critical to the global energy budget. Considering that the time scales of the APE generation and collapses are typically one month, a study of the responsible processes is consistent with the GEWEX objectives to study the 'fast climate' system of energy changes. The manuscript (Wintels and Gyakum 1999) is being prepared for submission to TELLUS. Figure 1 shows an example of the temperature changes occurring during one of the most significant APE collapses of the period from 1979 through 1995. The strong warming in the northern part of the MRB is associated with a strong warm advection from a very strong North Pacific cyclone, while the strong cooling in the southern part of the MRB is associated with a strong anticyclone's cold surge that ultimately reached Central America. The important point is that Northern Hemisphere's APE depletion is focused in the MRB. f) A comprehensive diagnostic study of Inter-Hemispheric Mass Exchanges has yielded the following surprising result. An analysis of the past 20 years of data from the NCEP reanalyses has shown that a predecessor to a large mass depletion event for the Northern Hemisphere is a build up of high pressure in the MacKenzie River Basin. Then, the building surface anticyclone surges equatorward to the east of the Rocky Mountains, and ultimately transports its cool air across the equator into the Southern Hemisphere. Therefore, we have identified the Mackenzie River Basin as a source region for mass that ultimately is transported across the equator. Additionally, this mass buildup is responsible for very strong North American cold surges (Schultz et al. 1998). Marco Carrera is currently writing up this work as a component of his Ph.D. Thesis, for submission to Monthly Weather Review. Figure 2 illustrates this sea-level pressure anomaly structure at the onset of the equatorward cold surge.


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Figure 1 Change in thermal field during APE depletion event of 1200 UTC 29 January through

0000 UTC 03 February 1989; 1000-500 hPa thickness tendency (shaded, interval 12 dam) and local APE tendency (solid positive, dashed negative, interval 10x106 Jm-2).

Figure 2 Onset of seven-day fall of anomalous Northern Hemisphere mass; sea-level pressure anomalies by the standard deviation (13 cases).


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g) A paper entitled, "Heavy cold-season precipitation in the northwestern United States: Synoptic climatology and an analysis of the flood of 17-18 January 1986" is currently being revised for publication in the journal Weather and Forecasting (Lackmann and Gyakum 1999). The principal findings of this work include a large-scale composite flow anomaly structure similar to that found by Lackmann and Gyakum (1996) for precipitation events in the MRB. Moisture transport into the region, responsible for the precipitation, is accomplished by surface cyclonic disturbances originating in the subtropical Pacific. This finding is in accord with that found by Lackmann, Gyakum, and Benoit (1998) for the MRB. 3. Relevant Collaborations with MAGS and/or non-MAGS Projects a) Robert Benoit (see Lackmann et al. 1998) b) Da-Lin Zhang (see Carrera et al. 1999) c) Gary Lackmann (see Lackmann and Gyakum 1996, 1999; Lackmann et al. 1998)

d) Jim Abraham (AES, Dartmouth, Nova Scotia). Collaborative work focuses on Extratropical Transitions (ETs), which are tropical cyclones that transform into middle and higher-latitude disturbances. Such systems may be particularly responsible for large water vapour transports into the MRB.

4. Scientific Results Principal results are summarized above in the Progress section. The figures show the importance of the MRB as a regional contributor to the Northern Hemisphere's Available Potential Energy (Figure 1), and to the Hemisphere's atmospheric mass during an anomalously-large interhemispheric mass transport event (Figure 2). 5. Applicability of Results to Overall MAGS Objectives The objectives of MAGS include:

1. To understand, quantify and model the critical components of the water and energy cycles that affect the Mackenzie Basin climate system.

2. To improve the capability to predict changes to the water resources of the Mackenzie Basin that

are influenced by natural climate variability and that which may be altered by anthropogenic climate change.

The following letters correspond to those projects discussed in the Progress section above. a) The work of Lackmann et al. (1998) concerning water vapour transports into the MRB related directly to the issue of the water cycle affecting the MRB, since the case studied represents a significant portion of the region's seasonal precipitation climatology. b) The work of Carrera et al. (1998) concerning cyclogenesis relates to the physical processes that are crucial to the development of a system that is in turn responsible for water vapour transport to higher latitudes. c) The work of Gyakum and Danielson (1999) is a comprehensive study of North Pacific cyclone development mechanisms (including the source of moisture and latent heating). As pointed out above, these systems are responsible for transporting moisture into the MRB. d) The research performed by Alex Fischer that focuses on the differences between water vapour transports associated with both significant and non-significant precipitation events related directly to the understanding of the preferred means of moisture transports for particularly heavy precipitation.


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e) The Ph.D. work of Werner Wintels is providing an improved understanding of Available Potential Energy, and its conversion to kinetic energy on a Hemispheric scale. The recent finding that thermodynamic processes in the MRB are an important regional contributor to the Hemispheric Available Potential Energy supply, show the importance of further study of the energy cycle in the basin. f) The Ph.D. work of Marco Carrera relates regional atmospheric mass buildups in the MRB to inter-hemispheric mass exchanges. The study of this process, being surface anticyclogenesis, provides insight into the amplification of Available Potential Energy, and the associated cold surges that often are associated with precipitation in the MRB. g) The collaborative work with Dr. Gary Lackmann (Lackmann and Gyakum 1999) reinforces the important role of North Pacific surface cyclones in transporting water vapour needed for high-latitude precipitation events. Therefore, we gain an improved understanding of the water cycle. 6. Summary The research described focuses on the mechanisms that drive the crucial water vapour transports into the MRB. The mechanisms include surface cyclogenesis, and to a lesser extent, anticyclogenesis. The global cycle of Available Potential Energy has been studied, and we find a preferential relationship of this global quantity to the buildup and depletion of APE in the MRB. These APE depletion events are related to subsequent cold surges that extend to the subtropics, and may also be associated with anomalously strong mass buildups and subsequent mass transport to the Southern Hemisphere. 7. References Bosart, L.F. and co-authors, 1996. Large-scale antecedent conditions associated with the 12-14 March

1993 cyclone ("Superstorm '93") over eastern North America. Mon. Wea. Rev., 124:1865-1891. Fischer, A.P., 1997. A Synoptic Climatology of Montr�al Precipitation. Master’s Thesis, McGill

University, Montr�al, Qu�bec, 71 pp. Lorenz, E.N., 1955. Available potential energy and the maintenance of the general circulation. Tellus,

7:157-167. Schultz, D.M., W.E. Bracken, and L.F. Bosart, 1998. Planetary- and synoptic-scale signatures associated

with Central American cold surges. Mon. Wea. Rev., 126:5-27. 8. Papers in Refereed Literature Directly Related to GEWEX and Presentations Carrera, M.L., J.R. Gyakum, and Da-Lin Zhang, 1999. A numerical case study of secondary marine

cyclogenesis sensitivity to initial error and varying physical processes. Mon. Wea. Rev., 127, in press.

Carrera, M.L., J.R. Gyakum, and D.-L. Zhang, 1998. The role of ocean evaporation in a case of coastal secondary cyclogenesis. In: Proceedings of the 12th Conference on Numerical Weather Prediction, Phoenix, Arizona, 2 pp.

Gyakum, J.R., M. Carrera, J. Abraham, and S. Miller, 1998. An extreme case of mesoscale tropical cyclogenesis affecting the Canadian Maritimes and a climatology of similar occurrences. In: Proceedings of the First Conference on Tropical Cyclone Intensity Changes, Phoenix, Arizona, 4 pp.

Gyakum, J.R., and R.E. Danielson, 1999. Analysis of meteorological precursors to ordinary and explosive cyclogenesis in the western North Pacific. Mon. Wea. Rev., submitted.

Lackmann, G.M., and J.R. Gyakum, 1999. Heavy cold-season precipitation in the northwestern United States: Synoptic climatology and an analysis of the flood of 17-18 January 1986. Wea. Forecasting. (submitted)

Lackmann, G.M., J.R. Gyakum, and R. Benoit, 1998. Moisture transport diagnosis of a wintertime precipitation event in the Mackenzie River Basin. Mon. Wea. Rev., 126:668-691.


26

Lackmann, G.M. and J.R. Gyakum, 1996. The synoptic and planetary-scale signatures of precipitating systems over the Mackenzie River Basin. Atmos-Ocean, 34:647-674.

Wintels, W., and J.R. Gyakum, 1999. Collapses of northern hemisphere available potential energy: Climatology and synoptic structure. Tellus. (in preparation)

-1998. Moisture Transport to Arctic Drainage Basins. Invited presentation at the NATO Advanced Research Workshop on the Freshwater Budget of the Arctic Ocean, April 27-May 1, 1998, Tallinn, Estonia.

-1998. The Ice Storm of 1998: Large-scale Dynamic Precursors and Moisture Transports. CMOS Congress, Dartmouth, Nova Scotia, June 1998.

-1998. Moisture Transports in the Ice Storm 1998 and in Other Important Extratropical Weather Events. Invited seminar at the University of Wisconsin-Milwaukee, August 4, 1998.

-1998. Water Vapour Transports and Heavy Precipitation in Extratropical Transitions. Invited presentation to the Risk Prevention Initiative Workshop on the Transition of Tropical Cyclones to High Latitude Storms, Hamilton, Bermuda, September 15-16, 1998.

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1.5 Low-level Inversions, Precipitation Recycling and Air-Land Interactions over the Mackenzie Basin

Kit. K. Szeto

Atmospheric Environment Service, Downsview, Ontario

Introduction and Background The present study is an expanded investigation of the works proposed in the new 1998/1999 MAGS proposal entitled, “Development and structure of low-level inversions over the Mackenzie Basin and their effects on the energy and water budgets over the region” submitted by the author. Air-land interactions play an important role in governing the climate of various regions of the continents. The primary agents for these interactions are the energy and water vapour exchanges at the land surface. This study focuses on two particular aspects of this complex problem over the Mackenzie River Basin (MRB): (i) low-level temperature inversions, which is related to the energy exchange at the surface; and, (ii) precipitation recycling, which is related to the exchange of water vapour at the surface, over the region.

Thermal and radiative exchanges at the surface have great impacts on the development of persistent and widespread surface-based temperature inversions (SBIs) at high latitudes during cold seasons. Such inversions can affect significantly the regional energy and water budgets. First, the large static stability of the inversion inhibits vertical mixing and, therefore, it effectively decouples the free atmosphere from surface processes. Second, radiative fluxes (and, therefore, surface processes which are critically dependent on the surface radiation balance, such as snowmelt and evapotranspiration) are very sensitive to the temperature of the inversion. Third, the temperature inversion might affect the vertical distribution of water vapour (e.g., the development of moisture inversions) as well as the trapping of aerosol-type pollutants, both of which affect significantly radiative transfer and, therefore, surface energy and water balances. Fourth, the enhancement of near-surface inversions can help maintain the continental minimum temperatures, which in turn affects the development and preservation of permafrost in the region. Although the influence of different processes (e.g., radiation, advection, subsidence, and surface melting/freezing) on the formation, conservation and elimination of low-level inversions is known qualitatively, the roles of individual processes and their interactions with the environment in actual cases are still poorly understood.

Evaporation from the land surface contributes water vapour and latent energy to the atmosphere, which are critical ingredients for the formation of precipitation. Hence, evaporation couples the natural variability in land surface hydrology to atmospheric processes. The study of precipitation recycling, i.e., the contribution of local evaporation to local precipitation, is essential to the quantification of regional water cycle and in defining the role of land-atmosphere interactions in regional climate. In particular, the precipitation recycling ratio, defined as the relative contribution of recycled precipitation to total precipitation, provides a useful diagnostic measure of the potential for air-land interactions over a region. While the precipitation ratios had been estimated for several regions around the world (e.g., the Amazon, Mississippi, and Eurasia basins), a systematic study of the issue over the MRB has not yet been carried out. Scientific Objectives The objectives of the proposed research are:

1) to study and document the spatial/temporal variability of the inversion characteristics and precipitation recycling over the region and their relationship to environmental conditions;


28

2) to investigate the processes responsible for spatial/temporal variability of (i) low-level inversions; and, (ii) precipitation recycling, over the MRB;

3) to assess the capability of the RCM in reproducing the observed variability of inversion and precipitation recycling characteristics over the region.

Progress and Scientific Results During the first phase of this study, the National Centers for Environmental Prediction (NCEP)/NCAR reanalysis dataset was used to investigate the spatial/temporal variability of SBIs and precipitation recycling over the Mackenzie Basin. The temporal and spatial resolutions of the NCEP dataset are 6 h and 2.5o, respectively. Although the resolution of the NCEP data is too coarse for studies of local processes, it provides a dynamically consistent dataset appropriate for examining the large-scale variability of these phenomena. As a start, we have so far considered only the years 1994 and 1995. These preliminary results are summarized in this section. 1) Inversion The spatial monthly mean inversion structure over the basin was examined for the years 94/95. The frequency and strength (defined as temperature differences between 850 mb or 925 mb and the 1000 mb levels) of the SBIs are generally highest and strongest in January and towards the northern region, reflecting the seasonal and latitudinal variations in the surface net radiation balance. The correlation of the inversion strength with surface temperatures and other variables have also been examined for several selected locations. Although the SBIs are generally strongest in winter months when surface temperatures are lowest, this correlation between SBI strength and surface temperatures is not robust across the years. For example, although January 94 is substantially colder than January 95 over the MRB, the strength of the SBI was stronger in January 95. The surface energy budgets, low-level temperature advections and large-scale vertical motions are currently being examined to understand the temporal and spatial variability of SBI over the region. 2) Precipitation Recycling The precipitation recycling ratio ρ was calculated for the MRB by using the method outlined in Eltahir and Bras (1996). While there is substantial seasonal and annual variability of ρ over the region, precipitation recycling over the region is generally highest (~0.2 to 0.3, comparable to those estimated for the Amazon) during the warm seasons (April to August) and almost negligibly low during the cold seasons, reflecting the high potential in the summer months and low potential during the cold seasons for air-land interactions over the region. This seasonal variability of ρ is much less evident for tropical basins like the Amazon (e.g., see Eltahir and Bras 1994). There is also substantial spatial variability of ρ over the region. Precipitation recycling is generally highest in the northeastern portion of the basin, with local monthly mean values in exceed of 0.8. This later result is consistent with those calculated from the CRCM AMIP results (Mackay, et al. 1998) and is largely a result of the predominant westerlies over the region. Although precipitation recycling over the basin is negligible throughout a major portion of the year, the annual mean recycling ratio is relatively high (~0.25) when compared to those estimated over the Mississippi (~0.1 to 0.24) and the Amazon (~0.25 to 0.35, see Eltahir and Bras 1996). This relatively high annual estimate of ρ for MRB is due to the positive correlation of monthly mean precipitation (which is used as the weighing factor for the lumped and temporal average of ρ) and ρ over the region. Extension of the study to include more years is currently underway.

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1.6 High Latitude Atmospheric Moisture Transport

G.W.K. Moore and Vladimir Smirnov Dept. of Physics, University of Toronto, Toronto, Ontario

1. Objectives The objective of this project is to characterize the dynamic processes responsible for the atmospheric transport of moisture through the Mackenzie River Basin. Included in this project is an assessment of the role that coherent atmospheric weather systems play in this transport. We are also interested in understanding the intra-annual variability, as well as the inter-annual variability in the transport. Knowledge of the atmospheric processes responsible for the transport moisture through the basin and its variability on the seasonal and annual timescales are important if we are to understand the hydrology of the basin.

2. Progress and Collaborations To achieve our objectives, we make use of the Reanalysis data generated by the ECMWF. During this past fiscal year, we have completed our analysis of the entire 15 year time period (1979-1993) that has been processed. This involved the computation of the 3D global moisture transport, the moisture convergence and related fields over the basin. My group continues to collaborate with Professor Asuma and his colleagues at Hokkaido University and the University of Tokyo on the analysis of data arising out of BASE. This year, a student of Asuma visited the University of Toronto to begin running MM5, NCAR’s mesoscale forecast model, on cases of cyclogenesis observed during BASE. 3. Scientific Results From these transport fields, we have computed seasonal statistics for the transport through the basin that are in general agreement with earlier work based on radiosonde data. The results shown in Figure 1 indicate that the peak convergence of moisture occurs in the fall with a distinct minimum in the summer. Paradoxically, the peak storage of moisture in the column over the basin peaks in summer and during the fall maximum in convergence, the storage is a minimum. The largest discrepancies between the two analyses occur during the spring and fall. In contrast to these earlier studies, our archive of the full 3D transport fields at 6 hour temporal resolution allows us to explore the dynamics behind the seasonality in the transport. Figure 2 show 6 hourly and monthly mean convergence into the basin during 1988. The seasonal pattern illustrated in Figure 1 is apparent in the monthly mean values for 1988 with the largest convergence occurring in the fall and a minimum in the summer. The 6 hourly data shows evidence of many high frequency dipole events in which a period of moisture convergence is followed immediately by a period of divergence. Smirnov and Moore (1998) showed that these dipole events are a signature of the large role that cyclones play in the transport through the basin. Peak values are an order of magnitude larger than the monthly mean values. Throughout the winter, spring, and fall, the magnitude of convergence events greatly exceeds that of the divergence events resulting in a net convergence of moisture into the basin. In contrast, during the summer, the magnitude of both events are of similar magnitude resulting in a greatly reduced amount of moisture


30

Figure 1 A comparison of the monthly mean moisture convergence <Q> and moisture storage <dW/dt> over the Mackenzie Basin as computed by Walsh et al. (1994) (red & thin) using radiosonde data and Smirnov and Moore (1998) (black & thick) using the ECMWF Reanalysis.

Figure 2 Convergence into the basin during 1988 as deduced from the NCEP Reanalysis. The

thin solid line represents the 6 hourly values; the thick solid line represents the monthly mean with the error bars representing the standard deviation about the monthly mean.


31

This difference in the magnitudes of the moisture inflow and outflow can be more clearly seen in Figure 3, which shows the monthly mean magnitude of both the inflow and outflow over the entire 15 years of the dataset. There is a slight reduction in the magnitude of the inflow during the summer. This, combined with the increase in the magnitude of the outflow during this period accounts for the minimum in moisture convergence illustrated in Figures 1 & 2. The maximum in the fall is the result of both an increased inflow and a reduction in the outflow. Our detailed analysis suggests that the seasonal variability in the location and intensity of cyclones that track through the region can explain much of seasonality that we see in the transport.

Figure 3 Monthly mean value of all moisture inflow and outflow events over the basin as

represented in the 15 year ECMWF Reanalysis dataset.

4. Summary This work firmly establishes that a proper characterization of this transport on the monthly, seasonal, and annual timescale requires an understanding of the dynamics of cyclones, including their intensity, life-cycle, and track that pass through the area. 5. Recent Publications and Presentations Asuma, Y., I. Soshi, K. Katsuhiro, G.W.K. Moore, K. Tsuboki and R. Kimura, 1998. Precipitation

features observed by Doppler Radar at Tuktoyaktuk, Northwest Territories, Canada, during the Beaufort and Arctic storms experiment. Monthly Weather Review, 26:2384-2405.

Cao, Z. and G.W.K. Moore, 1998. A diagnostic study of moist potential vorticity generation in an extra-tropical cyclone. Advances in Atmospheric Sciences, 15:30-45.

Smirnov, V. and G.W.K. Moore, 1998. Spatial and temporal variability of the high latitude moisture flux. Journal of Climate. (in press)

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Proceedings 4th MAGS Workshop Session 2: November, 1998 Land Surface Process Studies

32

2.1 Evaporation from Wetlands and Large Lakes

Wayne R. Rouse1, Peter D. Blanken2, Andrea K. Eaton1, and Richard M. Petrone1 1School of Geography and Geology, McMaster University, Hamilton, Ontario 2Dept. of Geography, University of Colorado at Boulder, Boulder, Colorado

1. Scientific Objectives

a) To determine controls on evaporation and the surface energy balance for different terrain units in the subarctic.

b) To measure and model the evaporation from Great Slave Lake as representative of the large lakes in the Mackenzie Basin.

2. Progress and Collaborations

a) Controls on evaporation from different terrain types in the lower Mackenzie Basin A study involving the response of the surface energy budget of three distinct terrain types to the synoptic climatology for central and western subarctic regions in Canada has been completed and the results are outlined in Section 3. This has been a collaborative project between The National Hydrologic Research Institute and McMaster University. This work forms the basis for the completed M.Sc. thesis of Richard Petrone, which is listed below.

A second ongoing project will form the basis of Andrea Eaton�s M.Sc. thesis. The purpose is to determine and compare the controls on annual evaporation from the following sites. 1. Dryland Forests: Havikpak Creek Spruce 1996 Trail Valley Creek Willow-Birch 1997 2. Wetland Forests: Churchill Spruce-Tamarak-Spruce 1990-97

Churchill Willow-Birch 1990-91

3. Wetlands: Churchill Sedge Fen 1990-97 TVC Tussock Tundra 1996, 1997

4. Dryland Heaths:

Churchill Lichen-Heath 1991, 1995 TVC Upland Birch 1997, 1998 Churchill Upland Beach 1996

5. Shallow and Deep Lakes:

Golf Lake 1991, 1995 Great Slave Lake 1997, 1998

The following controls are being examined: location; temperature; precipitation; wind speed and wind direction; soil moisture; water table position; soil type (physical, chemical, and hydrological characteristics); depth of active layer; vegetation type; LAI; phenological cycles.


33

b) Evaporation from Great Slave Lake The project is a collaborative one involving McMaster University; Atmospheric Environment

Service and National Water Resources Institute, Environment Canada, and the Hydrological Research Institute, U.K. The purpose is to measure and model evaporation and the energy balance of Great Slave Lake as representative of the Mackenzie Basin great lakes. Accompanying this is a comparative analysis with the Laurentian Great Lakes of which more is known. There is the intention of using the results of the study to aid in developing a deep lake component for CLASS, the surface energy balance submodel for the Canadian General Circulation Model. 3. Scientific Results Wetland sites in central and western subarctic regions demonstrate similar evaporation regimes despite differences in seasonal precipitation between the two regions. This shows the importance of the surface organic layer in transporting and storing water for evaporation. The magnitude of convective and conductive heat fluxes is strongly correlated with temperature and hence with synoptic-scale influences. An objective hybrid classification of daily surface weather maps for the two regions yields seven dominant synoptic types during the snow free period, which account for 90% of the days. High pressure cells to the northeast bring the coolest air to the western subarctic, while high pressure systems approaching from the northwest bring the coolest conditions to the central subarctic. High pressure approaching from the west-southwest brings warm air to the western region, whereas, stationary high pressure to the south brings warm air to the central region. The most efficient precipitation systems in both regions are those associated with the frequent passage of cold fronts. In the lower Mackenzie Basin this is related to synoptic type 4 (Table 1). The largest evaporation efficiencies are associated with systems that produce warm, dry, and clear conditions, related to centered high pressure cells with strong continental components to their flow. In the lower Mackenzie Basin this is related to synoptic types 3 and 8 (Table 1). Synoptic climatology can provide a useful link between smaller-scale surface process studies and larger-scale modelling studies. Table 1 Ratio of incoming solar radiation (K↓↓↓↓ )/extraterrestrial solar radiation (Io), Bowen ratio

(ββββ), precipitation (P), evaporation (E), precipitation efficiency (Rij) and evaporation efficiency (Dij) for both study regions and all synoptic types. Cw is central subarctic wetland site; Ww is western subarctic wetland site; Wd is western subarctic dryland site.

Synoptic Type

Parameter Site 3 4 5 6 7 8 9 10 K↓↓↓↓ /Io C 0.44 0.61 0.52 0.42 0.60 - 0.43 0.59

W 0.40 0.46 0.51 0.47 - 0.33 0.48 0.49 ββββ Cw 0.87 0.64 0.32 0.75 0.37 - 0.49 0.48 Ww 0.51 0.44 0.38 0.43 - 0.56 0.47 0.50 Wd 0.60 0.56 0.42 0.43 - 0.72 0.61 0.54

P Cw 2.5 0.2 5.1 1.7 0.3 - 5.9 1.0 (mm) Ww 0.6 1.7 0.7 1.3 - 0.6 0.8 0.9

Wd 0.6 1.7 0.7 1.3 - 0.6 0.8 0.9 E Cw 2.1 2.7 2.8 2.5 3.0 - 2.4 3.3

(mm) Ww 2.1 2.2 2.5 2.7 - 1.7 2.6 2.5 Wd 1.7 1.7 2.0 2.2 - 1.4 2.0 2.1

Rij C 9.9 1.7 31.3 12.3 3.9 - 29.8 6.1 W 10.9 28.5 9.2 10.1 - 16.4 6.5 13.9

Dij Cw 6.7 15.5 13.9 14.4 38.8 - 9.4 16.1 Ww 15.2 14.3 13.0 8.1 - 17.2 8.2 14.9


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Wd 16.2 13.8 13.6 8.6 - 18.6 7.9 16.0 It was hypothesized that the seasonal energy balances of the Mackenzie Basin great lakes would be similar to those of the Laurentian Great Lakes. That is, near the summer solstice, most of the net radiation would be used to heat the water with minimal evaporation. Evaporation would steadily increase into the fall when it would be at a maximum, the energy being supplied by a release of the stored heat as, at this time of year, net radiation would be minimal. Measurements to test this hypothesis indicate that the hypothesis is false. The seasonal energy balance of Great Slave Lake (GSL) is completely different from that of the Laurentian Great Lakes. The seasonal pattern of net radiation is similar for both southern and northern Great Lakes, but similarities end there. Great Slave Lake evaporation began about the same time as for Lakes Huron and Ontario. The time of maximum evaporation for GSL occurred 8 to 10 weeks earlier than for an average of Lakes Ontario, Huron ,and Superior (Figure 1). Late-season evaporation from the southern lakes is fueled by the release of stored heat energy, but in GSL there is little or no late-season evaporation (Figure 1). The northern lake�s total heat storage expressed in equivalent mm of evaporation for 1997, was 78 mm. As this storage energy must be released (i.e., the annual heat storage should approach zero), the 78 mm added to the measured (eddy-correlation) evaporation of 82 mm gives a seasonal total evaporation of 160 mm. This value matches the annual evaporation estimated using mass transfer equations with on-site measured parameters. The relatively short ice-free period in GSL is not sufficient to allow significant accumulated summer heat storage, which can then fuel late-season evaporation. As a result, total annual evaporation is substantially less than one-half that of the deepest Laurentian Great Lakes (Figure 1).

May Jun Jul Aug Sep Oct Nov Dec Jan Feb

Cum

ulat

ive

Evap

orat

ion

(mm

)

0

100

200

300

400

500

600

Great Slave Lake Great Lakes

Figure 1 Evaporation � Great Slave Lake and Great Lakes. (adapted from Blanken et al., in

preparation; Schertzer 1997) 4. References


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Blanken, P.D., W.R. Rouse, A.D. Culf, C. Spence, L.D. Boudreau, J.N. Jasper, B. Kochtubajda, and D. Verseghey. Eddy Covariance Measurements of Evaporation from a Large Deep Northern Lake. (prepared for submission)

Petrone, Richard, 1998. Synoptic Controls on the Surface Energy Balance of Subarctic Regions.� M.Sc Thesis, McMaster University, 120 p.

Schertzer, W.G., 1997. Freshwater lakes. In: W.G. Bailey et al. (Eds.), Surface Climates of Canada, McGill-Queens Press, Montr�al, Qu�bec, pp. 124-147.

5. Summary The scientific objectives are to determine controls on evaporation and the surface energy balance for different terrestrial terrain units and to measure and model the evaporation from Great Slave Lake as representative of the large lakes in the Mackenzie Basin. Richard Petrone�s study, involving the response of the surface energy budget of distinct terrain types to the synoptic climatology for central and western subarctic regions, indicates that wetland sites in central and western subarctic regions demonstrate similar evaporation regimes. The magnitude of convective and conductive heat fluxes is strongly correlated with temperature and hence with synoptic-scale influences. Synoptic climatology can provide a useful link between smaller-scale surface process studies and larger-scale modelling studies. The purpose of Andrea Eaton�s M.Sc. research is to determine and compare controls on annual evaporation using recent data for a variety of terrain units representative of the central and lower Mackenzie Basin. The seasonal energy balance of Great Slave Lake (GSL) is completely different from that of the Laurentian Great Lakes. Late-season evaporation from the Great Lakes is fueled by the release of stored heat energy, but in GSL there is little or no late-season evaporation. As a result, total annual evaporation is substantially less than one-half that of the deepest Laurentian Great Lakes. Thus, climate warming can have a very large impact on the Mackenzie Great Lakes. 6. Recent Publications and Presentations Blanken, P.D., W.R. Rouse, A.D. Culf, C. Spence, L.D. Boudreau, J.N. Jasper, B. Kochtubajda, and D.

Verseghey. Eddy Covariance Measurements of Evaporation from a Large Deep Northern Lake. (prepared for submission)

Petrone, Richard, 1998. Synoptic Controls on the Surface Energy Balance of Subarctic Regions.� M.Sc Thesis, McMaster University, Hamilton, Ontario, 120 p.

Rouse, W.R., 1998. A water balance model for a subarctic sedge fen and its application to climatic change. Climatic Change, 38:207-234.

Rouse, W.R., M.S.V. Douglas, R.E. Hecky, G.W. Kling, L. Lesack, P. Marsh, M. McDonald, B.J. Nicholson, N.T. Roulet and J.P. Smol, 1997. Effects of climate change on fresh waters of Arctic and subarctic North America. Hydrologic Processes, 11:873-902.

Stewart, R.E., H.G. Leighton, P. Marsh, G.W.K. Moore, H. Ritchie, W.R. Rouse, E.D. Soulis, G.S. Strong, R.W. Crawford, and B. Kochtubajda, 1999. The Mackenzie GEWEX Study: The Water and Energy Cycles of a Major North American River Basin. Bulletin of the American Meteorological Society. (in press)

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2.2 Cross-Lake Variation of Evaporation, Radiation, and Physical Limnological Processes in Great Slave Lake

W.M. Schertzer1, W.R. Rouse2, and P.D. Blanken3

1National Water Research Institute [NWRI/CCIW], 867 Lakeshore Rd., Burlington, Ontario 2McMaster University, Hamilton, Ontario

3University of Colorado, Boulder, Colorado, USA

1. Scientific Objectives

1) To assess the spatial and temporal variation of lake evaporation along a mid-lake transect of the main body of Great Slave Lake and to collaborate with Rouse and colleagues in developing a comprehensive model of lake evaporation.

2) To evaluate the climatology of the primary components of the surface energy exchange. 3) To assess the cross-lake thermal development and other physical limnological components in

response to surface forcing as they relate to the evaporation process. 4) To enhance the data availability for development of a deep lake component of the CLASS model.

2. Progress and Collaborations Meteorological buoys and thermistor chains were deployed at Hay River (HR), ODAS (AES, 3 m buoy), NWRI-1, and NWRI-2 (Figure 1) to form a cross-lake transect, which included observations at Inner Whaleback Island (MAC) (see Blanken et al., 1998a,b for details of the MAC site). Cross-lake transect length was 156 km. Meteorological fields (Table 1) were observed at 10 minute intervals (except at ODAS, which was hourly) and all data have been formed into hourly and daily averages. Thermistor arrays HR (0, 5, 10, 15 m), ODAS (0, 2, 5, 7.5, 10, 13.5, 15, 20, 25, 30, 40, 56 m), NWRI-1 (0, 2, 5, 7.5, 10, 13.5, 15, 20, 25, 30, 40, 50, 60 m), NWRI-2 (0, 2, 5, 7.5, 10, 13.5, 15, 20, 25, 30, 40, 50, 75, 100 m) recorded at 20 minute intervals were also formed into hourly and daily averages. Instrumentation was deployed on June 16/98 and retrieved on September 9/98. The ODAS buoy instrument array was augmented with the installation of a relative humidity sensor (Vaisala HMP35CF) and this site continued to operate after the NWRI retrievals into October. Preliminary assessment of the seasonal meteorological components, wave height calculations, thermal development, evaporation and heat flux components along a mid-lake transect of Great Slave Lake was conducted with this data base. This investigation forms part of the continuing collaboration with Rouse (and colleagues) in the overall assessment of processes controlling evaporation in this lake. In order to facilitate determination of year-round heat storage in Great Slave Lake, a winter thermistor array was installed in the vicinity of the ODAS site to operate from September 9/98 to July/99.


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Figure 1 Station locations along the cross-lake transect of Great Slave Lake and wind direction

frequency over the field season June 16, 1998 (day 167) to September 11, 1998 (day 254).

Table 1 Meteorological, radiation, and thermal fields observed at Hay River (HR), ODAS,

NWRI-1, NWRI-2, and the MAC site. (see Blanken, et al. 1998a,b) HR ODAS NWR-1 NWR-2 MAC air temperature * * * * * relative humidity * * * * * wind speed * * * * * wind direction * * * * * solar radiation * - * * - incoming longwave - - - - * net radiation - - - - * infrared temperature - - - - * latent heat - - - - * sensible heat - - - - * surface water temperature - * * * * thermistor array * * * * * precipitation * - - - * atmospheric pressure - * - - * wave height/period - * - - -


38

3. Scientific Results Meteorological variables: Meteorological variables vary between nearshore and mid-lake regions. In particular, mid-lake air and water temperatures lag the nearshore by as much as five weeks (June-July). Wind speed also varies along the transect. Figure 1 shows wind roses for all stations over the study period based on a maximum of 2760 hourly observations. The main axis of the cross-lake transect is at 47° from north similar to the main axis of the lake. Mean wind speeds (8 m winds) over the study period varied between sectors of each station HR (2.7 to 5.5 m s-1), ODAS (4.6 to 6.8 m s-1), NWRI-1 (1.7 to 5.7 m s-1) and at NWRI-2 (3.8 to 6.4 m s-1). Wind speeds are generally higher over the mid-lake. Highest hourly mean wind speeds approached or exceeded 14 m s-1 once at the shore station at Hay River and eight times at offshore locations during intense episodic storm events - peak winds can be significantly higher. Sea state (waves): Surface conditions influence the rate of evaporation from a lake surface. The ODAS buoy included wave measurements from which wave models could be tested for their applicability on Great Slave Lake. Surface wave characteristics were approximated through application of conventional static wave models based on empirical relationships between surface waves and concurrent wind speed, fetch and/or duration. Examples of such models include Groen and Dorresteyn (1976), Bretschneider (1970), and Donelan (1980), amongst others. Such models have been applied successfully over a large range of lakes. Over-lake fetch was determined for 15 degree sectors centered on north. Maximum over-lake fetch sectors are for HR (15° to 75°, 170 km), for ODAS (15° to 45°, 134 km), for NWRI-1 (225° to 255°, 100 km), NWRI-2 (225° to 255°, 143 km) and MAC (225° to 255°, 182 km). Figure 2 shows correspondence between observed and computed wave height using the Groen and Dorresteyn model as an example. Figure 2 indicates that observed and computed wave heights at the ODAS buoy site are generally in phase and that the model is capable of simulating the peak wave events. Analysis indicates that there were at least nine events in which the significant wave height (SWH) exceeded 2.5 m with an extreme event on days 194-197 with SWH of 4 m. Wave heights were computed at all stations for possible future inclusion of sea state in a comprehensive analysis of evaporation.

Figure 2 Comparison of computed and observed wave height at the ODAS site.

Thermal structure: A times-series of vertical temperature profiles at Hay River, ODAS, NWRI-1 and NWRI-2 (see Rouse Progress Report for MAC site) were derived from thermistor observations by interpolation using cubic spline procedures. An example of the thermal response for Great Slave Lake is indicated in Figure 3 for the deepest station at NWRI-2 (103 m). An important feature of Figure 3 thermal development is the deep vertical mixing during an intense storm in the period day 194-197 where the developing thermal stratification was disrupted and the upper mixed layer deepened from ~5 m to 20 m with wind stress peaking at 4.5 dynes cm-2 (17.06 m s-1) at day 194 (July 13, 2100 GMT). Hourly isotherms show large amplitude thermocline oscillations at the inertial period (13.7 hrs) of the lake. The event corresponded with high significant wave heights (e.g., 4 m observed at ODAS). The intense


39

vertical mixing also reduced the temperature of the upper mixed epilimnion layer and the surface water temperature, which affects the rate of evaporation.

Figure 3 Thermal structure development at mid-lake buoy NWRI-2 for the period June 16 to

September 14, 1998. Evaporation: Evaporation at each station was computed by various mass transfer relationships (e.g., Quinn and den Hartog, 1981) and on an hourly basis using regression coefficients derived from measured evaporation vs. the product of wind speed (8 m) and vapour pressure difference (es - ea) from the 1997 MAC site observations (Blanken, per. com.). The preliminary MAC relationship used was the following:

E U e es a= + −0 0087 0 0105 8. . * ( * ( )) where, E is evaporation in mm/hr, U8 is wind speed m s-1 adjusted to 8 m height, es is saturation vapour pressure (kPa) at Ts (°C), and ea is the ambient vapour pressure (based on Ta and RH). Figure 4 shows preliminary hourly computed evaporation at Hay River, ODAS, NWRI-1 and NWRI-2. Significant differences are evident between evaporation in the shallower west part of the lake at Hay River, which warms faster compared to the deeper, cooler mid-lake stations. The Hay River site experiences more intense episodes of evaporation compared to the mid-lake stations and over the period of record appears not to have extended periods of condensation to the lake surface. Alternatively, NWRI-2 at the deepest part of the lake experiences extended periods of condensation in the early part of the lake heating season and periods during late August and early September. Similar characteristics also occur at NWRI-1 and less so at ODAS. As indicated by Blanken et al. (1997), the evaporation at the MAC site appears to be episodic with 54% of evaporation occurring on 25% of the days. The episodic nature of evaporation is also evident along the cross-lake transect. As indicated by Rouse at the MAC site, the ice-free season in Great Slave lake is relatively short and may not be sufficient to allow significant increase in the lake heat storage to be released in higher evaporation totals as occurs in the


40

Laurentian Great Lakes. Over the period day 167-254, none of the four lake stations in this investigation showed a prominent trend to increased fall evaporation, although a slightly increased evaporation is evident from day 270 onwards at the ODAS site. Not all stations were operational over the period day 167-254 making it difficult to directly compare computed evaporation totals at the four sites. Assuming an arbitrary constant hourly evaporation of 0.025 mm/hr for missing hours provides a first approximation of the total evaporation at Hay River (~67 mm), ODAS (~51 mm), NWRI-1 (~42 mm), and at NWRI-2 (~58 mm). During 1997, evaporation at the MAC site over a similar period was 82.7 mm. This implies that evaporation may be expected to be higher along the nearshore regions of the lake and significantly reduced in the mid-lake.

Figure 4 Comparison of computed hourly evaporation (mm/hr) at stations along the mid-lake

transect of Great Slave Lake.


41

Radiation Components: Incoming global solar radiation was measured at Hay River, NWRI-1 and NWRI-2. Incoming longwave radiation was measured at NWRI-1 and NWRI-2. These data combined with meteorological data and surface water temperature allowed computation of the main components of the surface heat flux at all stations. Figure 5 shows an example of the preliminary daily-averaged heat flux computations for the ODAS buoy location for radiation (Q*), latent heat flux (Qe), sensible heat flux (Qh) and the overall surface heat flux (Qt = Q* - Qe - Qh). Daily-averaged fluxes indicate that net radiation is positive throughout the investigation, with energy going to heat the lake. Sensible heat flux is a small term in the heat budget at this open-lake location and is also used in heating of the lake. Latent heat flux is generally positive to the atmosphere. From this preliminary analysis, it appears that the total surface heat flux (Qt) is significantly affected by the large episodic latent heat losses that occur (e.g., see days 228, 231).

Figure 5 Seasonal variation of net radiation (Q*), latent heat flux (Qe), sensible heat flux (Qh)

and the surface heat flux (Qt = Q* - Qe - Qh) at the ODAS buoy site for the period June 16 to September 9, 1997.

4. Summary This was the first field season for the evaluation of factors affecting evaporation along a mid-lake transect of the lake. A significant data base was collected along the mid-lake transect including meteorological variables, waves, water temperature profiles, and radiation components. These were fine-scale observations (meteorology: 10 min.; thermistors: 20 min.) which were formed to hourly and daily values. The data base allowed a comparison of the meteorological variables along the transect and formed the basis for evaluation of cross-lake variations in meteorology, wave heights, lake thermal response. evaporation, and energy balance components. Results are preliminary, however, it appears that combined with observations from collaborators (e.g., Rouse and colleagues) these data will be valuable for the detailed description of the processes controlling evaporation and energy exchange in Great Slave Lake, as well as providing a first step in the analysis of variability in evaporation, radiation, and limnological fields on a lake-wide basis and future parameterization for a deep lake component of CLASS. 1999 planned activities: Next year�s plans are to reinstall the measurement platforms along the main-lake cross-section to begin assessment of interannual variability of the over-lake meteorological variables, sea state (waves), thermal response, evaporation, and heat flux components. A winter thermistor mooring has been installed at ODAS to begin evaluation of the annual heat content of GSL. Testing of thermal models that integrate atmospheric forcing and lake thermal responses is planned. This study is conducted in close collaboration with detailed analyses conducted at Inner Whaleback Island (Rouse and colleagues).


42

5. Recent Publications and Presentations Blanken, P.D., W.R. Rouse, C. Spence, A.D. Culf, L.D. Boudreau, J. Jasper, B. Kochtubajda, and D.

Verseghy, 1998a. �Processes controlling evaporation from Great Slave Lake.� In: G.S. Strong and Y.M.L. Wilkinson (Eds.), Proceedings of the 3rd Scientific Workshop for the Mackenzie GEWEX Study (MAGS), 17-19 November, 1997, Atmospheric Environment Service, Downsview, Ontario, pp. 37-39.

Blanken, P.D., W.R. Rouse, A.D. Culf, C. Spence, L.D. Boudreau, J. Jasper, B. Kotchtubajda, and D. Verseghy, 1998b. Eddy Covariance Measurements of Evaporation from a Large, Deep Northern Lake. (in preparation)

Murthy, C.R. and W.M. Schertzer, 1994. �Physical limnology and water quality modelling of North American Great Lakes, Part I. Physical Processes.� Wat. Poll. Res. J. Canada, 29(2/3):157-184.

Rouse, W.R., R.L. Bello, and P.M. LaFleur, 1997. �The low Arctic and Subarctic.�, Chapter 9, in: W.G. Bailey, T. Oke, and W.R. Rouse (Eds.), The Surface Climates of Canada, McGill-Queens University Press, Montr�al, Qu�bec, pp. 198-221.

Schertzer, W.M., 1999. �Physical limnological characteristics of Lake Erie and implications of climate changes.�, In: M. Munawar (Ed.), The State of Lake Erie: Past, Present and Future, Backhuys Publishers, The Netherlands, 26 p. (in press)

Schertzer, W.M., 1997. �Freshwater Lakes.� Chapter 6, in: W.G. Bailey, T. Oke, and W.R. Rouse (Eds.), The Surface Climates of Canada, McGill-Queens University Press, Montr�al, Qu�bec, pp. 124-148.

Schertzer, W.M., 1994. �Physical limnology and water quality modeling of North American Great Lakes, Part II. Water Quality Modelling.� Wat. Poll. Res. J. Canada, 29(2/3):157-184.

Schertzer, W.M. and T.E. Croley II, 1997. �Climate change impact on hydrology and lake thermal structure.� In: F.M. Holly, A. Alsaffar, and S.S.Y. Wang (Eds.), Vol. 2 (Theme B) Water for a Changing Global Community, Proceedings of the 27th Congress of the International Association for Hydraulic Research and the American Society of Civil Engineers, ASCE Publishers, New York, New York, pp. 919-924.

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2.3 Biome Scale Representation of Snow Cover Development and Ablation in Boreal and Tundra Ecosystems

J. W. Pomeroy

National Water Research Institute, NHRC, Saskatoon, Saskatchewan

1. Objectives

(1) Define mass and energy fluxes governed by the land surface processes of snow interception, redistribution, sublimation and ablation.

(2) Formulate process-based algorithms that represent snow cover development and ablation in boreal, alpine and arctic regions.

(3) Integrate these algorithms in distributed basin, continental-scale and global hydrometeorological models.

This study addresses MAGS objectives by identifying, quantifying and synthesizing at multiple scales the energy and mass fluxes associated with snow cover development and ablation in both forest and open land covers. Algorithms describing the processes are being incorporated in larger-scale models and these models are tested using field datasets. It is the only MAGS government study using both field observations and physically-based modelling to: ��develop and test hypotheses of the hydrological processes that lead to redistribution and sublimation

of snow throughout the Mackenzie domain; ��examine the role of the forest canopy in modifying fluxes between the atmosphere and snow surface;

and, ��verify model representations of snow redistribution, sublimation and subcanopy melt, and the

associated mass and energy fluxes. 2. Progress and Collaborations Field Work Measurements of snow fluxes have been collected in recent campaigns conducted at four Canadian GEWEX "research basins" in the MAGS domain: ��Southern boreal forest: Beartrap Creek, Waskesiu, SK with pine, mixed-wood, burned, clear-cut and

regenerating pine clear-cut sites - winter forest accumulation and spring ablation: turbulent and radiative energy fluxes from young jack pine, snow distribution, canopy temperature, intercepted snow load, melt rate, soil temperature, and heat flux during melt.

��Boreal-alpine transition: Wolf Creek, Whitehorse, Yukon with alpine, shrub-tundra, and spruce forest

sites - winter alpine accumulation and spring ablation: intercepted snow load, blowing snow flux, snow drifts on alpine hillsides, snow distribution, melt rate on alpine hillsides, snow-covered area depletion in alpine, surface temperatures and heat flux during melt.

��Subarctic spruce forest-tundra: Havikpak Creek, Inuvik, NWT - winter subarctic accumulation:

intercepted snow load, snow distribution. ��Arctic tundra: Trail Valley Creek, north of Inuvik, NWT sparse tundra � winter arctic accumulation:

snow distribution, blowing snow flux.


44

An invited one-month visit to the Cryospheric Environment Simulator of the National Institute for Earth Science and Disaster Prevention, Japan Science and Technology Agency, Shinjo, Japan has provided a controlled snow environment for experiments designed to improve present theories on the physics of sensible heat advection to melting snow patches. Modelling The measurements have been complemented by modelling of blowing snow and intercepted snow processes and linkages with land-surface models, hydrological models, and GCMs. ��Coupled snow interception, unloading and sublimation model: A coupled model based on snow

exposure, intercepted snow accumulation, unloading, and energy balance calculations has been developed and tested for determination of snow sublimation from coniferous canopies. Improvements have been proposed for CLASS calculation of snow interception.

��Winter energy balance of the boreal forest: The winter energy budget of boreal forest and lakes has

been quantified, compared, and modelled in a regional atmospheric model (RAMS). Boreal forest albedo has been quantified and modelled, the improvements have contributed to improved ECMWF simulations of the boreal forest surface temperature in spring.

��Snowmelt dynamics in the boreal forest: The influence of the co-distribution of subcanopy energy

flux and snow water equivalent on snowmelt rates in the boreal forest has been quantified and coded into an algorithm for snow-covered area depletion in boreal forests.

��Blowing snow model for GCMs: An existing blowing snow model (PBSM) has been substantially

redeveloped so that it is suitable for coupling to GCMs. ��Blowing snow in a hydrological model: An existing large-scale hydrological model, SLURP, was

recoded using blowing snow physics into PBS-SLURP, which calculates snow redistribution between landcover types within ASAs, sublimation loss within an ASA and then snowmelt infiltration into frozen soils. Initial testing of model performance was conducted.

��Blowing snow fluxes over complex terrain: PBSM was run with the MS3DJH/3R complex terrain

wind flow model to calculate sublimation, transport, and accumulation of blowing snow over irregular arctic terrain. Results were compared to field measurements of snow distribution.

Collaborations Strong collaborations were maintained at the research basins with Granger, Marsh, Woo, Gray, and Janowicz, and in the laboratory with Sato. The important collaboration with Gray has been strongly pursued, with co-supervision of graduate students, technicians, research officers, post-doctoral fellows, and common field and modelling strategies. Modelling was conducted in concert with Pietroniro, Marsh, Gray, Woo, Verseghy, Soulis, Kite, Harding, Yau, Essery, and Davies through algorithm/code exchange, data exchange, and planned co-development of modelling strategies.

3. Scientific Results Recent results are highlighted by: ��Snow interception algorithm: field results show that leaf area, canopy closure, species type, time

since snowfall, snowfall amount, and existing snow load control the efficiency by which snow is intercepted.. A physically-based algorithm (first of its kind and winner of two awards) describing these results has been field validated at Beartrap Creek and is being tested at Wolf Creek and Havikpak Creek (Figure 1). Results of this study have been presented at the 1997 CGU and CMOS


45

Conferences, published in the Proceedings of the Western Snow Conference and Hydrological Processes. A thesis on this topic by Mr. N. Hedstrom under my supervision is being finalized. Initial examination of CLASS supports a recommendation that CLASS and other land surface schemes, incorporate the Snow Interception Algorithm to correct an order of magnitude underprediction of intercepted snow.

Figure 1 Modelled interception efficiency (snow interception/snowfall) as a function of a) winter leaf area index and air temperature, b) snowfall and initial canopy snow load (Lo).

��Exposure parameterization of intercepted snow: fractal geometry indexes the exposure of intercepted

snow in the forest canopy, an important parameter for sublimation rate calculations and for calculating the �resistance� of intercepted snow to sublimation. The relationship between fractal dimension of snow and canopy resistance for evaporation calculations is being examined. The fractal geometries of intercepted snow in forests of the research basins can be measured by digitized canopy photographs, and modelled for input to sublimation algorithms as described below.

��Coupled snow interception, unloading, and sublimation algorithm: a coupled model of snow

interception, unloading and sublimation, based on snow exposure, intercepted snow accumulation and energy balance calculations can determine snow sublimation from coniferous canopies. Sublimation losses are 30 to 45% of annual snowfall for conifers in the southern and montane boreal forest. Initial tests of the coupled model at Beartrap Creek are highly successful and have been presented at the 1997 CMOS Congress, as invited lectures to Quebec & Japan and to user groups in northern Saskatchewan. A paper describing the model has been published in Hydrological Processes.

��Winter energy balance of the boreal forest: the latent heat flux in winter was found to be large and

variable, its direction governed by conifer coverage and the load of intercepted snow. Shortwave radiation is extinguished and longwave emitted by conifer canopies, the downward longwave flux found to be controlled by the angle of incoming shortwave. A canopy radiation model based on these observations describes this phenomenon and its implications for sublimation and snowmelt. The implications are important; high net radiation in the canopy provides energy for mid-winter sublimation and radiation attenuation by dense canopies lengthens the snowmelt period 3-fold compared to open areas. Frozen lakes were found to have energy fluxes of differing magnitude, direction, and diurnal pattern from forests. Aggregation of fluxes from frozen lake and boreal forest surfaces was found to be complicated by local-scale advection of energy between lake and forest. The local-scale advection was described using a regional atmospheric model (RAMS) and shown to involve complex patterns of divergent or convergent �snow breezes� between small lakes and

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a)


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adjoining forest. The implications are that aggregation of fluxes from such differing surfaces may not necessarily be successfully accomplished by tiling or blending height techniques without further improvements in scaling techniques. Papers describing this were published in the Journal of Geophysical Research, Journal of Climate, Hydrological Processes, and International Association of Hydrological Sciences Publ. No. 240.

Figure 2 Modelled and simulated intercepted snow load in a pine forest: change in intercepted

snow load is due to precipitation, unloading, and sublimation. Measured snow load is derived from the mass of snow weighed on a suspended pine tree, scaled to areal snow water equivalent by comparative measurements of above canopy snowfall and below canopy snow accumulation. (after Pomeroy, Parviainen, Hedstrom, and Gray 1998)

��Snowmelt dynamics in the boreal forest: a coupling between subcanopy energetics and snow water

equivalent has been detected, and provides the basis for a snowmelt scaling algorithm that scales processes operating at the individual tree level up to canopy or regional scale snowcover depletion curves. The co-distribution of sub-canopy snowmelt energy and SWE (smaller SWE is associated with higher energy) significantly accelerates the depletion of snow-covered area during melt - results were presented at the 1997 CMOS Congress and the International Union of Geodesy and Geophysics Congress - Morocco and are being finalized in a thesis under my supervision �Distributed Snowmelt Energetics in the Boreal Forest� by Mr. D. Faria.

��Distributed blowing snow model (DBSM): Landscape classifications, an irregular windflow model,

snowmelt, and blowing snow process routines can be used to determine blowing snow fluxes over complex land surfaces. Initial tests with a DBSM represented the distribution of snow water equivalent in test basins and matched basin snow accumulation within 6%. Sublimation losses were small for the subarctic basin, about 21% over the arctic basin and 30% from tundra surfaces. Subsequent tests with a more physically-based DBSM show that arctic tundra is composed of a variety of blowing snow flow zones, largely controlled by vegetation cover. Results with suppressed sublimation (Taylor�s hypothesis) produced snow accumulation in vegetation that was much greater than that observed, whilst results that included sublimation produced snow accumulation

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distributions near to values measured. An example of the mapped snow water equivalent distribution for an arctic domain is shown in Figure 3. The results were published in Hydrological Processes and Applications of Remote Sensing in Hydrology and presented at the International Conference on Snow Hydrology.

Figure 3 Mapped distribution of late winter snow accumulation (mm SWE) in the Trail Valley

Creek domain, simulation produced with a version of PBSM coupled to the Walmsley/Salmon/Taylor MS3DJH/3R complex terrain boundary-layer model. (after Essery, Li, and Pomeroy 1998)

��Blowing snow model for GCMs and hydrological models: the probability of occurrence of blowing

snow over time or space (for uniform terrain) follows a cumulative normal distribution, which is controlled by snow temperature, snow age, vegetation exposure, and occurrence of melt or rain. An algorithm describing blowing snow probability provides a means to scale blowing snow fluxes from point to large areal averages in a computationally simple manner. An example of the model operation for tundra surfaces at Trail Valley Creek is shown in Figure 4. The model has been revised for potential coupling to land surface schemes and, as a demonstration, has been coded along with a frozen soil infiltration scheme into the SLURP hydrological model as PBS-SLURP. Tests of PBS-SLURP in a prairie catchment were extremely promising in that the snowmelt runoff hydrograph was correctly simulated without the calibration that is normally necessary with SLURP. The revised model is described in Journal of Geophysical Research, Journal of Applied Meteorology, a NWRI Report, a paper given to 1997 CMOS Conference, published in the Proceedings of the Western Snow Conference and in two manuscripts submitted to Journal of Geophysical Research.


48

Figure 4 Modelled PBSM single-column spatially-scaled results for Trail Valley Creek open tundra site. (after Pomeroy and Li 1998). Accumulated blowing snow loss is due to transport and sublimation of blowing snow, snow water equivalent is estimated based on measured snow depth and density, corrected to areal snow surveys, the sum of snow water equivalent, and blowing snow losses should equal snowfall if the modelled and estimated values are correct.

��Snow accumulation and ablation process recommendations for land surface schemes: a major review

paper detailing a series of recommendations on appropriate modelling strategies for snow accumulation and ablation processes in land surface schemes was presented as the Plenary Talk to the Eastern Snow Conference, 1998, an invited lecture to the University of East Anglia, England, published in the Proceedings of the Eastern Snow Conference and in Hydrological Processes. A subsequent paper is being prepared for presentation and publication in an IAHS symposium in the IUGG 1999.

These results apply to MAGS objectives by providing an identification and understanding of snow redistribution, sublimation, and melt in the MAGS area - demonstrating the incorporation of this understanding in multi-scale representations that are linked to large-scale models and providing a means of verifying large-scale models in the MAGS domain. 4. Summary Substantial progress has been made in defining the mass and energy fluxes governed by snow interception, redistribution, sublimation, and ablation processes. Algorithms have been devised to describe these processes, the state of developed ranges from verified to provisional. Substantial progress has been made for the arctic and boreal forest environment, with the effort now to be concentrated on the more complex alpine environment. Initial progress has been made to integrate the algorithms in GCM land surface schemes, regional atmospheric models, and large-scale hydrological models; however, substantial problems have also been identified. Critical multiple-scale horizontal fluxes of mass and energy have been detected near the surface for all the processes examined. The scaling of these horizontal fluxes to provide larger-scale representations of vertical fluxes is not trivial and will require a large effort in the future.

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WE

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5. Publications and Presentations for MAGS Elliott, J.A., B.M. Toth, R.J. Granger, and J.W. Pomeroy, 1998. Soil moisture storage in mature and

replanted sub-humid boreal forest stands. Canadian Journal of Soil Science, 78:17-27. Essery, R., L. Li, and J.W. Pomeroy, 1998. Blowing snow fluxes over complex terrain, 1, distributed

modelling. J. Hydrological Processes. (submitted) Granger, R.J. and J.W. Pomeroy, 1997. �Sustainability of the western Canadian boreal forest under

changing hydrological conditions -2- summer energy and water use.� In: D. Rosjberg, N. Boutayeb, A. Gustard, Z. Kundzewicz, and P. Rasmussen (Eds.), Sustainability of Water Resources under Increasing Uncertainty. International Association Hydrological Sciences Publ. No. 240, IAHS Press, Wallingford, UK, pp. 243-250.

Harding, R.J. and J.W. Pomeroy, 1996. The energy balance of the winter boreal landscape. Journal of Climate, 9:2778-2787.

Hedstrom, N.R. and J.W. Pomeroy, 1998. Measurements and modelling of snow interception in the boreal forest. J. Hydrological Processes, 12:1611-1625.

Hedstrom, N.R. and J.W. Pomeroy, 1997. �Accumulation of intercepted snow in the boreal forest.� In: Proceedings 65th Annual Western Snow Conference, pp. 130-141.

Janowicz, J.R., Gray, D.M., and J.W. Pomeroy, 1997. �Snowmelt and runoff in a subarctic mountain basin.� In: Proceedings of the Hydro-ecology Workshop on the Arctic Environmental Strategy. NHRI Symposium No. 16, pp. 303-320.

Li, L. and J.W. Pomeroy, 1997. Probability of Blowing snow occurrence by wind. J. Geophysical Res, 102:D18, 21,955-21,964.

Marsh, P. and J.W. Pomeroy, 1996. Meltwater fluxes at an arctic forest-tundra site. J. Hydrological Processes, 10:1383-1400.

Marsh, P. and J.W. Pomeroy, 1995. �Water and energy fluxes during the snowmelt period at an Arctic treeline site.� In: International GEWEX Workshop on Cold-Season/Region Hydrometeorology, International GEWEX Project Office, IGPO Publ. No. 15, Washington, DC, pp. 197-201.

Marsh, P., J.W. Pomeroy, and N. Neumann, 1997. Sensible heat flux and local advection over a heterogeneous at an arctic tundra site during snowmelt. Annals of Glaciology, 25:132-136.

Marsh, P., J.W. Pomeroy, and W. Quinton, 1995. �Application of snow and evaporation models for predicting water fluxes at the arctic treeline in northwestern Canada.� In: International GEWEX Workshop on Cold-Season/Region Hydrometeorology, International GEWEX Project Office, IGPO Publ. No. 15, Washington, DC, pp. 47-50.

Marsh, P., W. Quinton, and J.W. Pomeroy, 1995. �Hydrological processes and runoff at the arctic treeline in northwestern Canada.� In: K. Sand and A. Killingtveit (Eds.), Proceedings, 10th International Northern Basins Symposium and Workshop, SINTEF Report STF 22. Trondheim, Norway, pp. 368-397.

Maxfield, A.W., P. Marsh, J.W. Pomeroy, and W.L. Quinton, 1997. �Arctic snow and soil observations by radar satellite.� In: G.W. Kite, A. Pietroniro, and T.J. Pultz (Eds.), Applications of Remote Sensing in Hydrology. NHRI Symposium No. 17, National Hydrology Research Institute, Saskatoon, SK, pp. 199-210.

Pomeroy, J.W. and E. Brun, 1998. �Physical properties of snow.� In: H.G. Jones, J.W. Pomeroy, D.A. Walker, and R. Hoham (Eds.), Snow Ecology. Cambridge University Press. (in press)

Pomeroy, J.W., T. Brown, G. Kite, D.M. Gray, R.J. Granger, and A. Pietroniro, 1998. PBS-SLURP Model. NHRI Contribution Series No. CS-98003. Report to Saskatchewan Water Corporation, 24 p. plus appendices.

Pomeroy, J.W. and K. Dion, 1996. Winter radiation extinction and reflection in a boreal pine canopy: measurements and modelling. J. Hydrological Processes, 10:1591-1608. Also, presented at the Eastern Snow Conference, In: Proceedings of the Eastern Snow Conference, 53:105-118.

Pomeroy, J.W. and B.E. Goodison, 1997. �Winter and Snow.� Chapter 4, In: W.G. Bailey, T.R. Oke, and W.R. Rouse (Eds.), The Surface Climates of Canada, McGill-Queen's University Press, Montr�al, Qu�bec, pp. 68-100.


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Pomeroy, J.W. and R.J. Granger. 1997. �Sustainability of the western Canadian boreal forest under changing hydrological conditions -I- snow accumulation and ablation.� In: D. Rosjberg, N. Boutayeb, A. Gustard, Z. Kundzewicz, and P. Rasmussen (Eds.), Sustainability of Water Resources under Increasing Uncertainty. International Association Hydrological Sciences Publ. No. 240, IAHS Press, Wallingford, UK, pp. 237-242.

Pomeroy, J.W. and D.M. Gray, 1995. Snowcover Accumulation, Relocation and Management. NHRI Science Report No. 7, Environment Canada, Saskatoon, SK, 134 p.

Pomeroy, J.W., D.M. Gray, K.R. Shook, B. Toth, R.L.H. Essery, A. Pietroniro, and N. Hedstrom, 1998. An evaluation of snow accumulation and ablation processes for land surface modelling. Hydrological Processes, 12. (in press) Also, presented at the Eastern Snow Conference, In: Proceedings. Eastern Snow Conference, 55. (in press)

Pomeroy, J.W. and H.G. Jones, 1996. �Wind-blown snow: sublimation, transport and changes to polar snow.� In: E. Wolff and R.C. Bales (Eds.), Chemical Exchange between the Atmosphere and Polar Snow. NATO ASI Series I 43. Berlin, Springer-Verlag, pp. 453-489.

Pomeroy, J.W. and L. Li, 1998a. Areal snow cover mass balance using a blowing snow model, I, model structure. J. of Geophysical Research. (submitted)

Pomeroy, J.W. and L. Li, 1998b. Areal snow cover mass balance using a blowing snow model, II, application to Prairie and Arctic environments. J. of Geophysical Research. (submitted)

Pomeroy, J.W. and L. Li., 1997. �Development of the Prairie Blowing Snow Model for application in climatological and hydrological models.� In: Proceedings 65th Annual Western Snow Conference, pp. 186-197.

Pomeroy, J.W. and P. Marsh, 1997. �The application of remote sensing and a blowing snow model to determine snow water equivalent over northern basins.� In: G.W. Kite, A. Pietroniro, and T.J. Pultz (Eds.), Applications of Remote Sensing in Hydrology. NHRI Symposium No. 17, National Hydrology Research Institute, Saskatoon, SK, pp. 253-270.

Pomeroy, J.W., P. Marsh, and D.M. Gray, 1997. Application of a distributed blowing snow model to the Arctic. J. Hydrological Processes, 11:1451-1464.

Pomeroy, J.W., P. Marsh, and D.M. Gray, 1995. �Application of an Arctic blowing snow model.� In: International GEWEX Workshop on Cold-Season/Region Hydrometeorology, International GEWEX Project Office, IGPO Publ. No. 15, Washington, DC, pp. 56-60.

Pomeroy, J.W., P. Marsh, H.G. Jones, and T.D. Davies, 1995. �Spatial distribution of snow chemical load at the tundra-taiga transition.� In: K.A. Tonnessen, M.W. Williams, and M. Tranter (Eds.), Biogeochemistry of Seasonally Snow-covered Catchments. International Association of Hydrological Sciences No. 228, IAHS Press, Wallingford, UK, pp. 191-206.

Pomeroy, J.W., J. Parviainen, N. Hedstrom, and D.M. Gray, 1998. Coupled modelling of forest snow interception and sublimation. J. Hydrological Processes, 12. (in press). Also, presented at the Eastern Snow Conference, In: Proceedings. Eastern Snow Conference, 55. (in press)

Taylor, C.M., R.J. Harding, R.A. Pielke, J.W. Pomeroy, P.L. Vidale, and R.L. Walko, 1998. Snow breezes in the boreal forest. J. Geophysical Res. D18, 103, 23,087-23,103.

- 1998. Plenary Presentation to Eastern Snow Conference. - 1998. Invited Talk to University of East Anglia, Norwich, UK. - N.D. Numerous other presentations in Ontario, Quebec, New Hampshire, Vermont, Norway, Japan,

England, Saskatchewan, Alberta, Yukon.

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2.4 Hydrological Processes In Cold Regions

D. M. Gray1, J.W. Pomeroy2, C.P. Maulé3, D.H. Male4, P. Marsh5

1Division of Hydrology, College of Eng., University of Saskatchewan, Saskatoon, Saskatchewan 2 Dept. of Agricultural and Bioresource Eng., NHRC, Saskatoon, Saskatchewan

3 College of Eng.,University of Saskatchewan, Saskatoon, Saskatchewan 4Dept. of Mechanical Eng., College of Eng., University of Saskatchewan, Saskatoon, Saskatchewan

5 Dept. of Geography, NHRC, Saskatoon, Saskatchewan

1. Objectives To study three processes important to the water and energy cycles of northern environments, namely:

1) ablation of seasonal snowcovers; 2) coupled heat and mass transfer in snow and underlying ground; 3) wind transport of snow; and, to develop physically-based algorithms that describe these processes using field measurements in boreal, alpine and arctic environments.

2. Progress and Collaborations Field Work In anticipation of the CAGES field year, major field campaigns were conducted at:

1) Trail Valley Creek, Inuvik: Dec 1997 and March 1998 for blowing snow measurements. 2) Beartrap Creek, Waskesiu: Dec 1997-April 1998 for snowmelt infiltration measurements in

boreal forest. 3) Wolf Creek, Whitehorse: March-May 1998 for snowmelt ablation, melt energetics, and

infiltration to frozen soils in irregular alpine tundra and boreal forest. Modelling New algorithms of the following cold regions hydrological processes have been developed:

1) infiltration into frozen soils � operational algorithm; 2) ground heat flux during snowmelt infiltration into frozen soils; 3) boreal forest snow-covered area ablation; 4) coupled blowing snow � irregular terrain windflow; 5) intercepted snow accumulation/unloading/sublimation.

Collaborations Collaborations in field work, modelling and analysis with GEWEX investigators: Pomeroy, Marsh, Granger and Pietroniro (NHRI); Woo (McMaster), with DIAND-Yukon, Whitehorse; Aurora College, Inuvik; Hadley Centre for Climate Prediction and Research. 3. Scientific Results Ablation of Seasonal Snowcovers Effect of Spatial Distribution of Snowmelt Energy on Ablation of Boreal Forest Snowcover: Previous research by Shook (1995) and Donald et al. (1995) has shown that the depletion of snow-covered area is affected by the distribution of snow water equivalent. For open environments, the distribution can be described by a log-normal distribution and modelled as a function of the mean and coefficient of variation of snow water equivalent (SWE) (Pomeroy, et al. 1998). Faria (1998) identified a co-distribution of melt energy and SWE for melting snowcovers in the boreal forest. The effect of the energy distribution is to increase energy inputs to shallower snow and, therefore, increase the rate of depletion of snow cover with respect to uniform or random energy conditions. Figure 1 shows the simulated depletion of snow-covered area as a function of the fraction of snowmelt for snowcovers with


52

(a) a constant initial coefficient of variation of SWE (CV=0.22) and (b) varying measured co-distributions of melt rate with SWE found in several common forest cover types. The less uniform the co-distribution of melt energy with SWE, the more rapid the depletion of snow covered area. Faria found for model runs with actual CV and melt energy distribution that the depletion of snow-covered area was underestimated by uniform melt models from 9% to 78%. Initial comparisons of model results with field data show improved predictions of snow cover depletion under boreal forest canopies.

Figure 1 Output of boreal forest distributed snowmelt algorithm for uniform melt and five

linear distributed-melt functions (initial CV is held constant at 0.22 for the six simulations).

Coupled Heat and Mass Flow in Frozen Ground Infiltration: A general parametric correlation for estimating snowmelt infiltration into frozen soils was developed (Zhao and Gray 1997, 1998). The expression relates cumulative infiltration (INF) to the soil surface saturation during melting (So), the total soil moisture saturation (water + ice) (SI,), and temperature (TI,) at the start of snow ablation, and the infiltration opportunity time - the time that meltwater is available at the soil surface for infiltration, t, as:

( ) 44.045.064.192.2 )15.273

15.273(1 tTSCSINF IIo

−−−=

in which C is a bulk coefficient that characterizes the effects on infiltration of differences between model and natural systems. Representative values of C for frozen sandy soils in a boreal forest and various fine-textured (sandy loam, loam, silty clay, and clay) frozen prairie soils were determined from field measurements made in the two ecosystems during snowmelt. These calibrations gave best-fit values of C=1.3 and C=2.05 for the boreal forest and Prairie sites, respectively. Estimates of cumulative infiltration with the appropriate value of C are compared against measured data in Figures 2a and 2b. The standard deviation of the difference among values for the boreal forest sites is 10 mm and the majority of the predicted values (75%) fall within the error band (Figure 2a). Similarly, the standard

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deviation of the difference among values for the prairie sites is 10 mm and the majority of the predicted values (88%) fall within the error band (Figure 2a). These results suggest that the correlation, with appropriate calibration, will provide acceptable estimates of the snowmelt infiltration into frozen mineral oils for use in operational hydrology schemes. (a) (b)

Figure 2 Comparison of calculated and measured cumulative infiltration for boreal forest (a) and prairie (b) sites.

Ground Heat Flux Infiltration into frozen ground involves simultaneous coupled heat and mass transfers with phase changes. Therefore, the presence of infiltrating water affects heat transfer into the ground and the soil temperature regime. Field measurements (Kane and Stein 1983) and model simulations (Zhao et al. 1997) demonstrate that both the infiltration rate and the surface heat transfer rate (conduction) in a frozen soil decrease with time following the application of meltwater to the surface (Figure 3). Zhao et al. (1997) separate these variations into two regimes, a transient regime and a quasi-steady state regime. The transient regime follows immediately the application of water on the surface and during this period the infiltration rate and the heat transfer rate decrease rapidly. The quasi-steady state regime occurs where the changes in the infiltration rate and the heat transfer rate with time are relatively small. The duration of the transient period is usually short (a few hours) and the energy used to increase the soil temperature is largely supplied by heat conduction at the surface (high heat transfer rate at the surface). In the quasi-steady state regime, the energy used to increase the soil temperature at depth is supplied by latent heat released by the refreezing of percolating meltwater in the soil layers above (low heat transfer rate at the surface. Zhao et al. (1997) estimate that as much as 90% of the latent heat (say 90%) released by the refreezing of meltwater is conducted deeper in the soil where it used for melting and increasing the soil temperature. Most simulations of ground heat in land process models are based on heat transfer by conduction using the temperature gradient approach and simulated soil temperatures at 3 or 4 levels in a soil profile that extends to the rooting depth of the crop or below. The application of this approach for estimating the ground heat flux in frozen soils during snowmelt infiltration is not straightforward. The difficulty arises because the most important heat and mass transfer processes affecting the flux occur in the surface layers of the soil. Consequently, the temperature gradient at the soil surface is determined by soil temperature profile near the surface (top 10 cm) and the temperature gradient at depth (below) is established by the downward conduction of latent heat released by the freezing of percolating water. Therefore, the processes of heat and mass transfers into frozen soils during infiltration can only be

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described properly by a mult-ilayered model having a reasonably small grid spacing. For those models with only a few soil layers, the ground heat flux should not be calculated by estimating the temperature gradient. Instead, it is likely that the assumption of a very small value for ground heat or the use of parametric or empirical correlations for estimates of both the ground heat and infiltration will give better results.

Figure 3 Variations in infiltration rate, dINF/dt, and surface heat flux rate, dQ/dt, with time

during snowmelt infiltration into a frozen silty clay soil. Wind Transport of Snow Blowing Snow Fluxes over Complex Terrain: PBSM was simplified, spatially-distributed and driven using a terrain windflow model MS3DJH/3R over the complex arctic terrain of Trail Valley Creek on an hourly time step (Essery et al., 1998). Topography was permitted to vary according to measurements contained in a geographic information system (digital elevation model). Probability of blowing snow occurrence algorithms in the simplified PBSM were sensitive to vegetation type and burial of vegetation by snow, and used to index the effect of variable vegetation roughness on blowing snow. The simulation was run for Trail Valley Creek over the winter of 1996-97 on an hourly time step with a spatial resolution of 80 m. Mean SWE and CV of SWE are within a standard deviation of measured values at the end of the winter season. A simulation with suppressed sublimation provided much greater predicted snow accumulation than that observed. Several new open terrain landscape classes were identified based on windflow regimes: windswept, windward, divergent, neutral, and convergent. The mean SWE and CV of SWE are notably different amongst these regimes. Figure 4 shows predicted frequency distributions for end of season SWE in various terrain types. The differences are the result of wind redistribution. Normal distributions of SWE, fitted to the frequency histograms predicted by the complex terrain blowing snow model (Figure 4) can be used to initialize models of snow-covered area depletion. The distributions are also the first physically-modelled estimates of the variability of SWE over complex tundra terrain and are critical to �scaling up� snowcover estimates for the Mackenzie Basin.

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Figure 4 Histograms showing modelled snow water equivalent (expressed as mass) frequency

compared to summed lognormal distributions for terrain types of varied vegetation and topographic placement in Trail Valley Creek, spring 1997.

Coupled Interception-Sublimation Model A series of process-based algorithms has been developed to describe the accumulation, unloading and sublimation of intercepted snow in forest canopies (Pomeroy et al., 1998). These algorithms are unique in that they scale-up the physics of interception and sublimation from small-scales, where they are well understood, to forest stand-scale calculations of intercepted snow sublimation. The interception algorithms are based on that of Hedstrom and Pomeroy (1998). The sublimation algorithm is that used in the blowing snow model PBSM, with modifications to account for exposure of snow in a forest canopy (Pomeroy and Schmidt, 1993). Figure 5 shows measured and modelled daily sublimation from intercepted snow, using the model and measurements of snow mass and mass loss from a suspended, weighed tree. It indicates that a reasonable estimation of sublimation fluxes can be achieved. Evaluation of results from the set of algorithms against measured interception and sublimation in a southern boreal forest jack pine stand during late winter, found the coupled model provides reasonable approximations of both interception and sublimation losses on half-hourly, daily, and event basis. Cumulative errors in estimate of intercepted snow load over 23 days of test were 0.06 mm SWE with a standard deviation of 0.46 mm SWE. Sublimation losses during the evaluation were high, approximately two-thirds of snowfall within this period. Seasonal intercepted snow sublimation as a portion of annual snowfall at the model test site was lower than sublimation during the tests, ranging from 13% for a mixed spruce-aspen, 31% for the mature pine and 40% for a mature spruce stand. The results indicate that sublimation can be a significant abstraction of water from mature evergreen stands in northern forests and that the losses can be calculated by application of process-based algorithms.

010002000300040005000

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Figure 5 Daily measured sublimation fluxes, calculated from the loss of snow mass from a

weighed pine tree versus modelled sublimation. 4. Summary The results listed above demonstrate that cold regions hydrological processes can have profound and previously undocumented impacts on the calculation of surface water and energy fluxes in the Mackenzie Basin. Progress has been made in describing many of the processes in a physical manner and in developing operational algorithms for some of the processes. The observed multi-scale operation and horizontal interaction of some of these processes means that phenomena operating at very small scales can affect large-scale water and energy balances. 5. Literature Cited Donald, J.R., E.D. Soulis, N. Kouwen, and A. Pietroniro, 1995. A land cover-based snow cover

representation for distributed hydrological models. Water Resources Research, 31(4): 995-1009. Faria, D., 1998. The Energetics of Boreal Forest Snowmelt. Unpublished M.Sc. Thesis, University of

Saskatchewan, Saskatoon, SK, 158 p. Kane, D.L. and J. Stein, 1983. Water movement into seasonally frozen soils. Water Resources Res.

19(6):1547-1557. Shook, K., 1995. Simulation of the Ablation of Prairie Snowcovers. Ph.D. Thesis. University of

Saskatchewan, Saskatoon, SK, pp. 1-189. 6. Recent Publications and Presentations Elliott, J.A., B.M. Toth, R.J. Granger, and J.W. Pomeroy, 1998. Soil moisture storage in mature and

replanted sub-humid boreal forest stands. Canadian Journal of Soil Science, 78:17-27. Essery, R., L. Li and J.W. Pomeroy, 1998. Blowing snow fluxes over complex terrain, 1, distributed

modelling. J. Hydrol. Processes. (submitted) Granger, R.J. and J.W. Pomeroy, 1997. �Sustainability of the western Canadian boreal forest under

changing hydrological conditions - 2- summer energy and water use.� In: D. Rosjberg, N. Boutayeb, A. Gustard, Z. Kundzewicz, and P. Rasmussen (Eds.), Sustainability of Water Resources under Increasing Uncertainty, International Association Hydrological Sciences Publ. No. 240, IAHS Press, Wallingford, UK, pp. 243-250.

Hedstrom, N.R. and J.W. Pomeroy, 1998. Measurements and modelling of snow interception in the boreal forest. J. Hydrol. Processes, 12:1611-1625.

Hedstrom, N.R. and J.W. Pomeroy, 1997. �Accumulation of intercepted snow in the boreal forest.� In: Proceedings, 65th Annual Western Snow Conference, pp. 130-141.

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Li, L. and J.W. Pomeroy, 1997. Probability of Blowing snow occurrence by wind. J. Geophysical Res., 102:D18, 21,955-21,964.

Marsh, P., J.W. Pomeroy, and N. Neumann, 1997. Sensible heat flux and local advection over a heterogeneous at an arctic tundra site during snowmelt. Annals of Glaciology, 25:132-136.

Maxfield, A.W., P. Marsh, J.W. Pomeroy, and W.L. Quinton, 1997. �Arctic snow and soil observations by radar satellite.� In:. G.W. Kite, A. Pietroniro and T.J. Pultz (Eds.), Applications of Remote Sensing in Hydrology, NHRI Symposium No. 17, National Hydrology Research Institute, Saskatoon, SK, pp. 199-210.

Pomeroy, J.W. and R.J. Granger. 1997. �Sustainability of the western Canadian boreal forest under changing hydrological conditions -I- snow accumulation and ablation.� In: D. Rosjberg, N. Boutayeb, A. Gustard, Z. Kundzewicz, and P. Rasmussen (Eds.), Sustainability of Water Resources under Increasing Uncertainty, International Association Hydrological Sciences Publ. No. 240, IAHS Press, Wallingford, UK, pp. 237-242.

Pomeroy, J.W., D.M. Gray, K.R. Shook, B. Toth, R.L.H. Essery, A. Pietroniro, and N. Hedstrom, 1998. An evaluation of snow accumulation and ablation processes for land surface modelling. J. Hydrological Processes (in press). Also, presented at the Eastern Snow Conference, In: Proceedings Eastern Snow Conference, 55 (in press).

Pomeroy, J.W. and L. Li., 1997. �Development of the Prairie Blowing Snow Model for application in climatological and hydrological models.� In: Proceedings, 65th Annual Western Snow Conference, pp. 186-197.

Pomeroy, J.W. and P. Marsh, 1997. �The application of remote sensing and a blowing snow model to determine snow water equivalent over northern basins.� In: G.W. Kite, A. Pietroniro, and T.J. Pultz (Eds.), Applications of Remote Sensing in Hydrology, NHRI Symposium No. 17, National Hydrology Research Institute, Saskatoon, SK, pp. 253-270.

Pomeroy, J.W., J. Parviainen, N. Hedstrom, and D.M. Gray, 1998. Coupled modelling of forest snow interception and sublimation. J. Hydrological Processes (in press). Also, presented at the Eastern Snow Conference, In: Proceedings, Eastern Snow Conference, 55 (in press).

Shook, K. and D.M. Gray, 1997. �Ablation of shallow seasonal snowcovers.� In: .I.K. Iskandar, E.A. Wright, B.S. Sharratt, P.H. Groenvelt, and L. Hinzman (Eds.), International Symposium on Physics, Chemistry and Ecology of Seasonally-frozen Soils, June 10-12, 1997, Fairbanks, Alaska, Special Rept. 97-10, US Army Cold Regions Research and Engineering Lab., Hanoever, NH, pp. 280-286.

Shook, K. and D.M. Gray, 1997. The role of advection in melting shallow snowcovers. J. Hydrol. Processes, 11:1725-1736.

Taylor, C.M., R.J. Harding, R.A. Pielke, J.W. Pomeroy, P.L. Vidale, and R.L. Walko, 1998. Snow breezes in the boreal forest. J. Geophysical Res., D18, 103, 23,087-23,103.

Zhao, L. and D.M. Gray, 1998. Estimating snowmelt infiltration into frozen soils. J. Hydrol. Processes. (in press)

Zhao, L. and D.M. Gray, 1997. A parametric expression for estimating infiltration into frozen soils. J. Hydrol. Processes, 11:1761-1775.

Zhao, L. and D.M. Gray, 1997. �Estimating snowmelt infiltration into medium and fine-textured, frozen soils.� In: I.K. Iskandar, E.A. Wright, B.S. Sharratt, P.H. Groenvelt, and L. Hinzman (Eds.), International Symposium on Physics, Chemistry and Ecology of Seasonally-frozen Soils, June 10-12, 1997, Fairbanks, Alaska, Special Rept. 97-10, US Army Cold Regions Research and Engineering Lab., Hanoever, NH, pp. 287-293.

- N.D. Plenary presentation to Eastern Snow Conference. - N.D. Invited talk to Universitiy of East Anglia, Norwich, UK. - N.D. Numerous other presentations (>25) in Ontario, Qu�bec, New Hampshire, Vermont, Norway,

Japan, England, Saskatchewan, Alberta, Yukon.

◆◆◆


58

2.5 Snowcover Melt and Runoff in Boreal and Tundra Ecosystems

P. Marsh, N. Neumann, C. Onclin, A. Pietroniro, J. Pomeroy, W. Quinton, and R. Essery

National Water Research Institute, National Hydrology Research Centre, Saskatoon,, Saskatchewan 1. Objectives

(1) to better understand the processes controlling snowcover melt and runoff; (2) to determine the magnitude of the individual components of the mass and energy balance for the

boreal/tundra transition zone in the zone of continuous permafrost, for both seasonal and daily periods;

(3) to develop process based algorithms of the energy and water fluxes during the spring melt and summer periods; and,

(4) to incorporate and test these algorithms in distributed models at a variety of scales. 2. Field Measurements From 1993 to present, field studies have been conducted at NHRI/NWRI research basins in the Inuvik area, a site representative of the forest/tundra transition in the zone of continuous permafrost, which is typical of much of the northern and north-western parts of the Mackenzie Basin. Each field season has concentrated on a separate component of the overall long-term objectives. As a result, detailed process based field studies have included the following: (1) 1993 - point surface energy balance measurements and hill slope runoff; (2) 1994 - snow percolation studies and hillslope runoff; (3) 1996 - basin scale energy balance measurements to consider the role of local advection in surface

fluxes and development of a streamflow measurement system; and, (4) 1997 - analysis of storage components. In order to provide continuous observations during three of these years (1993, 1996, and 1997) effort was expended in order to collect data on all of the major water balance components. In addition, NHRI/NWRI have maintained a remote weather station at the research basins and WSC, with enhanced measurements from NHRI, have collected streamflow measurements for the period 1993 to present. It must be realized that the autostations are unmanned for much of the year and therefore some of the data (radiation for example) are unreliable for extended periods. Only during years with enhanced streamflow observations, are streamflow during the melt period reliable. Other parameters (air and ground temperature, soil moisture, snow depth, etc.) do not require frequent attention and, therefore, are much more reliable over an entire annual cycle. In the fall of 1997, the Trail Valley and Havikpak autostations were upgraded through joint funding provided by CAGES and NWRI. This included the installation of GOES transmitters, and the resulting data is now available daily on the MAGS web page. This data is currently being downloaded at NWRI daily and a preliminary quality control check is carried out on a weekly basis. 3. Results (a) Snowmelt and changes in snow covered area during melt Spatial variations in snow water equivalent at the end of winter (see Pomeroy for description of controlling processes and predictive methods) combined with spatial variations in snowmelt, result in a patchy snowcover during much of the spring melt period. Estimates of the spatial variation in melt energy have been obtained from both changes in wind speed over the basin and estimates of local scale advection.


59

A wind flow model (Essery, et al. 1998) applied for conditions with continuous snowcover, demonstrates variations in wind speed from 0.85 to 1.10 times the mean wind speed. In order to illustrate the potential importance of spatial variations in wind on snowmelt, one example shows that for a continous snowcover, which was melting, sensible heat flux ranged from 80 to 125 w/m2 (Figure 1a). This would result in significant spatial variations in melt. The impact of such spatial variations in melt on snowcover distribution is visible on SPOT images where the first snow free areas correspond to zones with higher average wind speed. Early meltout in these areas is likely due to both increased wind scour and shallower snow pack at the end of winter, and increased melt energy. (a) (b)

Figure 1. Variations in sensible heat for melting snowcovers in the Trail Valley Creek area: (a) continuous snowcover with surface temperature 0ΕΕΕΕC - sensible heat (positive is towards the surface), estimated using wind speed from a wind flow model applied to Trail Valley Creek (Essery, et al. 1998) and constant air temperature; and, (b) patchy snowcover - sensible heat (negative is towards the surface), estimated using the UK Met Office Boundary Layer Model for constant atmospheric conditions (i.e., wind speed), but including local scale advection of sensible heat from snow-free patches to snow patches.

Once a patchy snowcover forms, the spatial variability in melt is further enhanced by the horizontal transfer of energy at a small-scale, a process termed local advection. The magnitude of this process was estimated from both field measurements and using the UK Met Office Boundary Layer Model (BLM) (Essery 1997). These both show that the efficiency of local scale advection increases with decreasing snowcover, increasing wind speed, and decreasing patch size. Results suggest that average sensible heat flux to a melting snow patch increases over 2 times as snowcover decreases. A simple parameter relating advection efficiency (FS) to snowcover area (Figure 2) has been developed, and ongoing work will include the role of wind speed and snow patch �size�. Fs may be used to estimate the advection of sensible heat (QA) to patchy snowcovers by:

SS

VHA F

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Q V��

��

�=

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Figure 2 Advection efficiency term (FS) vs. snow-free fraction (PV) as estimated from field data,

from the BLM using a snowcover determined from SPOT images, and from the BLM, but with a single snow patch. The vertical line extending from the BLM single snow patch line at 50% snow-free fraction illustrates the increase in FS for same snowcover fraction, but with patch size decreasing from 4 km (i.e., one large snow patch) to 20 m (many small patches).

(b) Snowmelt percolation Due to the initial cold content of the snowcover, soil heat flux, and the requirement to fill liquid storage within the snowcover, there is considerable lag time between the beginning of melt and runoff. Determination of the delay is further complicated by the occurrence of flow fingers at the leading edge of the wetting front. These flow fingers typically carry approximately 20% of the total meltwater over only 10% of the horizontal area. The result is that meltwater in the flow fingers move more quickly through the snowcover, and portions of the meltwater reach the base of the snowcover significantly earlier than would be expected if it is assumed that the flow is homogeneous. When combined with differences in snowcover depth, the timing of initial runoff varies greatly over the study basins. Such variations play a critical role in controlling both the timing and magnitude of runoff since approximately 30% of the total basin snow storage occurs in only 10% of the basin area. A simple model of wetting front advance, and resulting runoff, was presented by Marsh (1991) and Marsh and Pomeroy (1996). This shows that for the Trail Valley Creek area, the availability of water at the base of the snowcover occurs up to 10 days later for the deep drifts than for the shallow tundra snowcovers (Figure 3), with a total delay of up to 15 days between the start of melt and runoff. Using mapped snowcover depths, Marsh and Pomeroy (1996) used this information to map spatial variations in runoff. Ongoing work will link this model with the modelled variations in snowcover and melt (see earlier section) to better estimate spatial variations in the timing and volume of melt.


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Figure 3 Wetting front movement through tundra, shrub tundra and drift snowcovers for the

Trail Valley Creek area. The first wetting front reaching the base of the snowcover represents the arrival of flow fingers at the base of the snowcover and indicates the first date at which runoff from the pack may occur. At this time, only approximately 20% of total melt is available for runoff. The second wetting front, representing the background wetting front, denotes the time when the entire pack is wet and isothermal at 0C. After this time, all of the surface melt is available for runoff. Note that there is an approximate 15 day delay between the start of melt 9, i.e., when wetting fronts initially go below the snow surface) and all of the melt being available for runoff.

(c) Snowmelt runoff pathways Many tundra soils are heterogeneous in the horizontal direction, due to the presence of mineral earth hummocks. On hummock-covered hillslopes in the Arctic-tundra (which are the most extensive landform in the permfrost areas), the horizontal hydraulic conductivity integrated over the saturated layer is three orders of magnitude higher in the inter-hummock area than in the hummocks. Consequently, surface runoff is uncommon, and the task of delivering runoff rapidly to the streambank is accomplished by the process of rapid subsurface flow. Such runoff from hummock-covered hillslopes occurs preferentially through the relatively permeable inter-hummock area, which serves as the hillslope drainage network. Tundra soils are also heterogeneous in the vertical direction due to the changes in physical and hydraulic properties of the peat with depth. The rate of flow through the inter-hummock area, therefore, depends strongly upon the elevation of the saturated layer within the peat profile. When the saturated layer is within the highly conductive near-surface peat, subsurface flow can occur at velocities as high as for overland flow. Although flow in these peats occurs at velocities similar to overland flow, analysis shows that the flow is laminar (Figure 4) and that Darcy�s Law is applicable.


62

Figure 4 Moody plot of Reynolds number versus friction factor for porous media flow. Since Reynolds number varies linearly with friction factor, this demonstrates that flow is laminar. If pore diameter is known, then the hydraulic conductivity can be directly estimated from the slope of the best fit line.

Using measured water level in the inter-hummock zone, in conjunction with estimates of active layer depth, hydraulic conductivity, the size and frequency of the inter-hummock channels, and melt of the deep drifts within the stream channels allows an estimation of streamflow (Figure 5). The similarity between predicted and observed streamflow demonstrates that the majority of meltwater is transferred from the uplands and hillslopes to the stream channels as flow through the inter-hummock channels. Ongoing studies are aimed at developing appropriate, physically based algorithms to predict inter-hummock flow, thus allowing a coupling of the upland and hillslope snowmelt to stream flow. (c) Integrated modelling The above process based algorithms will be tested for study sites in the Inuvik area and compared with observed changes in snowcovered area and observed water balance components shown in Figures 6 and 7. Similar water balance data is available for 1993 and 1997, and will be collected for the entire CAGES period (1998/99). In addition, WATFLOOD is currently being tested on both Trail Valley Creek and Havikpak Creek. Initial runs will be compared to estimated water balance components as shown in Figures 6 and 7. Once available, WATFLOOD/CLASS will be run for these study basins and predictions compared to observed as well as to the predictions of the detailed process based models. This will lead to recommendations for improving WATFLOOD and WATFLOOD/CLASS for use in these arctic environments.

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Figure 5 Measured and predicted streamflow for a tributary of Trail Valley Creek,

demonstrating that streamflow may be estimated from inter-hummock flow and melt within the stream channel.

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E

Stor

Figure 7 Annual water balance totals for Trail Valley Creek, 1996.

4. Summary Ongoing studies are considering the wide range of processes controlling the fluxes of water and energy at the arctic treeline. Field and modelling studies have demonstrated the role of variable wind speed and local scale advection of sensible heat in controlling the spatial variation in melt. When combined with predicted variations in snowcover, this will allow an improved prediction in the change in snow covered area over the melt period, the flux of sensible and latent heat to the atmosphere, albedo, and snowmelt runoff. In addition, improved physically based algorithms for routing meltwater through the snow pack and horizontally from the uplands and hillslopes to the stream channel. Physically based models of these processes, and WATFLOOD and, when available, WATFLOOD/CLASS will be compared to measured water balance terms for the study areas. This will lead to recommendations for improving WATFLOOD and WATFLOOD/CLASS for use in these arctic environments. 5. Recent Publications and Presentations Marsh, P. and J.W. Pomeroy, 1999. Spatial and temporal variations in snowmelt runoff chemistry. Water

Resources Research. (in press) Marsh, P. and J.W. Pomeroy, 1996. Meltwater fluxes at an arctic forest-tundra site. Hydrological

Processes, 10:1383-1400. Marsh, P., J. W. Pomeroy, and N. Neumann, 1997. Sensible heat flux and local advection over a

heterogenous landscape at an arctic tundra site during snowmelt. Annals of Glaciology, 25:132-136. McGurk, B.J. and P. Marsh, 1995. �Flow-finger continuity in serial thick-sections in a melting Sierran

snowpack.� In: Biogeochemistry of Seasonally Snow-Covered Catchments, Tonnessen, K.A., M.W. Williams, and M. Tranter, M. (Eds.), July 1995, Boulder, Colorado. IAHS Publication No. 228, pp. 81-88.

Neumann, N. and P. Marsh, 1998. Local advection in the snowmelt landscape of arctic tundra. Hydrological Processes, 12:1547-1560.

Pomeroy, J.W., P. Marsh, and D.M. Gray, 1997. Application of a distributed blowing snow model to the Arctic. Hydrological Processes, 11:1451-1464.


65

Pomeroy, J.W., P. Marsh, H.G. Jones, and T.D. Davies, 1995. �Spatial distribution of snow chemical load at the tundra-taiga transition.� In: Biogeochemistry of Seasonally Snow-Covered Catchments, Tonnessen, K.A., M.W. Williams, and M. Tranter, M. (Eds.), July 1995, Boulder, Colorado. IAHS Publication No. 228, pp.191-203

Quinton, W.L. and P. Marsh, 1998. �Meltwater fluxes, hillslope runoff and streamflow in an arctic permafrost basin.� In: Proceedings, 7th International Conference on Permafrost, June 1998, Yellowknife, NWT. (in press)

Quinton, W.L. and P. Marsh, 1998. The influence of mineral earth hummocks on subsurface drainage in the continuous permafrost zone. Permafrost and Periglacial Processes. (in press)

Stewart, R.E., H.G. Leighton, P. Marsh, G.W.K. Moore, H. Ritchie, W.R. Rouse, E.D. Soulis, G.S. Strong, R.W. Crawford, and B. Kochtubajda, n.d. The Mackenzie GEWEX Study: The water and energy cycles of a major North American River basin. Bulletin of the American Meteorological Society. (in press)

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2.6 Effects of Seasonal Frost and Permafrost on the Hydrology of Subalpine Slopes and Drainage Basins

M.K. Woo1, S.K. Carey1, and L.W. Martz2

1School of Geography and Geology, McMaster University, Hamilton, Ontario 2Dept. of Geography, University of Saskatchewan, Saskatoon, Saskatchewan

1. Objectives The overall objective of this project is to understand and quantify the thermo-hydrological processes operating at slope and small catchment scales in the subarctic so as to enhance the modelling of heat and moisture fluxes in cold environments. The specific goals for Year 2 research were to: (1) expand the process studies to further our understanding on the variability and interaction of

thermal and hydrological activities under complex terrain and discontinuous permafrost conditions;

(2) improve the spatial representation of soil and vegetation, and to obtain their related thermo-hydrological parameters within Wolf Creek Basin;

(3) develop a model framework that will integrate the physical processes in cold regions with the purpose of applying this model to the permafrost environment.

Important progress was made to attain all three goals. Field studies during 1998 provide better understanding of the physical processes operating in the subarctic, thus helping to improve the modelling capability of the energy and water fluxes in the cold environment. Parameterization of Wolf Creek Basin will enhance the upscaling of point measurements to large areas. These are contributions to the overall objectives of MAGS. 2. Progress and Collaborations Progress of Year 2 (FY 97-98) Field programme Field studies in Wolf Creek Basin, Yukon, spanned between April and September 1998. In addition to the two (North and South) experimental slopes, which were instrumented in 1996, two others (East and West) were added to expand the process study in order to:

(1) determine the temporal variability of the thermo-hydrological processes by repeated field investigations on the N and S slopes; and,

(2) understand the spatial variability as influenced by changes in micro-climate, topography, soil and frost conditions on a sub-basin-scale. The physical characteristics of the four sites are summarized in Table 1.

At each site is an instrumented meteorological tower, several ground temperature and soil moisture measurement plots, groundwater observation wells and, whenever runoff occurs, small weirs to manually measure the flow in rills. The 1997 data for N and S slopes were analysed, while the 1998 data for all sites are being quality-controlled and filed.


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Table 1 Physical characteristics of the four subarctic experimental slopes, Wolf Creek Basin.

N-slope

S-slope

E-slope

W-slope

Position

long slope with glacial deposits

middle of a short slope segment

base of a colluvial fan

base of a straight slope

Gradient

0.2

0.6

0.1

0.2

Mineral soil

boulder-clay

silt

silt to boulders

sandy silt

Organic layer

0.05-0.3 m peat

leaf litter, humus

0.2-0.3 m peat

>0.3 m peat

Vegetation

spruce, shrubs of willow and Labrador tea

aspen, shrub undergrowth

spruce, shrubs of willow and Labrador tea

tall willow and shrubs of alder

Frost condition

ice-rich permafrost

seasonal frost only

seasonal frost only

ice-rich permafrost

Two years of intense field work at N and S slopes confirmed the effects of frost and the organic soil layer on the hydrological processes. As summarized in Figure 1, the N slope with permafrost and an organic soil layer behaves differently from the S slope, which possesses neither such attributes. In the spring, snowmelt is advanced by approximately one month on the S slope due to greater radiation receipt. Meltwater infiltrates its seasonally frozen soil with low ice content, recharging the soil moisture reservoir, but yielding no lateral runoff. Summer evaporation depletes this recharged moisture and any additional input, at the expense of surface or subsurface flow. The N slope with an icy substrate hinders deep percolation. Snow meltwater is impounded within the organic layer to produce surface runoff in rills and gullies, and subsurface flow along pipes and within the matrix of the organic soil. During the summer, most surface flows are confined to the organic layer, which has hydraulic conductivity orders of magnitude larger than the underlying boulder-clay. Evaporation on the N slope declines as both the frost table and water table descend in the summer. The 1998 study of E and W slopes shows that the former, without any permafrost, yielded surface runoff, but the latter (W slope with permafrost) did not. This is a contrast to the N and S slope findings, but such an apparent contradiction can be explained. The physiography of the E slope site (base of a colluvial fan) renders it a wet location, being at the discharge point of a concave slope where the coarseness of the substrate allows easy transmission of groundwater. The absence of permafrost may be due to convective heating by groundwater, a situation common to the formation of taliks (frost-free zones) in the subarctic environment. For the W slope, a thick and relatively undissected layer of peat permits large quantities of water to be stored and, when saturated, move downslope as subsurface flow, to the detriment of surface runoff. The presence of an icy mineral soil beneath the peat attest to the high moisture content at the base of the active layer, a condition similar to the N-facing permafrost slope. In summer, N slope appeared to be wetter than W slope and this may be attributed to the former having a larger upslope catchment area as a supplier of inflow to the site. At present, these findings are tentative and need to be confirmed.

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Figure 1 Major hydrologic process occurring in subalpine forests south-facing slope (left); north facing slope (right).


A water balance study of the N and S slopes was completed (Table 2), providing quantification and comparison of the relative contributions of various processes to subarctic slope hydrology. Table 2 Water balance of N and S slopes, April 6 to September 22, 1997. The resumoisture excN slope promseasonal defiadditional sosoil moisturebalance closehas to be dewoodland. Paramete Extensiveand examine viz boreal forcharacteristictexture, surfic The charinformation fextent of theFigure 2. Althe key criterand local topvariability withe basis for b

S slope N slope Gains: Snow Icing Rain Subsurface flow

160 0

169 0

187 19

169 245

Losses: Sublimation Evaporation Surface runoff Subsurface flow

10 372 0 0

18 344 155 97

Storage change

-53

6

All values in mm of water.

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lts show that vertical hydrological processes of infiltration and evaporation dominate hanges on the S slope, whereas the retardation of deep drainage by icy frost and clay on the otes a strong lateral flow component, both in the peat and along the rills. For the S slope, a cit of 55 mm suggests that the spring and summer water demand has to be satisfied by some urce. This may be provided by 70 mm of rain that fell in October 1996, which enriched the storage to be available for withdrawal in the 1997 field year. For the N slope, the water s within the expected error range, but there was an inflow of 97 mm to the site. This water livered from upslope, possibly as far as the alder-willow shrub zone above the subarctic

rization and model assessment field work was carried out in different parts of Wolf Creek Basin to collect soil samples permafrost conditions and vegetation cover at selected plots at all major hydrologic zones, est, open woodland, subalpine shrub, alpine tundra, wetland, and lake. A summary of some s relevant to the zonal hydrology (excluding lakes) is provided in Table 3, including soil ial deposits, and vegetation.

acterization at the basin level was done by integrating the field data with available rom other sources (including GSC and Agri-Food Canada) into a GIS database. The spatial major hydrologic zones was defined using this integrated information and is illustrated in so shown in Figure 2 are maps of the vegetation coverage and surficial geology, which are ia in the zonal classification. These two criteria implicitly reflect the controls of elevation ographic setting, themselves being factors governing the micro-climatic and hydrologic thin the Wolf Creek Basin. The derived hydrologic zonation map, while tentative, will form asin-scale hydrologic modelling in the future.


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Table 3 Characteristics of various hydrologic zones, Wolf Creek Basin.

Hydrologic Zones

Alpine Tundra

Subalpine Shrub

Subalpine Woodland

Boreal Forest

Wetland

Soil B horizon texture (% by wt) - Sand 65 55 46 58 - - Silt 23 33 35 33 - - Clay 13 12 19 9 -

Surficial deposit (% by area) - Till 50 65 62 82 46 - Alluvium 6 19 19 14 24 - Bedrock 44 8 7 4 4 - Colluvium - - 1 - - - Glaciofluvial - - 4 - - - Glaciolacustrine - - 4 - 20

Vegetation (% by area) - Anthropogenic disturbance 1 - - - - - Lodgepole Pine - Lichen Forest - - - 43 - - Trembling Aspen - Bearberry Forest - - - 4 - - White Spruce - Feathermoss Forest - - - 11 - - White Spruce / Willow - Dwarf Birch Forest - - - 41 -

- Open White Spruce / Willow- Dwarf Birch - - 100 - - - Willow - Dwarf Birch Shrubland - 100 - - - - Willow - Dwarf Birch / Grass-Sedge Meadow - - - - 100 - Tundra (Willow- Dwarf Birch / Grass-Forb-Lichen)

82 - - - -

- Unvegetated (Bare Rock) 18 - - - -

The integration of cold regions processes is to be carried out using a basin-scale model. Such a model is later to be applied to some test catchments in tandem with the application of a large-scale model to the same locations to compare the model performance. The VSAS2 model was originally proposed for this project, but as field research continued, we had doubts concerning its applicability to the subarctic. In 1997-98, we critically re-examined VSAS2 in terms of its thermal and hydrological functions, its model structure for adaptation to northern basins and the ease of upscaling. We find serious deficiencies in its capability to handle heat transfer and freeze-thaw, the partitioning of surface and subsurface flows in the presence of organic soils; and it requires major structural changes to be rendered suitable for integrating the cold regions processes and for upscaling. We have, therefore, rejected it as a candidate for our study and will explore or develop an alternative modelling framework as part of our on-going research.

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Figure 2 Wolf Creek Basin: major hydrologic zones (top); vegetation (lower right); and surficial geology (lower left).


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Relevant Collaborations Our Wolf Creek research continues its association with other MAGS investigators from the government sector (Pomeroy and Granger). A collaborative study on the water balance of a small alpine sub-basin in Wolf Creek catchment was established to validate the methodology and the quantitative results from our several process studies. Our project is also linked to other research, both hydrologic and non-hydrologic, that is conducted in the area. The research groups include several branches of the Federal and Territorial governments, universities, and Yukon College. We share our results through discussions and workshops. On the scale of the Mackenzie River Basin, we have been collaborating with Kite in developing automated segmentation and parameterization capability for the SLURP model under the government GEWEX program. Currently, collaboration with Pietroniro to develop similar capabilities for the WATFLOOD model offers considerable scope for expanding the application for coupled models at the regional scale. 3. Scientific Results Key Scientific Results The interactions among three major factors significantly affect subarctic slope hydrology: frost and its ice content, organic layer thickness and properties, and wetness of the site, which depends upon the water balance. The generation of runoff from slopes is of paramount importance to hydrologic modelling, regardless of the scale of investigation. In the subarctic context, slope runoff is favoured by ice-rich permafrost with an organic layer of high hydraulic conductivity and at sites with ample water supply (from snowmelt, rainfall, or inflow). Water balance study shows that vertical processes prevail on some slopes, but horizontal water transfer is significant on slopes underlain by icy permafrost. Inflow to slopes in the wooded area may come from the subalpine willow-alder zone. Hydrological linkages between these sectors in the catchment remain unknown, but knowledge on the shrub-to-woodland transition processes is essential to coupling the 'hydrological response units' in modelling. From the above findings, it is clear that at any time of the year, only part of the catchment yields runoff to the streams. This is equivalent to the variable source area concept for the temperate latitudes, but is here operating in accordance with a different suite of hydrological and thermal processes. Applicability to Overall MAGS Objectives MAGS seeks to understand the large-scale energy and water exchanges within and between the atmosphere and the land, particularly in a cold region setting. Results from this project pertaining to the processes governing vertical and lateral transfers of water from subarctic slopes, and on parameterization, have important applications to large-scale modelling of energy and water fluxes on the terrestrial side.

(1) Not all parts of the basin contribute to runoff; hence to avoid spurious modelled results, there is a need to address the spatial variations of frost, organic soil, vegetation, and terrain.

(2) Parameterization using the TOPAZ scheme enables spatial representation of the above and other parameters, as well as the delineation of hydrological units (e.g., sub-basins) efficiently, thus greatly enhancing upscaling procedures.

(3) Further research will better define and quantify the thermo-hydrological processes special to the cold regions, thus providing the requisite information to improve basin-scale and large-scale models.


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4. Summary For subarctic wooded slopes, meltwater is the main water input during the snowmelt season and evaporation is a major water loss term in the summer. Water balance study shows that vertical processes prevail on some slopes but horizontal water transfer is significant on slopes underlain by ice-rich permafrost. While icy frost impedes vertical water movement to enhance lateral flow, coarse materials and organic layer facilitate the transmission of water downslope. These factors and their associated thermo-hydrological processes produce spatially and temporally changing zones in the slopes from which water is emanated to sustain streamflow. To model runoff from subarctic catchments, the variable source area of surface water has to be considered to take proper account of the dynamics of thermal and hydrological interactions. Like most mountainous subarctic basins, the Wolf Creek catchment comprises a mosaic of segments with different soil, frost, topographic, and vegetation conditions. An efficient and accurate scheme for parameterization and for spatially distributing the variables is required to define, characterize, and couple the various segments for thermo-hydrological modelling. Progress using TOPAZ algorithm enables the application of such a technique to the Wolf Creek Basin for hydrological investigations. Future research will link the process studies with modelling and TOPAZ will play a useful role. 5. Recent Publications and Presentations Carey, S.K. and M.K. Woo, n.d. Hydrology of two slopes in subarctic Yukon, Canada. Hydrological

Processes. (submitted) Carey, S.K. and M.K. Woo, 1998. Snowmelt hydrology of two subarctic slopes, Southern Yukon,

Canada. Nordic Hydrology. (in press) Carey, S.K. and M.K. Woo, 1998. The effect of frost on the water balance of two subarctic slopes.

Paper presented at the Canadian Geophysical Union Annual Meeting, May 1998, Qu�bec City, Qu�bec.

Carey, S.K. and M.K. Woo, 1997. �Snowmelt hydrology of subarctic slopes.� In: Proceedings, Northern Research Basin Symposium/Workshop, Vol. II, Prudhoe Bay to Fairbanks, Alaska, pp. 15-35.

Lacroix, M. and L.W. Martz, 1998. �APPENDIX 2: Using the TOPAZ digital landscape analysis model and the SLURPAZ interface to generate SLURP input files.� In: Manual for the Slurp Hydrological Model, Geoff Kite, National Hydrology Research Institute, Environment Canada, pp. 103-117.

Lacroix, M. and L.W. Martz, 1998. �Assessing the impact of varying sub-basin-scale on hydrological model response.� In: Abstract Volume, Carrefour in Earth Sciences: Joint Meeting of GAC, MAC, APGGQ, IAH, CGU, May 18-20, 1998, Qu�bec City, Qu�bec, p. A-99.

Lacroix, M. and L.W. Martz, 1998. �The application of digital terrain analysis modelling techniques for the parameterization of a hydrologic model in the Wolf Creek Research Basin.� In: Abstracts, Wolf Creek Research Basin Workshop, March 1998, Whitehorse, Yukon.

Lacroix, M., L.W. Martz, and G.W. Kite, 1998. Using Digital Terrain Analysis Techniques for the Parameterization of a Hydrologic Model. (in review, 28 pp.)

Martz, L.W., 1998. �Hydrologic characterization of the surface materials of Wolf Creek Basin.� In: Abstracts, Wolf Creek Research Basin Workshop, March 1998, Whitehorse, Yukon, pp. 15.

Woo, M.K. and S.K. Carey, 1998. �Permafrost, seasonal frost and slope hydrology, Central Wolf Creek Basin, Yukon.� In: Proceedings, Wolf Creek Workshop, Whitehorse, Yukon. (in press)

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2.7 Isotopic Tracing of Water-Balance Processes in the Mackenzie Basin

T.D. Prowse1, J.J. Gibson2, and A. Pietroniro1 1National Water Research Institute, National Hydrology Research Council, Saskatoon, Saskatchewan

2Wetlands Research Centre, University of Waterloo, Waterloo, Ontario

1. Scientific Background The Mackenzie Basin is comprised of a number of unique hydroclimatic regimes that vary because of significant differences in atmospheric and landscape characteristics that control the magnitude and relative importance of their water-balance components (Prowse 1990). One of these regimes is the vast zone of high boreal wetlands that characterize much of the Interior Lowlands and feed the lower portions of the Liard River, one of the largest tributaries of the Mackenzie River - contributing over 25% of the Mackenzie flow that reaches the Arctic Ocean. Although a majority of the total annual Liard flow originates from headwaters in the Western Cordillera, flow from the wetland regime of the lower Liard is seasonally significant, particularly during the early spring melt (Prowse 1984). Moreover, it is the sequential timing of flow from the wetland-dominated tributaries that determines how dynamic the spring breakup flood is on the Liard River and on the Mackenzie River near Fort Simpson, the trigger location for breakup of the lower Mackenzie (Prowse 1986; Prowse and Marsh 1989). The hydrology of this wetland-dominated regime is believed to be especially sensitive to the effects of climatic warming because it is located within the zone of sporadic discontinuous permafrost and many of the hydrologic divides are suspected to be cored by relatively warm permafrost. Hence, pronounced changes in water storage and runoff pathways are likely to occur with only a slight degree of additional ground heating. Detailed field studies were undertaken in the late 1980s and early 1990s (e.g., Craig 1991; Gibson 1991; Gibson, et al. 1993a,b; Reedyk, et al. 1995) to understand the dominant physical processes operating in this regime. Given the complexity and difficulties of conducting detailed field programs in wetland-dominated terrain, research was expanded to include an evaluation of remote-sensing based hydrologic models (Hamlin, et al. 1998; Pietroniro, et al. 1995, 1996). As part of the continuing field program, it was also decided to extend earlier research based on the use of natural isotopes to identify major flow sources and pathways. Information that is virtually impossible to obtain in such terrain, especially during the main runoff periods when conventional hydrometric techniques are impracticable, but is a prerequisite to improving hydrologic models for application in this northern system. Isotopic results detailed in this report are being used as a building block to produce a more physically relevant hydrologic model for this important Mackenzie hydrologic regime. Details on the modelling efforts are found in the companion report by Pietroniro et al. (1998) in this volume. 2. Scientific Objectives As outlined above, this study was motivated by the need to investigate the occurrence and importance of basic hydrological processes in discontinuous permafrost wetlands, as a first step towards improving model representation of surface hydrology in the Mackenzie Basin. The specific objectives are:

(i) to provide daily discharge estimates (m3/day) and equivalent depths (mm/d) of �snowmelt�, �groundwater�, and �surface water� contributions to tributary streamflow in the lower Liard River Basin, to critically evaluate the performance of the WATFLOOD distributed runoff model; and,

(ii) to develop isotopic methods for partitioning of water balance components during both ice-free

and ice-on periods to improve the qualitative and quantitative description of hydrologic mechanisms operating in discontinuous permafrost wetlands.


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3. Progress and Collaborations MAGS-related activities during 1998/99 have included a second major field campaign in the Liard River Basin, laboratory-based isotopic analysis, modelling, and data synthesis. The work has been presented and discussed in several publications and presentations. MAGS field activities have included snow, ice, and discharge surveys in selected tributaries to the Liard and Mackenzie Rivers near Ft. Simpson in early March, a streamflow and precipitation sampling program from early May to mid-October, and a concurrent water sampling program for wetland fens, lakes, tributary streams, groundwater seeps, and precipitation. A total of 267 water samples have been submitted for analysis of oxygen and hydrogen stable isotopes. Although only 15% of these analyses have been completed to date, it is expected that all required samples will be run before February 1999. A detailed list of scheduled activities and deliverables as provided in the 1998/99 proposal is given below. Note that all items have been completed in timely fashion. Field/Lab Work: (as stated in 1998/99 proposal)

Activity

Description Date Promised Completed

Snow surveys and sampling near Ft. Simpson March & April 1998 ✔ Streamflow/ Rain Sampling high frequency

(5 day intervals) mid-April to early-June 1998

✔

Streamflow/ Rain Sampling low frequency (2 week intervals)

late-June to mid-Oct1998 ✔

Groundwater, Fen, Lake Sampling

monthly intervals May to Oct 1998 ✔

Isotopic Analysis laboratory testing July 1998 to Jan 1999 partial, on schedule

Milestones/Deliverables: (as stated in 1998/99 proposal)

Activity and Description Date Promised

Completed

Presentation of results at CGU annual meeting May 1998 ✔

Submission of first journal paper on hydrograph studies July 1998 ✔

Presentation/preliminary report of 1998/99 study at MAGS Workshop Nov 1998 forthcoming

Submission of journal paper on lake studies Nov 1998 forthcoming

Final Report on 1998/99 studies Feb 1998 forthcoming


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4. Scientific Results Environmental stable isotopes of water (oxygen and hydrogen) are nearly ideal tracers of water cycling due to their ability to label water parcels according to origin and hydrologic evolution. As shown on a plot of δ18O versus δ2H (Figure 1), various waters collected in the Fort Simpson area, including snow, rainfall, groundwater, surface waters and streamflow, are systematically labelled by their isotopic composition. Rain and snow plot close to the Meteoric Water Line (MWL) of Craig (1961) reflecting negligible evaporative modification, while surface waters plot along a local evaporation line (LEL) reflecting differential modification by evaporation during residency in lakes and wetlands. Streamflow and groundwaters plot intermediate between snow, rain and groundwaters, and display a pronounced range due to seasonal shifts in hydrologic mechanisms affecting relative contributions of these components. Within MAGS, isotopic tracers are being applied to partition snowmelt contributions to streamflow during the spring freshet, and to partition surface water/groundwater contributions to streamflow during the ice-free and ice-on seasons. Preliminary results of these activities are discussed below.

δδδδ18O (‰)

-35 -30 -25 -20 -15 -10 -5

δδ δδ2 H (‰

)

-260

-240

-220

-200

-180

-160

-140

-120

-100

-80

-60

surface waters (sw)

rain

snow

streamflow

MWL

LEL

groundwater(gw)

Figure 1 Plot of δ18O vs. δ2H in waters collected in the Fort Simpson area during 1997.

Streamflow data are from five wetland-rich streams ranging from 202 km2 to 1390 km2.

Snowmelt Partitioning Temporal changes in the volume of snowmelt contributions to streamflow are being compared in five streams near Fort Simpson to examine the effect of basin characteristics such as gradient, size, and vegetation coverage and distribution on the hydrograph response. A two-point mixing approach has been employed, which relies on the distinct isotopic signatures of snow versus summer streamflow. Extensive snow surveys, including isotopic sampling, were conducted prior to snowmelt for each terrain classification unit used in the WATFLOOD model (Pietroniro, et al. 1998, this volume). These results, in combination with land classification data for each basin, have been used to estimate snow water equivalent and snowpack isotopic composition for each basin. Importantly, the isotopic composition of the snowpack in open-water and wetland areas is found to be substantially more variable than in forested areas. This is attributed primarily to incorporation of lake or fen water into the snowpack by overflow/subsidence of ice over the course of the winter.


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The isotopic composition of summer streamflow, collected during late July through early October, is found to be distinct for each basin, primarily reflecting differences in the fraction of contributions from evaporated versus non-evaporated source waters. Isotopic data for snowpack and summer streamflow are used to partition snowmelt contributions to streamflow between the onset of melt and late July (day 200). An example of results obtained for the Blackstone River is shown in Figure 2. Most notably, the abrupt decline in snowmelt contributions around day 150 corresponds to the observed transition from runoff via macropore/interflow to groundwater flow. Such information will be useful to compare with the model results. Similar results were obtained in all five basins; however, the timing of the snowmelt hydrograph is also found to be distinct for each basin, due not only differences in the mean transit times of water, but also potentially due to variations in the relative importance of flow pathways. Importantly, variability in basin isotopic response appears to be systematically related to basin gradient and land classification units, which supports the use of a distributed model approach in the present setting. Very different responses were observed for individual basins for 1997 and 1998 (not shown), primarily due to a lighter-than-normal snowpack during the latter year.

Blackstone R.

day of year 1997100 120 140 160 180 200

discharge (m3/s)

0

25

50

75

100

125δ18O (‰)

-25

-24

-23

-22

-21

-20

-19

-18

-17

SNOWMELT

SUMMERSTREAMFLOW

SNOWPACK

(-18.7)

(-29.0)

Figure 2 Time-series of discharge from the Blackstone River during the spring freshet of 1997

(Water Survey of Canada), and snowmelt discharge based on δ18O of streamflow (grey circles) and surveys of snowpack and summer streamflow.

Isotope Reconstructions from Ice Archives Isotope stratigraphy of river ice is also being developed as an ancillary activity of this MAGS component. As shown in Figure 3, reliable reconstruction of over-winter isotopic composition of streamflow from ice archives has been achieved (see also Gibson and Prowse 1997, submitted). This novel technique will serve to extend partitioning studies into the winter season to study the groundwater recession characteristics in each of the five study basins. The ice-on period is characterized by a gradual decline in total discharge. As shown for the Blackstone River (Figure 3), decline in discharge is accompanied by a prominent isotopic shift to compositions reflecting winter baseflow (groundwater only). A partitioning analysis of surface water versus groundwater contributions will be used to gain a better understanding of freeze-back processes, which are poorly known in discontinuous permafrost terrain.


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Blackstone R.

days since Jan. 1, 1997100 150 200 250 300 350 400 450 500 550

δδ δδ18O

(‰)

-25

-24

-23

-22

-21

-20

-19

-18

-17

reconstructed fromice stratigraphy

ice-off ice-on ice-off

Figure 3 Time-series of streamflow δ18O in the Blackstone River for 1997-98 based on water

sampling and isotope stratigraphy. Reconstruction of water compositions from ice assumes a constant ice-water fractionation of 2.91� obtained by Gibson and Prowse (in press).

Model Comparison Due to appreciable delays in obtaining streamflow and precipitation data, WATFLOOD model simulations of streamflow and components for 1997 are just getting underway. Detailed comparisons of isotopic and modelled contributions to streamflow will proceed, as results from the latter activity become available. 4. Summary Overall, isotope tracers are providing valuable insight into the understanding of basic hydrological processes in complex, discontinuous-permafrost wetlands. Application of isotope techniques such as hydrograph separation, and development of new approaches such as isotope stratigraphy of ice covers undertaken within this component of MAGS, will likely become standard tools for hydrologic investigations in remote and unknown or poorly-understood northern areas such as the Mackenzie Basin. 5. References Craig, D., 1991. �Geochemical evolution of water in a continental high boreal wetland basin:

preliminary results.� In: T.D. Prowse and C.S.L. Ommanney (Eds.), Northern Hydrology, Selected Perspectives, National Hydrology Research Institute [NHRI] Symposium No. 6, NHRI, Saskatoon, Saskatchewan, pp. 47-55.

Gibson, J.J., 1991. Isotope Hydrology and Water Balance Investigations in the Manners Creek Watershed, District of Mackenzie, Northwest Territories. Unpublished M.Sc. Thesis, University of Waterloo, Waterloo, Ontario, 215 pp.

Gibson, J.J., T.W.D. Edwards, G.G. Bursey, and T.D. Prowse, 1993. Estimating evaporation using stable isotopes: quantitative results and sensitivity analysis for two catchments in northern Canada. Nordic Hydrology, 24(3):65-78.


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Gibson, J.J., T.W.D. Edwards, and T.D. Prowse, 1993. Runoff generation in a high boreal wetland in Northern Canada. Nordic Hydrology, 24(3):213-224.

Pietroniro, A., T.D. Prowse, L. Hamlin, N. Kouwen, and R. Soulis, 1996. Application of a grouped response unit hydrologic model in a discontinuous permafrost region. Hydrological Processes, 10:1245-1261.

Pietroniro, A., T.D. Prowse, and V. Lalonde, 1995. Modelling of spring freshet in a muskeg-wetland regime using LANDSAT-TM. Canadian Journal of Remote Sensing, 22(1): 45-52.

Prowse, T.D., 1990. �Northern hydrology: an overview.� In: T.D. Prowse and C.S.L. Ommanney (Eds.), Northern Hydrology: Canadian Perspectives, National Hydrology Research Institute [NHRI] Science Report No. 1, Environment Canada, NHRI, Saskatoon, Saskatchewan, pp. 1-36.

Prowse, T.D., 1986. Ice jam characteristics, Liard-Mackenzie River Confluence. Canadian Journal of Civil Engineering, 13(6):653-665.

Prowse, T.D., 1984. Liard and Mackenzie River Ice Break-up, Fort Simpson Region, N.W.T., 1983. National Hydrology Research Institute [NHRI], Environment Canada Report for Water Resources Division, Department of Indian Affairs and Northern Development, NHRI, Saskatoon, Saskatchewan, 72 p.

Prowse, T.D. and Marsh, P., 1989. Thermal budget of river ice covers during break-up. Canadian Journal of Civil Engineering, 16(1):62-71.

Reedyk, S., Woo, M-K., and Prowse, T.D., 1995. Contribution of icing ablation to streamflow in a discontinuous permafrost area. Canadian Journal of Earth Sciences, 31:13-20.

6. Recent Publications and Presentations Froehlich, K. and Gibson, J.J., 1998. A first-derivative technique for evaluating isotopic exchange

parameters using drying evaporation pans. Hydrological Processes. (submitted) Gibson, J.J., Edwards, T.W.D., and Prowse, T.D., 1998. Pan-derived isotopic composition of water

vapour and its variability in northern Canada. Journal of Hydrology. (accepted Feb/1998, in press) Gibson, J.J. and Prowse, T.D., 1997. �Isotopic characteristics of ice cover in a large northern river

basin.� In: Proceedings, 14th International IAHR Symposium on Ice, July 27-31, 1997, Clarkson University, Potsdam, New York, pp. 196-205. Also, submitted to Hydrological Processes (July 1998).

Gibson, J.J., and Prowse, T.D., 1998. �Water balance trends across northern treeline inferred from isotopic enrichment in lakes.� In: Isotope Techniques in the Study of Environmental Change, International Atomic Energy Agency, Vienna, IAEA-SM-349/22, pp. 204-224.

Gibson, J.J., and Prowse, T.D., 1997. Regional Variations in Water Balance Regime in the Continental Arctic Using Isotopic Tracers. Presented at the Canadian Meteorological and Oceanographic Society, 31st Annual Congress, June 2-5, 1997, Saskatoon, Saskatchewan.

Gibson, J.J., and Prowse, T.D., 1997. Modern Analogues for Interpreting Isotopic Signals Preserved in Organic Sediments of Northern Lakes. Presented at the American Geophysical Union Fall Meeting, Hydrology Special Session H18, December 8-12, 1997, San Francisco, California, USA.

Gibson, J.J., Prowse, T.D., and Pietroniro, A., 1998. Isotopic Portioning of Streamflow in Five Discontinuous-Permafrost Catchments, Mackenzie Basin, Canada. Presented at the Canadian Geophysical Union, May 18-20,1998, Qu�bec City, Qu�bec.

Gibson, J.J., Reid, R. and Spence, C., 1998. A six-year isotopic record of lake evaporation in the Canadian Subarctic: results and validation. Hydrological Processes, 12(8). (in press)

Prowse, T.D., and Gibson, J.J., 1998. Winter Discharge and its Variability in a Northern River. Presented at the Canadian Geophysical Union, May 18-20, 1998, Qu�bec City, Qu�bec.

Prowse, T.D., and Gibson, J.J., 1997. Over-Winter Flow Sources and Variability in the Liard River and its Tributaries: Evidence from Stable Isotope Signatures in River-Ice Profiles. Presented at the 14th International IAHR Symposium on Ice, July 27-31, 1997, Clarkson University, Potsdam, New York.

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Proceedings 4th MAGS Workshop Session 3: November, 1998 Remote Sensing Studies

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3.1 Evapotranspiration and Energy Balance Components from Satellite Data

Normand Bussi��res1 and Raoul Granger2

1Climate Processes and Earth Observation Division, Climate Research Branch, Environment Canada, Downsview, Ontario

2National Water Research Institute, National Hydrology Research Centre, Saskatoon, Saskatchewan

1. Objectives AVHRR satellite data and field measurements for MAGS water year 1994/95 were collected and analysed over the past years by the principal investigator [PI] and collaborators. Objective is to complete the data analysis and the publication of results for 1994/95, including maps of evapotranspiration based on AVHRR data. 2. Progress and Collaborations Data analysis progressed with computations of land/water surface temperature over all 54 AVHRR scenes for 1994 and 29 scenes for 1995. Evapotranspiration analysis with Granger’s feedback algorithm was done on 21 of the 1994 cases. Extensive AVHRR database was shared. It was accessed by other PIs and used in their analysis. Normand Bussières accepted the responsibility to share expertise for the creation of a quantitative AVHRR database for CAGES. Data is received daily from Edmonton HRPT site since June 1998 and is kept and further processed at AES Downsview. Tests were made for a principal investigator data access protocol; a simple WEB access protocol may work for a few AVHRR scenes, but not for PIs who will require large portions of the 40 Gb AVHRR database. 3. Scientific Results Time series of land and water surface temperatures, as well as maps of evapotranspiration were presented at conferences listed below. These data at 1 km resolution serve to determine boundary conditions and verification of key terms in the water and energy balance computations of models over a 2000 km x 2000 km area. The spatial patterns from the AVHRR evapotranspiration algorithm have to be interpreted simultaneously with model outputs. Validation of the split window algorithm for temperature adjustments (6 degree C on average) indicate an over-estimation at higher temperatures. 4. Summary Temperature and evapotranspiration estimated from AVHRR are being developed to set-up boundary conditions and comparisons with MAGS models. Significant effort was made in evaluating AVHRR land surface temperature estimates. 5. Recent Publications and Presentations Bussières, N., 1999. Thermal Features of the Mackenzie Basin from Multiple NOAA AVHRR Sensor

Observations for Summer 1994. Journal of Climate. (draft) Bussières, N., 1998. Canadian Mackenzie Basin GEWEX and Other Cold Climate Studies. Special

seminars presented in Japan, July 14 and 24, 1998 at the Tokyo Institute for Global Change Research; and July 17, 1998 at the Tohoku University, Geophysics Department.


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Bussières, N., 1998. AVHRR Temperatures Time Series for Land Surface Process Modelling. Fourth International Workshop on Applications of Remote Sensing in Hydrology, November 4-6, 1998, Santa Fe, New Mexico.

Bussières, N. and D. Verseghy, 1999. Evaluation of the Water Class Underestimation in an AVHRR Land Cover Classification. Water Resource Research. (draft)

S.O. Ogunjemiyo, N. Bussières, P.H. Schuepp, R.L. Desjardins, and J.I. MacPherson, 1998. Comparaisons entre les cartes des flux d'humidité et de chaleur dérivées de mesures aéroportées et satellitaires pour un écosystème forestier boréal. Le Climat, Vol. 15(1), October.

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3.2 Parameterization of Evaporation/Evapotranspiration

Raoul J. Granger National Water Research Institute, National Hydrology Research Centre,

Saskatoon, Saskatchewan

1. Objectives

��to develop and evaluate parameterizations for the application of remotely-sensed data within operational evapotranspiration models;

��to develop a framework for assessing GCM evapotranspiration algorithms using remotely-sensed regional data in conjunction with operational evapotranspiration models (this remains as a long-term goal, and will be developed once the feedback algorithm has been successfully applied on a large scale);

��to develop new parameterizations for the estimate of lake evaporation using remotely-sensed data.

2. Progress and Collaborations During the 1998 snow-free season, data collection was continued at the Prince Albert and Whitehorse research sites. At the Prince Albert sites, five instrument towers are maintained (at Jackpine, mixed wood, a recent clearcut, a regenerating cut site, and a recent burn). At the Wolf Creek Watershed (Whitehorse), three instrument towers are maintained (at jackpine forest, highbush taiga, and alpine sites). Data from these sites are used for the development and calibration of the remote sensing algorithms used to estimate evapotranspiration. At the Wolf Creek Watershed a smaller basin (Granger sub-basin) was instrumented with three towers (valley bottom, north- and south-facing slopes); the data will be used to develop appropriate parameterizations for the evapotranspiration on sloped surfaces. Note: virtually all techniques and algorithms currently in use were developed for semi-infinite flat planes and do not provide reliable estimates for slopes. For lake evaporation, an analytical solution of advection over lakes (unstable case) was tested against data from the 1993 HEATMEX study (Quill lake); results show that the method is promising for application with remote sensing; however, further analytical development is required for stable cases. Collaboration was maintained with AES Downsview (N. Bussières), with the Prince Albert Model Forest project investigators (Dr. J. Pomeroy, NWRI), and with Wolf Creek investigators (R. Janowicz, DIAND, Dr. D. Gray, University of Saskatchewan). Collaboration was being initiated with Dr. M. K. Woo, University of Waterloo, for the development parameterizations of evapotranspiration and sensible heating on sloped surfaces (study in the Wolf Creek Basin). 3. Scientific Results Lake Evaporation: Data from the 1993 HEATMEX study of Quill Lake, Saskatchewan, along with data from a concurrent energy balance study adjacent to Quill Lake, were used to test the applicability of analytical solutions to the advection over water for the estimate of lake evaporation. The numerical study done by Weisman and Brutsaert (1973) was used. Although, it was only done for the unstable case (lake temperature greater than land temperature), it was deemed of interest for application to remote sensing, since the approach makes use of the surface parameters (i.e., those available through remote sensing). The results of the comparison indicate that the approach works well for the unstable situations (night-time) for which the numerical analysis was done (Figure 1). Application to remote sensing will require further work: numerical modelling of advection during the stable day-time situations, and development of appropriate algorithms for use with satellite data.


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Figure 1 Comparison of estimates of evaporation from Quill Lake using the Weisman-Brutsaert

numerical analysis (W-B) with evaporation derived from profile measurements over Quill Lake and evapotranspiration over the adjacent land surface, for three days in 1993.

Analysis of the 1998 Data: Analysis of the 1998 data from the north- and south-facing slopes of the Granger sub-basin at Wolf Creek has just begun. Preliminary examination of the data indicates that, although screen-height air temperatures (upon which many flux algorithms are based) are relatively similar for both surfaces, there are, or can be, large differences in the other important parameters (wind speed, humidity, surface temperatures, soil temperatures) and in the fluxes of sensible and latent heat from these surfaces. The relationship between sensible heat flux (observed with eddy correlation equipment) and the temperature gradient is different for the north- and south-facing slopes, indicating that the parameterizations required for estimating the sensible (and latent) heat fluxes will be different for the two surfaces. Analysis of the data will continue with the objective of developing appropriate parameterizations. A comparison of the significant parameters for the two slopes was presented at the GEWEX workshop (November 1998). Applicability: Remote sensing of lake evaporation will be of significant value to MAGS, since the basin includes several large water bodies. A significant portion of the Mackenzie Basin is covered by mountainous terrain, and these are the major sources of runoff in the basin; a better understanding of the land surface fluxes on surfaces with significant slopes and an improved capability for estimating these is required. 4. Summary Results of a numerical analysis of advection of water was compared successfully with evaporation over Quill Lake (HEATMEX study 1993); the results to date are only applicable during unstable conditions (lake temperature greater than air temperature). Further numerical analysis is required for the stable case. The method shows some promise for application with remote sensing since it makes use of the observable surface parameters.

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A study of the partitioning of energy and turbulent fluxes of latent and sensible heat on sloped surfaces was begun. Preliminary analysis confirms that the significant parameters and fluxes are different for north- and south-facing slopes, and that distinct parameterizations are required for sloped surfaces. 5. Recent Publications and Presentations R.J. Granger, 1998. The Feedback Approach for the Estimate of Evapotranspiration Using Remotely-

Sensed Data. Presented to the International Workshop on Remote Sensing estimation of Evapotranspiration, April 1-3, 1998, Menemen, Turkey.

R.J. Granger, 1998. Partitioning of Energy During the Snow-Free Season at Wolf Creek Research Basin. Presented to the Wolf Creek Research Basin Long-term Planning Workshop, March 5-7, 1998, Whitehorse, Yukon. (In: Proceedings, in press)

R.J. Granger, 1998. A New Remote Sensing Approach to the Estimate of Lake Evaporation. Presented to the Fourth International Workshop on Applications of Remote Sensing in Hydrology, November 4-6, 1998, Santa Fe, New Mexico. (In: Proceedings, Hydrological Processes, special issue, in press)

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3.3 Surface Radiation Budgets in the Mackenzie River Basin

Henry Leighton Dept. of Atmospheric and Oceanic Sciences, McGill University, Montr�al, Qu�bec

1. Objectives

��To obtain shortwave radiation budgets at the top of the atmosphere and at the surface for the MAGS region, with particular emphasis on the 1994-95 and 1998-99 (CAGES) water budget years.

��To compare the radiation budgets derived from the satellite data with surface observations and with budgets generated by the atmospheric models.

��To evaluate the significance of the differences between the satellite-derived budgets and the model-generated budgets on the hydrology of the basin.

2. Progress and Collaborations There are two sources of data that are useful for generating radiation budgets for MAGS, the AVHRR on the NOAA polar orbiting satellites and data from the ScaRaB instrument. The AVHRR data from the polar orbiters offer the advantages of more than one pass over the MAGS region each day and of long-term continuity of coverage. They have the disadvantage that the data are narrowband and not well calibrated. ScaRaB, on the other hand, has both a well-calibrated broadband channel that covers the whole solar spectrum, and a narrowband channel that approximately corresponds to the AVHRR visible channel. The first ScaRaB instrument (FM1) was mounted on the Russian Meteor-3 satellite on an inclined orbit and so provides useful coverage over MAGS for some periods and poor coverage at others. The FM1 only functioned for about one year from March 1994 to February 1995. In July of this year the second ScaRaB instrument (FM2) was successfully placed in orbit on the Russian Ressurs-01/4 satellite, in this case in a sun-synchronous polar orbit. Our approach is to use data from the ScaRaB instruments to calibrate the AVHRR data. We will then use combined ScaRaB and AVHRR data to generate top-of-the-atmosphere (TOA) solar radiation budgets. From the TOA data we will use techniques that we have developed for use with previous earth radiation budget data to produce the surface radiation budgets. New narrowband to broadband conversion functions have been developed from the coincident narrowband and broadband ScaRaB data. The relationships take into account the solar and viewing solar zenith angles, the land surface type and the cloud cover, and are focused on the MAGS region. Based on radiative transfer calculations, theoretical transfer functions are being developed to relate AVHRR narrowband radiances to ScaRaB narrowband radiances. These transfer functions are being compared with the results from simultaneous and coincident AVHRR and ScaRaB measurements (not limited to the MAGS region). The relationships between AVHRR narrowband and ScaRaB narrowband radiances and between ScaRaB narowband radiances and ScaRaB broadband fluxes allows one to deduce broadband fluxes from AVHRR radiances. We have been proceeding in parallel on improving and verifying the procedures for deriving the TOA fluxes over MAGS, while at the same time applying the techniques described above to the AVHRR data that has been assembled by Bussières for the 1994-95 water year. Surface fluxes will be deduced from the TOA fluxes by the methods described in Li et al. (1993) and Masuda et al. (1995). We anticipate that we will have generated TOA and surface fluxes for the portion of the 1994-95 water year, for which AVHRR data are available by the end of January 1999. AVHRR data for CAGES is being assembled in Downsview by Bussières and its dissemination is imminent. The ScaRaB data from FM2 will also start to be disseminated to ScaRaB science team


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members shortly. As soon as these data are available we will start processing the data to generate radiation budgets for CAGES. We are collaborating closely with the German group based at GKSS, headed by Dr. Rolf Stuhlmann, which is undertaking a similar study for BALTEX. Dr. Stuhlmann and one of his students, Rainer Hollmann, have visited McGill to join forces on this work several times. One of my students, Jian Feng, is spending two months at GKSS (October-December 1998) where he is taking advantage of their data analysis facilities and extensive satellite data. I am confident that this very beneficial collaboration between our groups will continue. It has led to several joint conference presentations and joint journal articles are being planned. The success of this work is dependent on the close collaboration and good will that we enjoy from Normand Bussières. Normand is assembling an archive of satellite data in a format that is convenient for the other MAGS researchers and is disseminating that data. We have had countless communications about the satellite data. As we get beyond the stage of data processing and into the stage of comparing the satellite derived radiation budgets with surface observations and the models, and then to assessing the importance of these differences, we expect to broaden our collaborations to other members of the MAGS team. 3. Scientific Results As indicated above, we are now at the point where we are starting to generate solar radiation budgets from AVHRR data for MAGS for 1994-95. In order to be confident that the AVHRR results are consistent with the ScaRaB data, we need to compare co-located and coincident ScaRaB and AVHRR data. Unfortunately, there are no such coincidences for the MAGS region from the FM1. However, there are a few cases of reasonably close coincidences over the BOREAS experiment region. The BOREAS experiment was conducted in 1994 in a region to the south of the MAGS region. AVHRR data have been archived for BOREAS and so we are able to compare the TOA fluxes from the AVHRR and the ScaRaB FM1 for BOREAS. Figure 1 shows such a comparison for July 24, 1994. Apart from the obvious differences, due to the greater spatial resolution of the AVHRR pixels, there seems to be good correspondence between the fluxes. Figure 2, which summarizes the differences in the fluxes deduced from the two instruments, shows only small departures from the one-to-one line. A few other similar cases are available from BOREAS, but with poorer time coincidence and so greater deviations in the results from the two instruments. We are collaborating with our colleagues at GKSS to look at many more pairs of AVHRR and ScaRaB data sets and, hence, a much more complete validation of the AVHRR fluxes. This work is clearly focused on the MAGS region and will be very useful in evaluating the fluxes deduced from the atmospheric models. In spite of its focus on MAGS, we anticipate that the procedures that we are developing will be broadly applicable.


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Figure 1 Comparison of TOA fluxes from the AVHRR and the ScaRab FM1 for BOREAS for

July 24, 1994.

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Figure 2 Differences in the fluxes deduced from the two instruments, the AVHRR and the

ScaRaB FM. 4. Summary Knowledge of the surface radiation budgets is essential to understanding the energy and water budgets of the Mackenzie Basin. The variability of the surface solar radiation budget is great and cannot be captured from surface observations. Techniques exist that allow the surface budgets to be deduced from satellite measurements of the outgoing fluxes. We are applying these techniques to TOA fluxes deduced from two types of instruments: a broadband radiometer, ScaRaB; and, the narrowband AVHRR. We are now at the stage where we are generating surface radiation budgets for MAGS. 5. References Li, Z., H.G. Leighton, K. Masuda, and T. Takashima, 1993. J. Climate, 6:317-330. Masuda, K., H.G. Leighton, and Z. Li, 1995. J. Climate, 8:1615-1629. 6. Recent MAGS-Related Publications and Presentations Feng, J., R. Hollmann, J. Müller, R. Stuhlmann, and H.G. Leighton, 1998. Solar radiation Budgets for

MAGS and BALTEX. In: Proceedings of the 9th Conference on Satellite Meteorology and Oceanography, Paris, France, pp. 283-286.

Hollmann, R., J. Feng, H.G. Leighton, J. Müller, and R. Stuhlmann, 1998. Application of Broadband Fluxes from Scarab to BALTEX and MAGS. Presented at the 32nd COSPAR Scientific Assembly, Nagoya, Japan.

Hollmann, R., J. Feng, J. Müller, H.G. Leighton, and R. Stuhlmann, 1998. Application of Broadband Fluxes from ScaRaB and AVHRR Narrowband Radiances to BALTEX and MAGS. In: Proceedings of the 9th Conference on Satellite Meteorology and Oceanography, Paris, France, pp 114-117.

Leighton, H.G., J. Feng, R. Hollmann, J. Müller, and R. Stuhlmann, 1999. Solar Radiation Budgets for MAGS and BALTEX. To be presented at the ALPS99 Symposium Working Group on Clouds and Earth Radiation Budget, Meribel, France.

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3.4 Snow Cover and Lake Ice Determination in the MAGS Region Using Passive Microwave Satellite and Conventional Data

Anne Walker, Arvids Silis, John Metcalfe, Michael Davey,

Ross Brown, and Barry Goodison Climate Research Branch, Atmospheric Environment Service, Downsview, Ontario

1. Objectives This study investigates snow cover variations in the Mackenzie Basin using conventional and remotely sensed data. The main focus is on the determination of snow water equivalent (SWE) and extent from SSM/I satellite passive microwave radiometer data, incorporating variations in surface land cover. The main objective for FY 98/99 is to test and evaluate new forest SWE algorithms that were developed by the investigators using airborne microwave data acquired over the BOREAS northern and southern boreal forest study sites. SWE maps for the MAGS region will be produced using these algorithms and SSM/I EASE-Grid data (25 km resolution). The derived SWE information will be validated using data from existing snow courses, station data, and snow surveys conducted at the MAGS research basins by other investigators. Based on the results of the SSM/I SWE algorithm testing and evaluation, a strategy for additional snow survey requirements for the MAGS study area during CAGES will be prepared. The lake ice component of this investigation focuses on assembling a time series of Great Slave Lake and Great Bear Lake ice freeze-up and break-up using historical SSM/I 85 GHz data for the period 1987 to present. The time series will consist of a series of images for each lake documenting each ice freeze-up and break-up season during the time period and providing dates corresponding to complete freeze-over and ice-free conditions for each year. During FY 98/99, activities will focus on generating lake ice freeze-up and break-up maps for the two target lakes using available SSM/I EASE-Grid data and performing initial analyses of spatial and temporal variability. 2. Progress and Collaborations Snow Cover: The testing/evaluation process for the SSM/I SWE forest algorithms required the availability of SSM/I EASE-GRID brightness temperature for the target time periods (1994/95 water year) and land cover information corresponding to EASE-GRID 25 km grid. In early summer 1998, NSIDC agreed to process the USGS/IGBP 1 km global land cover data set onto the EASE-GRID format and the resulting EASE-GRID-based land cover data set was provided to us in July 1998. For each 25 km EASE-GRID grid cell, the fractions (percentages) of each of the 17 USGS/IGBP land cover classes present within the grid cell are provided within this data set. Around the same time, we also received the SSM/I EASE-GRID brightness temperature data sets for the period December 1991 to May 1995. EASE-GRID brightness temperature data files were extracted for three periods in winter 1995 (February, March, April) that were previously identified as having good conventional data records. The SSM/I SWE forest algorithms were applied to these brightness temperature data sets, with the weighting of each algorithm (open, sparse forest, deciduous forest, coniferous forest) determined using the land cover percentages contained EASE-GRID land cover data set. The SWE values resulting from each algorithm run were contoured and mapped over the MAGS study region and compared with the conventional SWE measurements from the snow course data sets. For the forested areas of the basin, the SSM/I SWE values were generally higher than values produced previously using the prairie SWE algorithm, but were still lower than the snow course measurements, especially in the area of Fort Simpson and south of Great Slave Lake. The SSM/I SWE forest algorithms


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do not take into account forest density, which may be another factor that needs to be incorporated into the algorithm and will be examined using NOAA AVHRR visible imagery. Discussions were held over the past several months with Phil Marsh and Al Pietroniro regarding access to the snow survey data they have acquired during the past few years at their MAGS research sites. Both agreed to provide us with their snow measurements to help with our SWE algorithm validation. Another topic addressed during the discussions was their plans for snow surveys at their MAGS study sites during the CAGES time period. Both investigators indicated that they plan to conduct snow surveys at their sites during Spring 1999. A meeting on CAGES snow survey plans and requirements will be held during the MAGS science workshop in Montr�al. Another area of collaboration has been the 1994/95 water year study. Information on snow cover characteristics during the 1994/95 water year are being compiled. An analysis of conventional snow course data for the different sub-basins indicated that the maximum SWE values for April 1, 1995 were close to the average value for the period of record for these stations. Further analyses will focus on the areal coverage of snow over the basin and the SSM/I-derived SWE. Lake Ice: Generation of the Great Slave and Great Bear lake ice maps continued using the available SSM/I EASE-Grid data (up to May 1995). The following freeze-up and break-up seasons have been produced for both lakes to date: Freeze-up: 1988, 1992, 1993, 1994 Break-up: 1988, 1992, 1993, 1994 The years 1989 to 1991 are missing due to a data gap in the SSM/I EASE-Grid dataset. The 85 GHz data were not processed into EASE-Grid format for these years, due to the degradation of the 85 GHz vertical polarization channel in early 1989. The 85 GHz horizontal polarization data are generally more reliable over this time period. Options to fill in this data gap are being investigated. Analysis of the freeze-up and break-up process for the two lakes for seasons beyond 1994 have been conducted using SSM/I orbital data available in near real-time from the CMC operational database. Of particular note was the 1998 break-up season, where both lakes were clear of ice approximately three weeks earlier than usual due to the effects of El Nin�. SSM/I EASE-Grid data for June 1995 to early 1998 will be acquired from NSIDC during the next couple of months and the lake ice time series of freeze-up and break-up images will be extended to cover at least the 1995, 1996, and 1997 seasons. 3. Scientific Results The following figure presents the lake ice freeze-up and break-up time series for Great Slave Lake and Great Bear Lake for 1988 to 1998, based on the analysis of SSM/I EASE-Grid data sets and near real-time orbital data. The graphs illustrate the inter-annual variability in the timing of the ice-free (break-up) and complete ice cover (freeze-up) conditions for both lakes. Of particular note is the timing of the 1998 break-up, where Great Slave Lake exhibited “ice-free” conditions at the end of May and Great Bear Lake the end of June. In both cases, these dates are several weeks earlier than usual, where in most years the lakes are just beginning the break-up process at these times. A comparison with shore-based observations of freeze-up and break-up at Back Bay near Yellowknife is provided with the Great Slave Lake ice data. This comparison shows that freeze-up and break-up for the main body of the lake occurs several weeks after the Back Bay observations. The difference in this timing is important knowledge for any modelling activities where the timing of ice freeze-up and break-up are used as input to the model; the incorporation of the conventional data into such a model will not be representative for the entire lake body.


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4. Summary The snow cover and lake ice components of this investigation are progressing towards their respective objectives. In both cases, progress over the past few years has been affected by the availability of SSM/I EASE-Grid data from NSIDC. The recent acquisition of the data up to May 1995 and the impending acquisition of the June 1995 to 1998 data will speed up the progress significantly, especially with respect to the lake ice objectives. The SSM/I SWE forest algorithm testing will continue focused on the historical EASE-Grid SSM/I data sets (1987/88 winter to 1994/95 winter) and available conventional snow cover measurements. An additional investigation into the influence of forest cover density on the SSM/I SWE retrievals will be initiated during the remainder of FY 98/99, with the objective of developing a methodology for incorporating this characteristic in the forest algorithm. 5. Recent Publications and Presentations A presentation on the SSM/I lake ice freeze-up and break-up work, entitled Lake Ice Monitoring Using Passive Microwave Satellite Data – Current Capabilities and Future Potential, was given by Anne Walker at the Canadian Ice Service on September 18, 1998.

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Break-up Date

GREAT BEAR LAKE ICE FREEZE-UP & BREAK-UP DATES

13-Nov

22-Nov28-Nov

30-Nov

20-Nov10-Dec

15-Oct 25-Oct 4-Nov 14-Nov 24-Nov 4-Dec 14-Dec 24-Dec

1988198919901991199219931994199519961997

Freeze-up Date

SSM/I (Entire Lake)

18-Jul

15-Jul

19-Jul

5-Jul

15-Jul

30-Jun

14-Jun 24-Jun 4-Jul 14-Jul 24-Jul 3-Aug

1988

1989

1990

1991

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1995

1996

1997

1998

Break-up Date


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3.5 Satellite Rainfall Estimates Over the Mackenzie Basin

I. Zawadski1, A. Bellon1, M. Ravivarma, and R. Laprise2

1J.S. Marshall Radar Observatory, MacDonald College, Ste Anne-de-Bellevue, Qu�bec 2Universit� du Qu�bec � Montr�al, Montr�al, Qu�bec

1. Objectives The initial objective of our contribution to the MAGS project was to apply the RAINSAT technique to GOES data in order to derive monthly precipitation estimates over the Mackenzie Basin. It soon became apparent after the first year of research, that such an approach can be skillful only during the summer months. Consequently, the emphasis of our research was redirected towards the validation and tuning of regional climate models (RCM) in order to improve their ability to correctly diagnose areas of precipitation. Fine-scale observations of precipitation as can be provided by radar will constitute the ultimate verification field. 2. Progress and Collaborations Monthly RAINSAT rainfall estimates during the summer months (June, July, and August) for the last three years have been favourably compared with the corresponding analysis of surface rainfall. The latter is an experimental product combining point gauge rainfall measurements and model forecasts made available to us by Richard Hogue of the Operational Services Division of the Canadian Meteorological Centre (CMC). Recently, Ekaterina Radeva of CMC found that the ensemble predictions of their spectral model coupled with CLASS nicely fit the RAINSAT satellite estimates. An article is being prepared on this topic. We continue to rely on the availability of Carvel radar data, being sent to us by Richard Serna of the Alberta Forecast Office, needed for calibrating the GOES visible and IR data that are archived for us by Arnie Alfheim of RPN. As a result of the change in emphasis of our research, we are collaborating with Prof. René Laprise of the Université du Québec à Montréal in co-supervising a Ph.D. student, who is investigating the predictability skill of the RCM in delineating areas of precipitation. 3. Scientific Results Validation of the Canadian Regional Climate Model (Ravivarma, Zawadzki, and Laprise) Regional Climate Models (RCM) are widely used to study the climatology of a limited region on the globe at high resolution with the help of GCM simulated fields as initial and boundary conditions. In particular the Canadian Regional Climate Model (CRCM) is widely used within the Canadian contribution to GEWEX. Since the RCM simulated fields contain mesoscale structures, which were not present in the driving GCM fields, it is important to establish how realistic these structures are. As a first step toward a validation of the CRCM we took the following approach:

1) We use the analysis of a high resolution CRCM run (35 km grid spacing) over a domain of (4830-km)2 as the control run. The RFE model (35 km resolution) provides initial and boundary conditions for this run. This run will be called RCM1.

2) A Fourier truncation of the analysis provides coarse fields such as could be given by a GCM (225 km grid spacing km in our case).

3) The resulting coarse fields are used as initial and boundary conditions of a new CRCM run with 35 km resolution over a domain of (4120 km)2. This run will be called RCM2.


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4) RCM1 and RCM2 simulations are compared with each other and the growth of their difference with time can be a measured at all scales. This provides a measure of how realistic the small-scale features of the RCM simulations are.

The validation can be done on a case-by-case basis (model used as a forecast or as a diagnostic) or in a climatological sense. Preliminary results from this study using the CRCM are given in Figures 1 and 2. The comparison here is done on spectral domain, which will help us to decompose the fields into different scales and to study the growth of error in each scale present in model simulations. A fast Fourier transform technique to compute the spectra of the fields over a limited-area domain is employed to get these results. The simulation was done during the period of January 9-12, 1996 over the Mackenzie River Basin during the passage of an eastward-moving cyclone, which produced a considerable amount of precipitation over the Mackenzie Basin. Figure 1(a) gives the vertically integrated spectrum of geopotential height field from the CMC analysis (using RFE) at the initial time of CRCM run. The corresponding spectrum after 24 hours is shown in Figure 1(b) along with the spectrum of the model simulated geopotential height field (RCM1, in dashed lines) and the spectrum of the difference field (in dotted lines). Similar figures for the integrated spectra of kinetic energy (KE) are also depicted in Figures 1(c) and 1(d).

Figure 1 (a) Vertically integrated spectrum of geopotential height (GZ) field at the initial time

(00 hrs. January 9, 1996). (b) Same as in (a) after 24 hours; solid line is for CMC (RFE) analysis field which drives the RCM1, dashed line if for RCM1 simulated field and dotted line is the spectrum of the difference field between the two. (c) Same as in (a) for the KE from the wind fields (u and v). (d) Same as in (b) for KE.


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The relative error variance at various scales for the CRCM run with high resolution initial and boundary conditions (RCM1), when compared with the driving CMC analysis, is shown in Figure 2(a). The corresponding figure for the CRCM run with low resolution of the initial and boundary conditions (RCM2), when compared with the RCM1 simulation is shown in Figure 2(b). Thus, values well below unity indicate good predictability while values above one represent no skill at all. The sharp jump in the error variance for the RCM1 in Figure 2(a) at around 100 km is due to the distortion of the spectrum of GZ from the CMC analysis as seen from Figure 1(a) and 1(b). At small scales, there is an unrealistic variance present in CMC analysis. However, it is not present in the CRCM simulations and that contributes to the error. Figure 2(b) does not show this behavior because the comparison is done between RCM1 and RCM2. It can be concluded from Figure 2(b), that the small scales present in CRCM show considerable predictability. However, the relative error variance grows with time for all scales. It is to be noted that the peak of the error variance are at the scales just below the minimum scale present at initial time (~450 km), that is at the jump between the nesting and the nested models.

Figure 2 (a) The relative error variance with scale (wavelength) present in CRCM simulation 1

(RCM1), at different times, when compared to the driving RFE (35 km scale CMC analysis). Error variance at each scale is normalized by the variance at that scale of RCM1. The simulation hour corresponding to each line is as indicated. Relative error variance of 1 means that error has the same variance as the simulated field itself and the simulation becomes useless. (b) The same as in (a) but for the CRCM simulation 2 (RCM2) when compared to and normalized by RCM1.


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In future studies, importance will be given to the effects of lateral boundary conditions on the simulations using RCM. Advection may be playing a very important role in the simulations of small scales by RCM besides the physics in the model, as well as the effects of topography and other surface inhomogeneities. All these may be case dependent too and should be studied on a number of cases. RCM will also be used to study the monthly climatological simulations instead of case to case simulations. In this study, we just considered the skill of RCM in reproducing the fine scale structure regardless of the scales present in the boundary conditions. The jump in scale between the nested and the nesting model must be optimized for best predictability (we have used here the scale factor usually used in RCM runs). The final validation of the model will be made by comparison with fine scale observations, such as provided by radar data

Rainsat Rainfall Estimates over the Mackenzie River Basin (Bellon and Zawadzki)

As with the '96 and '97 data, we have continued to compare the monthly GOES/RAINSAT estimates with the CMC analysis of surface precipitation. The latter are derived from a combination of point gauge measurements and of 0-6 hr model forecasts. After calibrating the (VIS,IR) measurements with 30-minute rainfall accumulations obtained from the Carvel radar located in the southernmost part of the basin, we have estimated 1-day accumulations over the entire basin using a (VIS,IR) - rainfall rate relationship during the daylight hours and an "IR only" relationship during the night. The 1-day accumulations are then simply added to derive monthly totals, with a multiplicative factor being applied to account for any missing days.

However, a series of setbacks beyond our control occurred this year that rendered the monthly estimates of lesser quality than those from the two previous years. Large gaps in the satellite archival records occurred before May 18, precluding any complete analysis for that month. Then, during the month of July, the quality of the GOES-9 data began to deteriorate to such an extent that, by July 27, it had to be replaced by GOES-10, which at that time was located at 105º W longitude. It did not arrive at its station of 135º W longitude until August 21st. Moreover, at the moment of analysis, the calibration parameters relating IR counts for GOES-10 to temperature were not known; therefore, those for GOES-9 have been used. Finally, a 4-day gap also occurred from August 27 to 30 inclusively, adding to the uncertainty for the estimates of that month. Data gaps totaling 2 and 3.5 days also occurred in each of the months of June and July, respectively. Table 1 MC-RAINSAT comparisons of monthly rainfalls over the Mackenzie River Basin

performed at 16 km resolution. The scores obtained by adjusting the RAINSAT estimates according to the observed bias are provided in parenthesis.

VIS,IR Rain Bias COEFF % MAD % RMSD

JUNE '98 63 0.82 0.64 37 (36) 52 (47)JULY '98 54 0.85 0.51 35 (34) 48 (44)AUG '98 32 1.40 0.43 57 (44) 68 (54)

Avg 0.52 43 (38) 56 (48)IR only - JJA '98 0.49 (39) (49)

VIS only - JJA '98 0.54 (37) (48)VIS-IR - JJA '97 0.63 (29) (41)IR only - JJA '97 0.52 (32) (45)VIS-IR - JJA '96 0.55 (32) (41)IR only - JJA '96 0.46 (33) (42)


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As shown on Table 1, the comparison at 16 km resolution over the area of the Mackenzie basin in terms of the usual parameters (MAD: Mean Absolute Difference, RMSD: Root-Mean-Square Difference and cross-correlation coefficient COEFF), reveals a noticeable reduction in skill compared with the '97 results. Because we are not dealing with real-time forecasts and since we seek to determine the extent with which the RAINSAT estimate can reproduce the pattern of rainfall rather than the absolute quantities of rainfall, we concentrate on the statistics from which the bias has been removed (in parenthesis on Table 1). The mean correlation coefficient drops from 0.63 in '97 to 0.52 this year and the %MAD and %RMSD increase from 29 to 38 and from 41 to 48, respectively. A comparison in terms of a scatter plot between the RAINSAT and CMC estimates is provided in Figure 3 where, again, the tendency of the RAINSAT algorithm to underestimate the more intense rainfalls is clearly evident.

Figure 3 Scatter diagram of the CMC analysis of precipitation and of the corresponding

RAINSAT estimates for June to August 1998, inclusively, performed over areas of (48 km)2 over the Mackenzie Basin. Solid line is the least squared fit; dashed line is the 1:1 ratio.

While for the '96 and '97 results the comparison of RAINSAT estimates and CMC analysis was good, with a number of coinciding minima and maxima, this year's results of the comparisons, as exemplified in Figure 4 for the month of June, are less satisfactory. The general maximum in Southern Alberta and the broad band of minimum rainfall north of it, extending from a region between Lake Athabasca and Lake Great Slave to Central British Columbia, are in reasonable agreement. However, the sharp circular


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maximum in northeastern BC is totally absent from the RAINSAT estimates. A similar circular maximum in the CMC analysis also occurred during the month of July, suggesting perhaps a possible problem on the analyses caused by spurious gauge data. The smaller, but distinct, maximum in the northern branch of the Great Slave Lake present in the CMC analysis is likewise totally missed by the RAINSAT technique. Another area of rainfall maximum between the Great Bear and Great Slave lakes; however, appears on both maps, but the CMC analysis includes an additional elongated maximum southwest of Great Bear Lake that is absent on the RAINSAT map. Color examples of the comparison for July and August '98 were discussed at the workshop.

Figure 4 RAINSAT rainfall estimates for June ’98 overlaid with the CMC analysis of surface

precipitation in contours. The small labels refer to the RAINSAT gray shade levels, while the larger labels refer to the contoured analysis from CMC.

Returning to Table 1, previous work has shown that the "IR only" technique generally displays lesser skill, but is only marginally less skillful than the VIS,IR technique when corrected for bias. In fact, for about 45% to 60% of the time depending on sun angle, an "IR only" algorithm has to be used for 1-day accumulations. However, it is possible that the inclusion of the IR information, which is at a coarser resolution than the visible, may reduce the skill inherent in the visible measurements. An investigation by King et al. (1995) has shown that the Canadian RAINSAT technique proved to be superior to other techniques mainly because it includes visible data in its algorithm. We have followed one of their


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suggestions and attempted to derive 1-day accumulations using only the visible information and accounting for the missing data by multiplying the "VIS only" estimates by the ratio (24/daylight hours). The results of this approach are included as part of Table 1. Even though it effectively makes use of less than half of the available data, the skill of such a procedure is nonetheless similar to the basic "(VIS,IR) and IR only" technique based on 24 hours of data. (The skill of a (VIS,IR) technique extended over a 24-hour period by the appropriate ratio is currently being determined and the results presented at the workshop).

References King, P. W. S., W. D. Hogg, and P. A. Arkin, 1995. The role of visible data in improving satellite rain-

rate estimates. J. Appl. Meteor., 34:1608-1621.

4. Summary The comparison of RAINSAT monthly estimates with CMC surface analyses for the months of June, July, and August of the past three years has resulted into a correlation coefficient of the order of 0.5 to 0.6, a mean absolute difference ranging from 30 to 40% of the mean rainfall over the basin and an RMS difference of 40 to 50%. The skill of the RAINSAT procedure is limited by its tendency to underestimate the more intense rainfalls. The availability of a radar data training set in a more northerly section of the Mackenzie Basin, than that currently provided by Carvel, would improve the skill obtained so far, but the dependence on an "IR only" algorithm at night remains a major limitation. A preliminary investigation on the predictability of precipitation at the smaller scales using the Canadian Regional Climate Model (RCM) has revealed a good skill at reproducing the small scales regardless of the resolution of the initial input and of the boundary conditions. At least close to 50% of the variability at small scales. This implies that the physical processes causing a cascade of energy from the larger to the smaller scales proceed in a consistent manner, lending some credibility to the patterns being generated. The poor skill at scales in the range where the scale jump between the nesting and the nested model occurs needs further investigation.

5. Recent Publications and Presentations The RAINSAT procedure is based on previously published research, see King et al. (1995) and its implementation over the MAGS area was not expected to constitute by itself original work. The efforts by Radeva alluded earlier; however, may result in a publication.

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3.6 (a) IPIX Radar Activities in Support of CAGES

Simon Haykin1, Brian Currie1, David Hudak2, Ron Stewart3, and Bob Kochtubajda4

1Communications Research Laboratory, McMaster University, Hamilton, Ontario 2Atmospheric Environment Service, King City, Ontario

3Atmospheric Environment Service, Downsview, Ontario 4Environment Canada, Edmonton, Alberta

The provision of the surface-based radar operations for MAGS/CAGES is a cooperative effort between McMaster University and AES. The joint leads are Brian Currie of McMaster (under the overall leadership of Dr. Simon Haykin of McMaster University), responsible mainly for the radar sensor, and David Hudak of AES, responsible mainly for radar meteorology issues. 1. Objectives The Communications Research Laboratory (CRL) of McMaster University is operating its IPIX radar during the intense operating periods (IOP) of CAGES. The fully coherent radar operates at X-band (9.4 GHz, 3.2 cm wavelength), providing Doppler measurements, and offers dual-linear polarization with pulse-to-pulse switching on transmit to permit measurements of the full scattering matrix. McMaster personnel are heavily involved in calibration, accuracy and precision issues related to the measurements. They are working closely with AES personnel in the design and execution of the field experiments. The operational strategies and corresponding data measurements that were employed in the first CAGES IOP in Fort Simpson, NWT, are discussed below. Together with AES personnel, the intention is to collect radar data with which to study the quantitative estimation of precipitation, precipitation formation mechanisms, and mesoscale wind patterns in the Fort Simpson area of the Mackenzie Basin. One of Dr. Haykin’s students, Hugh Pasika, has been studying the use of data fusion techniques to combine the measurements from a number of sensors to improve the prediction of cloud base height. Although Mr. Pasika is about to complete his own studies, his techniques may have application to radar, satellite, radiosonde, other measurements, and numerical modelling information during CAGES to provide better characterization of various meteorological parameters. McMaster has had extensive experience in the characterization of nonlinear dynamic systems (such as turbulence) using chaos theory. Special data sets of the radar returns from rain and snow, collected during CAGES IOP-1, will be analysed to determine if they admit chaotic behaviour. 2. Progress The primary objective for 1996/97 was to purchase and install a new transmitter tube into the IPIX radar. The tube was ordered in May 1997, and delivered in March 1998. Installation had to be undertaken outdoors (requiring warm, dry weather) and took place in July 1998 after the radar returned to the Canada Centre from Inland Waters (CCIW) from off-site experiments. Installation and preliminary testing have been satisfactorily completed. The main objectives for 1997/98 were (i) the preparation of the radar for CAGES field use; (ii) transportation to and installation of the system at Fort Simpson airport (including initial testing); and, (iii) execution of two CAGES IOPs (fall and early winter 1998). All objectives scheduled to date have been met as described below. The second CAGES IOP is scheduled to start December 2, 1998.


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System preparation For the period from December 1997 to early March 1998, the radar system was located in Grimsby, Ontario, on a shore site overlooking Lake Ontario. The system was used for two purposes: to conduct studies into radar returns from the lake surface (supported under separate funding), and to prepare and evaluate various radar data collection techniques for CAGES. There was a significant learning curve in the understanding and use of the radar, both for Brian Currie of McMaster (who has taken over responsibility for its operation from Vytas Kezys), and for Dave Hudak of AES. In consultation with Mr. Kezys, radar control and data collection routines were modified specifically for CAGES use, and tested at the Grimsby site. Also at Grimsby, radar data were collected in support of an AES aircraft icing study being conducted under the direction of Dr. George Isaac. The NRC Convair 580 research aircraft overflew the Grimsby radar site, providing in-situ verification of cloud particle properties. The data are still being analysed. The system was moved to CCIW from March until early August 1998. During this period, significant effort was expended in continuing to finalize the CAGES operational techniques, system calibration, installation and testing of the new transmitter tube, and preparation of the system for shipment to Fort Simpson. Transportation and installation in Fort Simpson The two trailers that comprise the radar system (a 40-foot laboratory trailer and a 15-foot antenna trailer) were transported from CCIW to Fort Simpson using rail car and flat-bed truck over the period August 11 to 27. The radar arrived in Fort Simpson on August 28th, a few days later than expected. Brian Currie and Dave Hudak were in Fort Simpson from about August 21 to September 4. The first few days were spent making local contacts and making arrangements for installation of power and phone service. Once the radar arrived, it took several days to unpack, position and level the antenna trailer, cable the trailers together, and connect and test the computers and radar system. Some preliminary data collection was performed to confirm operations. A suitable balloon inflation enclosure for the radiosonde operations was also located, and arrangements made to have it installed before CAGES IOP-1. CAGES IOP-1 Brian and Dave arrived in Fort Simpson on September 18th to begin preparations for the CAGES IOP-1. Much of the first few days was spent in continuing to confirm proper radar hardware and software operation, and establishing data collection and archival (i.e., CD burning) logistics. Significant effort was also applied to assisting the radiosonde personnel (Richard Poersch and Chris Fogarty) to get their system installed in the radar trailer, and in troubleshooting the radiosonde equipment. The CAGES IOP-1 began formally on September 23rd (local time) once the radiosonde system was (more or less) operational. Radar operations continued until the end of CAGES IOP-1 on October 11th. The radar personnel left Fort Simpson on October 13/14th. The IPIX radar system, designed for research and not operational use, is a very ‘hands-on’ system. It requires the full-time attention of the operator to use it properly. With the need to simultaneously off-load and archive the large volumes of data collected, a second person is required to manage the CD burning process. With only Brian and Dave on site for the radar program, it was not possible to run the system on a 24-hour basis. The approach taken was to adjust the radar operational schedule daily according to the expected weather events. Every effort was made to cover the significant parts of events, if capturing the whole event was not possible.


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During CAGES IOP-1, a total of 64 CDs of data were collected. The various types of collections are detailed in the Results section. Since returning from the CAGES IOP-1 field campaign only a few weeks ago, the initial effort has been in: (i) cataloguing the collected data; (ii) preparing software for data visual review; (iii) data quality checking; and, (iv) determining the other types of data available (e.g., surface observations, soundings, satellite imagery, weather forecasts, and model outputs). CAGES IOP-2 The next IOP for the radar program is scheduled for December 2 to 15. Plans are in place for one, and possibly two, soundings per day. 3. Scientific Results Before describing the data products that the radar is able to provide, it is important to point out three characteristics of the radar that should be kept in mind. First, the receivers are linear, having an instantaneous dynamic range of 40-50 dB (depending upon noise and integration). The receiver gain is fixed versus range. With the inverse range-squared variation in power, it is possible for close-in strong reflectivity to cause clipping in the A/D converters if the gain is set to receive weaker longer-range echoes. Part of the data quality checking involves marking locations where clipping has occurred. Second, the digitized radar data are handled somewhat differently depending upon the expected reflectivity of interest. For ‘normal’ operation, each sweep (radar transmission) is used directly, for pulse-pair processing or for integration (simple averaging) over the group of sweeps contained within one antenna beamwidth. However, due to its excellent coherence, the radar permits another approach that significantly improves its ability to measure very weak reflectivity, such as in non-precipitating clouds. The radar is set to maximum gain. The radar pulse repetition frequency (PRF) is increased (e.g., to 8000 Hz). Every sweep is digitized, then groups of successive sweeps (e.g., 20) are coherently integrated to produce a single output sweep for use in the normal manner. The coherent integration provides significant signal to noise improvement, in addition to the noise reduction from the normal processing. This high sensitivity method of operation can only be used for short ranges due to the short unambiguous range of the high PRF. It is used for the vertical profiling of non-precipitating clouds, and for cloud VADs, as described below. Third, the radar is most often operated with a maximum range of 75 km, representing a trade-off between radar coverage and a PRF providing a sufficient number of pulses per beam width for processing at a reasonable antenna rotation rate. With an antenna beam width of 0.9 degrees, there are 400 beam widths per 360 degree scan. Using a pulse length of 2 µs (300 m spacing), there are about 250 samples in range. The typical antenna rotation rate is 2 rpm. The data can be stored in one of two forms: ‘raw’ in which all the digitized values are saved, or ‘moments’ in which pulse-pair processing is used to calculate the zeroth and first moments of the sweeps contributing to each beamwidth, and only the moment values (together with DC offsets) are saved. Also saved with either type of data file are the structures describing the state of the radar, and header values indicating antenna position information. A ‘raw’ save for a single antenna scan typically requires 90 Mb of storage, the ‘moment’ version about 9 Mb. Obviously the latter is used more often. Storing of the moments, rather than final display products, enables the post-experiment development of alternate display processing if desired, and facilitates data integrity checking.


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The following is a list of the various data collection types, and their associated products. Plan Position Indication (PPI) This is a single antenna scan in azimuth at a single elevation angle and a single polarization. It is used as a periodic surveillance check to look for incoming weather. The radar is operated in ‘normal’ mode with saving of moments only. Data can be used to generate displays of reflectivity (dBZ), radial velocity (Vr), and linear depolarization ratio (LDR) (i.e., the ratio of cross-polarized to like-polarized reflectivity). Volume Scan This is one of the primary data collection uses of the radar. The radar acquires a series of PPI scans at successive (typically 3) elevation angles. Most often the radar is configured to use both alternating polarization and dual pulse repetition interval (PRI) operation. The transmit sequence is H1 V1 H2 V2, where the letter gives the transmitted polarization, and the number indicates which PRI. Using a 4:3 PRI ratio permits unfolding of the radial velocity (Vr) by a factor of 3. For each antenna beam width, 26 such 4-pulse groups are transmitted. Using the H1 and H2 data streams, the HH reflectivity can be estimated. Similarly, the VV reflectivity can be estimated from V1 and V2. The differential reflectivity, ZDR (the ratio of HH to VV reflectivity) can then be estimated. Linear depolarization ratio (LDR) can be calculated using HV and HH reflectivities. The H1 and V1 (and similarly the H2 and V2) data can be used to estimate ∆HV, the correlation between the HH and VV polarizations. The dot products for data pairs H1&V1 and V1&H2 can be used to estimate the differential phase angle Νdp and the radial velocities (Vr) and spectral widths (Φw) for PRI 1, and pairs H2&V2 and V2&H1 used similarly for PRI 2. The two Νdp estimates can be averaged. The PRI 1 and PRI 2 velocity estimates can be combined to provide an unfolded velocity. In summary, this data collection method provides PPI-format images (at each of the series of elevation angles) of dBZ, Vr, Φw, LDR, ZDR, ∆HV, and Νdp. Data is most often collected in ‘moment’ form, occasionally in ‘raw’ form. Range-Height Indication (RHI) The antenna is scanned downward in elevation from 90 degrees (vertical) to slightly below horizontal (typically -0.8 degrees elevation), at a fixed azimuth angle. The radar is configured as described in the volume scan above, with provision of all products as described there.

Stare With the antenna fixed at a desired angle in azimuth and elevation, the raw data for all pulses over about a one-second duration are saved. Alternating polarization is used. All the products given above can be calculated, and full Doppler spectra versus range can be created. The maximum range is usually 75 km (at 300 m range resolution) for probing at lower elevation angles, or 10 km ( at 90 m range resolution) for probing at high elevation angles, including vertical. Vertical Profile This product uses the radar in its high sensitivity mode. The radar antenna is pointed vertically. A burst of pulses at a fixed polarization is transmitted, and all the pulses are processed (through a combination of coherent and non-coherent integration) to provide a single estimate of reflectivity and velocity versus height. Bursts are repeated every 35 seconds (limited by processing time). Running for a reasonable number of bursts, a time history of the vertical profile reveals the nature of the cloud field passing overhead. The reflectivity and velocity images are saved, as well as a periodic capture of the raw data from a single burst. Figure 1 shows an example of a vertical profile reflectivity image, taken October 01/98 at 19:50 local time. The radar is able to detect two distinct cloud systems: an upper layer of non-precipitating cloud, while the lower layer is producing light precipitation, more so as time


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progresses. (The companion image of radial velocity is not included here, since it is best interpreted using colour. However, colour versions of the radar images will be posted to the MAGS data archive as time permits.) Part of our research will involve the comparison of the ground-based radar’s cloud image information with that deduced from AVHRR imagery, including cloud tops.

Figure 1 Vertical profile image showing radar reflectivity. the gray-level scale ranges from -–0

to +10 dBZ. The ordinate axis shows height in metres, and abscissa axis shows time in seconds (8000 seconds is about 2.2 hours). Two distinct cloud layers are detected: the lower one producing light precipitation, the upper one is non-precipitating. Radar transmission is periodically turned off, and noise-only data collected for calibration use. This results in the periodic black vertical lines.

Velocity Azimuth Display (VAD) By rotating the antenna in azimuth at a high elevation angle, the variation of velocity with azimuth can be used to infer the wind speed and direction as a function of height (i.e., range). Thus a vertical profile of the wind can be developed. This approach, of course, only applies if there is some source of reflectivity at a given height, since it is the wind-borne scatterers that are actually being measured. There are two VAD measurement techniques used by the radar. In precipitation, the radar can be used in its ‘normal’ mode, since the reflectivity of the precipitation is large enough to permit useful velocity estimates. However, the radar can also be operated in its high sensitivity mode (� la vertical profile), such that velocity estimates can be made from non-precipitating clouds as well! This permits VAD


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estimates at much higher elevations than would normally be possible if only precipitation echoes were used. It often also permits wind field estimates at low heights (< 2 km) since the radar is sensitive to clear air echoes that may be present. All the data were collected in one 30-second rotation of the antenna, then processed to produce ‘vertical-like’ profiles at 100 positions spaced around one scan. Saved data for ‘normal’ mode is in the PPI form, while for high sensitivity mode the images of reflectivity and velocity in height versus azimuth form are saved. 4. Publications and Presentations As indicated above, the radar data from CAGES IOP-1 has only been available for a short period. Two conference presentations are planned for 1999. The first is at the 29th AMS Radar Conference in Montr�al, Qu�bec in July. The second is at the Remote Sensing for Weather Forecasting and Climate Application IUGG Meetings in Birmingham, England. A journal paper is also being planned.

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3.6 (b) IPIX Radar Observations during CAGES

D.R. Hudak1, Robert Nissen1, Simon Haykin2, Brian Currie2, Isztar Zawadzki3, Frederic Fabry3, and Bob Kochtubajda4

1Atmospheric Environment Service, King City, Ontario 2CRL, McMaster University, Hamilton, Ontario

3McGill University, Montr�al, Qu�bec 4Prairie and Northern Region, Environment Canada, Edmonton, Alberta

1. Objectives The goal of this work is to:

(1) work with the Communications Research Laboratory of McMaster University in the preparation of the radar for CAGES and in the operation of the radar during the intensive operating periods of CAGES.

(2) analyse the radar data so collected to: a) describe the macroscopic and kinematic properties of significant cloud systems impacting the

central Mackenzie Basin; b) determine microphysical characteristics of these systems and to identify important mesoscale

features. 2. Progress and Collaborations In collaboration with the Communications Research Laboratory of McMaster University, progress has been made in the following areas:

(1) The development and testing of the data acquisition and product generation software associated with the IPIX radar.

(2) The quality control of IPIX radar raw data collected at Grimsby during the winter of 1997/98 by comparison with concurrent King City radar data, as well as the data collected by the Convair 580 research aircraft in the vicinity of the Grimsby site on February 11, 1998.

(3) The deployment of IPIX radar to the Fort Simpson airport in August, 1998. (4) The operation of the IPIX radar during the first CAGES Intensive Operating Period from

September 23, 1998 to October 12, 1998. 3. Scientific Results A signal processing scheme that includes alternating polarization and dual PRF scanning has been implemented. Data products now available from the IPIX radar system include the following:

a) Reflectivity factor (Z) b) Doppler velocity (vr) c) Spectral width (σw) d) Differential reflectivity (ZDR) e) Linear depolarization ratio (LDR) f) Total differential phase (φDP) g) Correlation coefficient (ρhv(0))

Ground clutter maps were constructed from the radar site at the Fort Simpson airport. As expected from the computer simulations using the digital terrain database of the area, there were no significant terrain blockages. However, because the antenna trailer was at ground level with the center of the dish about 3 m above the ground, local buildings and the surrounding trees caused significant blockage. The minimum elevation scanning angle was determined to be about 2° in the western sector and 5° in the


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eastern sector. As a result, the site is not suitable for comprehensive large area hydrological measurements with the radar. Also, the lack of hard clutter targets precludes the use of the radar to obtain refractivity measurements in the lower atmosphere. The radar was operated from September 23, 1998 to October 12, 1998, with only minor technical difficulties. There were two basic modes of operation. The first was implemented when significant precipitation was in the vicinity of the radar, i.e., within 75 km of the radar site. In this mode, conventional, Doppler and polarization capabilities were available from a variety of scanning strategies that included PPIs, RHIs, volume scans, sector volume scans, and staring. The number of each type of task run is summarized in Table 1. Table 1 A summary of the data from CAGES IOP 1 for the precipitation mode.

Type of Scan Total PPIs 270 RHIs 107

Volume 422 Sector Volume 395

Stare 690 The second mode was invoked when there was cloud, but no significant precipitation in the area. In this mode, the radar parameters were configured for maximum sensitivity, but no polarization information was possible. Conventional and Doppler products were available from either a vertically staring or a high angle PPI scanning configuration. A summary of these tasks is given in Table 2. Table 2 A summary of the data from CAGES IOP 1 for the cloud mode.

Type of Scan Total Vertical Stare 198

High Angle PPI 95 4. Summary Considerable progress has been made in expanding the capabilities of the IPIX radar system to include meteorological applications. This work was highlighted by the successful operation of the radar at Fort Simpson during CAGES IOP 1. The information collected is very appropriate in describing the macroscopic and kinematic properties of significant cloud systems and as input to analyses that will determine microphysical characteristics of these systems and identify important mesoscale features. 5. Recent Publications and Presentations Gultepe, I., G. Isaac, D. Hudak, R. Nissen, and W. Strapp, 1998. Dynamical and microphysical

characteristics of Arctic clouds during BASE. J. Atmos. Sci. (accepted) Szeto, K.K., I. Halevy, J.M. Hanesiak, R.E. Stewart, D.R. Hudak, J.M.C. Young and R.W. Crawford,

1997. A Beaufort mesoscale vortex: its structure, evolution and occurrence. Tellus. (submitted) Szeto, K.K., A. Tremblay, H. Guan, D.R. Hudak, R.E. Stewart, and Z. Cao, 1997. On the dynamics of

freezing rain storms over eastern Canada. J. Atmos. Sci. (in press)

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Proceedings 4th MAGS Workshop Session 4: November, 1998 Modelling Studies

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4.1 Hydrologic Investigation of a Canadian Shield Basin

Chris Spence1, Al Pietroniro2, Bob Reid3, Wayne Rouse4, Ming-ko Woo5, Phil Marsh2, Jesse Jasper1, Dale Ross6, and Doug Halliwell1

1Arctic Section, Atmospheric & Hydrological Sciences [AHSD], Environment Canada, Yellowknife, North West Territories

2National Water Research Institute [NWRI], NHRC, Saskatoon, Saskatchewan 3Indian and Northern Affairs Canada [INAC], Yellowknife, North West Territories

4McMaster University, Hamilton, Ontario 5University of Waterloo, Waterloo, Ontario

6Water Survey of Canada [WSC], Yellowknife, North West Territories 1. Objectives The objectives of the project are twofold. First, to expand the database of information on those processes relevant to northern Canadian Shield hydrology such as spring snowmelt, active layer dynamics, wetland hydrology, and lake storage. Secondly, to test hydrologic models of streamflow using the improved database and compare these model results to estimates from linked hydrologic/atmospheric models developed in MAGS. This will provide key validation results for MAGS. 2. Progress and Collaborations

(1) DEM creation and Landsat TM land cover classification of the Yellowknife Basin completed. (2) Water Survey of Canada hydrometric gauge and Environment Canada climate station constructed

at Lower Carp Lake.

(3) Field site at Lower Carp Lake instrumented to measure water and energy balance components (Figure 1).

(4) SLURP has been applied for the period of 1994 to 1997. Work on a summary paper in

cooperation with Dr. Alain Pietroniro and Bob Reid is ongoing. Parameterization of Watflood has begun.

(5) Collaborations include sharing eddy correlation data with Dr. Phil Marsh and Dr. Wayne Rouse,

sharing water balance data with Dr. Ming-ko Woo, cooperation with Indian and Northern Affairs evaporation studies, and inclusion of the Lower Carp Lake study site within the Yellowknife EMAN site. Streamflow data has been provided to Miramar Con Mine to assist with the management of hydroelectric power generation facilities. Stable isotope samples continue to be taken. Continuous water quality monitoring has taken place at Lower Carp Lake during the summer of 1997.

3. Scientific Results Field results from Lower Carp Lake provide physical process data from Canadian Shield terrain to MAGS researchers. They allow comparisons of model results not only to streamflow, but also to other components of the water balance such as evapotranspiration. Analysis of 1997 and 1998 data suggest that losses to the atmosphere are a minor component of the water balance during snowmelt (Figure 2). Evaporation rates increase into June and July, surpassing precipitation and leading to a decrease in shallow soil water storage. In contrast, water levels on the Yellowknife River and its tributaries peak in July (Figure 3). The delay between snowmelt and the rise in water levels on large order streams may not


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be due to lake storage, as there is little difference in the time of peak freshet flow between tributaries with a significant lake area on their main stem (i.e., Yellowknife River below Lower Carp Lake) and those without (i.e., Cameron River). Some snowmelt may infiltrate and enter fractures and soil/bedrock contacts. The lag in spring peak flow on main streams may be due to the time needed for the active layer to grow to a depth required to allow transmission of this water. The source for the freshet flow would then be from the subsurface. Active layer monitoring and stable isotope signatures may be used to prove this theory. Evaporation decreases and precipitation increases in August and September, increasing storage and in some circumstances, creating surface runoff. A significant amount of rainfall is needed to generate a runoff response from both first and larger order streams, suggesting that low and high order basins are not usually hydrologically connected late in the summer. Model output of streamflow and evaporation are accurate on an annual time step, but daily computed values are sometimes suspect (Figure 4). Flow routing through large order streams in the lake dominated system is performed accurately. Comparisons with measured water balance components in first order basins suggest that the model is fairly accurate at that scale, though it underestimates evaporation in the late fall. Therefore, the major problem is the ability of the model to correctly route runoff from first order basins through to larger order basins. Since the model structure assumes that runoff from first order streams reaches larger order streams and, as explained above, this is not necessarily the case, the model sometimes misidentifies precipitation events capable of increasing streamflow on large order streams.

Figure 1 Location of Lower Carp Lake.

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Figure 2 1998 upland water balance at Lower Carp Lake.

Figure 3 1997 streamflow sites within Yellowknife river basins.

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Figure 4 Results from 1995 SLURP simulation of Yellowknife River at outlet of Prosperous lake. 4. Summary Good progress has been made on both objectives and the project is well placed to deal with the up coming challenges expected with modelling Canadian Shield hydrology. The number of collaborating researchers in and outside of MAGS continues to grow. The field site at Lower Carp Lake provides new data that has already contributed to the understanding of Shield hydrology - especially the role of subsurface storage and evaporation. Understanding how storage in the basin affects streamflow is very important to accurately model Canadian Shield terrain. 5. Recent Publications and Presentations Spence, C. D., 1997. “Hydrologic Investigation of a Canadian Shield Basin.” In: G.S. Strong and Y.ML.

Wilkinson (Eds.), Proceedings of the 3rd Scientific Workshop for the Mackenzie GEWEX Study [MAGS], November 17-19, 1997, Downsview, Ontario. Environment Canada Publication, ISSN: 1480-5308, pp. 82-87.

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4.2 Integrated Hydrological Modelling for MAGS

E.D. Soulis, N. Kouwen, F. Segelenieks, K. Snelgrove, E. Whidden, A. Graham, M. Lee, and S. Solomon

Dept. of Civil Engineering, University of Waterloo, Waterloo, Ontario 1. Scientific Objectives This project is to develop meso-scale hydrologic models for MAGS. The work consists of three closely related tasks:

(1) Prepare a long-term land surface water balance for the Mackenzie Basin. This is to consist of high-resolution (approximately 10 km) monthly normal precipitation, evapotranspiration and runoff fields for the Mackenzie Basin.

(2) Develop and implement a modelling framework for combined atmospheric and hydrologic

modelling for MAGS. This involves integration of the atmospheric, land surface, and hydrologic models being used in MAGS and includes solving the practical problems associated with a one-year, high resolution hydrologic simulation of the basin.

(3) Incorporate results from the hydrologic research basins in the modelling framework. This

involves reviewing the research basin modelling results and developing parameterizations for the integrated modelling scheme.

2. Land Surface Water Balance 2.1 Progress in 1997/98 This work is an analysis of existing AES and WSC station data to determine the long-term monthly normal precipitation, evapotranspiration and runoff fields for the basin. The results are important reference data for water year simulations. Also, they are the normals being used by AES/CCRM to generate the monthly 50 km gridded time series of precipitation and temperature for MAGS. The approach we are using is a well-established scheme for interpolation of sparse environmental data sets. It uses elevation, a set of derived physiographic characteristics (such as barrier height in a given direction), and land cover data as interpolating fields. We use regression and kriging methods with each field, as well as require that the three fields balance on a 30 km basis. The procedure is iterative, using the rms differences between recorded and simulated monthly streamflows as an objective function. For MAGS, the original technique is being modified from an annual to a monthly approach and procedures for error estimation are being added. A preliminary analysis, without iteration, was completed in prior years including repeating the process with the revised climate station data generated this year by AES/CCRM. We attempted error assessment using split-sampling techniques with mixed success, largely due to the uneven distribution of the stations in the basin. Development of the monthly water balance procedure was continued this year. The computer code is complete and recession factors necessary to link runoff and storage have been determined from historical streamflow records for each of the 82 WSC gauges used in the study. However, this was deferred when a new opportunity arose. The team was engaged by the Monitoring and Data Interpretation Division of the Climate Research Branch to conduct an analysis for all of Canada using corrected temperature and precipitation station data. This would include the MAGS area and


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would result in substantially improved estimates for MAGS for several reasons. The analysis would be based on many more stations (470 precipitation and 948 temperature stations), would be conducted over a larger area, and would use the finer resolution DTM (GTOPO30) now available. The first phase of this project is complete, and preliminary monthly maps for precipitation and temperature are available. The second phase, which is scheduled for next year, will be to generate final maps after validation steps; namely, anomaly checks and split sampling tests have been completed. This phase will also include an error assessment study using a jack-knife “leave-on-out” procedure. The MAGS monthly water balance will follow. 2.2 Plans for 1998/99 Next year’s activity will involve balancing the three monthly fields. This involves iteratively running the monthly water balance model for the study period (1951-present). The possibility of using the monthly water balance model as a validation tool during CAGES will be explored. 3. Modelling Framework 3.1 Progress in 1997/98 This work in directed toward the coupling of CLASS and WATFLOOD (Level II modelling) for the eventual use with RCM. It includes preparation of the databases (drainage and landcover data) to run the combined model. In prior years, the code for WATFLOOD/CLASS was developed. This year involved a strengthening of the soil physics aspects of the linked model, as well as extensive parameter identification on southern Ontario watersheds. The physical basis of the parameters used in the combined model was supported by the results, which showed, for example, that model parameters are consistent with literature values for hydraulic conductivity for soils. We continued testing the operational version of WATFLOOD on the Mackenzie. This version has a simpler land surface scheme (e.g., Priestley-Taylor evaporation), but lets us test the integrity of our database and data handling procedures. In 1996/97 we used two sets of forcing fields. The first was interpolated from the GCMII surface output. The results demonstrate that the routing capability of WATFLOOD is satisfactory for the basin, but as we expected, show that the GCMII precipitation for the basin is too high, generating unrealistically high streamflows for the Mackenzie at Arctic Red River. The second set is from the 35 km GEM archive for the period 01 April 96 to 31 March 97. We used the t=0 surface fields of the 0000Z operational forecast, but will explore other possibilities. Streamflow simulation and water balance results were satisfactory. This year the forcing data set was extended from November 1993 to March 1997. We conducted a three-year simulation of the basin and produced monthly and annual water balances for the six MAGS sub-basins for the 94/95 and 95/96 water years (Table 1 and Figure 1). Simulated basin storage changed by about -3 mm and 19 mm during the two years, respectively, which demonstrates that year-over-year storage changes are a significant term in the annual water balance. Achieving these results was more work than we expected. The dominance of near-surface interflow in the basin could not be accommodated by WATFLOOD’s interflow routine, which made successful simulation impossible. Therefore, we revised the drainage scheme to a soil physics approach using a shallow aquifer, variable conductivity solution to Richard’s equation. The improvement to the simulations is extremely encouraging. We also substantially improved our debugging and visualization tools. The code has been paralleled, the optimization routines enhanced, and WATCHFLOOD, a state variable visualization package, developed.


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Work also continued on the implementation of WATFLOOD/CLASS on the Mackenzie. The primary issue is model performance. WATFLOOD/CLASS, because of its more rigorous physics, is ten times slower than WATFLOOD. Fortunately, the land surface energy and water budget calculations are 1-D in space and are readily conducted in parallel for each model element. Tests on a parallel version, using a SGI four processor work station using a small data set for southwestern Ontario, have been successful. The second focus was data manipulation. WATFLOOD/CLASS needs seven forcing data fields at 3 hr intervals. We settled on GRIB file format and implemented a GRADS visualization scheme for management of the three year GEM Mackenzie data set.

MeasuredPrecipitation Evaporation P-E Runoff Delta Storage Runoff

Oct-94 to Sep-95 462 325 137 140 -3 125.8Oct-95 to Sep-96 463 314 149 130 19 163.1

MeasuredPrecipitation Evaporation P-E Runoff Delta Storage Runoff

Oct-94 39.0 16.9 22.1 7.3 14.8 13.9Nov-94 33.5 2.2 31.3 3.2 28.1 5.1Dec-94 22.7 0.9 21.8 2.7 19.1 5.6Jan-95 11.8 2.4 9.4 2.5 6.9 6.3Feb-95 24.7 1.0 13.4 2.0 21.7 5.0Mar-95 31.4 4.1 15.8 1.9 25.4 5.3Apr-95 34.6 21.2 16.5 6.3 7.1 5.2May-95 43.6 62.7 18.7 34.5 -53.6 19.1Jun-95 59.7 76.8 8.1 29.9 -47.0 17.1Jul-95 71.5 55.8 10.7 23.7 -7.9 14.3Aug-95 64.1 50.4 19.3 17.4 -3.6 14.7Sep-95 25.2 30.3 9.9 8.9 -14.0 14.4Oct-95 29.3 12.9 6.3 5.1 11.3 10.9Nov-95 34.5 1.6 4.3 3.5 29.4 5.0Dec-95 17.1 0.6 3.6 2.9 13.6 5.4Jan-96 20.2 1.5 3.1 2.6 16.1 5.3Feb-96 14.0 2.2 2.6 2.0 9.8 4.7Mar-96 17.1 3.0 2.4 1.4 12.8 4.8Apr-96 23.8 15.7 8.8 4.6 3.5 4.8May-96 39.5 48.7 18.1 16.6 -25.8 16.3Jun-96 64.1 70.3 22.8 30.5 -36.7 29.1Jul-96 78.1 67.5 25.4 26.1 -15.4 27.7Aug-96 73.3 54.5 21.3 19.8 -0.9 26.0Sep-96 51.7 35.8 18.1 14.9 1.0 23.1

Table 1 - Preliminary Water Year Balances - Mackenzie River Basin

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Figure 1 Monthly and annual water balances for the Mackenzie Basin.

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3.2 Plans for 1998/99 The work will proceed to parameter identification on the Mackenzie with WATFLOOD/CLASS, using preliminary values estimated using WATFLOOD. This will result in a modelling capability that will be compatible with the RCM. 4. Incorporation of Process Study Results 4.1 Progress for 1997/98 We have continued to monitor progress in the research basin studies and have begun the dialogue with the investigators to incorporate their findings to date. The primary issues continue to relate to snow processes, permafrost, and lake and wetland routing. To date, the revised WATFLOOD drainage scheme, which is consistent with the work by Quinton and Marsh, was implemented. We have made tentative changes to the snow-related algorithms. 4.2 Plans for 1998/99 Revising the physics in WATFLOOD/CLASS to improve the representations of cold region processes will be a major task this year. Currently, we are modifying WATFLOOD/CLASS to address the wetland routing difficulties identified by A. Pietroniro in his results for the Fort Simpson area. As well, we have revised CLASS to improve the ground temperature representation under snowcover, but testing is still in progress. We look forward to implementing other snow process changes (e.g., sublimation and redistribution) in cooperation with J. Pomeroy and P. Taylor, frozen soil changes in cooperation with H. Woo and D. Gray, as well as other results from the research basin studies. 5. Relation to Water Year Activities We have been able to study both 94/95 and 95/96 water years, based on the availability of 35 km operational CMC data. We will provide P-E-R-∆S monthly fields for the both years at model resolution (approx. 25 km). These will be based on our monthly water balance model, WATFLOOD, and WATFLOOD/CLASS simulations. They can be compared with the results of other studies. We will also provide sub-basin water balance summaries, as well as time series of most important land surface state variables.

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4.3(a) Hydrologic Response of Lower Mackenzie System in the Discontinuous Permafrost/Wetland Zone

A. Pietroniro1, T. Prowse1, J. Gibson2, E.D. Soulis2, and N. Kouwen2

1National Water Research Institute [NWRI], Saskatoon, Saskatchewan 2University of Waterloo, Waterloo, Ontario

1. Objectives

This study focuses on the meso-scale hydrologic simulation of a discontinuous permafrost and wetland dominated region. The Fort Simpson area is an NHRI long-term study site and is representative of large wetland regime feeding the lower Liard System. The Liard River is a main tributary of the Mackenzie system and acts as "trigger" for break up of the Mackenzie River ice-cover. This discontinuous permafrost/ wetland regime covers a significant portion of the Mackenzie Basin. The focus for this past year's proposal was on expanding the hydrologic modelling in the region through the use of the WATFLOOD/CLASS modelling scheme. Given the detailed snowmelt data collected through past studies (1995, 1997, and 1998) and radiation information along with the landcover maps, it was possible to implement and successfully test the WATFLOOD model on the Simpson basins. We are still assembling data from the WSC for implementation of WATFLOOD for the 1997 and 1998 spring runoff. We are in the processing of testing the CLASS scheme on 1995 snowmelt data for different cover types. Most of our efforts this year were in keeping the data collection (radiation, rainfall, streamflow) continuous into the CAGES period. 2. Progress and Collaborations We continued supporting the stream gauge operation at Scotty Creek and collected initial snow depth/snow water equivalent for the 1997 and 1998 freshet, as well as global incoming radiation for the melt period and throughout the summer in anticipation of CAGES in September 1998. We worked closely with Drs. Prowse and Gibson and contributed to isotope samples and enhance rainfall collection this past year. We are in the process of getting ready for the March 1999 snow surveys under this current budget. Significant GEWEX funds from this project were used to assist in the CAGES enhanced observations for the Simpson Wetland, Forest, and airport synoptic site. This past year was a data collection year and we are still in the processes of collating some of this data. Radiation for the 1998 spring freshet and snow survey data for spring of 1998 initial snow conditions has been collated and documented. WSC data (including contracted precipitation and Scotty Creek flow gauge) are still pending. This study is working hand in hand with both the macro-scale hydrological work proposed in GEWEX and using the results of the isotopic studies for enhanced modelling of this region. 3. Scientific Results This study focuses on the meso-scale hydrologic simulation of a discontinuous permafrost and wetland dominated region. The Fort Simpson area (Figure 1) is an NHRI long-term study site and is representative of large wetland regime feeding the lower Liard System. The Liard River is a main tributary of the Mackenzie system and acts as "trigger" for break up of the Mackenzie River ice-cover. This discontinuous permafrost/ wetland regime covers a significant portion of the Mackenzie Basin. This study is also a catalyst for collaboration with other GEWEX investigators examining meso-scale modelling in a number of distinct physiographic regions throughout the Mackenzie Basin.


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Figure 1a Fort Simpson study area.

Figure 1b Landsat derived classification.

Figure 1c DEM generation for region.

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Modelling studies contribute directly to the MAGS/GEWEX program through an increased understanding of the hydrology in this region. The MAGS modelling strategy is to achieve long-term forecast/simulation expertise. However, as has been recognized by other researchers, hydrologic simulation at the meso-scale is often more difficult than at the macro-scale. Parametrization and calibration is necessary at the meso-scale for hydrologic modelling in order to properly simulate the entire Mackenzie system. The work completed thus far in the Fort Simpson region has shown poor transferability of parameters between temperate regions and the Fort Simpson region. (Pietroniro, et al. 1996). We concluded in our initial assessment, that there were a host of difficulties in simulating runoff in this regime. Past years results have focused on using the existing WATFLOOD model, deriving the correct physiographic (Figure 1b) and land-cover characteristics (Figure 1c, Pietroniro, et al. 1995) for the region and applying the model. The focus has been on spring freshet simulations and enhanced data collection for the 1995, 1997, and 1998 spring runoff seasons. An extensive field snow survey program has been in place for those years. Further data analysis this past year examined hydrograph separation using isotopic methods. The data for spring of 1997 has been analysed with the exception of streamflow data, which is still forthcoming. Spring snow surveys will continue for this year and are proposed for the CAGES enhance observation period. Recent calibrations within the region have shown successful simulation of snowmelt, with simple index approaches (Hamlin 1996; Hamlin, et al. 1998) for the 1995 data sets (Table 1 and Figure 2). Runoff hydrographs could then be calibrated successfully; however, in many cases validation in time was still problematic. Table 1 Statistical analysis of calibrated hydrographs - Spring 1995. (Hamlin 1996)

Average Daily Flow Peak Flow Statistical Criteria

River Basin Measured Simulated Measured Simulated R2 Dv (%) DG Jean-Marie 5.442 6.492 25.9 33.0 0.875 -19 0.885

Martin 7.553 9.118 52.3 46.5 0.914 -21 0.963 Birch 2.890 3.640 17.8 20.4 0.829 -26 0.869

Blackstone 8.759 6.923 64.5 51.3 0.876 +21 0.884 Scotty 0.456 0.626 2.4 2.7 0.882 -37 n/a

To model the snowcover depletion in the northern wetland dominated river catchments of the lower Liard River valley, both a radiation-temperature and a temperature index snowmelt model was calibrated and produced good results. However, the radiation-temperature index model, while more data intensive, produced better results during this calibration process. The calibration of snowmelt parameters was developed from the 1995 detailed snow surveys with results shown in Figure 3. Further to calibration of snowmelt parameters, the model has also been calibrated for the vertical water budget components present in the current version of the WATFLOOD model. Although calibrated runoff hydrographs showed very good agreement, validation on previous years gave mixed results. This was partly due to the lack of representative inputs as well as shortcomings of the existing vertical water budget model (see Pietroniro, et al. 1996; Hamlin, et al., 1998). The results of these initial studies showed that calibration of either of these snowmelt algorithms requires detailed and representative snowcover data as well as spatially representative meteorologic records. Previous model calibration efforts in this regime using historic operational data were simply not representative inputs for the model (see Pietroniro, et al. 1996). The extensive snow surveys conducted during the spring of 1995, 1997, and 1998 provided enough spatial and temporal detail to successfully determine reasonable snowmelt


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parameters and/or initial conditions for calibration and validation. Both the 1997 and 1998 snow surveys included isotopic sampling of the snow for snowmelt hydrograph separation estimates as performed by Prowse and Gibson in a companion GEWEX-MAGS study.

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. Figure 3 Snowmelt calibration for the Liard sub-basins.

Although index approaches work well, this data set now allows for more rigorous testing using a more physically based land-surface scheme (CLASS/WATFLOOD). This work is still underway. The data obtained through this study provides a critical test bed for meso-scale hydrologic modelling. Successful parameterization with CLASS/WATFLOOD at the meso-scale for these basins will provide the necessary parameterizations for this type of terrain unit for larger macro-scale modelling efforts of the entire Mackenzie system. Further verification and calibration in time and space is necessary to provide greater confidence in applying these models with a greater degree of confidence in this regime. Enhanced observations and isotopic tracers will provide much of the needed data to continue our work in the region. This project is very closed linked with Prowse and Gibson and has contributed significant financial resources towards isotopic sampling to assist in the modelling efforts. Early results for 1997 using hydrograph separation techniques are promising and will be used in the calibration procedure

Figure 4 Hydrograph separation for the Blackstone Basin.

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4. Summary This study focuses on two main issues. First, supplement the existing (and sparse) existing data within this area for the purposes of meso-scale modelling. This includes contributing efforts to the CAGES program in the Fort Simpson region that is now completed. This also includes using new regional techniques such as the isotopic hydrographic separation estimates to help calibrate and validate the models. The second issue is to work to provide simple validation of CLASS on a landscape basis and parameterization of hydrologic models including WATFLOOD, SLURP, and CLASS/WATFLOOD in this region. This fiscal year was mainly focusing on continuing our data collection and continuity in the region providing more validation opportunities and gearing up for the CAGES hydrologic year. 5. Recent Publications Hamlin, L, 1996. Improved Hydrologic Modelling of a Northern Wetland Dominated Region. M.Sc.

Thesis, Department of Civil Engineering, University of Waterloo, Waterloo, Ontario, May, 1996. Hamlin, L., A. Pietroniro, T.D. Prowse, N. Kouwen, and E.D. Soulis, 1998. "Snowmelt hydrologic

modelling of the Lower Liard Valley." International Journal of Hydrologic Processes. (in press) Pietroniro, A., T.D.Prowse, and V. Lalonde, 1996. "Classifying terrain in a muskeg-wetland regime for

application to a GRU type distributed hydrologic model." Canadian Journal of Remote Sensing, 22(1):45-52.

Pietroniro, A. , T.D. Prowse, L. Hamlin, N. Kouwen, and E.D. Soulis, 1996. "Application of a Grouped Response Unit hydrologic model to a northern wetland region." International Journal of Hydrologic Processes, 10:1245-1261.

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4.3(b) Scaling of Hydrologic Models for MAGS

A. Pietroniro1, L. Martz2, E.D. Soulis3, N. Kouwen2, P. Marsh1, J. Pomeroy1, and C. Spence4

1National Water Research Institute [NWRI], Saskatoon, Saskatchewan 2University of Saskatchewan, Saskatoon, Saskatchewan

3University of Waterloo, Waterloo, Ontario 4Environment Canada, Yellowknife, North West Territories

1. Objectives This project deals with hydrologic modelling of the four research areas identified by the GEWEX Science Committee and the macro-scale modelling of the entire MAGS area. These regions (Wolf Creek, Inuvik, Fort Simpson, and Yellowknife) have all been previously funded for a variety of process studies, which in many cases are still ongoing. This research project focuses on WATFLOOD and WATFLOOD/CLASS application in all of these regions, with particular emphasis on Wolf Creek in the first year. We proposed to evaluate and modify the TOPAZ model to test different techniques of basin discretization for the purposes of hydrologic modelling. This includes integrating both the landcover and digital elevation data for the Wolf Creek region, and generating the required physiographic files for WATFLOOD and WATFLOOD/CLASS. The purpose of this research is to assist with scaling issues through automated basin discretization. This research will contribute directly to all the meso-scale and macro-scale hydrologic modelling projects and contribute directly to the parameterization of the WATFLOOD and WATFLOOD/CLASS models through a synergistic combination of the TOPAZ and WATFLOOD models. Another major restriction in successful model implementation is the insufficient availability of precipitation data. Additionally, it is necessary to obtain knowledge about the optimal utilization of the available precipitation information toward satisfactory modelling at different spatial scales. The research is intended to deal with this problem as well. A framework for spatial interpolation, cross validation and sub-area estimation for continuous daily time series of precipitation and other variables has already been developed integrating several conventional and geo-statistical methods. First results show improved flow simulations when using the geo-statistical interpolation methods, indicate the scale dependence of the results, and encourage the proposed data assimilation scheme (Haberlandt and Kite 1997). Also, an evaluation of different atmospheric models has shown their potential and limitations for hydrological modelling in the Mackenzie River Basin (Kite and Haberlandt 1997).

2. Progress and Collaborations This multi-scale modelling project attempts to identify landscape based parameterization for the WATFLOOD and WATFLOOD/CLASS models in all the regions outlined above. This work will also provide the required tools for automated discretization of basin information leading to analysis of parameterization and scaling problems that will be critical to the overall success of MAGS. The research will generally benefit the understanding of macro-scale hydrological processes and give better possibilities for investigating the climatic change impact on regional hydrology. Precipitation estimations in sparsely gauged regions for hydrological modelling are expected. The validation of numerical weather prediction models and general circulation models, as well as the coupling of those atmospheric models with hydrological models, will benefit from the results of this research.


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Progress to date has been limited to the evaluation of the TOPAZ and Mapmaker models for the Wolf Creek and Yellowknife basins. These basins were chosen because they represent the extremes in terms of their hypsometry. We are currently operationalizing and testing TOPAZ to run on the Yellowknife Basin. It has been successfully applied to the Wolf Creek Basin. An evaluation of MapMaker, a computer program to generate the physiographic files required for the WATFLOOD square grid model was performed. Modification of the code was needed and variable grid size files needed for WATFLOOD were successfully produced with this automated procedure. 3. Scientific Results This project began in May of 1998 and has resulted in some significant testing of the WATFLOOD algorithm for the Wolf Creek Basin. Preliminary results are shown in the appendix. The ability to transfer the software application to the Yellowknife Basin has so far yielded poor results. This is mainly due to the low relief in the area, and the difficulty in establishing flow pathways in such terrain.

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4.4 MAGS RCM, Climate System and Cloud Field Studies

Ron Stewart1, Murray Mackay2, Zuohao Cao2, and Kit Szeto2

1Climate Processes and Earth Observation Division, AES, Downsview, Ontario 2Climate Research Branch, AES, Downsview, Ontario

1. Objectives The objectives of this project are to better understand the Mackenzie Basin’s climate system, quantify the ability of the Regional Climate Model to represent the critical Basin water and energy cycles, and to pay special attention to the role and representation of cloud fields on the overall climate system. This project, therefore, is dealing directly with the major goals of MAGS, which are to understand the region’s climate system and to improve our climate model for replicating the water and energy cycles of this region. In addition, it is working on a particular critical aspect of the problem, the cloud fields. MAGS needs this project to realize its 2000/01 goal of being able to quantify the processes that operate over the Mackenzie Basin, and to assess our capability for handling these. 2. Progress and Collaborations 2.1 Strategy There are three focal points underway under this effort. First, a great deal of information on the region’s water and energy cycles is being brought together to characterize and understand the coupled climate system. Second, large-scale forcing and the observational information is being accessed for initializing and validating the regional climate model. Third, high resolution cloud model simulations are being run and results used for assessing the capabilities of large-scale models to account for cloud systems. In 1998/99, substantial work is being undertaken to achieve the following:

(1) Year-long RCM runs and other experiments will be completed and analysed. (2) The coupled climate system of the Basin will be better understood in part through a study of a

particular water year. (3) Improvements in the representation of cloud fields in the RCM will be advanced.

2.2 Relevant Collaborations This effort has strong interaction with many other projects. For example, to adequately address the ability of the RCM to replicate the Basin’s water and energy cycles, validation data are required from several other groups. Within Canada, this effort is operating in a cooperative manner with many participants within MAGS. The water year study in particular needs to be considered to some degree as a MAGS-wide effort and even though all the other contributors are not mentioned here; ensuing journal articles will be multi-authorship to reflect the work. Strong interactions are also ongoing with UQAM (the developers of the RCM) and with Diana Verseghy (leader of the CLASS initiative). This effort also represents a significant Canadian contribution to the GEWEX Hydrometeorology Panel (GHP) and the GEWEX Cloud System Study (GCSS). There have already been strong interactions with BALTEX and in 1998/99 and beyond there will be more interactions with ACSYS, GCIP, and GAME. 2.3 Data Management/Exchange Relations All of the model and observational data acquired or produced with this project either are or will be fully available. A prime example of this is the BASE information and all of the ISCCP, GVAP, GPCP,


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RCM, and other information will be available in 1998/99 through the GEWEX Data Management system. 3. Scientific Results 3.1 Approach and Scope The regional climate model was initialized by the global data assimilation system of the CMC in order to quantify differences in predictions over the Basin between the RCM and observed fields. In order to accomplish this, a suite of diagnostic tools was developed with IDL software for displaying and diagnosing many parameters from the model and for comparing against available observations on time. A journal article on the RCM effort is being prepared for the four month autumn 1994 period to document capabilities linked with seasonal changes, with a particular emphasis on precipitation. This simulation will be extended for the entire 1994/95 water year. Many datasets were acquired (such as International Satellite Cloud Climatology Project, as well as others associated with water vapour, precipitation, discharge, and lake levels) and have been examined in considerable detail and their capabilities assessed in comparison with surface-based observations. This information is being used to develop long-term climatology, to examine the water cycle during anomalous discharge and temperature years, and to act as validation datasets for the RCM. A journal article was completed in the summer of 1998. Substantial progress was made in the preparation of a consistent dataset for assessing the cloud field parameterization within the RCM through the analysis of detailed information obtained in BASE. High resolution (a few kilometers) cloud model simulations were carried out with the MC2 and GESIMA (from Germany) models and detailed comparisons against observations were carried out. The next step (underway) is to use these high resolution runs as validation information with the use of a column model to test parameterization schemes in the RCM. In addition, a CD was produced of the validation dataset. 3.2 Key Scientific Results The results of these efforts have led to several scientific results, which are briefly summarized here: From the RCM/GCM effort: From the limited autumn 1994 runs carried out so far:

(1) It appears that the RCM produces total Basin monthly precipitation in good agreement with the best observational estimates.

(2) The spatial distribution of the monthly precipitation is also reasonably well simulated, particularly in the center of the Basin. Some (generally positive) bias exists near the western Basin boundary; this likely associated with orography.

(3) The lack of lakes within the current version of the RCM may lead to an underprediction of autumn snowfall over the eastern basin, although the significance of this factor still needs to be evaluated.

From the climate system and cloud effort:

(1) Some of the critical features associated with the water budget of the Mackenzie Basin climate system (such as summer temperature) operate within relatively narrow boundaries.

(2) The amount of water vapour in the atmosphere increases with increasing surface temperature, but at least in the winter, less precipitation appears to fall during warm periods.

(3) Anomalously warm winter periods are linked with low level descent, circulations conducive to bringing warm air from the southwest; the presence of the orographic barrier critically affects many of the processes responsible for such warming.


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(4) According to the available information, a single autumn storm is never capable of completely covering the Basin with snow, but in some years only 2-3 such storms are required to achieve this.

(5) For the 1994/95 water year, low discharge levels were linked with low large lake levels, but only slightly smaller amounts of precipitation (see Figure 1). The reasons for such apparent discrepancies are still not resolved.

(6) The current representation of clouds in the RCM does not produce a proper tropospheric heating profile in association with cloud formation and condensation; a study to improve this situation is currently underway.

Figure 1 Values of monthly-scale parameters over the July 1, 1994 to October 31, 1995 period.

For the values shown in Figure 1, the parameters are basin averaged fractional cloud cover (%), basin averaged precipitation (mm), the number of lightning strokes within the basin (x103), basin averaged fractional snowcover (%), and the discharge of the Mackenzie River (mm). The months are indicated by their first letter and the two vertical dotted lines indicate the boundaries of the 1994/95 water year. Other datasets are being examined including water vapour, moisture flux, lake levels, precipitation types, and lake ice cover. The study is a collaborative effort involving many researches from MAGS, and this particular figure, for example, has relied upon information courtesy of B. Hogg, B. Kochtubajda, P. Louie and A. Walker. 3.3 Applicability of results to overall MAGS objectives These projects are directly applicable to the objectives of MAGS. In summary, we expect by 2000/01 this effort will have better understood the Mackenzie Basin’s climate system and quantified the degree to which our climate model represents Basin water and energy cycles under differing conditions and it will have ensured that cloud fields are better handled within models.


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4. Summary The past year has been an excellent one for MAGS research and the overall effort has moved ahead substantially. Over the last couple of years, considerable time has been spent acquiring and developing the tools needed to realize the project’s objectives and this is now really paying off in terms of scientific productivity. Over the rest of 1998/99 and beyond, we will be able to further exploit these background efforts. 5. Recent Publications and Presentations Burford, J.E. and R.E. Stewart, 1998. The sublimation of falling snow over the Mackenzie River Basin.

Atmos. Res. (in press) Cao, Z., R.E. Stewart, and W. Hogg, 1997. Extreme winter warming over the Mackenzie basin: dynamic

and thermodynamic contributions. J. Meteor. Soc., Japan. (submitted) Mackay, M.D. and R.E. Stewart, 1997. “Modelling the hydrological cycle in the Mackenzie Basin with

the Canadian Regional Climate Model.” In: Proceedings, Polar Processes and Climate Change, Seattle, Washington, pp. 119-121.

Mackay, M.D., R.E. Stewart, and G. Bergeron, 1997. Downscaling the hydrological cycle in the Mackenzie Basin with the Canadian Regional Climate Model. Atmos.-Ocean. (in press)

Stewart, R.E., 1998. The Variable Climate of the Mackenzie River Basin: its Water Budgets, Feedbacks and Fresh Water Discharge. NATO ASI Series, Springer-Verlag. (submitted)

Stewart, R.E. and D.G. Malcolm, 1998. “Recent warming over northwestern Canada and its impacts on society and ecosystems.” In: Global Warming and its Impacts, Expo 2000 Themenpark Series, Campus Verlag GmbH, Frankfurt. (submitted)

Stewart, R.E., Z. Cao, M.D. Mackay, R.W.Crawford, and J. E. Burford, 1998. “The processes leading to and affected by the variable climate of the Mackenzie River Basin.” In: Proceedings 2nd BALTEX Conference, Rugen, Germany, pp. 208-209.

Stewart, R.E., R.W. Crawford, and J.E. Burford, 1998. On the water cycle of the Mackenzie River basin. Cont. Atmos. Physics. (submitted)

Stewart, R.E., H.G. Leighton, P. Marsh, G.W.K. Moore, W.R. Rouse, E.D. Soulis, G.S. Strong, R.W. Crawford, and B. Kochtubajda, 1998. The Mackenzie GEWEX Study: the water and energy cycles of a major North American river basin. Bull. Amer. Meteor. Soc. (accepted)

Stewart, R.E., K.K. Szeto, R.F. Reinking, S.A. Clough, and S.P. Ballard, 1998. Midlatitude cyclonic cloud systems and their features affecting large scales and climate. Rev. Geoph., 36:245-273.

Formal invited presentations were made by Ron Stewart on this work at Prairie and Northern Region in Edmonton, the NWT Forest Group in Yellowknife, as well as in Germany (GKSS and the University of Hamburg). Murray Mackay gave an invited talk on this work at the international ACSYS Conference in November 1997.

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4.5 Developing a Global Numerical Weather Prediction System for the Canadian GEWEX Program

H. Ritchie1, Yves Delage1, Pierre Gauthier1, C. Beaudoin2, R. Hogue3, and E. Radeva1

1Recherche en Prévision Numérique (AES/RPN), Dorval, Qu�bec 2Meteorological Research Branch, AES, Downsview, Ontario

3Canadian Meteorological Centre, Dorval, Qu�bec

1. Objectives

The objective for 98/99 is to develop a CLASS-based land-surface data assimilation for MAGS. Our 97/98 MAGS project involved quantifying the impact of the Canadian Land Surface Scheme (CLASS) on the Mackenzie River Basin (MRB) water and energy monthly budgets as predicted by our global system. We found that the way CLASS predictive variables are initialized could significantly affect those budgets.

The objective of the current work is to develop a data assimilation system that will integrate surface analyses and CLASS physical packages to produce high-quality land-surface and soil data over the MRB area. The system will enable the incorporation of meteorological observations gathered through MAGS enhanced measurements into gridded data sets suitable for model initialization. It will provide consistent data for some hard-to-measure MAGS physical characteristics, in particular soil moisture, which has a critical impact on both the runoff and the fluxes of moisture/heat to the atmosphere. The fields resulting from the assimilation system will be verified against available conventional and/or non-conventional observations. This focus on the data assimilation and validation areas is considered to be complementary and beneficial to the overall GEWEX modelling program. 2. Progress and Collaborations Our main objectives this year are to develop and test a CLASS-based data assimilation cycle, validate its output, and evaluate the impact of the generated fields on MAGS energy and water budgets with our global prediction system. This is being accomplished in a step-wise fashion starting by inserting the forecast model used by Radeva and Ritchie (1998) as the driving model in a 6-hour intermittent data assimilation cycle using the 3-dimensional variational data assimilation method (3DVAR). The coding has been prepared for this insertion and we have performed a preliminary examination for our summer 1996 case. As a control run we have the integration performed when a forecast is initiated from standard climatology/analyses as in Radeva and Ritchie (1998). For a first experimental run (to test the sensitivity of the water and energy budgets over the MRB area to the initial fields used by CLASS), we produced the soil-related and snow-related CLASS initial fields in a spin-up integration beginning one month prior to the initial time for the desired forecast and running for one month without re-initialization. Then we used these balanced CLASS-generated fields to initiate a one-month simulation (hereafter called SPIN-UP) and compared the resulting surface fluxes with their counterparts from the integration fed with climatology/analysis values (hereafter CLIM). As a second experimental run, we performed a one-month 3DVAR data assimilation cycle with CLASS included in the assimilating model over the one month period prior to the initial time for the desired forecast (hereafter 3DVAR). The water and energy budgets over the subsequent one month forecasts were then compared with each other and with the corresponding budgets calculated from the MAGS CMC archive (Hogue et al. ) to evaluate the impact of this CLASS land data assimilation system on the MAGS water and energy budgets in our global prediction system.


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This project is complementary to MAGS data gathering efforts and will make use of enhanced measurements carried out under CAGES. The generated data sets will be available to other projects examining the performance of CLASS in the regional climate model within the land surface node by Verseghy et al., as well as to projects examining the coupling with a hydrological model (Soulis et al. “Development of an integrated hydrologic modelling scheme for GEWEX”; also related work by D. Verseghy). The project will have close interaction with the companion government GEWEX project, “CMC model archives and activities in support of GEWEX” (Hogue et al.). 3. Scientific Results The comparison between simulations SPIN-UP and CLIM (see above) shows little difference in averaged monthly accumulations of water and energy budgets in snow-covered areas. However, the fluxes over the snow-free areas, produced by SPIN-UP, verify better against the GEWEX archive then the ones of CLIM. With CLASS included in the assimilating model, the CLASS fields (the soil moisture and temperature are considered to be especially important) adjust in response to the meteorological data assimilated throughout the cycle. Our preliminary results based on the subsequent one-month integration indicate that this indirect assimilation of meteorological data into the CLASS fields seems to improve the Mackenzie Basin water budget as compared against available observations. This appears to be due to slightly more realistic evaporation during the integration. So far the tests have been carried out only for the summer season; tests for other seasons are to follow. Further steps will also include introducing and testing available upgrades to the CLASS model and testing the 3DVAR approach in a regional GEM model configuration over the MAGS region. This work has in fact only begun recently, since the MAGS funding received for 1998/1999 is not sufficient to support the project for a full year, and we decided to suspend the project for the first portion of this fiscal year. 4. Summary Preliminary results indicate that the modelled water and energy budgets over the MAGS region are sensitive to the initial state of the CLASS fields used in the simulations. As a consequence, it is expected that realistic initial conditions for these fields are necessary in order to produce realistic water and energy budgets in the subsequent simulations. With the current state of available data and data assimilation methods, CLASS initial fields produced by a 3DVAR atmospheric data assimilation system with CLASS being included in the assimilating model are expected to produce more realistic results than the former integrations in which CLASS was fed by analysis/climatological values. This expectation is supported by our preliminary results as reported above, and will be examined more thoroughly in the coming months. 5. Recent Publications and Presentations Ek, N. and H. Ritchie, 1996. Forecasts of hydrological parameters over the Mackenzie River Basin:

sensitivity to initial conditions, horizontal resolution, and forecast range. Atmos.-Ocean, 34:675-710. Radeva, E. and H. Ritchie, 1998. Predicting Monthly Energy and Water Budgets over the Mackenzie

River Basin using the Canadian Land Surface Scheme. Presented at the 32nd Annual CMOS Congress, 1-4 June, 1998, Halifax, Nova Scotia.

Radeva, E. and H. Ritchie, 1997. “Developing a Global Numerical Weather Prediction System for MAGS.” In: G.S. Strong and Y.ML. Wilkinson (Eds.), Proceedings of the 3rd Scientific Workshop for the Mackenzie GEWEX Study [MAGS], 17-19 November, 1997, Downsview, Ontario. Environment Canada Publication, ISSN: 1480-5308, pp. 103-106.

Ritchie, H., R. Hogue, and E. Radeva, 1997. RPN/CMC Model Archives and Activities in Support of GEWEX. Presented at: GCIP-PRA/PI Session, UCAR Facilities, Boulder, Colorado, 5-6 November, 1997.


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Stewart, R.E., H.G. Leighton, P. Marsh, G.W.K. Moore, H. Ritchie, W.R. Rouse, E.D. Soulis, G.S. Strong, R.W. Crawford, and B. Kochtubajda, 1999. The Mackenzie GEWEX Study: The Water and Energy Cycles of a Major North American River Basin. Bulletin of the American Meteorological Society. (in press)

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4.6 High Resolution Simulations of "Warm" and "Cold" Mesoscale Precipitation Systems over the Mackenzie River Basin

M.K. (Peter) Yau1 and Da-Lin Zhang2

1Dept. of Atmospheric and Oceanic Sciences, McGill University, Montr�al, Qu�bec 2Dept. of Meteorology, University of Maryland, College Park, Maryland

1. Objectives The main objective is to understand the impact of mesoscale convective systems and their interaction with the surface on the water and energy budgets in the Mackenzie River Basin (MRB) and to improve the representation of important physical processes in regional weather prediction and climate models. Another objective is to investigate the effect of blowing snow on the heat and moisture budget of the basin. The objectives for this study are central to the goal of MAGS to quantify and to understand the water and energy budgets over the Mackenzie River Basin 2. Progress and Collaborations As stated in our original proposal, the objectives will be accomplished through the completion of the following five tasks:

(1) To implement and evaluate physics modules, including warm and cold rain microphysics schemes and convective parameterization schemes in the Mesoscale Compressible Community (MC2) model.

(2) To carry out the simulation of "warm" (mostly liquid precipitation) and "cold" (mostly solid precipitation) mesoscale precipitation systems over the Mackenzie River basin.

(3) To study the effects of topography, surface heating/forcing, and synoptic-scale flow on the organization and distribution of precipitation in the simulated systems in task (2). The role of slantwise convection will also be investigated.

(4) To compute the heat, moisture, vorticity, and momentum transports of convective and mesoscale elements in the simulated mesoscale precipitation systems.

(5) To examine and quantify the feedback of the simulated cloud and mesoscale precipitation systems on the large-scale flow.

In our original milestone definition and schedule, Tasks (1) and (2) would be completed by the end of 1997. Task (3) will be completed in 1998. Tasks (4) and (5) will be accomplished respectively in 1999 and 2000. We are on schedule in completing our tasks. Some results for Tasks (1), (2), and (3) have already been reported. Specifically, Kong and Yau (1997) developed and implemented an explicit warm rain and ice phase microphysics scheme into MC2. The new scheme includes predictive equations for cloud water, rain water, ice/snow, and graupel/hail. Bensimon, Yau, and Zhang (1998),Yau, Li, and Benoit (1998), and Ryan et al. (1998) have applied the scheme in summer and winter time precipitation systems. Bensimon, Yau, and Zhang (1997) also presented results of sensitivity experiments, which show that the mountains significantly influence the distribution of precipitation in the MRB. Further progress made in 1998 will be given in the section on Scientific Results. Relevant collaborations with MAGS and/or non-MAGS projects I am collaborating with Drs. Kit Szeto and Ron Stewart on the simulation of the September 30 BASE storm. The three of us are also involved in GCSS (GEWEX Cloud System Study) Working Group 3 to improve the parameterization of extra-tropical layered cloud systems in GCM and NWP models (see Ryan, et al. 1998). Collaboration is continuing with Dr. Burkhardt Rockel of GKSS, Germany under the Canada-Germany Agreement on Cooperation in Research to compare the modelling of atmospheric transport processes over MAGS and BALTEX. We are beginning a collaboration with Dr. John Pomeroy to study a case of blowing snow over Trail Valley Creek.


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3. Scientific Results (a) Moisture and heat budget study over MRB Postdoctoral Fellow Dr. Vasu Misra and I (Misra and Yau 1998a) have completed a moisture budget study associated with three cyclones over the MRB using MC2. The budget is performed on three cases of lee cyclogenesis, which occurred during BASE. The first case is the September 24-26 storm, which made its passage through the northern part of the basin. The second is the September 14-16 lee cyclone, which traversed the southern portion of MRB. The third episode is the September 18-19 case, which crossed the central portion of the basin. For each of the experiments, a pilot integration of 36 hours at a coarser resolution of 50 km was performed using the Canadian Meteorological Center (CMC) analysis as the initial conditions. This was followed by a higher resolution 24 h simulation at 18 km using the initial conditions from the coarser resolution run. The results showed that during the 24 h period of lee cyclogenesis and its passage the moisture flux convergence in the basin is significant. During the initial formative period of each of the lee cyclone there is a large influx of moisture from the western boundary. But as the cyclones move eastward, a significant amount of moisture is withdrawn through the eastern and southern boundaries of the basin. The net moisture convergence was positive for the first two storms. For the third storm, which moved through the central part of the MRB, the outgoing lateral flux of moisture was very large resulting in a net drying of the basin over a period of 24 h. Furthermore, surface evaporation is relatively large during the local day time. The evaporation, together with frontal lifting, play a vital role in initiating convection to the south of 60o N in the basin. The explicit microphysical processes produced a significant amount of resolved precipitation. The most dominant processes are condensation, deposition, autoconversion and accretion of cloud water to rain, accretion of cloud to ice, melting of ice to rainwater and evaporation of cloud and rain water. The processes related to graupel were insignificant throughout the integration. In two of the three cases, the total water substances (sum of vapor, cloud water, rain water, ice content, and graupel content) in the basin increases over a 24 h period. The calculated cumulative rainfall is nearly 1.4 times the surface evaporation. The precipitation efficiency, defined as the ratio of total precipitation over the sum of moisture convergence and surface evaporation, ranged from 60-85%. As an example, we present a summary of the September 25-26 case in Table 1. Here the mixing ratios for water vapor, cloud water, rain water, ice/snow and graupel particles are denoted respectively by Qv, Qc, Qr, Qi and Qg. The budget is calculated for 21 h to minimize the effect of model spin-up during the first 3 h of the integration. A negative sign signifies a sink term for a particular water substance. A positive sign represents a source. As is shown, there is a net increase of total water into the basin from moisture convergence and surface evaporation. Total water is removed from the basin in the form of precipitation. The storage term, which represents the changes in water substances in the atmosphere, is also not negligible. Table 1 Total atmospheric water budget of a lee cyclone tracing northern region of MRB (25

Sept., 0300 UTC - 26 Sept., 0000 UTC, 1994). Units: Megatons.

Storage -∇∇∇∇ .vqx Microphysics Stratiform Convective Surface

Qv 7412.77 11098.4 -5936.16 -4776.55 7027.07

Qc 28.04 172.54 -144.46

Qr -19.85 -63.17 4714.39 -4671.07

Qi -269.49 -1085.9 1358.07 -541.66

Qg -.03 -.18 8.15 -8.01

Total 7151.49 10121.7 0.00 -5220.73 -4776.55 7027.07


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We have also calculated the vertical distribution of the apparent heat source Q1 and apparent moisture sink Q2 (Misra and Yau 1998b). An example is shown in Figure 1 for the south moving storm. These curves were obtained by averaging spatially over the whole MRB domain and over the 21 hour period of the lee cyclone simulation. It is clear that cloud condensation (Cloud cond), convective heating (Convc. Htg), ice deposition (Ice depos) are major heat sources and moisture sinks. Cloud evaporation (Cloud evap), IR cooling (QR), and rain evaporation (Rain evap) are some of the major heat sinks. The vertical diffusion of sensible heat flux (Vert. diff.) is largely upward since the surface is warmer than the overlying atmospheric layer in this case. The vertical diffusion of moisture flux (Vert. diff.) caused by surface evaporation represents a major source of moistening.

Figure 1 The major contributing components of the a) Q1 and b) Q2 budget averaged spatially over

the whole Mackenzie River Basin and temporarily over a 21 hour period of the model integration for a case of a lee cyclone that tracked through the southern part of the Basin from Sept 14, 0000 UTC through Sept 15, 0000 UTC. The ordinate is pressure in hPa and the abscissa is heating rate in deg day-1.

(b) Blowing snow climatology and modelling With Ph. D. student Stephen Dery, we are investigating the effect of blowing snow in the hydrology of the MRB. Dery and Yau (1998a) compiled a global and regional climatology of blowing snow events using the European Centre for Medium Range Weather Forecasts (ECMWF) Re-Analysis (ERA) dataset for the period 1979-1993. The results indicate that globally, the blustery icefields and ice shelves of Antarctica and Greenland, the frozen Arctic Ocean and polar seas, as well as the Arctic tundra, are high frequency zones for blowing snow. The frequency of events is largely controlled by geography (e.g., surface cover, latitude, altitude, etc.) and meteorological variables, most notably wind speed. Similar trends are found for the Mackenzie River Basin (see Figure 2), where few blowing snow events occur in the boreal forest region because the wind speed is generally not large. However, upon reaching the open


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Arctic tundra in the northern and northeastern sections of the basin, the frequency of blowing snow increases significantly. Interannual variability is also observed in the frequency distribution of blowing snow and some evidence exists for a possible teleconnection between ENSO, as well as a volcanic eruption and the number of blowing snow events, although a longer time series should be examined to arrive at a definitive result. To determine the synoptic scale features contributing to blowing snow, we performed a composite analysis of sea-level pressure, surface temperature and surface wind speed, stratified according to the wind directions in four quadrants at Yellowknife, NWT, located centrally within the MRB, when blowing snow events occur. It was found that the presence of strong pressure gradients producing wind speeds >7 m s-1 and subfreezing temperatures are the necessary ingredients to produce blowing snow over a snow-covered surface. For the four quadrants examined, we note that intensifying anticyclones are dominant features in all but one of the four composites. Additional strengthening of the pressure gradient is provided by lee cyclogenesis for SW, NE and SE events while in a quasi-stationary low over Hudson Bay is critical for NW events. Deviations in SLP from the monthly climatological mean showed a “dipole” structure in 3 out of the 4 composites, with Yellowknife sandwiched between an area of positive and negative SLP departures. Thus strong departures from the climatological mean SLP in the vicinity of Yellowknife are conducive to adverse meteorological conditions there. We also noted positive temperature deviations from the climatological means near or at Yellowknife in all 4 composites.

Figure 2 Mean annual frequency of blowing snow events in the Mackenzie River Basin (denoted

by the thick line) for the period 1979 to 1993.


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As a first step to determine the effects of the transport of snow and its sublimation on the water and energy budgets of the MRB, we developed a bulk blowing snow model in the boundary layer based on the work of Dery et al. (1998, Boundary Layer Meteorology, in press). In the Dery et al. (1998) model, the size distribution of the blowing snow is solved explicitly using a large number of size categories, making it impractical for a three-dimensional simulation of blowing snow. Dery and Yau (1998b) assume that the blowing snow size distribution is given by a Gamma function with parameters α and β. The value of α is assumed 2 and β is obtained as a function of height by solving a steady-state diffusion-sedimentation equation. With α and β determined, the complete size distribution becomes known and the governing equations for blowing snow can be simplified to a single equation for blowing snow mixing ratio. Comparison of results from the bulk model with those from the detailed model of Dery et al. (1998) shows excellent agreement in terms of the vertical profile of the blowing snow mixing ratio, as well as the time evolution of the sublimation rate and the rate of erosion of snowcover. A great advantage of the bulk model is that it runs at least 100 times faster than the detailed model. Thus it is practical to couple it to a mesoscale model to simulate blowing snow events in three-dimensions. (c) Conditionally symmetric instability and precipitation bands over the MRB With Ph.D. student Liang Ma, we are investigating the importance of slantwise convection (or conditional symmetric instability) in high latitude precipitation systems. We have completed a climatological study of the distribution of Convective Available Potential Energy (CAPE) and Slantwise CAPE (SCAPE) using the ECMWF (1979-1993) reanalyzed dataset over the MRB. We simulated the September 30 warm front case, which occurred during BASE using a grid size of 5 km. Many observed features of the storm, including the characteristic features of the cloud head, the dry intrusion, the precipitation amount, and banded structures in the cloud field were well simulated. Analysis of vertical cross-sections of absolute momentum and equivalent potential temperature indicated that conditional symmetric instability may be a plausible mechanism to organize cloud and precipitation into bands. Our results are highly relevant to MAGS objectives. The development of a good physics package is essential to simulate well the development of precipitation. The clarification of the role of topography, surface evaporation, conditional symmetric instability, and blowing snow leads to a better understanding of the distribution of precipitation. The calculation of the heat and moisture budgets over the MRB is central to the goals of MAGS. 4. Summary Progress has been made in (a) the development of a microphysics package for MC2, (b) the simulation of a number of storms observed during BASE, (c) the compilation of climatology for blowing snow and slantwise convection over MRB, (d) the understanding of the role of topography, surface evaporation, and conditional symmetric instability in the distribution of precipitation over MRB, (e) the development of an efficient model for blowing snow, and (f) the calculation of the heat and moisture budgets over the basin. 5. Recent Publications and Presentations Bensimon, D.R., M.K.Yau, and D.L. Zhang, 1998. The interaction of extratropical cyclones with

topography during BASE. Atmosphere-Ocean. (submitted) Dery, S.J. and M.K. Yau, 1998a. A global and regional climatology of blowing snow, blizzard and high

windchill events. Journal of Geophysical Research. (submitted) Dery, S.J. and M.K. Yau, 1998b. A simple and efficient column model of sublimating, blowing snow.

Boundary Layer Meteorology. (submitted) Dery, S.J. and M.K. Yau, 1998a. A climatology of significant winter-type events for the Mackenzie

River Basin inferred from the ECMWF re-analysis data. Preprints AMS 14th Conference on Hydrology, January 1999, Dallas, Texas, 2 pp.


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Dery, S.J. and M.K. Yau, 1998b. Blowing snow modelling and parameterization. Preprints AMS 14th Conference on Hydrology. January 1999, Dallas, Texas, 2 pp.

Kong, F. and M.K. Yau, 1997. An explicit approach of microphysics in MC2. Atmosphere Ocean, 35:257-291.

Misra, V. and M.K.Yau, 1998a. Atmospheric water budget study traced over the history of mesoscale simulations of lee cyclones over the Mackenzie River Basin. Tellus. (submitted)

Misra, V. and M.K. Yau, 1998b. The apparent heat source and apparent moisture sink from mesoscale simulation of lee cyclones over the Mackenzie River Basin. Tellus. (to be submitted)

Ryan, B.F., J.J Katzfey, D.J Abbs, C. Jakob, U. Lohmann, B. Rockel, L.D. Rotstayn, R.E. Stewart, K.K. Szeto, G. Tselioudis, and M. K. Yau, 1998. A Methodology for Analyzing "Aussie" FRED (Frontal Rainband Experiments and Diagnostics) to Improve Cloud Parameterizations in Climate and Weather General Circulation Models. Bull. Amer. Meteor. Soc. (to be submitted)

Yau, M.K., C. Li, and R. Benoit, 1998. A multi-scale simulation of a case of outbreak of severe convection and moisture transport over the Alberta foothills. Monthly Weather Review. (to be submitted)

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4.7 GEWEX - Northern Boundary-Layer Modelling

Peter A. Taylor, Jingbing Xiao, Dr. Wensong Weng, Lucilla Chan, and Jingnan Zhou Dept. of Earth & Atmospheric Science, York University, Toronto, Ontario

1. Objectives Our objectives for this study continue to be centred on blowing snow. Comparisons between predictions from our PIEKTUK model (D�ry et al. 1998) and the Prairie Blowing Snow Model (PBSM) developed by Pomeroy et al. (1997) show that there is still considerable uncertainty concerning modelled blowing snow sublimation rates that needs to be resolved, before we can accurately assess the importance of this process for the Mackenzie Basin for other areas of Canada, and for Arctic and Antarctic regions. In typical high wind cases our version of the PBSM predicts rates that are an order of magnitude higher than those obtained from PIEKTUK. We have focused on refinements to the model and comparisons with published field data in our attempts to resolve this issue during Year 2 of the project. 2. Progress and Collaborations During the first part of the year, we concentrated on refinements to the PIEKTUK model and revisions to the journal paper (Déry et al. 1998) describing the model. These revisions included sensitivity testing of the assumptions made concerning particle settling velocity, eddy diffusivity for particles and lower boundary conditions on particle size distribution. In the latter half of the year, the focus has been on comparisons against Schmidt's (1982) field data and setting up the three way model intercomparison discussed below. Given some divergence of opinion between ourselves and the Saskatoon group (Pomeroy, Gray) concerning the reliability of predictions based on the PBSM and PIEKTUK models, we have so far concentrated on testing and validation of the PIEKTUK model against field data obtained, near Laramie, Wyoming in April 1974 by R.A. Schmidt of the USDA Forestry Service (Schmidt, 1982). Although rather old, these are among the best data available to us and Dr. Schmidt has been extremely co-operative in making additional information available. We are also in the process of looking at Antarctic data collected by British Antarctic Survey scientists and partially analysed by Graham Mann of the University of Leeds, UK. Also, we have started investigating the possibility of utilizing some of the tower and observer data collected by US scientists in the recent (1997/8) SHEBA experiment in the Arctic. In addition to comparisons against observations, we are leading a three way model intercomparison involving PIEKTUK and somewhat similar models developed by Graham Mann, Stephen Mobbs and Sarah Dover at University of Leeds, and by Richard Bintanja at University of Utrecht, Holland. We have agreed some basic cases to run, have performed the necessary calculations with PIEKTUK and are now awaiting comparable results from the other groups; Stephen Déry from McGill is also involved. Full details of this work are available at (www.yorku.ca/research/blayer/snow/snow.html). Work on modelling stably stratified flows is continuing and progress is being made towards improved representations of gravity wave drag, based on our work with linear models. However, work with both of our detailed models of stably stratified flow in complex terrain has encountered difficulties. The linear MSFD-STAB model, which works well in two-dimensional situations, still has some difficulties in 3D cases


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and we continue to have problems with gravity wave radiation conditions at the upper boundary of our 2D non-linear model. 3. Scientific Results In blowing snow research, several numerical models have been developed (Pomeroy 1988; Mobbs and Dover 1993; Déry et al. 1998; Bintanja 1998; and Liston et al. 1993). The results from the models are controversial and proper validation of their predictions is essential. However, accurate blowing snow observation is hard to make and the data available are very limited. In part of our work, we are trying to compare our model predictions with the field data reported in Schmidt (1982). By comparison with these data, we anticipate that the results will be useful for both the improvement of models and in planning further experimental observations. In terms of the overall MAGS objectives, we hope to be able to provide a much improved and tested blowing snow model, on which to base estimates of expected sublimation rates. In addition, these could be utilized in the development (at McGill) of parameterizations for use in mesoscale models such as MC2 and RCM. However, it is clear from our work so far that model construction and predictions are critically dependent on assumptions made concerning: a) lower boundary conditions, applied so far at the top of the saltation layer; and b) the ratio (β) between diffusivities for ice/snow particles of various sizes (Ks) and the eddy viscosity (Km). The most critical boundary conditions concern the drift density and the particle size distribution (Mobbs, personal communication, also propounds this view), but lower boundary conditions on temperature and humidity are also factors. Our early models assumed Ks = Km or that Ks < Km, however, improvements in the agreement between model predictions and Schmidt's observations can be obtained if we assume Ks > Km, in agreement with Mann (1998). A further factor affecting our comparisons with Schmidt's data involves the estimations of the velocity profile parameters z0 and u*. Schmidt estimates these from cup anemometer measurements in the lowest 1m of the boundary layer. Reanalysis of his data to account for cup overspeeding corrections has been completed. This leads to slightly higher u* and z0 values, but the profiles predicted still indicate an imperfect match to the reported 10m level winds. Tests with velocity profile parameters determined from the 10 m and 1 m winds, which give different u* and z0 values, sometimes lead to better agreement between model predictions and observed drift densities. Thermal effects and density increases due to the presence of blowing snow can both lead to stable density stratification and velocity profiles that are non-logarithmic. These effects may account for the discrepancies in computed profile parameters. To illustrate some of our comparisons with Schmidt's field data, Figure 1 shows vertical profiles (just for the lowest 1 m) of particle number density, mean radius and the α parameter (obtained from a fit to the two parameter gamma distribution) for Schmidt's Run 4. The water vapour deficit profile (100%-RH%) is also shown. It is assumed that the field measurements were made after a downwind fetch of 1km over a uniform mobile snow surface. Unfortunately no detailed upstream conditions were measured and we have to infer these from the profiles available for the measurement site. For run 4 we assume a uniform upstream profile for temperature (-5.2C) and relative humidity (75% relative to ice). Four different PIEKTUK predictions are shown, based on versions 1,2,4 and 5 of this simulation. PIEKTUK 1 is based on our initial model, which, in particular, uses the assumptions for particle numbers proposed by Pomeroy et al. (1993) and used in the PBSM as the lower boundary condition, at z = 0.8u*/g. For the Laramie site, the observed particle numbers appear to be significantly lower than predicted by this version of the model, and in the other versions shown we impose a lower boundary condition based on observations of particle flux divided


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by the local wind speed at zlb. In the PIEKTUK2 run the only change is through the lower boundary condition. In PIEKTUK4 we use u* and z0 values based on a logarithmic profile and the 1 m and 10 m wind measurements in place of Schmidt's values, and this does give better agreement with both number density and mean radius profiles. Particle number densities for the field data have also been recalculated from the observed particle fluxes for these velocity profile parameters and labelled Schmidt4. In PIEKTUK5, we have tuned the model to improve the agreement of the particle number density profile by adjusting β, the ratio of eddy diffusivities, for each run, although values are assumed independent of z. Although both PIEKTUK4 and 5 lead to improved agreement with the observed profiles of particle number density and of mean particle radius, none of the versions tested so far has any significant effect on the vertical variation of the α parameter obtained when the predicted particle size distributions at each height are fit to two parameter gamma distributions. PIEKTUK predictions (Figure 1c) show little variation in α with height (as has been observed in some field studies), whereas Schmidt's data show quite a strong variation. There are also discrepancies between the predicted and observed water vapour deficit profiles (Figure 1d). Schmidt's data show an almost linear variation with height while the model predictions suggest a variation that is better matched to the logarithm of z. Note that although in the original versions of PIEKTUK we always assumed 100% relative humidity at zlb, we have relaxed this and impose values based on the observations. These range from 91 to 99% over Schmidt's runs and we use a value of approximately 93% for Run 4. In Figure 2 we show vertical profiles of sublimation rate as computed by Schmidt from his measurements (and checked by us) and as predicted by the model. Schmidt4 curves correspond to our revised estimates of velocity profile parameters. Both Schmidt's calculations and our model results are based on Thorpe and Mason's (1966) expression for mass change of individual snow particles. The results are for experimental Runs 4 and 10. For Run 4 the profiles predicted by PIEKTUK4 and 5 are in good agreement with Schmidt's estimates while the agreement for run 10 is less satisfactory. This comparison with Schmidt's field data is very much "work in progress". The comparison exercise is forcing us to take a careful look at many of the assumptions made in the development of the PIEKTUK model, and at the reliability of some of the field data. At this point, we plan to focus on issues related to the parameter β and see if we can establish a more solid basis for its specification. Although we have considered the possibility of using Lagrangian Stochastic Models to simulate the trajectories of snow particles as an alternative approach to blowing snow modelling, at the present time this has been given a low priority. In principle, such models could provide a better theoretical base than the diffusive assumptions presently employed in PIEKTUK, but treatment of the temperature and humidity change aspects remains far easier in our present modelling approach.


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Figure 1 Vertical profiles (for the lowest 1 m) of particle number density, mean radius and the αααα parameter (obtained from a fit to the two parameter gamma distribution) for Schmidt’s Run 4.


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Figure 2 Vertical profiles of sublimation rate as computed by Schmidt from his measurements

(and checked by us) and as predicted by the model. 4. Summary The modelling of the many processes involved in blowing snow events is providing an interesting challenge. Large differences between the predictions of the PBSM and PIEKTUK models for sublimation rate have forced us to step back and attempt detailed checks of our predictions against observational data. These data are generally incomplete from the point of view of detailed model verification but we are doing what we can with the data available to us. Ideally, we would like to mount a definitive experiment, but our group has neither the equipment nor funds and personnel with the expertise necessary to undertake this task. Blowing snow is, of course, an intermittent and somewhat unpredictable phenomenon, which adds to the logistical difficulties and, in the context of MAGS, a major "process" experiment may be hard to justify. Our approach has been to work collaboratively with other international groups involved in both model development and field studies in an to attempt to intercompare model predictions and to utilize field data and model sensitivity tests, as well as to identify those processes or aspects of the models that are most critical and that need further study. At the present time, the critical areas appear to be the specification of lower boundary conditions and the eddy diffusivity for particles.


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5. Recent Publications and Presentations Déry, S.J., P.A. Taylor, and J. Xiao, 1998. The thermodynamic effects of sublimating, blowing snow in

the atmospheric boundary layer. Boundary-Layer Meteorology, 89(2). (in press) Kwan, J., J. Salmon, P. Taylor, J. Walmsley, and W. Weng, 1998. Guidelines, Model Developments.

Presentation to CMOS Conference, May 1998. Taylor, P.A., 1998. Turbulent boundary-layer flow over low and moderate slope hills. J. Wind, Eng. and

Industr. Aerodyn. 74-76, 25-47. Weng, W., L. Chan, P.A. Taylor, D. and Xu, 1997. Modelling stably stratified boundary-layer flow over

low hills. Quart. J. R. Meteorol. Soc., 123:1841-1866. Xiao, J., S. Déry, and P. Taylor, 1998. Blowing Snow Modelling with PIEKTUK – Comparisons with

Schmidt’s Field Data. Presentation to CMOS Conference, May 1998. Zhou, J, P.A. Taylor, and Y. Qi, 1999. On wave drag, form drag and parameterization of sub-grid scale

topography in large-scale models. Boundary-Layer Meteorology. (accepted, in preparation) Zhou, J. Y. Mengesha, P.A. Taylor, and Y. Qi, 1998. Stably-Stratified Flow over Hills and Wave Drag.

Presentation to CMOS Conference, May 1998.

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Proceedings 4th MAGS Workshop Session 5: November, 1998 MAGS Support and Operational Inputs

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5.1 CMC Model Archive and Activities in Support of GEWEX

Ekaterina Radeva1 and Richard Hogue2 1Recherche en Prevision Numerique [AES-RPN], Dorval, Québec

2Canadian Meteorological Center, Dorval, Québec 1. Objectives The objectives of the CMC archiving project is to provide high-resolution model data to the scientific community involved in the Mackenzie GEWEX Study (MAGS) and the GEWEX Continental-Scale International Project (GCIP). To this end, we maintain a special GEWEX-dedicated archive, monitoring the scientific quality of the model data and their dissemination in a variety of meteorological formats. We also serve as local contacts for all questions concerning the CMC forecasting system, i.e., the operational models and the data assimilation system that produce the data. 2. Progress and Collaborations The GEWEX archive consists of three parts: analyses, forecasts, and time series. Currently, the analyses are produced by a regional assimilation system using the 3D-VAR data assimilation scheme to incorporate available observations into a background (trial) field of the operational Global Environmental Multiscale (GEM) model in a 12-hour spin-up cycle. We archive 15 atmospheric fields from the 00Z, 06Z, 12Z and 18Z analyses. The archived grid is the GEM regional native grid, which uniform portion covers North America with a horizontal resolution of 0.22 x 0.22° or ~24 km. As for the vertical resolution, the upper-air variables are output at 28 eta levels. The forecast part of the archive comprises 44 fields taken from the 24-hour forecasts of the GEM model produced twice daily at 00Z and 12Z. Most of the fields, especially the surface ones, are output at every 3 hours. Like the analyses, the forecasts are archived on the GEM native grid. We keep time series of 55 variables for 252 locations. They represent 36-hour spot forecasts produced twice daily at 00Z and 12Z and archived at every hour. Latest improvements of the CMC operational forecast system include the implementation of a higher-resolution (24 km) version of the regional GEM model using the Fritsch-Chappel's scheme for deep convection on September 15th 1998. On October 14th 1998, we replaced the spectral model (SEF) utilized to drive the global assimilation cycle and to produce medium-range forecasts with a global uniform-grid version of the GEM model running at a similar resolution (100 km). With this implementation, CMC now has a unified forecasting system in which a single model (GEM) is used in different configurations (global, regional, local). 3. Results During the past seven months, we processed requests from various researchers implied in the MAGS project: � Prof. John Gyakum (McGill University) � Ken Snelgrove and Prof. E.D. (Ric) Soulis (University of Waterloo) � Brian Proctor (NHRC) � Dr. Muyin Wang (Dalhousie University) � Aldo Bellon (McGill Weather Observatory) � Prof. Peter Schuepp (McGill University)


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Figure 1 shows the number of requests/inquiries handled as well as the volume of the data sent per month.

We continue to be actively involved in the model intercomparison phase of the GCIP project. Findings from a study on modeled surface fluxes using our GEM data have been submitted for publication to the Journal of Geophysical Research and were partially published in the GEWEX News journal (Berbery et al. 1998). Moreover, part of our model data (MORDS, MOLTS) is made available to GCIP and other researchers through the NCAR data acquisition system. In the nearest future we expect to continue collaborating with the GEWEX scientific community. 4. Recent Publications and Presentations Berbery, E.H, K. Mitchell, S. Benjamin, T. Smirnova, H. Ritchie, R. Hogue, and E. Radeva, 1998.

Assessment of land surface energy budgets from regional and global models. Journal of Geophysical Research. (submitted)

Berbery, E.H, K. Mitchell, S. Benjamin, T. Smirnova, H. Ritchie, R. Hogue, and E. Radeva, 1998. Assessment of surface heat fluxes from regional models. GEWEX NEWS, Vol. 8, No. 3, pp. 3-4.

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5.2 MAGS Data Management

Bob Crawford Atmospheric Environment Service, Downsview, Ontario

Data Management for the Mackenzie GEWEX Study has continued and been expanded in 1998. Activities have centered around three initiatives to promote data sharing within MAGS, archive MAGS data and document it for future use. The WWW site at: http://www.tor.ec.gc.ca/GEWEX/MAGS.html continues to be the primary means of disseminating data to project participants and information about the project to the world. With the commencement of CAGES operations this fall, the CAGES portion of the web site has been given greater prominence and been greatly expanded. Information on the enhanced observations being made during CAGES can be found on the CAGES site, as can information on many of the operational sites. Selected datasets from most of the sites are available in near real time, including skew-T plots from sounding sites. Additional near real time data is available through the special “Participants Only” section of the web site. This password protected section was set up to promote the exchange and archiving of participant generated data under the Data Access Policy adopted last year. This policy states that MAGS Principal Investigators (PIs) are required to make their datasets available exclusively to other MAGS PIs within one year of collection for a period of one year before the data is made public. Passwords were distributed to all PIs last year. The near real time data available includes GOES (4 channels) and AVHRR (IR and visible) satellite imagery and enhanced observations from the MAGS surface sites. The GOES imagery is received approximately biweekly and the AVHRR data is received within 30 minutes of capture. The enhanced datasets from the surface sites are transmitted daily and contain enhanced temporal resolution data (for example, 15 minute pressure measurements) and non-standard measurements (such as soil temperatures). Also available on the “Participants Only” section, is access to the AEP Climate Archives and Utilities for mapping sites and data over the basin. The AEP Climate Archives contain data from the operational stations within the basin and have been made available to MAGS PIs for their GEWEX studies. The second initiative begun this year is the production of at least three series of permanent archives to provide a lasting legacy of the project. The current series include, “Processes and Individual Phenomena” (Series I); “Case Studies” (Series II); and, “Water-Years” (Series III). Table 1 gives the current status of each of these series. This is being supplemented with an effort to produce MAGS Data Documentation Guidelines. Future plans for MAGS Data Management include continuing to provide MAGS PIs with the needed data; further enhanced near real time data access; a concerted effort to make more PI datasets available through the “Participants Only” site; and additional permanent archives, including 1994-95 and 1998-99 Water Year datasets.



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Table 1 MAGS Permanent Archives.

Series Volume Version Title Status 1 1.0 Vertical Profiles through Precipitating

Clouds released Sept 1998

2 Mackenzie Basin DEMs in planning (Jan 1999)3 Mackenzie Basin Land Cover in planning (Jan 1999)4 1.0 MAGS Satellite Observations in production 5 Water Vapour Diurnal Cycle in MAGS in planning 6 IPIX Radar Observations in production

Series I Processes and Individual Phenomena

7 MAGS Enhanced Surface Observations

in planning

1 2.0 BASE Observations Sept 30 1994 released Sept 1998 Series II Case Studies

2 1.0 CAGES Case Study Observations ? to be identified

1 1994-1995 in preparation (Jan 1999) Series III

Water Years 2 1998-1999 in planning (Sept 2000)

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5.3(a) CAGES Update

Bob Kochtubajda Atmospheric and Hydrologic Sciences Division,

Atmospheric Environment Branch, Prairie and Northern Region, Edmonton, Alberta 1. Objectives After several years of preparations, the CAnadian GEWEX Enhanced Study (CAGES), a 14-month field experiment phase for MAGS started in June 1998. The objective of CAGES is to provide adequate spatial and temporal measurements of the key variables required to determine the water and energy cycles of the Mackenzie River Basin. Some measurements will be made over the entire year, but the major effort will be focused on gathering measurements during several intensive observational periods of the year.

2. Progress and Collaborations The enhancement of the surface-observing network was completed this past year. The equipment that was installed at each site, the heights where the sensors are located along with identification codes and satellite transmission times are summarized in Table 1. The MAGS weather stations located at Lower Carp Lake, Fort Simpson Airport, Lindberg Landing, MacMillan Pass, and at Trail Valley Creek transmit meteorological information hourly via satellite and received in Edmonton within 20 minutes of the upload. These data undergo preliminary quality control procedures and are then transferred to the MAGS web site the next day. Further quality control procedures are described by Louie and Kochtubajda (1998, in this volume). The data from the additional temperature, snow depth, and wind speed sensors installed at Watson Lake and Dease Lake are sent as e-mail attachments following inspection visits by staff in the Pacific and Yukon Region. A separate forest site at the Lindberg Landing location has been established to monitor snow depth, soil moisture, and soil temperature. Data from this site are collected on a NWRI-donated data logger. A net radiation sensor has also been installed in the valley below the upper air station at Inuvik and the data are sent back to the radiation data center in Downsview. Sensor and communication upgrades were carried out at the Havikpak Creek research site in Inuvik, and a wetlands micro-meteorological station was installed in the Fort Simpson area in September. Many elements of other project activities are well underway and Table 2 highlights some of the accomplishments during the past year.

Proceedings 4th M

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MAGS sites Ft Good Carp Lake Ft Lindberg Lindberg Watson MacMillan Dease TVC Inuvik HPC Checkpoint Hope Simpson A Landing forest site Lake A Pass Lake A Inuvik U/A Inuvik micro-met Latitude N 66 16 63 36 61 45 61 07 61 06.929 60 07 63 14 58 25 68 44 68 19 68 19 61 20.903 Longitude W 128 37 113 51 121 14 122 50 122 50.792 128 49 130 02 130 00 133 30 133 32 133 30 120 46.662 Elevation (m MSL) 81.7 373.4 169.2 183 195 689.5 1379 816.3 85 93 220 Station ID ZGH XLC XFS XLL YQH WNV YDL XTV YEVu/a HPAK WMO number 71491 71680 71681 71682 71953 71990 71958 71683 71957 Climat ID 2201450 220N004 2202115 220N003 2100693 220N005 2202582 Land Cover Type tundra N. Shield mixed forest shrub taiga tundra taiga forest wetland Installation-1998 Mar 26-30 Jun 2-4 Jun 5-7 Jun 8-10 Sep 28-Oc 2 Jun 11-12 Jun 14-16 Jun 18-19 Aug 17-21 Aug 17-21 Aug 17-21 Sept 28-Oct 2 Sat. transmission time modem min 44-45 min 46-47 min 45-46 min 42-43 min 28-29 tape min 29-30 Air temp/ RH HMP35CF 1.6 2.6 2.62 2.5 2.57 NWRI NWRI x Radiation shield-RMY41004 x x x x x NWRI NWRI x Air temperature-107F 2.05 2.07 Screen SS Gill Gill Gill Gill Gill Gill Gill Gill Precipitation-Belfort 2.0 1.9 2.0 1.93 1.6 x NWRI t/b Alter Shield X X X X X X Snow depth-SR50 2.0 1.97 1.44 on NWRI 21X 1.54 1.59 1.7 NWRI NWRI x Pressure-SETRA SBP 270 1.2 x x x x NWRI x x Wind speed/direction RMY 10.0 10.0 10.0 10.0 10.0 NWRI NWRI x MET 1 Anemometer 2.00 2.00 2.00 2.03 2.32 2.30 2.43 x KIPP pyranometer CM21 1.8 2.2 1.67 x Ventilator radiometer x x x x Pyranometer Rebs PDS 7.1 NWRI NWRI Net pyradiometer-CN1 1.7 2.2 1.5 NR-LITE(1.85) 2.4 x System air purging x x x x x Net pyradiometer-Rebs Q7.1 NWRI NWRI Soil temperature (up to 7 lvls) 5,10,20,30,50,100 5,10,20,50 cm 10,20,40,75 NWRI Soil moisture cs615 on NWRI 21X x NWRI NWRI Data logger CR10X x x x x x x x x AES 21X NWRI - 21x x Multiplexer x x x x x Batteries x x x x x x NWRI x 30W solar panel x x x x x x x Surge protector bar + x x x x x x terminals Regulator CH12R x x x x x x x x NWRI x GOES antenna+transmitter x x x x x x x WESTCAN tower x x x x x x DELHI x Misc (wood, .etc.) x x x x x x x Inspection Report Apr 3-98 Jun 4-98 Jun 7-98 Jun 10-98 Jun 16-98 Jun 14-98 Jun 18-98 Aug 18-98

Table 1 CAGES surface-observing network – Summary of equipment installation, identification codes, satellite transmission times.


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Table 2 CAGES - project highlights.

Project

Summary of Activities

SATELLITE • Visible and IR GOES data have been automatically downloaded to the MAGS image archive since mid-May 1998.

• AVHRR data pre-processing and transfer infrastructure for CAGES has been established since June 1998.

• NOAA satellite data archive has been established since September 1998. SOUNDINGS • Science License granted.

• Summer 98 enhanced sounding program at Fort Smith [July17-31] completed.

• Autumn 98 enhanced sounding program at Whitehorse, Fort Nelson, Fort Smith, Norman Wells, Inuvik and Fort Simpson [Sep23-Oct11] completed.

RADAR • Science License granted. • Autumn 98 radar observing program at Fort Simpson [Sep23-Oct11]

completed. • Data archive of the PNR operational weather radar sites at Spirit River and

Carvel has been established since mid-June 1998. PRECIPITATION • Science License granted.

• All MAGS automatic weather stations installed and transmitting data onto the weather circuit by mid-June.

• Sensor and communications upgrades carried out at the Inuvik research basin in August.

• A wetlands micro-meteorological station in the Fort Simpson area installed in September.

• Surface weather data archive established on MAGS web site in June 1998. • A quality control procedure is being designed.

OROGRAPHIC PRECIPITATION

• Government permit granted. • Installation of stations along a distance-elevation transect near Fort Nelson,

BC completed in November 1998. EVAPORATION • HYDRA eddy covariance system and radiation sensor data collection on

Inner Whaleback Island in Great Slave Lake completed for the summer. • Buoy #45141 (near Hay River) as well as a new Hexoid buoy (co-located

near Inner Whaleback Island) data collection completed. SHIELD WATER

BALANCE

• Science License and all Government Reserves Granted for the Lower Carp Lake site.

• Lower Carp Lake snow surveys completed in April. • Spring streamflow and maintenance trip completed in May. • Upgraded slope hydrology site (upland soil moisture, tipping bucket, soil

temperature, runoff chemistry installed) in June. • Installation of research camp on Lower Carp Lake island completed in June. • Installation of WSC gauge at Lower Carp Lake completed in June.

DISCHARGE • Report on the measurement plan completed. AIRCRAFT • Research license application has received a favorable decision from the

Environmental Impact Screening Committee in Inuvik.


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3. Recent Publications and Presentations Kochtubajda, B., 1998. The Mackenzie GEWEX Study. Seminar presented at the Department of

Renewable Resources, “Landscape Ecology Seminar Series”, University of Alberta, January, 1998, Alberta.

Kochtubajda, B., 1998. Presentation on MAGS/CAGES given at the Hydrometric Monitoring Division Annual Meeting in Yellowknife, NWT, April, 1998.

Kochtubajda, B., 1998. Presentation on MAGS/CAGES given at the joint Environment Canada-Canadian Forestry Service Science Forum in Edmonton, Alberta, April, 1998.

Kochtubajda, B. and G.S. Strong, 1998. CAGES - An Enhanced Data Collection Period for the Mackenzie GEWEX Study. Abstract - 32nd CMOS Congress, Halifax, Nova Scotia.

Stewart, R.E., H.G. Leighton, P. Marsh, G.W.K. Moore, H. Ritchie, W.R. Rouse, E.D. Soulis, G.S. Strong, R.W. Crawford, and B. Kochtubajda, 1998. The Mackenzie GEWEX Study: The water and energy cycles of a major North American river system. Bull. Amer. Meteor. Soc. (in press)

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5.3(b) Radiosonde Operations during CAGES IOP-1 17 July - 01 August and 23 September - 11 October, 1998

G.S. Strong1, John Gyakum2, and Bob Kochtubajda3

1National Hydrology Research Centre, Saskatoon, Saskatchewan 2McGill University, Montréal, Québec

3Environment Canada, Edmonton, Alberta 1. Objectives There were two periods of intensive radiosonde operations during or leading up to IOP-1. The first involved radiosonde releases at 3-hour intervals only at Fort Smith, NWT during 17 July to 01 August, 1998. These were carried out specifically to help quantify the diurnal signature in atmospheric vapour mass resulting from local evapotranspiration. The two weeks of data are being merged with a similar set of data from early-August of 1997. The second period involved release of sondes at 6-hour intervals at six Canadian and one U.S. sites during 23 September to 11 October inclusive. One of these sites, Fort Simpson, NWT, was established by MAGS specifically for CAGES. 2. Progress and Collaborations MAGS is very fortunate to have the excellent cooperation of Environment Canada regional offices (PNR and PYR) to obtain these data, and to NOAA who provided 6-hour soundings at Yakutat free of charge. Table 1 summarizes soundings from each site during these periods. Statistics are not yet available from Yakutat as these data are in transit. Table 1 Soundings released in support of CAGES IOP-1, July and September-October, 1998,

and IOP-2, December, 1998.

Station ID Station Location Lat. (º)

Long. (º)

Elev. (m)

No. Soundings

17 July-01 August, 1998 YSM Fort Smith, NWT 60.003 111.933 203 87 IOP-1, 23 Sept-11 Oct, 1998 YSM Fort Smith, NWT 60.003 111.933 203 74 XSI Fort Simpson, NWT 61.760 121.237 169 72 YEV Inuvik, NWT 68.317 133.533 103 76 YVQ Norman Wells, NWT 65.280 126.750 95 76 YXY Whitehorse, YT 60.717 135.067 703 76 YYE Fort Nelson, BC 58.833 122.600 382 77 Total Canadian soundings during CAGES IOP-1 538 Add U.S. soundings: YAK Yakutat, Alaska 59.52 139.67 10 79 Total soundings during CAGES IOP-1 617 IOP-2, 01-15 Dec, 1998 XSI Fort Simpson, NWT 61.760 121.237 169 23 Total soundings, CAGES IOPs-1/2 640


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3. Technical Results The Vaisala sounding system was used exclusively at all sites, including Yakutat. Canadian sites can alternate between Omega-VLF, Loran-C, and GPS tracking systems, but this involves three different sonde types specific to the tracking systems. Loran-C tracking accuracy deteriorates significantly north of 60-70N latitude. The GPS sonde provides wind data by locking onto 4 to 8 satellites in order to obtain reliable sonde position data. It is expected to become the major sonde and tracking system in the future, but had seen little operational testing up until CAGES IOP-1. During IOP-1, some sites encountered loss of GPS signals during some releases with subsequent loss of wind data. This was most noticeable during the July tests at Fort Smith which used 27 Loran-C and 49 GPS sondes during. The CAGES data will have further value in efforts to improve the GPS tracking capability. Table 2 is a brief summary of signal/wind problem soundings during the diurnal signature tests of 17 July to 03 August. Compared with the Loran performance during this period, 23.3% of GPS sondes provided no winds above 15 km, and 6.7% of GPS sondes provided no winds at all. These data include only soundings, which provided good thermodynamic data; that is, this table does not include failed releases. Table 2 Summary of GPS signal problems and missing winds during Fort Smith radiosonde

tests for diurnal signal, 17 July - 01 August, 1998.

LORAN GPS No. of Soundings with No Winds No. % No. %

………. at all 0 0 4 6.7 …above 5 km 0 0 7 11.7 ..above 10 km 0 0 10 16.7 ..above 15 km 0 0 14 23.3 Total No. Soundings 27 100.0 60 100.0 4. Summary The additional CAGES radiosonde data will be used primarily to enhance the temporal resolution of moisture budget analyses from soundings, and will also help quantify differences between observed and modelled data for these studies. Additionally, the Fort Simpson data are being used to augment and ground-truth radar data from the IPIX radar there during CAGES. A similar program of soundings is planned for IOP-3 (May/June/99) and IOP-4 (July/99). Only Fort Simpson participated in releasing additional sondes during IOP-2, 01-15 December, and these were primarily to support the IPIX radar studies. 5. Recent Publications and Presentations Kochtubajda, B. and G.S. Strong, 1998. An Enhanced Data Collection Period for the Mackenzie

GEWEX Study. Paper presented at 32nd Annual Congress, Canadian Meteorological and Oceanographic Society, Halifax, Nova Scotia, June, 1998.

Stewart, R.E., H.G. Leighton, P. Marsh, G.W.K. Moore, H. Ritchie, W.R. Rouse, E.D. Soulis, G.S. Strong, R.W. Crawford, and B. Kochtubajda, 1998. The Mackenzie GEWEX Study: The water and energy cycles of a major North American river system. Bull. Amer. Meteor. Soc. (in press)


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Strong, G.S. and B. Proctor, 1998. Diurnal Variations in Atmospheric Moisture During GEWEX/MAGS. Paper presented at 32nd Annual Congress, Canadian Meteorological and Oceanographic Society, Halifax, Nova Scotia, June, 1998.

Strong, G.S., M. Wang, B. Proctor, and A. Barr, 1998. Atmospheric Moisture Budgets Over the Mackenzie Basin. Paper presented at 32nd Annual Congress, Canadian Meteorological and Oceanographic Society, Halifax, Nova Scotia, June, 1998.

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5.4 Preliminary Analysis and Assessment of the CAGES Enhanced Surface Observations

Paul Louie1 and Bob Kochtubajda2

1Climate Processes and Earth Observation Division, Climate Research Branch, AES, Downsview, Ontario 2 Environment Canada, Edmonton, Alberta

1. Objectives A critical issue facing MAGS concerns the lack of adequate surface observations over the entire Basin. An enhancement of the surface-observing network has been set in place to more completely fulfill the requirements of MAGS. The measurement protocol has been configured to ensure that the data collected are compatible with the AES climatological network standards. The generation of standard high quality, hourly meteorological data sets will assist in process related studies and in the initialization and validation of GEWEX modeling efforts and remote sensing studies. 2. Progress and Collaborations The proposed activities and milestones for 1998/99 are as follows:

(1) Complete specification and testing of QC and adjustment procedures. Oct/98(2) Preliminary analysis and assessment of all the climate variable

measurements from the new enhanced observation sites. Mar/99

(3) Production of quality controlled data archives for the enhanced observation periods.

Mar/88 to Sept/99

The work in this proposal is progressing as planned and on schedule. The MAGS weather stations (located at Lower Carp Lake, Fort Simpson Airport, Lindberg Landing, MacMillan Pass and Trail Valley Creek) are transmitting meteorological observations via satellite hourly and received at the Edmonton auto-station data centre within 20 minutes of the initial upload. Initial quality control protocol procedures are applied and the data decoded. These “semi-quality controlled” data are then transferred to the MAGS web site a day later and are available to researchers in accordance with the MAGS data policy and with a caveat that the data have not been fully quality controlled. The MAGS surface data transfer protocol and proposed QC procedure is illustrated in Figure 1. The station data are accessed through an interactive geographic map on the CAGES link of the main MAGS web page. The datalogger output protocols are documented for each station (see example shown in Table 1). Efforts are now being directed at developing a general extractor program and quality control routines. Quality control procedures for the standard climate parameters (T, Pressure, RH, Wind, and Radiation) will be based on the procedures used for the CMC climate digital archive. QC and adjustment procedures will be developed for precipitation. QC procedures will also be developed for non-standard parameters such as acoustic snow depth and soil moisture. Once these routines are in place, a quality controlled set of standard hourly data from these new sites should be available on the MAGS web site 6-8 weeks after the beginning of the each month. Standard climate data from these sites will also follow the normal route of quality control and end up in the CMC climate digital archive in 9-12 months. Table 2 provides a summary of the station information and parameters available for the new sites.


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The work to date has been accomplished with the collaborations of PNR staff the MAGS data manager and staff from CMC.

Figure 1 MAGS surface sites: data flow and QC.

3. Summary The MAGS surface data transfer protocol and proposed quality control procedure has been designed and several elements are now in place. 4. Related Information Data acquisition program: Autostation Guidelines ref: http://ecoprn2.edm.ab.ec.gc.ca/guide20/ Data code conversion: MicroComputer Codecon ref: http://ecoprn2.edm.ab.ec.gc.ca/MCC/ Data Quality Control: CMC QC procedures: ref: http://wwwib.tor.ec.gc.ca/atiscap/qc/index.html Data archive: ref: http://www.tor.ec.gc.ca/GEWEX/CAGES/observations/enhancements.html

http://www.tor.ec.gc.ca/GEWEX/CAGES/observations/enhancements.html


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Table 1 Station file for Fort Good Hope. ;STATION PARTICULARS:;; Official Station Name: Fort Good Hope;; Latitude: 66 16 ssN Longitude: 128 37 ssW; Elevation: 52.0 m Climate No.: 2201450; Identifier: ZGH Synoptic Number: 71491;; Output Array Definitions:;; HOURLY DATA OUTPUT;; 1 - Table ID (160); 2 - Year; 3 - Julian Day; 4 - Hour-Minute (Data Logger Clock Time); 5 - Station ID; 6 - Data Availability - Percent; 7 - Station Pressure (hPa) - 1 min avg.; (On hour); 8 - Station Pressure (hPa) - 1 min avg.; (H-1+15); 9 - Station Pressure (hPa) - 1 min avg.; (H-1+30); 10 - Station Pressure (hPa) - 1 min avg.; (H-1+45); 11 - Air Temperature (øC) - 1 min avg.; 12 - RH (%) - 1 min avg.; 13 - Mean Wind Speed (Knots) - 2 min avg.; 14 - Mean Vector Magnitude (Kts) - 2 min avg.; 15 - Mean Wind Vector Direction - 2 min avg.; 16 - Sigma Theta - 2 min avg.; 17 - Peak 5-sec. Speed (Kts) - Past hour; 18 - Peak Wind Speed Time (HHMM) - Past hour; 19 - Peak wind speed direction - Past hour; 20 - Max 2-Min Wind Speed (Kts) - Past Hour; 21 - Weighing Gauge Reading (mm) - 15 Minutes; 22 - Weighing Gauge Reading (mm) - 30 Minutes; 23 - Weighing Gauge Reading (mm) - 45 Minutes; 24 - Weighing Gauge Reading (mm) - On the Hour; 25 - Weighing Gauge Pcpn (mm) - Past hour; 26 - Snow on Ground (cm) - Minute 59-60; 27 - Snowfall (cm) - Past hour; 28 - Mean Wind Speed (Knots) - Minute 50-60; 29 - Mean Vector Magnitude (Kts) - Minute 50-60; 30 - Mean Wind Vector Direction - Minute 50-60; 31 - Sigma Theta - Minute 50-60; 32 - Max 10-Min Wind Speed (Kts) - Past Hour; 33 - Temperature (øC) - 1 hour avg.; 34 - RH (%) - 1 hour avg.; 35 - Mean Wind Speed (Kts) - 1 hour avg.; 36 - Mean Vector Magnitude (Kts) - 1 hour avg.; 37 - Mean Wind Vector Direction - 1 hour avg.; 38 - Sigma Theta - 1 hour avg.; 39 - Sigma U (Knots) - 1 hour avg.; 40 - Maximum Air Temp. (øC) - Past hour; 41 - Minimum Air Temp. (øC) - Past hour; 42 - RF1 Radiation (W m-2) - 1 hour avg.; 43 - Max. RF1 Radiation (W m-2) - Past Hour; 44 - Min. RF1 Radiation (W m-2) - Past Hour; 45 - RF4 Radiation (kW m-2) - 1 hour avg.; 46 - Max. RF4 Radiation (kW m-2) - Past Hour; 47 - Min. RF4 Radiation (kW m-2) - Past Hour; 48 - RF1 Sunshine (hours) - Past Hour; 49 - 5 cm Soil Temp. (øC) - 1 min avg.; 50 - 10 cm Soil Temp. (øC) - 1 min avg.; 51 - 20 cm Soil Temp. (øC) - 1 min avg.; 52 - 50 cm Soil Temp. (øC) - 1 min avg.; 53 - 100 cm Soil Temp. (øC) - 1 min avg.; 54 - 150 cm Soil Temp. (øC) - 1 min avg.; 55 - 300 cm Soil Temp. (øC) - 1 min avg.; 56 - Minute 55-60 avg RF1 (wm-2) - Past hour; 57 - Minute 0- 5 avg RF1 (wm-2) - Past hour; 58 - Minute 5-10 avg RF1 (wm-2) - Past hour; 59 - Minute 10-15 avg RF1 (wm-2) - Past hour; 60 - Minute 15-20 avg RF1 (wm-2) - Past hour; 61 - Minute 20-25 avg RF1 (wm-2) - Past hour; 62 - Minute 25-30 avg RF1 (wm-2) - Past hour; 63 - Minute 30-35 avg RF1 (wm-2) - Past hour; 64 - Minute 35-40 avg RF1 (wm-2) - Past hour; 65 - Minute 40-45 avg RF1 (wm-2) - Past hour; 66 - Minute 45-50 avg RF1 (wm-2) - Past hour; 67 - Minute 50-55 avg RF1 (wm-2) - Past hour; 68 - Weighing Gauge Wind (knots) - 1-hour avg.; 69 - Soil Moisture - 1-hour avg.; 70 - SOG Standard Deviation - Past Hour; 71 - SR50 Distance-to-Gnd #1 (m) - 1 min avg.; 72 - SR50 Distance-to-Gnd #2 (m) - 1 min avg.; 73 - SR50 Distance-to-Gnd #3 (m) - 1 min avg.; 74 - SR50 Quality #1 - 1 min avg.; 75 - SR50 Quality #2 - 1 min avg.; 76 - SR50 Quality #3 - 1 min avg.;; NOTE: Value 56 is the last 5-Minute average; for the hour. Units watts per sq. metre.;

; Conditional TBRG Precipitation;; 1 - Table ID (400); 2 - Year; 3 - Julian Day of Year; 4 - Hour and Minute; 5 - Station Identifier; 6 - Precipitation Amount (mm);; Diagnostic/Climate Data (Daily) - User Selected;; 1 - Table ID (224); 2 - Year; 3 - Julian Day of Year; 4 - Hour and Minute; 5 - Station Identifier; 6 - Battery Voltage (At output data time); 7 - Program Signature; 8 - Maximum Battery Voltage; 9 - Minimum Battery Voltage; 10 - Last Significant Weigh. Gauge Reading (mm); 11 - Last Significant Snow-on-Ground (mm); 12 - Panel Temperature (øC); 13 - Maximum Temperature (øC); 14 - Maximum RH (%)/DewPoint (øC); 15 - Minimum Temperature (øC); 16 - Minimum RH (%)/DewPoint (øC); 17 - Weighing Gauge Precipitation Amount (mm); 18 - TBRG Precipitation Amount (mm); 19 - Snowfall Amount (cm); 20 - Snow on Ground (cm);; 0800 and 1700 LST Data Output;; 1 - Table ID (0800 = 208; 1700 = 217); 2 - Year; 3 - Julian Day of Year; 4 - Hour:Minute; 5 - Station Identifier; 6 - Maximum Air Temperature (øC); 7 - Minimum Air Temperature (øC); 8 - Weighing Gauge Precipitation (mm); 9 - TBRG Precipitation (mm); 10 - Snowfall (cm); 11 - Snow on Ground (cm); 12 - 5 cm Soil Temperature (øC) - 1-Min avg.; 13 - 10 cm Soil Temperature (øC) - 1-Min avg.; 14 - 20 cm Soil Temperature (øC) - 1-Min avg.; 15 - 50 cm Soil Temperature (øC) - 1-hour avg.; 16 - 100 cm Soil Temperature (øC) - 1-hour avg.; 17 - 150 cm Soil Temperature (øC) - 1-hour avg.; 18 - 300 cm Soil Temperature (øC) - 1-hour avg


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Table 2 Summary of the station information and parameters available for the new sites.

Ft Good Hope

Lower Carp Lake

Ft Simpson

LindbergLanding

LindbergForest

Watson Lake

MacMillanPass

DeaseLake

Inuvik TVC

Inuvik UA

HavikpakCreek

Check point

LAT 66 16 63 36 61 45 61 07 61 07 60 07 63 14 58 25 69 44 68 19 68 19 61 08 LONG 128 37 113 51 121 14 122 50 122 51 128 49 130 02 130 00 133 30 133 32 133 30 120 47

Insp Report x x x x x x x x Stn File x x x x x na na na na Real Ttime Data

x x x x x x x na na na

Archive Data

x x x x x x na na na

Temp x x x x x x x NWRI NWRI x RH x x x x x NWRI NWRI x Bara Press x x x x x NWRI x x Ws @ 10 m x x x x x NWRI NWRI x Wd @ 10 m x x x x x NWRI NWRI x Ws @ 2 m x x x x x x x x Precip x x x x AWOS x AWOS x NWRI Snow Depth x x x NWRI x x x NWRI NWRI x RF1 x x x NWRI NWRI x RF4 x x x x NWRI x NWRI x Soil Temp NWRI NWRI NWRI Soil Moist NWRI x NWRI NWRI

Notes: NWRI = data on NWRI logger AWOS = data on AWOS READAC system

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Proceedings 4th MAGS Workshop 6: Invited Presentations November, 1998 Betts and Viterbo

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Water Budgets of Seven Sub-basins of the Mackenzie from the ECMWF Analysis

Allan Betts1 and Pedro Viterbo2

1Pittsford, Vermont 2European Centre for Medium-Range Weather Forecasting [ECMWF], Reading, England

Abstract We analyse the liquid and frozen hydrology and the surface energy budget from seven sub-basins of the Mackenzie River from integrals calculated from the operational ECMWF model from September, 1996 to August, 1998. The model budgets show the spatial distribution of precipitation and snowfall for the two years, and give estimates of runoff and surface evaporation. Neither of the model budgets of liquid water and snow are closed, but the analysis of the model residuals suggests where the model physics lacks key processes, and so could be improved. 1. Introduction The Mackenzie River GEWEX study [MAGS] has as one of its objectives (MAGS 1996) to understand and model the hydroclimatology of this northern river and its sub-basins, which flows into the Arctic Ocean. The basin is large (drainage area is 1.8 106 km2), and surface and upper air observations are relatively sparse, so that models are essential to estimate the surface energy and water balance over the annual cycle. This paper summarizes the liquid and frozen surface water and energy budgets from the ECMWF operational model for two years from September 1, 1996 to August 31, 1998 for seven sub-basins of the ECMWF model, shown in Figure 1. The ECMWF analysis system has the capability of archiving averages for physics grid-points within quadrilaterals at hourly time resolution. For MAGS we have hourly basin integrals from the 11 to 35 hour forecast starting with every 1200 UTC analysis time, giving a continuous hourly time series of surface meteorological variables and accumulated surface energy and water fluxes. In Figure 1, basin 1 is the Peel River and Mackenzie delta, basin 2 is the Great Bear Lake sub-basin, 3 is the Great Slave Lake sub-basin, 4 is the Liard River, 5 and 6 are eastern and western sections of the Peace River, and 7 is the Athabasca River. The model integrals simply include all grid-points (shown as shaded dots) within each quadrilateral, so that some approximation of the basin areas is involved. Table 1 lists the basin drainage areas and their approximation in the ECMWF model. All our results will be presented as area averages. Similar recent studies, using nine years of the ECMWF reanalysis, have been completed for the sub-basins of the Mississippi (Betts et al. 1998a,b and 1999a). They showed that for the Mississippi Basin as a whole, the monthly model precipitation for the 12 to 24 hour forecast, when compared with gridded rainfall observations, had a high bias of 10%, and a correlation coefficient over 90%. For the sub-basins, the biases were greater and the correlation less. For the Mackenzie Basin, precipitation observations are less dense than over the Mississippi Basin, and the annual snowfall is higher (and more difficult than rainfall to measure accurately), so it is possible that the rainfall and snowfall forecast by a high resolution model might give our best basin-scale estimates of precipitation. However, the density of upper air observations used in the analysis cycle is also far lower over the Mackenzie than over the central United States.


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Figure 1 Representation of seven sub-basins of the Mackenzie River by quadrilaterals in the

ECMWF operational model. The dots are the model physics grid-points. Table 1 Mackenzie sub-basin drainage areas and their model approximation.

Sub-basin Drainage Area (km2)

ECMWF Model Area (km2)

1. Peel/Delta 117127 106950 2. Great Bear Lake 421191 344630 3. Great Slave Lake 378245 421489 4. Liard 273395 283828 5. Peace (E) (186237) 260712 6. Peace (W) (132873) 186007 7. Athabasca 285111 228839 Total 1791857 1832455

These same papers concluded that the runoff in the ECMWF model (which is all deep runoff from the base layer, because the surface runoff scheme is not activated) is less than the observed streamflow for the Mississippi basins. They also showed how the nudging of soil water plays an important role in the model liquid hydrology. It prevents long-term drifts of soil water, but it also attempts to compensate for model systematic errors in evaporation and runoff. Betts et al. (1998b) discussed briefly the model’s frozen hydrology for the upper Mississippi Basin, which is not in balance, because there is a new snow analysis at each analysis time, based on observations. This paper will discuss the model liquid and solid hydrology for the Mackenzie Basin, and comment on the water and energy imbalances in the current ECMWF land-surface model.


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1.2 ECMWF model land-surface scheme The current land-surface scheme (Viterbo and Beljaars 1995) became operational in August, 1993. This model version did not update the model frozen hydrology, which is described in Blondin (1991). The nudging of soil water based on short-term forecast errors in humidity was introduced in November 1994 (Viterbo and Courtier 1995). Soil water freezing and a revised stable boundary layer were introduced in September 1996 (Viterbo et al. 1998), and the albedo model for the boreal forests was changed in December 1996 (Viterbo and Betts 1998). This December 1996 change reduced the albedo of the boreal forests from 70 to 80% to about 20% in the presence of snow. For the two years of this data set, the model has only a single vegetation type (nominally grassland). The albedo calculation, after December 1996, accounts for the forested areas, but the evaporation calculation for snow (which is based on a potential evaporation calculation at the model skin temperature) is not aware that the snow is under the canopy. This leads to high snow evaporation in the model (Betts et al. 1998c). The surface evapotranspiration algorithms do not allow for the tight stomatal control of coniferous forests, so the model evaporative fraction is higher in summer (Betts et al. 1998c) than observed at a boreal spruce forest site (the dominant landscape class). Despite the introduction of soil freezing in the model thermal budget, soilwater continues to drain in winter, when the soil is frozen. The snow-melt algorithm. 2. Mackenzie Basin Monthly Surface Hydrology We will first show results for the entire Mackenzie Basin, and then the inter-basin variability in terms of monthly sums or averages. 2.1 Two-year mean annual cycle in the model Figure 2 shows key terms in the two-year average model hydrology for the whole Mackenzie Basin. All terms are in mm month-1, an average for the whole basin. The heavy solid line is the annual cycle of precipitation, showing a summer maximum of around 100 mm month-1. From November to March, almost all this precipitation is snowfall in the model (heavy short dashes). Evaporation (thin solid line) is plotted negative and subdivided into liquid evaporation and evaporation of snow, which has an April peak. Snow-melt, which also has an April peak in the model (near 80 mm month-1) is shown with long heavy dashes. The model runoff (fine dots) peaks a month later in May; this is instantaneous drainage from the model deepest layer, not surface runoff routed along the river channels. For comparison, we show the mean 1972-1990 stream flow of the Mackenzie River above the Arctic Red River, which peaks a month later in June. Although the spring peak is a month early, the model runoff for these two years is comparable to (but a little higher) than the observed climatological stream flow. 2.2 Liquid and frozen hydrology for the two years Figure 3 shows the two-year cycle of key terms in the model liquid hydrology: rainfall, snow-melt, runoff, liquid evaporation, soil water storage change, and the residual for the whole Mackenzie Basin. The x-axis is year and month with ‘97 marking January 1997. Snow-melt initially recharges the soil water reservoir in April, and then runs off through deep drainage (in the model) in May. Snow-melt came earlier in the model in 1998 than 1997 (because air temperatures were higher), and the spring runoff peak was a little higher. The model liquid hydrology, however, is not conservative (the residual is shown dotted), as the model hydrologic cycle has a significant spinup, and the model analysis cycle has a soil water nudging term. This will be discussed further in the next section.


161

Figure 2 Two-year average monthly average precipitation, snowfall, evaporation, snow-melt, and

runoff for the Mackenzie from the ECMWF model, and the climatological streamflow.

Figure 3 Key terms in the monthly liquid hydrology budget for the Mackenzie from September 1996 to August 1998.


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Figure 4 shows terms in the model frozen hydrology. The model source and sink terms are snowfall, melt, and the evaporation of snow. For each winter, we show the accumulated sum of these terms: SumSnow = 3(SnowFall - Melt - EvapSnow) (1) as a measure of a model calculation of the snow-pack at the end of each month (light dotted). However the model has an independent snow analysis at each model analysis time, based on observations of snow-cover and snow-depth, and these end-of-month snow-pack depths (in mm of water) are also shown (light solid). During the accumulation phase (October to March), the “analysis” snow-pack and the term SumSnow are in fair agreement (for the basin as a whole). However, the sum of the model terms representing loss of snow (Melt + EvapSnow) in April and May greatly exceed the end of March snow-pack, whether analysis or model calculated, with the largest error appearing to be in April. We shall show later that the sub-basins differ in this error signature.

Spring snowfall was less in 1998 than 1997, and the melt came earlier, because air temperatures were higher as mentioned above. Figure 4 Key terms in the monthly frozen hydrology budget for the Mackenzie from September

1996 to August 1998. 2.3 Monthly summary for Mackenzie River For comparison with other budget studies of the Mackenzie, we tabulate these results. Table 2 shows key terms in the ECMWF model liquid and frozen hydrology for the Mackenzie Basin.


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Table 2 Monthly hydrologic balance for Mackenzie Basin from the ECMWF model.

Year Month Precip Rain Snow Evap (liq)

Evap (snow)

Melt Runoff delSW del Snow S igL Sigsn Sigtot

96 9 66.1 59.3 6.9 -37.6 -0.7 0.2 14.4 6.7 0.3 0.8 5.6 6.4 96 10 46.4 20.9 25.5 -12.1 -4.5 0.7 17.6 2.8 16.8 -11.0 3.5 -7.5 96 11 26.0 3.9 22.0 -0.3 -5.0 0.0 13.0 -13.0 43.3 3.7 -26.3 -22.6 96 12 22.8 1.6 21.2 0.0 -2.1 0.0 10.3 -8.3 28.4 -0.3 -9.2 -9.6 97 1 26.0 3.6 22.4 0.0 -1.7 0.0 8.4 -5.9 16.9 1.1 3.7 4.8 97 2 22.8 4.2 18.7 0.0 -6.4 0.0 6.6 -4.4 -2.5 1.9 14.7 16.6 97 3 41.5 5.8 35.7 -0.1 -20.8 7.1 6.6 1.3 0.1 4.9 7.6 12.5 97 4 44.8 17.6 27.3 -3.6 -36.7 67.9 9.6 55.0 -36.0 17.2 -41.2 -24.1 97 5 60.4 43.7 16.6 -39.2 -20.1 61.1 42.9 8.4 -59.7 14.4 -4.9 9.4 97 6 104.8 103.8 1.0 -82.6 -0.7 5.0 29.2 -10.9 -7.8 7.9 3.1 11.1 97 7 118.2 118.0 0.2 -89.4 0.0 0.0 21.8 -2.7 0.0 9.6 0.1 9.8 97 8 74.0 73.7 0.3 -70.9 0.0 0.0 21.4 -4.1 0.0 -14.4 0.2 -14.2

96-97 654.0 456.3 197.7 -336.0 -98.7 142.1 201.8 24.8 0.0 35.8 -43.2 -7.4 97 9 77.5 70.6 6.9 -37.4 -0.6 0.9 24.6 -7.4 0.5 17.0 4.9 21.8 97 10 70.6 31.3 39.3 -12.0 -6.6 2.9 20.9 -10.6 9.6 12.0 20.1 32.1 97 11 23.5 6.4 17.1 -1.2 -6.1 0.7 15.0 -16.9 18.8 7.8 -8.4 -0.6 97 12 38.7 6.6 32.1 -0.2 -7.5 0.0 10.5 -10.2 25.2 6.0 -0.6 5.4 98 1 19.9 2.1 17.8 0.0 -1.3 0.0 8.4 -7.3 31.7 1.0 -15.2 -14.2 98 2 18.5 3.3 15.2 0.0 -4.7 0.0 6.4 -4.2 16.9 1.1 -6.4 -5.4 98 3 25.5 5.7 19.8 -0.3 -21.7 10.1 6.3 4.7 -9.0 4.4 -3.0 1.4 98 4 33.8 18.6 15.2 -10.7 -28.9 105.5 16.5 71.1 -44.7 25.8 -74.5 -48.7 98 5 51.3 46.0 5.3 -62.4 -8.5 41.0 46.6 -36.0 -46.0 14.0 1.8 15.8 98 6 93.0 92.6 0.4 -86.3 -0.3 2.4 21.6 14.9 -3.0 -27.8 0.7 -27.1 98 7 96.0 95.6 0.3 -100.9 0.0 0.0 21.4 -8.1 0.0 -18.5 0.3 -18.2 98 8 70.9 70.4 0.5 -81.9 -0.1 0.0 18.2 2.6 0.0 -32.3 0.4 -31.8

97-98 619.2 449.3 169.9 -393.3 -86.2 163.6 216.2 -7.2 0.0 10.5 -79.9 -69.4

For the liquid hydrology for the two years: Residual = 3(liquid) = 3[Rain + Melt - Evap(liq) – RunOff-)(SoilWater)] (2) = 456 + 142 – 336 – 202 – 25 = 36 mm for 1996-97 = 449 + 164 – 393 – 216 + 7 = 11 mm for 1997-98 The residual is about 3 to 10% of the rainfall in these two years. This liquid hydrology is not in balance for two reasons: the spinup of the model hydrologic cycle, and the imbalance in the model analysis cycle. The model analysis cycle does not conserve water, because soil water is added through a nudging term calculated from short-term forecast errors in the humidity at the lowest model level. This nudging term was introduced (Viterbo and Courtier 1995) to prevent the downward drift of soil water brought about by the low rainfall in the analysis cycle (in turn related to the


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spinup). In fact, the nudging also appears to compensate for other errors in the model physics in evaporation and runoff (Betts et al. 1998a,b, 1999a). For the Mackenzie sub-basins, the analysis cycle terms were not archived, so we do not have an estimate for the addition of water by nudging, or the analysis cycle rainfall, which is probably biased low. The rainfall in (2) which is from the 11 to 35 hr forecast, may be of order 25% greater than the rainfall in the analysis cycle (Betts et al. 1998a,b), and could be a better estimate of basin rainfall. These earlier studies (of the Mississippi basins) showed that the other terms have a much smaller spinup in the first 24 hrs of the model forecast. The model frozen hydrology balance is given by: Residual = 3(frozen) = 3[Snowfall + Melt - Evap(snow) – RunOff-)(Snowpack)] (3) = 198 – 142 – 99 = -43 mm for 1996-97 = 170 – 164 – 86 = -80 mm for 1997-98 The snow-pack is zero at the beginning of each September. The imbalance here is larger, with snow losses exceeding snowfall by 20% the first year and 45% the second year, because the model analysis cycle for snow is also non-conservative, as mentioned above. An independent snow analysis is introduced, based on observations of snow-cover and snow-depth at every analysis time. Throughout the accumulation phase of the snow-pack from October to March, on the Mackenzie basin-scale, the net model accumulation of snow is quite close to the growth of the snow-pack, so that the residual is small (see Figure 4). However, the residual is large when the snow-pack starts to dissipate in April. Melt and snow evaporation in April and May significantly exceed the depth of the snow-pack and, therefore, must be too high. We shall see later that the imbalance differs among the sub-basins. The sum of the residuals is the last column: 3(total) = 3[Precip – Evap(liq) - Evap(snow) – RunOff-)(SoilWater) - )(Snowpack)] (4) = - 654 – 336 – 99 –202 –25 = -7 mm for 1996-97 = - 619 – 393 –86 – 216 + 7 = - 69 mm for 1997-98 The residuals in the liquid and frozen budgets partly cancel, so that total precipitation, evaporation and runoff from these 11 to 35 hour forecasts balance to about 10% of the precipitation. The model annual precipitation for these two years of order 640 mm is substantially more than the recorded mean annual precipitation for the Mackenzie (MAGS, 1996) for the period, 1961-1990, which increases from below 300 mm in the north to over 600 mm in the southwest. While the model precipitation does increase in a similar manner, the model precipitation is about 40% higher than the long-term climatology. Basin 1 is an exception: the model precipitation is almost double that “observed” (although there appears to be only one observation site actually within this basin contributing to the climatology). 3. Inter-Basin Variability As well as showing the variability between the two years, the model shows the inter-basin differences. 3.1 Fluxes Figure 5 shows precipitation for the seven sub-basins. Basin 6, the western section of the Peace River, which starts in the Rocky Mountains has the most winter precipitation, while the northern and eastern basins (1 to 3) have the least. Summer rainfall is high in all the southern basins 4 to 7, and lower in the north.


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Figure 6 shows that the fraction of precipitation falling as snow generally falls from north-west to south-east. It is over 90% in winter in the north (on a monthly basis), and near zero from June to August: showing the very strong seasonal cycle for this northern basin. Note that in the warmer spring of 1998, less precipitation fell as snow in all basins. The model may be the best estimate of the fraction of precipitation falling as snow that we have on this basin-scale. Figure 7 shows the model runoff. The western branch of the Peace River (6), which has the deepest winter snowpack (see Figures 11 and 12 later) has the highest spring runoff peak. While all basins have a spring peak, basins 5, 6, and 7 also have a secondary maximum in the model in the fall. In our Mississippi studies, model runoff was less than observed streamflow by a factor of roughly two (Betts et al. 1998a,b and 1999a). However, the total annual runoff for these two years for the Mackenzie is close to the climatological stream flow (see Figure 2), although the peak is too early in the spring. Figure 8 shows the melt term in the model. Basins 1, 2, 4, and 6 have a May peak in 1997, a month later than basins 3, 5, and 7 in the east. In 1998, melt is earlier and only basin 6 has a May peak. Figure 9a shows the model liquid evaporation, which increases from north-west to south-east in summer, and is zero when the ground is covered with snow. Figure 9b shows the snow evaporation, which has a similar structure: snow evaporation is lower and peaks later in spring in the far north-west and is earlier and higher in the south-east, although basin 6 which has the greatest snowfall has the largest evaporation. The spring peak in snow evaporation is much higher than the fall peak, because the net radiation is higher in spring.

Figure 5 Monthly distribution of precipitation for the seven sub-basins.


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Figure 6 Monthly distribution for the fraction of precipitation falling as snow for the seven sub-

basins.

Figure 7 Monthly distribution for the model runoff for the seven sub-basins.


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Figure 8 Monthly distribution for the model snow-melt for the seven sub-basins.

Figure 9a Monthly distribution for the model liquid evaporation for the seven sub-basins.


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Figure 9b Monthly distribution for the model snow evaporation for the seven sub-basins.

3.2 Water storage terms Figure 10 shows the inter-basin variation of integrated column soil water, which increases from a minimum for basin 2 to a maximum for basins 5, 6, and 7. The annual patterns are very similar for all basins. Soil water falls unrealistically in winter as deep drainage continues, because the soil hydraulic parameterization is unaware the soil is frozen. This leads to a minimum soil water in the spring, just before a rapid recharge, of order 100 mm, with the melting of snow in April and May. Soil water is more variable in summer, as is rainfall. Figure 11a shows the variation of the snow-pack water storage in the analysis for each basin, ranging from a winter peaks of over 150 mm for the mountain basins 4 and 6, to only 70 mm for the northern basins. Figure 11b is a corresponding “model snow-pack” calculated for each winter as the sum of the model (Snowfall-EvapSnow-Melt) from equation (1). During the winter accumulation phase, the variation between basins is similar to Figure 11a. This is shown more clearly in Figure 12, which compares the maximum snow-pack in the analysis with this model accumulated snow-pack. The analysis snow-pack is much smaller for basin 1 (for which the model has much more winter snowfall than shown by the sparse observations), but a little greater for some basins such as 5 and 7. However, Figure 11b shows that during the spring melt phase, except for basins 1 and 4 (which have the lowest net radiation [not shown]), the spring melt and evaporation of snow exceed the water stored in the snow-pack, whether analysed or our model accumulated value. This suggests the model must overestimate either the evaporation of snow, or the melting, or both. One possible reason for this is that most of the southern two-thirds of the basin is forested, and the snow lies under the trees. The forest canopy intercepts much of the incoming solar radiation, and returns most of this back to the atmosphere as sensible heat (Betts et al. 1998c, 1999b). The model, however, has only a single surface energy balance, and the snow evaporation algorithm responds directly to the net radiation above the canopy. The north-western basins, 1 and 4, have a lower net radiation (presumably because of greater cloud cover), and consequently snow evaporation is less for these basins.


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In addition, there is no separate snow temperature field in the model: the snow has the temperature of the first soil layer. Consequently snow-melt and ground melt are coupled, and they both again respond to the single surface net radiation balance, even for forested areas. As the ground melts, the fluxes into the ground are very large, absorbing almost all the net radiation, while the fluxes to the atmosphere are small. Clearly in northern forested areas (which includes much of the Mackenzie) the model needs a separate energy balance for the snow-covered ground surface and the canopy.

Figure 10 Monthly distribution for the model column soil water for the seven sub-basins.

Figure 11a Snow-pack water equivalent in the model analysis.


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Figure 11b Snow-pack water equivalent calculated from the model snow budget terms.

Figure 12 Comparison of maximum winter snow-pack in the analysis, and as calculated from the

model snow budget.


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3.3 Summary by basin and hydrological year Table 3 Precipitation, evaporation, and runoff by basin.

Basin Precip Evap Runoff ))))(SoilWater) Resid 97 98 97 98 97 98 97 98 97 98

1 511 579 -271 -323 100 142 -19 31 159 82 2 437 494 -314 -375 97 110 -30 96 57 -88 3 541 519 -454 -484 119 143 65 -4 -97 -105 4 793 736 -375 -423 172 157 2 -30 243 186 5 735 586 -562 -596 305 288 36 -84 -168 -215 6 956 927 -472 -528 397 441 12 -25 75 -17 7 744 654 -556 -598 321 354 79 -58 -211 -241

All 654 619 -435 -480 202 216 25 -7 -7 -69 4. Energy Balance Figure 13 and Table 4 summarize the surface energy balance of the whole Mackenzie Basin for the two years. All values are monthly averages and the units are W m-2 . At these high latitudes, the net radiation (Rnet) has a strong annual cycle. Figure 13 shows the downward ground heat flux (G) as positive in summer and the upward sensible (SH) and latent heat (LH and LHsnow) as negative in spring and summer. The energy taken by the melting of snow is also shown negative: this is smaller than the evaporation of snow (although more water is involved) as the latent heat of melting is much less than that of sublimation. The SH flux is almost certainly too small in April, when the snow evaporation peaks. Over the boreal forest black spruce site in Betts et al. (1999b), the SH flux actually has two peaks, one in April and a second peak in June.

Figure 13 Model surface energy budget for the Mackenzie.


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Table 4 Energy balance terms for the Mackenzie Basin.

Year Month Rnet SH LH LHsnow Emelt G96 9 42.0 -9.3 -37.4 -0.8 0.0 -5.696 10 -6.8 5.2 -11.6 -4.8 -0.1 -18.096 11 -36.6 12.6 -0.3 -5.5 0.0 -29.896 12 -42.5 20.8 0.0 -2.2 0.0 -23.897 1 -32.5 24.4 0.0 -1.8 0.0 -9.997 2 -13.2 16.2 0.0 -7.5 0.0 -4.597 3 22.6 1.0 -0.1 -22.0 -0.9 0.697 4 72.1 -3.8 -3.6 -40.1 -8.7 15.997 5 110.8 -24.2 -37.2 -21.3 -7.6 20.697 6 131.2 -28.1 -81.0 -0.7 -0.6 20.697 7 125.7 -24.4 -85.1 0.0 0.0 16.197 8 95.9 -19.2 -67.2 0.0 0.0 9.4

96-97 39.1 -2.4 -27.0 -8.9 -1.5 -0.797 9 42.2 -2.9 -36.6 -0.6 -0.1 2.097 10 -1.9 4.0 -11.3 -7.0 -0.4 -16.697 11 -33.2 20.6 -1.1 -6.7 -0.1 -20.597 12 -37.7 35.1 -0.2 -7.9 0.0 -10.898 1 -32.5 15.1 0.0 -1.4 0.0 -18.998 2 -11.3 14.6 0.0 -5.5 0.0 -2.198 3 26.2 4.1 -0.3 -22.9 -1.3 5.798 4 79.9 0.4 -10.6 -31.6 -13.6 24.598 5 134.5 -37.1 -59.3 -9.0 -5.1 24.098 6 143.7 -38.5 -85.4 -0.3 -0.3 19.198 7 140.4 -29.5 -96.1 0.0 0.0 14.798 8 103.1 -16.4 -77.9 -0.1 0.0 8.8

97-98 46.1 -2.5 31.6 -7.8 -1.7 2.5 Figure 13 and Table 4 show that the annual average net radiation is considerably higher in 1997-1998, and with it the latent heat flux. The net ground heat flux is downward in 1997-98, but upward in 1996-97, when Rnet is less. Figure 14 shows evaporative fraction (EF) for the sub-basins from April to September, defined as: EF= (LH+LHsnow)/(SH +LH +LHsnow) (5) EF is high in April when snow is evaporating and melting (probably too high as mentioned above), low after snow-melt when the temperature is low, and then increases during the summer. There is a general increase in summer of model EF from the northwest basins to the southeast. For the forested areas these values are probably too high (Betts et al. 1998c, 1999b): the model evapotranspiration algorithm does not recognize different vegetation types, and it was developed using grassland data (Viterbo and Beljaars 1995).


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Figure 14 Average evaporative fraction [EF] for the seven sub-basins from April to September.

5. Conclusions We have presented the monthly surface energy and water balance terms from the operational ECMWF analysis for seven sub-basins of the Mackenzie River for a two-year period from September 1996 to August 1998. Other model and observational studies are underway as part of the MAGS program, but at this point little validation data is available for comparison with the model results. The value of model studies is that they provide representative area averages in regions of sparse data, and show well the spatial and temporal variability. As earlier studies have shown that the precipitation in the ECMWF model is a reasonable estimate of observed precipitation on the basin-scale, these budgets may provide a useful baseline for the Mackenzie sub-basins. In particular, the model estimates of snowfall and the fraction of cold season precipitation falling as snow may be superior on the basin-scale to measurements. Neither the model liquid or frozen hydrology are closed, albeit for different reasons. In the liquid budget, soil water nudging adds a significant amount of water to the model. Earlier studies for the Mississippi Basin (Betts et al. 1998a,b) have explored the projection of model errors on to this nudging term. However, our Mackenzie data set, from the 11 to 35 hour model forecasts, does not include the analysis cycle fluxes, so we cannot calculate here the nudging term explicitly, although some of its impact is visible as a residual. In the frozen hydrology, the budget is not closed because a new snow analysis based on observations is introduced at each analysis time. We found that during the winter accumulation phase, the sum of the model snowfall, snow evaporation and melt terms agrees reasonably well with the analysis snow-pack, but in spring the model melt and snow evaporation terms are too large: in total they exceed the amount of the snow-pack, except for the north-western basins which have the lowest net radiation.


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In this analysis we have only shown monthly values. The model data is hourly and so shows considerable detail associated with both the diurnal cycle and the passage of synoptic weather events. We can make these seven basin hourly data sets available to MAGS investigators. Acknowledgements Alan Betts acknowledges support from the National Science Foundation under Grant ATM-9505018, from the NOAA Office of Global Programs under Grant NA76-GP0255. References Betts, A.K., J. H. Ball, and P. Viterbo, 1999a. Basin-scale Hydrology of the Mississippi from the

ECMWF Reanalysis. Preprint, 14th AMS Conference on Hydrology, Dallas, Texas, 4 p. Betts, A.K., M.L. Goulden, and S.C. Wofsy, 1999b. Controls on evaporation in a boreal spruce forest. J.

Climate. (in press) Betts, A.K., P. Viterbo, and E. Wood, 1998a. Surface Energy and water balance for the Arkansas-Red

River Basin from the ECMWF reanalysis. J. Climate, 11:2881-2897. Betts, A.K., J.H. Ball, and P. Viterbo, 1998b. Energy and water budgets for the three western sub-basins

of the Mississippi from the ECMWF reanalysis. J. Geophys. Res. (submitted to GCIP, special issue) Betts A.K., P. Viterbo, A.C.M. Beljaars, H-L. Pan, S-Y. Hong, M.L. Goulden, and S.C. Wofsy, 1998c.

Evaluation of the land-surface interaction in the ECMWF and NCEP/NCAR reanalyses over grassland (FIFE) and boreal forest (BOREAS). J. Geophys. Res., 103:23079-23085.

Viterbo, P. and A.C.M. Beljaars, 1995. An improved land-surface parameterization in the ECMWF model and its validation. J. Clim., 8:2716-2748. In: Proceedings 2nd Scientific Workshop for the Mackenzie GEWEX Study [MAGS], 1996.

Viterbo, P. and P. Courtier, 1995. The importance of soil water for medium-range weather forecasting. Implications for data assimilation. Workshop on Imbalance of Slowly Varying Components of Predictable Atmospheric Motions. World Meteorol. Org., Beijing, China (Available from ECMWF, Shinfield Park, Reading RG2 9AX, England). In: Proceedings 2nd Scientific Workshop for the Mackenzie GEWEX Study [MAGS], 1996.

Viterbo, P. and A.K. Betts, 1998. The impact on ECMWF forecasts of changes to the albedo of the boreal forests in the presence of snow. J. Geophys. Res. (in press, BOREAS, special issue)

Viterbo P., A.C.M., Beljaars, J.-F. Mahfouf, and J. Teixeira, 1998. Soil moisture freezing and its interaction with the boundary layer. Q. J. R. Meteorol. Soc. (submitted)

◆◆◆

Proceedings 4th MAGS Workshop 6: Invited Presentations November, 1998 Raschke

175

BALTEX Recent Advances and Future Problems

Ehrhard Raschke

GKSS Research Center, Geesthacht, Germany Objectives, Deliverables, and Customers BALTEX, the preparatory phase which began in 1992, follows similar scientific objectives as MAGS and the other three GEWEX Continental-Scale Experiments adopted. They are all related to:

"a better understanding of energy and water cycles and of related climatic processes over a larger water catchment area",

in order to improve weather and climate forecasts, but also the modelling of past climatic developments. Deliverables should be numerical models coupling the atmosphere to hydrological processes at the surface and within near-surface layers, and also to the upper ocean (Baltic Sea!) layers and models or concepts, describing better than before the various transport and exchange processes. These models should be applicable to other regions of the earth with quite similar climatic properties. Customers of BALTEX results are all hydrometeorological services of all 14 countries draining all or most of their water into the Baltic Sea and their particular clients from various economic and societal organizations. But, interest also arose within a wide research community of other European countries to use BALTEX results for their ongoing activities. The BALTEX research activities are also of particular interest for several inter-governmental projects to unify this area around the Baltic Sea. The BALTEX area covers about 2.1 Mill km2. Unlike the MAGS area, it is populated by about 90 Mill. inhabitants in 14 countries who, along with their neighbors, intensively use its resources in many ways and have caused serious ecological damages in the past to both the continental part, and also to the Baltic Sea. The climate characteristics range from temperate zones in the South to subarctic climate in the North. The Baltic Sea drains annually a net water mass of about 470 km3 water into the North Sea, which almost corresponds to the runoff into it from all rivers and aquifers. During winter, often large amounts of saline and oxygen-rich water are pushed into the Baltic Sea by strong storms from the North-West. Strategy BALTEX activities arose in the past in 10 countries. For the future, commitments have been obtained from 40 research groups from 12 countries, where two of them, Austria and the Netherlands, are located outside the BALTEX drainage basin. The research strategy includes the development of numerical models coupling the various components of the climate system, and intensive process-oriented field studies supported by numerical modelling. Such field studies have already been performed and are in preparation in different climate zones with different vegetation, and also over the Baltic Sea. Particular attention is paid to collect during specified periods all available meteorological, hydrological and oceanographic data over the BALTEX area, which is not routinely reported to the world network as the GTS. Of the many available satellite data, the more recent developments to analyse the GPS signals, with respect to their information on total water and vertical water vapour profiles in the atmosphere, are considered. Such data helped to identify a wet bias of our model. A pilot project began to explore the information on evapotranspiration contained in temporal variations of gravity anomalies.


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Particular centers for meteorological, oceanographic, and hydrological data have been established at the Deutscher Wetterdienst in Oftenbach, the Finnish Institute of Marine Research in Helsinki and Swedish Meteorological and Hydrological Institute in Nork�pping. Satellite data is available through the EUMETSAT and other national organizations. Some Recent Advances Regional models, originating from operational weather forecast models, are used in some groups to compute energy and water budgets and transports within the above-mentioned periods. Intensive validation efforts began, showing systematic errors and sensitivities. A first interactively coupled model of the atmosphere with the Baltic sea led to improved forecasts of the wind field, due to the more realistic sea surface temperatures occurring as a consequence of the surface wind stress. Also, the cloud fields are reproduced quite well, while still significant errors occur in the computed convective precipitation. Significant errors of more than +50% still occur in predicted monthly amounts of precipitation. A scheme for distributed hydrological modelling of larger river basins is now applied to some selected rivers in the BALTEX area. Several field studies have been performed during the last two years near Upsala (NOPEX area in Sweden), Lindenberg (Germany) and over the Baltic Sea, whose data are now under investigation. Recently, work began to establish a "BALTEX climatology" and relate these results to global scale circulation phenomena, such as the E1-Nin� and NAO events. There are also first attempts to model the past climate state, which may have occurred about 350 years ago, despite of the still uncertain model performance. During the session, several examples have been shown. More details can be obtained from the Proceedings of the 2nd Scientific Conference on BALTEX, which are available from the BALTEX Secretariat, located in Geesthacht ([email protected]). Other details can be seen in the BALTEX home page (can be reached through http://w3.gkss.de/baltex/baltex-home.html). Future Problems Future work will concentrate on the data collection and analysis of the 2 year period BRIDGE, which partly coincides with the CEOP of all five GEWEX CSEs. Particular attention will be paid to the improvement of the performance of numerical models coupling the atmosphere with the land surface and also the ocean. There the following specific problems have been identified:

��parameterization of exchange processes in the regional models; ��coupling the atmosphere with land-surface schemes; ��error propagation in nested model schemes; ��assimilation of data to interpret regional scale process studies; ��estimates of more accurate amounts of precipitation from radar; ��determination of the evapotranspiration over larger areas/satellite input; ��effects of the complex orography on the water transports; ��coupling of the Baltic Sea model to sea ice and the atmosphere; ��description of soil moisture in the models and from adequate observations; ��more accurate simulation of the cloud-radiation interaction.

References Raschke, E. and co-authors, 1998. The Baltic Sea Experiment BALTEX: A brief overview and some

selected results of the authors. Surveys in Geophysics, 19:1-22. Baltex-Secretariat, 1998. Second Study Conference on BALTEX, Conference Proceedings. Available

through the Internet, BALTEX Secretariat at GKSS, Geesthacht, Germany.


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Figure 1 The permanent GPS network data, which are used in BALTEX studies. Additional

stations are located in Germany, inland, and in the Baltic States. (G. Elgered and colleagues, Onsala, Sweden)


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Figure 2 Total tropospheric water vapour (kg m-2) during the period August 20 to October 31, 1995. Derived from GPS and SSM/I data (left) and from a simulation with a nested regional model. Note: the model is about 2 kg m-2 wetter.

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SESSION SUMMARIES


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Session 1 - Atmospheric Moisture and Energy Budget Studies

Chair: Han-Ru Cho Rapporteur: Kit Szeto

1.1 The Effects of the Mackenzie River on the Canadian Weather and Climate (presenter: Han-Ru Cho)

��Results from CCM3 and NCEP analysis data (a) agree with the areal total, but (b) disagree with the spatial distribution of runoff over the MRB.

��The neglect of land surface slope effects in the land surface scheme in CCM3 is responsible for part of the discrepancies between CCM3 simulation result and observations.

1.2 Airborne Observations of Surface-Atmosphere Energy Exchange over the Northern Mackenzie

Basin (presenter: Peter Schuepp) ��Measurements of radiation and fluxes (of latent and sensible heat) are finally comparable to those

obtainable from towers. ��Preliminary intercomparisons of GEM predictions and aircraft/tower-based observations of

surface-atmosphere fluxes of sensible and latent heat are encouraging. ��Progress in linking airborne flux estimates over heterogeneous terrain to landscape characteristics

observed from satellite-based remote sensing. ��Airborne data will provide test data sets on area-averaged and regional fluxes and radiation

properties for model validation and both model predictions and remote sensing observations will be used in scaling up to larger areas of the MRB.

1.3 Atmospheric Moisture Budgets for MAGS (presenter: Brian Proctor)

��Moisture budget from radiosonde data compared to that computed from GEM outputs. ��GEM water budget not closed.

1.4 Cyclones and Their Role in High Latitude Water Vapour Transport (presenter: John Gyakum)

��Surface cyclogenesis and, to a lesser extent, anticyclogenesis are found to be crucial in transporting water vapor into the MRB.

��A preferential relationship of global Available Potential Energy (APE) to the buildup and depletion of APE in the MRB was identified.

��These APE depletion events are related to subsequent cold surges that extend to the subtropics, and may also be associated with anomalously strong mass buildups and subsequent mass transport to the Southern Hemisphere.

1.5 Low-level Inversions, Precipitation Recycling, and Air-Land Interactions over the Mackenzie

Basin (presenter: Kit Szeto) ��The temporal and spatial variability of surface-based temperature inversions over the MRB and

their relationships to the surface and atmospheric conditions over the region were investigated with NCEP analysis.

��The precipitation recycling ratio for the MRB was estimated from the NCEP data and its temporal/spatial variability and scaling over the region are compared to those estimated for other major basins.


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1.6 Water Budgets of Seven Sub-Basins of the Mackenzie from the ECMWF Analysis (presenter: Alan Betts)

��Preliminary intercomparisons of sub-basin water budgets and variability. ��Water cycle not closed in the ECMWF data. ��Snow model is not adequate in the ECMWF model and it has major problems during spring

snowmelt. 1.7 Atmospheric Moisture Transport (presenter: Vladimir Smirnov)

��Relationship between spatial structure of the water vapour flux field and the minima of P-E over MRB is identified.

��Annual water vapour cycle from ECMWF data tends to overestimate the total water budget over MRB.

��Correlation between strong moisture inflow into MRB and evaporation anomalies in the Pacific identified.

Session Synopsis There is a strong bias towards the investigations of water budgets over the studies of energy budgets. There is also a strong reliance on using analysis products (from NCEP, ECMWF, and CMC) in these studies. The limitations and bias of these analysis products need to be aware of and cross-scale investigations/validations using additional non-model-generated observations are encouraged.

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Session 2 - Land Surface Process Studies

Chair: Terry Prowse Rapporteur: William M. Schertzer

2.1 Evaporation from Wetlands and Large Lakes (presenters: Wayne Rouse and Richard Petrone) Wetlands: Convective and conductive heat fluxes are strongly correlated with temperature and synoptic scale influences. Efficient precipitation systems occur with frequent passage of cold fronts - warm, dry, and clear conditions produce the largest evaporation efficiencies. Synoptic climatology provides a useful link between studies of small-scale surface processes and large-scale modelling. Large Lakes: Great Slave Lake (GSL) evaporation is episodic and correlated with wind speed and vapour pressure difference. Maximum cumulative evaporation occurs 8-10 weeks earlier than the Laurentian Great Lakes (LGL). Summer heat storage appears to be insufficient to fuel late season evaporation. Interannual variability, refinement of evaporation formulae, and extension to other large lakes is required. Climate warming could significantly impact Mackenzie Great Lakes resulting in evaporation regimes similar to the LGL. 2.2 Cross-lake Variation of Evaporation, Radiation, and Physical Limnological Processes in Great

Slave Lake (presenter: William Schertzer) Over-lake meteorology varies significantly between nearshore and mid-lake regions. Episodic high wind events affect sea-state and thermal regime. Evaporation varies across the lake, is episodic and not a strong function of net radiation. Mid-lake regions have significant periods of condensation. Net radiation contributes to lake heating. Sensible heat flux is small and contributes to lake heating. Latent heat flux varies significantly across the lake with spring values in mid-lake regions contributing to lake heating. Total surface heat flux is affected by the episodic nature of the latent heat flux. Interannual variability is unknown, as is the annual total lake heat storage. Extension to other lakes is required. Thermal models integrating atmospheric forcing and lake thermal responses may provide a basis for parameterization for a deep lake component in CLASS. 2.3 Biome Scale Representation of Snow Cover Development and Ablation in Boreal and Tundra

Ecosystems (presenter: John Pomeroy) Physically based snow interception algorithm was recommended for inclusion in CLASS-WATFLOOD to correct under-predictions of snow interception in boreal forest canopies. A coupled model of intercepted snow accumulation and sublimation showed capability for estimating snow sublimation from coniferous canopies. Sublimation rates were up to 3 mm/day and seasonal losses up to 40% of seasonal snowfall. Boreal snowmelt dynamics show that a covariance between sub-canopy snowmelt energy and snow water equivalent significantly accelerated the depletion of snow covered area in melt. Such covariance should be incorporated in CLASS-WATFLOOD to correctly predict snowmelt runoff in the MAGS region. In alpine and arctic research sites, critical multiple-scale horizontal mass and energy fluxes have been detected near the surface and further research is required to provide large-scale representations. As a demonstration of using redistribution of snow by wind transport to drive a hydrological model, an algorithm capable of scaling blowing snow fluxes from point to large area averages has been coded into SLURP as PBS-SLURP. 2.4 Hydrologic Processes in Cold Regions (presenter: Richard Essery for Don Gray) Modification of single-column blowing snow model to uniform terrain by scaling based on probability occurrence is progressing. The model provides adequate estimates of snow accumulation for Prairie and Arctic terrain. Blowing snow physics has been coded into SLURP as PBS-SLURP. Further


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research is required for upscaling single column blowing snow model for complex terrain. A parametric equation for estimating snowmelt infiltration into frozen soils from measurable soil parameters has been developed and tested in boreal forest prairie eco-regions. Studies of coupled heat and mass transfers in frozen soils during snowmelt infiltration show that the soil temperature regime is controlled by the latent energy released due to freezing of infiltrating meltwater. The findings put to question the estimates of the ground heat flux determined by the temperature-gradient approach used by most existing models. Progress has been made towards development of a coupled model that appropriately upscales processes of snow accumulation, ablation, and infiltration for frozen soils. 2.5 Snow Cover Melt and Runoff in Boreal and Tundra Ecosystems (presenter: Phil Marsh) The role of local scale advection of sensible heat in areas of patchy snow cover has been studied using both field data and an atmospheric boundary layer model. Using these data, a simple algorithm has been developed for estimating advection from estimates of sensible heat from snow and snow-free areas and snow cover fraction. This can be used to provide better estimates of snowmelt. In order to couple the upland and hillslope runoff and route it to the stream channel, a snowpack wetting front model is being used in conjunction with physically-based algorithms of inter-hummock flow. This work allows the mapping of spatial variations in runoff and, therefore, improved estimates of streamflow. These estimates, along with full water balance observations, will be compared to WATFLOOD and eventually to WATFLOOD-CLASS. 2.6 Effects of Seasonal Frost and Permafrost on the Hydrology of Subalpine Slopes and Drainage

Basin (presenters: Lawrence Martz and Shawn Carey for Hok Woo) Field and map data on soil, permafrost, and vegetation cover were integrated into GIS database and used to produce a Hydrological Zones Map as a framework for basin-scale analysis and modelling. Field studies show that hydrological processes operate differently in N, S, W, and E slopes within a single hydrologic zone. Frost and organic soil layers have important effects on hydrologic processes. Only part of the hydrologic zone yields runoff directly to streams, which indicates the need for a variable source area approach to modelling. This must incorporate the concept of thermal control of variable source areas. Possible non-closure of water balance on small basins may occur due to variability in slope source areas. 2.7 Isotopic Tracing of Water Balance Processes in the Mackenzie Basin (presenter: Terry Prowse) Distinct isotopic signatures for different source waters were found throughout the wetland dominated regime that feeds the lower Liard River system. Differences permitted the separation of the flow component derived from snowmelt during the spring freshet; a separation not possible using conventional hydrometric techniques. Variability in basin isotopic response appears to be systematically related to basin gradient and land classification units supporting the use of a distributed model approach being developed in a companion GEWEX study. Isotope stratigraphy of river ice is also being developed to extend partitioning studies into winter to study groundwater recession characteristics and to identify source areas of winter flow. Partitioning analysis (surface water vs. groundwater) may provide understanding of freeze-back processes in permafrost areas. Comparisons between isotopic and WATFLOOD modelled contributions to stream flow are planned.

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Session 3 - Remote Sensing Studies

Chair: Anne Walker Rapporteur: Dave Hudak

There were essentially three types of remote sensing studies presented at the workshop: satellite-based remote sensing of surface properties (Bussières, Granger, Leighton, and Walker); satellite-based remote sensing of clouds (Zawadzki); and ground-based radar sensing of clouds and precipitation. The following sections discuss the various aspects, while Table 1 provides a summary of the studies. 1. Limitations With each of these studies, the main limitations to the degree in which they can be applied in the Mackenzie River Basin are the following:

a) Satellite Remote Sensing of Surface Properties � clouds and precipitation � evaporation from large lakes and from sloping terrain � heterogeneous terrain and land use � low light conditions b) Satellite Remote Sensing of Clouds

� the underlying assumptions during winter � lack of a suitable training set of radar data c) Ground-based Radar Sensing of Clouds and Precipitation

� ground clutter 2. Gaps Other potential opportunities in remote sensing that would be of great benefit to MAGS are:

� GPS measurements for water vapour retrieval � information on soil wetness 3. Data Sharing Among the Remote Sensing Studies It is important to establish a mechanism whereby the different remote sensing studies can take advantage of complementary work to minimize and/or at least quantify the shortcomings. Examples of this include the use of albedo information from AVHRR in SSM/I retrievals; the use of Spirit River radar data in Rainsat; the use of cloud top temperatures from AVHRR in radar cloud scanning mode; and, the use of radar cloud information in surface radiation budgets. 4. Validation with Measurements To meaningfully contribute to the MAGS objectives, remote sensing studies require validation by observations. Observational studies encompassing surface-based, upper air, and aircraft measurements as presented at the workshop by Strong, Kochtubajda, Schuepp, Rouse, and Schertzer need to be incorporated into the validation efforts of the various remote sensing techniques. In addition, the CMC analysis archives for GEWEX, as presented by Hogue, can provide another source of validation information. In general, the upper air and model generated analyses are adequate for validation studies. The airborne observations in the vicinity of Inuvik during the spring IOP are essential to some validation studies, as are the evaporation measurements in the Great Slave Lake area. The use of other remote sensing data for validation studies will also be important, although it is recognized that the temporal availability of the required observations is limited. All the remote sensing studies rely to some degree on surface meteorological observations. There is a problem in using a point measurement to validate a remotely sensed parameter that invariably is representative of a larger area. Without exception, all the


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studies indicate that the current surface network is inadequate. This will translate into a larger uncertainty in the parameters derived from these remote sensing analyses. 5. Modelling Applications There is a good strategy in place to make use of these studies in modelling applications. The remote sensing information will be used as input to, verification of, or for improvements in parameterizations in various models used to support the MAGS objectives. It is important that there is a concerted effort to develop partnerships between the relevant remote sensing work and mesoscale modelling (e.g., Yau, Taylor), regional climate modelling (e.g., Mackay, Cao), and hydrological modelling (e.g., Soulis, Pietronaro). One difficulty that needs to be addressed is the proper assimilation of the remote sensing information into models.

Proceedings 4th M

AGS W

orkshop N

ovember, 1998

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IPIC Radar

Sub-basin

CAGES IOPs

precipitation amount; precipitation type; vertical temperature & moisture profiles; AVHRRprecipitation observations inadequate in space & time; AVHRR limited in time

atmospheric mesoscale models (e.g., MC2)

Haykin/Hudak/Currie

Rainfall Estimates

EC Alberta Radars

Sub-basin

CAGES year

precipitation amount

precipitation observations inadequate in space & time

hydrological models; regional climate model

Zawadski

Rainfall

GOES/EC Alberta Radars

Sub-basin

1995 onwards (summer)

low level radar data; precipitation amount; model generated precipitation fields

radar data limited spatially; precipitation observations inadequate in space and time


Leighton

Radiation

ScaRaB/ AVHRR

Basin

94, 95 CAGES year

surface radiation fields; aircraft measured fluxes; model generated radiation fields

surface observations inadequate both spatially and temporally; aircraft observations limited temporally

regional climate model

Granger

AVHRR/sfc measurements

Sub-basin

93, 94, 95, CAGES year

Bussi��res

Evapotranspiration

AVHRR

Basin

94, 95 CAGES year

water & land surface temperatures; surface radiation; vertical temperature & moisture profiles; vertical water vapour flux measurements

surface temperature & radiation observations inadequate spatially; vapour flux measurements limited temporally

hydrological models (land surface modelling component, e.g., CLASS)

SSM/I Lake Ice

Sub-basin

1987 onwards (Nov-Dec; May-July)

AVHRR; LANDSAT; weekly ice fractions (CIS)

temporal availability limited

Walker

Winter Surface Characteristics

SSM/I Snow Cover

Basin

1987 onwards (winter)

snow cover measurements (SWE/depth); snow extent charts; AVHRR

snow cover measurements inadequate, both spatially and temporally


Table 1 Summary of the remote sensing studies on MAGS.

PI

Topic

Primary Data Source

Extent

Temporal Scope

Observations Required for Validation

Shortcomings of Validation

Data

Modelling Applications


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Session 4 - Modelling Studies

Chair: Peter Taylor Rapporteur: Peter Yau

4.1 Hydrologic Investigation of a Canadian Shield Basin (presenter: Chris Spence)

��Canadian Shield terrain not always hydrologically connected ��SLURP assumed the system is connected and worked well when it is (e.g., autumn 1995) ��delay in spring freshet may be due to temporary basin storage ��SLURP did not perform well with this temporary storage (e.g., spring 1996), but annual

predictions remain accurate as water appears later

4.2 Integrated Hydrologic Modelling for MAGS (presenter: N. Kouwen for Ric Soulis)

��testing of WATFLOOD on the MRB for WY94/95 and WY95/96 showed reasonable streamflow simulation

��water balance results indicated modelled runoff (WY94/95+WY95/96) in good agreement with observations

��storage increased by about 3 mm and 16 mm during the two years respectively

4.3 Hydrologic Response of Lower Mackenzie System in the Discontinuous Permafrost/ Wetland Zone / Scaling of Hydrologic Models for MAGS(presenter: Al Pietroniro) ��supported stream gauge operation at Scotty Creek. Collected radiation, rainfall, and streamflow

data continuous into CAGES period ��supported CAGES enhanced observations for Simpson wetland, forest, and airport synoptic site ��used isotopic hydrographic separation estimates to help calibrate and validate hydrologic models

4.4 MAGS RCM, Climate System, and Cloud Field Studies RCM Studies (presenter: Murray Mackay)

��determined the optimal size of the domain for CRCM simulation over MRB ��CRCM run for period September-November in Water Year 94-95 showed good agreement in

terms of monthly precipitation over MRB as verified against AES gridded precipitation climatology

The Greenhouse Effect Due to Water Vapour (presenter: Zuohuo Cao)

��theoretical work showed sign and magnitude of greenhouse effect governed mainly by the temperature difference between the surface and the atmosphere

��calculation using MODTRAN with standard and ECMWF profiles indicated strong seasonal variations of greenhouse effect in high latitudes; strong signals detected in summer with larger magnitudes in low than high latitudes

��low-level temperature inversion in high latitudes makes negative contribution to greenhouse effect

4.5 Developing a Global Numerical Weather Prediction System for the Canadian GEWEX

Program (presenter: Hal Ritchie) ��ensemble forecasts of water and energy fluxes over MRB with SEF show slightly more

uncertainty with CLASS than the force-restore land surface scheme ��modelled water and energy budgets over MRB sensitive to initial state of CLASS fields ��CLASS initial fields produced by a 3DVAR atmospheric data assimilation systems produced

more realistic modelled water excess when compared to station data


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4.6 High Resolution Simulations of Warm and Cold Mesoscale Precipitation Systems over the Mackenzie River Basin (presenter: Peter Yau) ��results from bulk version of PIEKTUK give excellent agreement with the spectral version, yet

runs 100 times faster ��blowing snow climatology compiled from ECMWF reanalysis data over MRB indicates few

events in boreal forest region, but frequency increases significantly in northern and northeastern sections of basin

��residual-free moisture and hydrometeor budgets obtained for 3 cases of lee-cyclogenesis over MRB; both convective and stratiform precipitation important; horizontal transport, topography, microphysics, and surface latent heat fluxes important for water balance

��5 km simulation essential to produce detailed banded structures in cloud and precipitation; bands contain areas of slantwise convective available potential energy

4.7 GEWEX - Northern Boundary-Layer Modelling (presenter: Peter Taylor)

��compare PIEKTUK-spectral calculation against observation of blowing snow over Wyoming ��computed vertical profile of blowing snow mixing ratio and number concentration of particles

sensitive to mass diffusion coefficient for blowing snow and terminal velocity of blowing snow particles

��modelled and observed profiles agree better when terminal velocity of particles reduced to half its original value and mass diffusion coefficient for blowing snow made larger than diffusion coefficient for heat and moisture

Gaps and Synthesis The session deals mainly with hydrological and atmospheric modelling. The models are at different resolutions and include SLURP, WATFLOOD, CLASS, PIEKTUK, SEF, RCM, and MC2. It is suggested that a good way to connect the different models is to adopt a strategy similar to that of GCSS WG3, where an observed case is simulated using different models. The results from the high resolution models can serve as a basis to improve the lower resolution models to address the problem of scaling.

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Session 5 - MAGS Support and Operational Inputs

Chair: Murray Mackay Rapporteur: Bob Kochtubajda

5.1 CMC Model Archive and Activities in Support of GEWEX

(presenter: R. Hogue) 5.2 MAGS Data Management

(presenter: R. Crawford) 5.3 CAGES Operations a) CAGES Update (presenter: B. Kochtubajda) b) Radiosonde Operations during CAGES IOP-1 (presenter: G. Strong) 5.4 Preliminary Analysis and Assessment of the CAGES Enhanced Surface Observations

(presenter: P. Louie) Summary Session 5 highlighted the recent changes and improvements underway to collect and provide properly calibrated and quality controlled data to MAGS investigators. Hogue reviewed the recent changes made in the CMC forecasting System. The changes to the surface process schemes, the convection and condensation schemes, combined with the increased spatial and vertical resolution in the regional and global GEM have resulted in improvements to the models’ mesoscale and synoptic scale forecasts (e.g., topographic flows, precipitation forecasts, the intensity and structure of jets, as well as the trough/ridge analyses have improved). Further cloud physics and surface process scheme improvements are planned. Future efforts will also develop improved analysis capabilities (e.g., new forecast error statistics, analysis on model ‘eta’ levels), integration of new data sources, and better quality precipitation analysis. Crawford reviewed the recent improvements made to the MAGS web site. Three new links were added to allow investigators access to both real time and archived data on the web. The CAGES link allows full or partial access to near real-time surface and upper air measurements taken during the enhanced study program and the intensive observing campaigns. A secure area for the exchange of PI data sets has been established through a Participants Only link. The Products link allows access to the compact disk libraries currently in place, including the Beaufort Arctic Storms Experiment (BASE) case studies CD, and the Satellite archive CDs. CAGES special observations data set CDs and the Water Year study series CDs are planned as well. Efforts are also underway to finalize a data documentation standard. Kochtubajda and Strong provided an overview of the CAGES project. Kochtubajda reported that the enhancement of the MAGS surface-observing network was completed and a surface data transfer protocol established. The weather stations located at Lower Carp Lake, Fort Simpson Airport, Lindberg Landing, MacMillan Pass and at Trail Valley Creek transmit meteorological information hourly via satellite and are received in Edmonton within 20 minutes of the upload. These data undergo preliminary quality control procedures and are then transferred to the MAGS web site the next day. Strong reported on the recently completed summer and fall enhanced sounding campaigns. With few data losses, all programs ran fairly smoothly. The sounding campaigns also proved useful in (1) giving operators experience in using the GPS, since procedures are somewhat different from VLF or Loran, (2) providing Vaisala with information to help resolve whatever GPS problems there are, and (3) providing any necessary recommendations for AEP management. Combining both sets of summer profiles (1997 +1998) an


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evapo-transpiration loss of 2 mm/day was estimated, which is consistent with other remote sensing techniques (e.g., Bussi�res, 1998). The cooperative contributions made to MAGS and CAGES by AES, NWRI, the regional Environment Canada offices, as well as participation on the local, and international levels were noted and acknowledged. Louie reviewed the MAGS surface data transfer protocol and proposed quality control procedure. The generation of standard high quality, hourly meteorological data sets (into EXCEL workbooks) will assist in process related studies and in the initialization and validation of GEWEX modelling efforts and remote sensing studies. Quality control procedures for the standard climate parameters (T, Pressure, RH, Wind, and Radiation) will be based on the procedures used for the CMC climate digital archive. QC and adjustment procedures will be developed for precipitation. QC procedures will also be developed for non-standard parameters such as acoustic snow depth and soil moisture. Once these routines are in place, a quality-controlled set of standard hourly data from these new sites should be available on the MAGS web site 6-8 weeks after the beginning of the each month. Standard climate data from these sites will also follow the normal route of quality control and end up in the CMC climate digital archive in 9-12 months. Questions, Issues, and Suggestions During the discussion session several issues and suggestions were raised:

1. Do we have all the available data sets [basic meteorological data] collected in the Basin and access to them?

2. How do we get data in a timely manner from PIs and water survey? 3. Can an overlay of the Mackenzie River be available for the satellite data? 4. Increase the number of precipitation gauges in the Fort Simpson area. 5. Quality control procedures on “additional” data sets can be onerous. 6. Efforts should be undertaken to ensure the longevity of the data after the project ends. 7. Data documentation is important.

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GENERAL DISCUSSIONS Reports from Working Groups


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D.1 Progress and Future Prospects of the MAGS Research Basins

Discussion Leader: A. Pietroniro Rapporteur: J. Pomeroy

This open discussion is based upon a recommendation from the Ad-hoc Working Group on MAGS Research Basins, whose report was filed with the MAGS Science Committee in October and is attached at the end of this summary. Dr. Al Pietroniro of NWRI moderated the discussion and began the discourse with a presentation on the development of hydrological models and the future progress of these models in capturing the important hydrological characteristics of northern Canada. Dr. Pietroniro’s presentation noted the development of spatial distribution methods in hydrological models from lumped to semi-distributed to fully-distributed and the problems associated with applying the current suite of modelling approaches to small basins in the North. Two major strains of hydrological modelling strategy are potentially of interest to MAGS and to solving the problems of hydrological simulation in small northern basins: 1. Hydrological Response Unit: The HRU (REA in some models) is defined as an areal element within

a basin, where the hydrologic properties are clearly definable and would not be significantly different if a smaller scale of discretization were used. It is possible for a HRU to transmit energy and mass with adjoining HRU without a stream being present.

2. Grouped Response Unit: The GRU (ASA in SLURP) is a grouping of all areas with a similar land

cover such that a grid square will contain a number of distinct GRUs. Runoff generated from the different groups of GRUs are then summed together and routed directly to the stream and river system.

The essential difference between HRU and GRU is that HRU can be sensitive to their location within the basin, i.e., soil moisture or snow supply affected by the uphill or upwind neighbour HRU, whereas GRU are insensitive to location within the basin and are routed directly to the stream. The computational simplicity of the GRU has made it more attractive for modelling efforts to date (WATFLOOD, SLURP) in well-drained basins in southern British Columbia and southern Ontario. However, research in the MAGS Wolf Creek and Trail Valley Creek Research Basins has identified strong spatial variations in snow redistribution, drainage, runoff generation, and atmospheric processes on slopes that may not be easily accommodated by the GRU approach. These variations appear to be enhanced in the cold, northern environment of MAGS compared to more temperate locations. Dr. Pietroniro also noted several levels of interaction between hydrological and meteorological models: LEVEL 0 - Meteorological forcing

� using atmospheric model output for hydrologic model inputs. This was accomplished earlier in MAGS using the Canadian GCM and SLURP.

LEVEL 1 - Atmosphere/land surface coupling

��full interaction between atmospheric and land surface models (e.g., CLASS) ��limited or no runoff calculations


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LEVEL II - Land surface/hydrological coupling ��full interaction between land surface and runoff models (e.g., WATFLOOD/CLASS) ��driven by prescribed measured, forecast, and/or interpolated fields of near-surface data ��no feedback to atmosphere ��primary tool for soil and vegetation process parameter identification

LEVEL III - Atmosphere / land surface / hydrological coupling � Full interaction both between atmosphere and land surface model, and between land surface and

runoff model The Level III approach was identified as the most suitable for application to small basins as a method for testing the coupled model and for scaling processes up or down in MAGS. It was noted that current modelling strategies are not working well in certain MAGS basins (wetlands near Fort Simpson, rocky shield basins near Yellowknife, frozen lake near Whitehorse, snow relocation near Inuvik). A topic of discussion was whether the grouped response unit (GRU) approach to modelling could be adjusted to handle smaller-scale situations dominated by advection, variable storage, cold process thermodynamics, and hillslope runoff. Such adjustments would be necessarily regional and empirical and there was not a consensus as to whether it was possible. An important comment was made that MAGS has not yet set up a 1-D CLASS-WATFLOOD single column model for testing at the research basins during CAGES. A further suggestion was that a full coupling of a 1-D version of RCM-CLASS-WATFLOOD be made available for testing, forced with upper atmospheric data and tested against research basin surface measurements networks. An alternative suggestion was to couple a RCM directly to a HRU type hydrological model and evaluate the results against RCM-CLASS-WATFLOOD as an aid to developing scaling techniques and evaluating the appropriateness of the modelling strategy. The group discussion made it clear that the problems of poor, variable drainage and importing temperate-zone modelling concepts and technologies to a cold regions environment make the delineation of a singular modelling strategy for MAGS problematic. GEWEX Research Basins Sub-group Discussion Report on a meeting of university/government investigators conducting cold regions process studies in GEWEX Research Basins to the MAGS Science Committee. Report compiled by Pomeroy with substantive input from all attendees. Discussion Attendees – Woo, Petrone, Martz, Gray, Essery, Toth, Marsh, Quinton, Pomeroy, Granger, Pietroniro, Ex officio: Strong Status - Currently we can or will shortly be able to: 1) Route water from GCMs – large-scale (see Soulis et al.). 2) Define the “important” hydrological processes driving energy and water fluxes at the land surface in

cold regions. 3) Identify the deficiencies, weaknesses and errors that may accrue in estimations of water and energy

fluxes by using “Accepted” temperate-zone technologies and procedures to describe “SOME” of these processes.

4) Provide “New” physics-based, field-verified “methodologies” (algorithms) to describe “SOME” of these processes.

5) Prepare the scientific basis for improved process representations (basin fieldwork, process-algorithm testing, theoretical studies).


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Prospects - In the Future, the basins sub-group envisions for GEWEX the following capabilities: 1) Comprehensive, physics-based representations of hydrological processes driving energy and water

fluxes at the land surface in cold regions. 2) Up-scaling of the processes and parameters. 3) Redistribution of water and energy in three dimensions at various scales. 4) Spatial testing of micro- and meso-scale models in cold regions. The Future Capabilities will be important for improved representations of water and energy fluxes at the continental-scale, but essential for development of meso-scale coupled models of water and energy for cold regions. To acquire this capability, experiments on cold regions process should be expanded in research basins in the second phase of GEWEX. On Thursday, 22 October, J. Pomeroy presented to the MAGS Science Committee some aspects of progress in research basin studies as illustrations of the above. At the GEWEX Meeting in Montr�al it is proposed that A. Pietroniro give a more formal synopsis of the progress with an open discussion of the integration of the Prospects with the future goals of GEWEX.

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D.2 The 1994-1995 Water Year Study

Discussion Leader: R. Stewart Rapporteur: R. Granger

Objectives 1. To quantify, understand, and validate all critical aspects of the energy and water cycles over one

water year. 2. To identify critical processes. 3. To understand associated couplings. 4. To assemble appropriate datasets to “describe” the basin water and energy cycles. The 1994-95 water year was an “interesting” year, with low discharge. Analysis showed that precipitation anomalies are translated into runoff anomalies. Stewart raised several questions. 1. Atmospheric issues:

��how is water made available? ��unusual circulation events? ��prolonged high pressure system in spring? ��where was ppt occurring over the basin ��more or less rain or snow? ��role of episodic events on ppt totals?

2. Surface issues: ��timing of freeze-up? ��are higher losses associated with early melt? ��surface radiation fields? ��was evapotranspiration typical or abnormally high? ��were the wind fields stronger than normal?

3. Hydrological issues: ��relationship between ppt and runoff? ��increased ET or increased storage?

Discussion ��Pomeroy and Marsh indicated that early melts are driven by large-scale advection of sensible heat. ��The timing and magnitude of peak water levels in Great Slave Lake indicate that snowmelt runoff

was being held in storage. ��Prowse suggested that it would be possible to check the storage response by comparing the Peace

River response with that of the Liard River. ��There is a need to better model the coupled Atmosphere-Hydrology regime to evaluate the lags and

storage effects observed in the basin.

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D.3 CAGES Data and Analysis

Discussion Leaders: G.S. Strong and B. Kochtubajda Rapporteur: B. Crawford

After a brief presentation stating the purpose of the Canadian GEWEX Enhanced Study (CAGES) to augment measurements and observations in the Mackenzie River Basin and showing some observations from the Autumn Intensive Observation Period (IOP), plans were outlined for the winter IOP, tentatively scheduled for December 1 to 15, 1998, with additional snow surveys scheduled for March 1999 and the spring IOP, which includes aircraft studies, tentatively scheduled for mid-May to mid-June in the Inuvik, Fort Simpson and Great Slave Lake areas. The discussion that followed centered around the adequacy of the measurements being made to meet the needs of MAGS. Some of the points discussed follow: ��While the complete measurement of the Basin’s water vapour is not possible with the sounding

measurements being performed within the basin, the enhanced sounding programme at Fort Simpson appears to be adequate to determine the diurnal cycle of water vapour and has proven extremely useful for the Arctic Weather Centre.

��Despite the concerns that some discharge measurements would be lost in the near future, Water

Survey of Canada has reported that all current measurement sites are safe from funding cuts this year. � The MAGS enhanced surface measurement sites are all up and running. All the sites are monitored

remotely daily, and visited annually by regional inspectors. On-site contractors also visit many of the sites monthly. Contingencies have been put in place to handle any problems that may arise with the site. This is a significant undertaking as many of the sites are remote; for example, MacMillan Pass requires a 4-hour helicopter trip to visit.

� Another concern is the effect of automation of sites within the basin. All the impacts of automation

are not known, so as a first step it was suggested that the individual station histories be made available, possibly including the inspectors’ reports.

� Precipitation was identified as the worst parameter being measured. It is measured sparsely across

the basin, and where it is measured there are significant difficulties in obtaining accurate measurements. A suggestion was made that numerous, basic measurements made by volunteers may be valuable, despite the standardization problems.

� The use of column models was suggested as a solution to some of the gaps identified in the

interactive scientific studies underway, if the RCM/CLASS/WATFLOOD combination is found to be inadequate. It was noted that, although column models are not appropriate in baroclinic environments, they may be helpful to fill gaps in our understanding. The use of the existing Model Output Location Time Series (MOLTS) data was also suggested as an easy alternative to column models, but they are limited due to the lack of interaction with the surface hydrology.

� The evapotranspiration in WATFLOOD is known to be inaccurate using the current temperature

scheme. Using ECMWF surface radiation values may yield better accuracy. A concern regarding the increased use of model reanalysis fields was expressed. There are known problems with the winds and moisture over oceans. This is being explored by the Surface Radiation Project of the International GEWEX.


197

The discussion concluded with several suggestions for the best forum to present some of the enhanced data and analysis that CAGES will provide. Suggestions included: a CAGES Water Year CD-ROM archive, CAGES workshop, and a special journal (possibly Atmosphere-Ocean) issue on CAGES.

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D.4 Post-MAGS - Where Do We Go From Here?

Discussion Leader: John Gyakum Rapporteur: Phil Marsh

As this meeting marks the half way point of the NSERC funding of MAGS, John Gyakum led a discussion aimed at encouraging MAGS investigators to begin thinking about the future of the MAGS project, and possible new directions that MAGS should explore in any follow-on study. The presentation began with a brief outline of the objectives of MAGS, followed by an outline of existing studies in order to provide a framework for the current status of the project. This presentation was followed by a broad discussion of possible future directions of MAGS. Gyakum’s presentation is shown as presented in point form in Appendix I. The following provides a brief, but not inclusive, overview of these discussions. It was felt that as we continue to progress, the use of large-scale models for predictability will increase, and that we may consider expanding to include other areas of Canada. One concern of such a strategy is that MAGS would lose its focus on cold region processes - an extremely important contribution of MAGS to the international community. Other aspects that MAGS may begin to consider are the effect of changes in land surface conditions, both natural and anthropogenic. Examples include forest fires and agriculture. The effect of such land surface changes on hydrology and the fluxes of energy and water must be considered in future work. From the hydrologic/land surface point of view, concerns were expressed on the issue of sub-grid scale heterogeneity and the need to demonstrate errors involved and to develop specific goals that will lead to improvements. From the climate perspective, it was noted that MAGS is not simply a study aimed at understanding or predicting monthly values, but that higher order aspects are very important, as climate is the average of mesoscale processes. Currently, MAGS is considering a single water-year in order to focus and integrate various studies. Similar studies should consider the CAGES year as well as extreme years in order to help improve our understanding of the wide range of conditions affecting the Mackenzie Basin. An improved understanding of these will help in improving models capable of considering the natural variability of the Mackenzie climate/hydrologic system. A critical component of this is the need to continue carrying out studies over a wide range of important processes controlling the fluxes of water and energy, and to continue to integrate this work into linked models. An interesting aspect of such work is the need to consider the impact of modelling at a variety of scales. The session ended after a lengthy discussion of the above and other concerns. The general feeling was that MAGS is making significant progress on many fronts, and that we are entering an exciting period when we will be able to use both enhanced measurements, model output and remote sensing products, to more fully consider the many interactions between the hydrologic and atmospheric systems. It was felt that it is necessary that the discussions during this session be followed up after the meeting with a more formal attempt to develop a scientific plan for a second phase of MAGS. Such a plan should outline the steps required to carry MAGS towards our overall goal of producing improved predictions of the water and energy cycle of the Mackenzie Basin, and of demonstrating the ability to transfer such results to other arctic regions.


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Appendix I - Gyakum’s Discussion Points MAGS Objectives: ��To understand, quantify, and model the critical components of the water and energy cycles that affect

the Mackenzie Basin climate system. ��To improve the capability to predict changes to the water resources of the Mackenzie Basin that are

influenced by natural climate variability and that which may be altered by anthropogenic climate change.

From the NSERC Proposal's Anticipated Outcomes (pp. 8-9): The results of the program will be an improved understanding of cold region, high latitude hydrological and meteorological processes and the role that they play in the global climate system. Canadian scientists will have developed a new generation of coupled atmospheric-hydrological models that will be ready for testing against data sets collected during MAGS and the other GEWEX Continental Scale Experiments. Cho: What is the effect of the Mackenzie River Basin (MRB) on Canadian weather? Schuepp: More comprehensive airborne observing of fluxes (Great Slave and Great Bear Lakes in the

fall). Proctor/Strong/Wang: Longer record of moisture budget studies (interranual variability). Gyakum: Determination of cold air mass generation mechanisms in the MRB; upstream influences (e.g.,

North Pacific cyclones) and downstream consequences (upper trough or potential vorticity anomalies that travel equatorward and eastward triggering North Atlantic cyclogenesis).

Szeto: Feedback of inversions onto precipitation systems (isentropic ascent above the cold, stable air masses).

Smirnov: Determination of source regions for water vapour that precipitates in the MRB. Rouse/Schertzer: Further sampling of Great Slave and Great Bear Lakes weather and fluxes for

additional 4 years. Strong: Improved understanding of spatial variability of heat fluxes. Pomeroy/Marsh/Spence/Walker: Completion of integration of algorithms in GCM land surface schemes,

regional atmospheric models, and large-scale hydrological models. Woo/Martz/Carey: To better define and quantify the thermo-hydrological processes special to the cold

regions, thus providing the requisite information to improve basin scale and large-scale models. Prowse: Expansion of ice-core isotope reconstruction studies; specific triggers for Liard breakup. Bussi�res/Granger: Additional work on parameterizing lake evaporation for stable cases; additional funds

are needed for analysis of older data sets from Quill Lake. Leighton: Continued comparison of radiation budgets derived from satellite data with surface

observations and with budgets generated by the atmospheric models. Zawadzki: Validation of Regional Climate Model with 30-day simulations. Haykin/Hudak/Currie: Better physical description of the significant weather events in the MRB. Soulis: Maturation of coupled modelling, which will be starting in 2000. Better understanding of sub-

grid scale processes. Pietroniro: Better validation of the CLASS WATFLOOD model. Mackay/Cao: Continued use of RCM to better understand the role of water vapour in its feedback on the

energy balance of the region. Ritchie: Improvement in CLASS, and updating for each season. Soulis: Need for a CLASS lake climatology. Yau: Analysis and understanding of blowing snow events. Taylor: 2-D and 3-D planetary boundary layer modelling; blowing snow studies in non-uniform terrain. Betts: Coordination of existing data set; quick turn-around for submission to Bob Crawford.


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With Strong: Get the diurnal and seasonal cycles of water vapour right. Goodison: Transfer of knowledge from BOREAS into MAGS. Need a timetable (strategy) for coupling

of atmospheric and hydrologic models. CLASS needs to be applied to the whole basin. Stewart: Make sure that we have achieved our original goals, before proceeding to later projects. Coupling of Analyses: ��More interactions with large-scale models for predictability (including specific prediction problems as

that of the North Pacific, the mountains, and the North Atlantic. ��More coordination of remote-sensing and modelling studies. ��Similar approaches applied to other regions of Canada (Atlantic, Prairies, Arctic). Land Surface Changes and Their Effects: ��Roles played by forest fires on regional climate and in altering the tree-line under global change. ��Roles played by agricultural practices on the region's climate. Feedback: ��"Memory" within the climate system of such a basin and its impacts on regional and larger scale

climate. Examples include inter-annual water storage, permafrost, soil wetness, vegetation and its changes.

��Water vapour. Woo: “It is my belief that hydrology plays a role possibly as large as atmospheric sciences in MAGS.

By this, I do not mean only providing some macro-scale models to integrate the moisture fluxes though this is one major service function. MAGS is also an opportunity to expand our understanding of the cold regions' hydrological processes through field investigations and micro-scale modelling of the near-surface moisture flux phenomena. While it is relatively easier to model, it takes time to study the processes and to scale them upward properly to the regional level. A second phase of GEWEX-Hydrological Investigations - should reflect this; otherwise, we are merely recycling what little is known about the cold-region hydrology.”

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FINAL DISCUSSION


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Statements on the Status of MAGS The objectives of MAGS as stated at the start of these proceedings can only be fully realized once we understand the whole Mackenzie Basin climate system. The figure on the following page can be viewed as a progressive series of steps towards this understanding and achievement of our objectives. As one measure of the progress of MAGS, a simple statement has been issued each year in conjunction with our Science Workshop. These statements follow. November 1995 Preliminary assessments of the water budgets of the Mackenzie Basin, as well as initial energy studies, have been carried out, but critical variables have not been measured adequately. We are completing the identification of key processes, we are carrying out background climatologies, and we are improving the representations of physical processes in our models. March 1997 All components of our overall strategy have been started. Assessments of the water budgets of the Mackenzie Basin are well underway, energy studies have been started, and plans to improve our measurement of critical variables have progressed substantially. We have identified the key processes, we have carried out several background climatologies, we are improving the representation of physical processes in our models, and we have started to assess the ability of our climate model to represent the Basin’s climate systems. Our archiving systems are in place and we, as part of our strategy, will focus on collective studies of appropriate water years. November 1997 All components of our overall strategy are underway. Special measurements of several critical variables have been and continue to be made and progress is being made in the use of remote sensing information. Plans for further observations have advanced, although there are many difficulties to overcome. We are assessing the water budgets using observations and models, we are better understanding the roles played by many phenomena on the Basin’s climate system, we are carrying out many model studies, and we are assessing the capabilities of our regional climate model. Our data management guidelines are being improved and we. as part of our strategy, have set out to conduct joint studies of some water years. November 1998 All components of the overall strategy are progressing. Special measurements of many critical variables are being made and our enhanced water year study (CAGES) is underway, although there are still significant problems in our observational datasets. Progress is being made at understanding critical surface, hydrological, and atmospheric issues affecting the Basin’s climate system. Basin-scale atmospheric/surface/hydrological models are being run and capabilities and deficiencies are being identified and recommendations for addressing these are being considered. Collective studies over full water years are underway to address the full, interacting climate system. Data management systems are in place and functioning. Activities have now commenced to produce dedicated issues of scientific journals and to map out our future activities and priorities.

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Workshop Concluding Remarks

The fourth MAGS Workshop was held in Montr�al, home to many MAGS researchers. There were more than 75 participants at the workshop. The general objectives of this workshop were: � To collectively present and discuss our research results. � To assess progress towards the goals of MAGS. � To develop and review plans for the next year and beyond.

This is a critical period in the development of MAGS. Many of the individual efforts are maturing and there is a need for greater synthesis as we collectively move forward to ensure that our understanding and modelling capabilities for the basin proceed effectively. In this regard, it is critical to note that our modelling tools are almost in place to allow for our large-scale coupled modelling studies, our special water year observational effort (CAGES) is well underway, and many of our datasets are starting to be applied to basin-scale issues. We need to move forward on the basis of our strong individual efforts in order to collectively address the complex scientific issues that affect and feed back onto the basin’s climate system.

MAGS is a very challenging effort for all of us and our progress, therefore, is all the more satisfying. We hope that you have enjoyed reading through these proceedings as one measure of our progress, and we hope that it spurs on your research and leads to more scientific interactions to help the overall effort.

Dr. Ronald Stewart Acting Chair, MAGS Scientific Committee

November, 1998


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REGISTERED PARTICIPANTS


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Participant List: Betts, Alan K., 58 Hendee Lane, Pittsford, Vermont 05763, E-mail: [email protected] Biner, Sebastien, Universit� du Qu�bec � Montr�al [UQAM], C.P. 8888, Succ. Centre-Ville, Montr�al,

Qu�bec, H3C 3P8, E-mail: [email protected] Burford, Jason, Atmospheric Environment Service [AES], 4905 Dufferin Street, Downsview, Ontario,

M3H 5T4, Fax: 416-739-5700, E-mail: [email protected] Bussi��res, Normand, Climate Processes and Earth Observation Division, Climate Research Branch,

Atmospheric Environment Service [AES], 4905 Dufferin Street, Downsview, Ontario, M3H 5T4, Fax: 416-739-5700, E-mail: [email protected]

Cao, Zuohao, Climate Research Branch, Atmospheric Environment Service [AES], 4905 Dufferin Street, Downsview, Ontario, M3H 5T4, Tel: 416-739-4371, Fax: 416-739-5700, E-mail: [email protected]

Carey, Sean, School of Geography and Geology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L85 4K1, Tel: 905-525-9140 (Ext. 24394), Fax: 905-521-2922, E-mail: [email protected]

C��t��, H��l��ne, Universit� du Qu�bec � Montr�al [UQAM], C.P. 8888, Succ. Centre-Ville, Montr�al, Qu�bec, H3C 3P8, Tel: 514-987-3000 (Ext. 6813), Fax: 514-987-7749, E-mail: [email protected]

Crawford, Robert, Atmospheric Environment Service [AES], 4905 Dufferin Street, Downsview, Ontario, M3H 5T4, Tel: 416-739-4392, Fax: 416-739-5700, E-mail: [email protected]

Currie, Brian, Communications Research Laboratory [CRL], McMaster University, 1280 Main Street West, Hamilton, Ontario, L85 4K1, Tel: 905-525-9140 (Ext. 24268), Fax: 905-521-2922, E-mail: [email protected]

de Elia, Raymon, McGill University, 805 Sherbrooke Street West, Ste Anne de Bellevue, Montr�al, Qu�bec, H3A 2K6, E-mail: [email protected]

D��ry, Stephen, Department of Atmospheric and Oceanographic Sciences, McGill University, 805 Sherbrooke Street West, Montr�al, Qu�bec, H3A 2K6, E-mail: [email protected]

Essery, Richard, Hadley Centre for Climate Prediction and Research, UK Meteorological Office, London Road, Bracknell, Berkshire, England RG12 2SY, E-mail: [email protected]

Fogarty, Chris, McGill University, 805 Sherbrooke Street West, Ste Anne de Bellevue, Montr�al, Qu�bec, H3A 2K6, E-mail: [email protected]

Goodison, Barry, Climate Research Branch, Atmospheric Environment Service [AES], 4905 Dufferin Street, Downsview, Ontario, M3H 5T4, Fax: 416-739-5700, E-mail: [email protected]

Graham, Karen, A., c/o Department of Civil Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, E-mail: [email protected]

Granger, Raoul, National Water Research Institute, Environment Canada, National Hydrology Research Centre [NHRC], 11 Innovation Blvd., Saskatoon, Saskatchewan, S7N 3H5, E-mail: [email protected]

Gyakum, John R., Department of Atmospheric and Oceanic Sciences, McGill University, 805 Sherbrooke Street West, Ste Anne de Bellevue, Montr�al, Qu�bec, H3A 2K6, Tel: 514-398-6076, E-mail: [email protected]

Hogue, Richard, Canadian Meteorological Center, Implementation and Operational Services Division, 2121 North Service Road, Trans Canada Road, Dorval, Qu�bec, H9P 1J3, E-mail: [email protected]

Hudak, Dave, Research Scientist, Atmospheric Environment Service [AES], 14780 Jane Street, King City, Ontario, S7B 1A3, Tel: 905-833-3896 (Ext. 242), Fax: 905-833-0398, E-mail: [email protected]



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Kochtubajada, Bob, MAGS Logistic Coordinator, AHRD, Prairie and Northern Region, Environment Canada, 4999-98th Avenue, NE Edmonton, Alberta, T6B 2X3, Tel: 403-951-8811, Fax: 403-951-8634, E-mail: [email protected]

Kroeker, Murray, G., Senior Engineer, Water Resources and Geotechnical Department, Power Supply Engineering, BC Hydro, 6911 Southpoint Drive (A02), Burnaby, British Columbia, V3N 4X8, Tel: 604-528-2912, Fax: 604-528-8133, E-mail: [email protected]

Leighton, Henry, Department of Atmospheric and Ocean Sciences, McGill University, 805 Sherbrooke Street West, Ste Anne de Bellevue, Montr�al, Qu�bec, H3A 2K6, Tel: 514-398-3766, Fax: 514-398-6115, E-mail: [email protected]

Lettenmaier, Dennis, Department of Civil Engineering, University of Washington, Box 352700, Seattle, Washington, 98195, Tel: 206-543-2532, Fax: 206-685-3836, E-mail: [email protected]

Louie, Paul, Climate Processes and Earth Observation Division, Climate Research Branch, Atmospheric Environment Service [AES/CRB], 4905 Dufferin Street, Downsview, Ontario, M3H 5T4, Tel: 416-739-4351, Fax: 416-739-5700, E-mail: [email protected]

Mackay, Murray, Climate Research Branch, Atmospheric Environment Service [AES], 4905 Dufferin Street, Downsview, Ontario, M3H 5T4, Tel: 416-739-5710, Fax: 416-739-5700, E-mail: [email protected]

Macpherson, Ian, Flight Research Laboratory, Institute for Aerospace Studies, National Research Council [NRC], Ottawa, Ontario, E-mail: [email protected]

Marsh, Phil, National Hydrology Research Centre [NHRC], 11 Innovation Blvd., Saskatoon, Saskatchewan, S7N 3H5, Tel: 306-975-5752, Fax: 306-975-5143, E-mail: [email protected]

Martz, Lawrence, Department of Geography, University of Saskatchewan, 9 Campus Drive, Saskatoon, Saskatchewan, S7N 0W0, E-mail: [email protected]

Nagarajan, Badrinath, McGill University, 805 Sherbrooke Street West, Ste Anne de Bellevue, Montr�al, Qu�bec, H3A 2K6, E-mail: [email protected]

Paquin, Dominique, Assistante de Recherche en Sciences de l'Atmosphere, Groupe de Modelisation Regionale du Climat, Departement des Sciences de la Terre, Universit� du Qu�bec � Montr�al [UQAM], C.P. 8888, Succ. Centre-Ville, Montr�al, Qu�bec, H3C 3P8, Tel: 514-987-3000, Fax: 514-987-7749, E-mail: [email protected]

Petrone, Richard, Department of Geography, McMaster University, 1280 Main Street West, Hamilton, Ontario, Tel: 905-525-9140 (Ext. 24082), Fax: 905-521-0463, E-mail: [email protected]

Pietroniro, Al, Environment Canada, National Hydrology Research Centre [NHRC], 11 Innovation Blvd., Saskatoon, Saskatchewan, S7N 3H5, Tel: 306-975-4394, Fax: 306-975-5143, E-mail: [email protected]

Pomeroy, John, National Hydrology Research Centre [NHRC], 11 Innovation Blvd., Saskatoon, Saskatchewan, S7N 3H5, Tel: 306-975-5511, Fax: 306-975-5143, E-mail: [email protected]

Proctor, Brian A., Climate Research Branch, Atmospheric Environment Service, National Hydrology Research Centre [NHRC], 11 Innovation Blvd., Saskatoon, Saskatchewan, S7N 3H5, Tel: 306-975-5688, Fax: 306-975-6516, E-mail: [email protected]

Prowse, Terry, National Water Research Institute/Canadian Centre for Inland Waters [NWRI/CCIW], 11 Innovation Blvd., Saskatoon, Saskatchewan, S7N 3H5, E-mail: [email protected]

Radeva, Ekaterina, Atmospheric Environment Service [AES/RPN], Recherche en Prevision Numerique, 2121 Trans Canada Road, Dorval, Qu�bec, H9P 1J3, Tel: 514-421-4646, E-mail: [email protected]

Raschke, Ehrhard, Director, Institute of Atmospheric Physics, GKSS Research Centre, Geesthacht, Germany, Tel: 49-4152-871533, E-mail: [email protected]

Ritchie, Hal, Atmospheric Environment Service [AES/RPN], Recherche en Prevision Numerique, 2121 Trans Canada Road, Dorval, Qu�bec, H9P 1J3, Tel: 514-421-4739 or 902-426-5610, Fax: 514-421-2106, E-mail: [email protected]

Rouse, Wayne, School of Geography and Geology, McMaster University, 1280 Main Street West, Hamilton, Ontario, L8S 4K1, Tel: 905-525-9140 (Ext. 24394), Fax: 905-521-0463, E-mail: [email protected]


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Schertzer, W.M. (Bill), National Water Research Institute/Canadian Centre for Inland Waters [NWRI/CCIW], 867 Lakeshore Road, Burlington, Ontario, L7R 4A6, E-mail: [email protected]

Schuepp, Peter, Department of Natural Resources Sciences, McGill University (MacDonald Campus), 805 Sherbrooke Street West, Ste Anne de Bellevue, Montr�al, Qu�bec, H9X 3V9, Tel: 514-398-7935, Fax: 514-398-7990, E-mail: [email protected]

Seglenieks, Frank , Department of Civil Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Tel: 519-888-4567, E-mail: [email protected]

Snelgrove, Ken, Department of Civil Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Tel: 519-888-4567 (Ext. 6112), E-mail: [email protected]

Silis, Arvids, Climate Research Branch, Atmospheric Environment Service [AES], 4905 Dufferin Street, Downsview, Ontario, M3H 5T4, Tel: 416-739-4358, Fax: 416-739-5700, E-mail: [email protected]

Smirnov, Vladimir, Department of Physics, University of Toronto, Toronto, Ontario, Tel: 416-978-2706, Fax: 416-978-8905, E-mail: [email protected]

Soulis, Ric, Department of Civil Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Tel: 519-888-4567, Fax: 519-888-6197, E-mail: [email protected]

Spacek, Lubos, Universit� du Qu�bec � Montr�al [UQAM], C.P. 8888, Succ. Centre-Ville, Montr�al, Qu�bec, H3C 3P8, Tel: 514-987-3000, E-mail: [email protected]

Spence, Chris, Arctic Section, Atmospheric and Hydrological Sciences, Environment Canada, Suite 302 5204-50th Avenue, Box 2970, Yellowknife, North West Territories, X1A 1E2, Tel: 867-669-4746, Fax: 867-873-8185, E-mail: [email protected]

Stewart, Ron, Acting Chair, MAGS Scientific Committee (1998), Climate Processes and Earth Observation Division, Atmospheric Environment Service [AES], 4905 Dufferin Street, Downsview, Ontario, M3H 5T4, Tel: 416-739-4122, Fax: 416-739-5700, E-mail: [email protected]

Strong, Geoff, GEWEX/MAGS Secretariat/Coordinator, National Hydrology Research Centre [NHRC], 11 Innovation Blvd., Saskatoon, Saskatchewan, S7N 3H5, Tel: 306-975-5809, Fax: 306-975-6516, E-mail: [email protected]

Szeto, Kit, Climate Research Branch, Atmospheric Environment Service [AES], 4905 Dufferin Street, Downsview, Ontario, M3H 5T4, Fax: 416-739-5700

Taylor, Peter, Department of Earth and Atmospheric Science, York University [EATS], 4700 Keele Street, North York, Ontario, M3J 1P3, Tel: 416-736-2100 (Ext. 77707), Fax: 416-736-5817, E-mail: [email protected]

Walker, Anne, Climate Research Branch, Atmospheric Environment Service [AES], 4905 Dufferin Street, Downsview, Ontario, M3H 5T4, Tel: 416-739-4357, Fax: 416-739-5700, E-mail: [email protected]

Wang, Muyin, Department of Physics, Dalhousie University, Halifax, Nova Scotia, Tel: 902-494-2952, Fax: 905-494-5191, E-mail: [email protected]

Whidden, Ted, Department of Civil Engineering, University of Waterloo, Waterloo, Ontario, Tel: 519-888-4567 (Ext. 6112), E-mail: [email protected]

Whittle, David, Metereologist, Arctic Weather Centre, Prairie and Northern Region, Environment Canada, #200, 4999-98th Avenue, Edmonton, Alberta, T6B 2X3, Tel: 780-951-8906, Fax: 780-951-8872, E-mail: [email protected]

Wilkinson, Brian, Director, Centre for Ecology and Hydrology, Wallingford, Oxfordshire 0X10 8BB, United Kingdom, Tel: 01491 692219, E-mail: [email protected]

Yau, Peter, Department of Atmospheric and Ocean Sciences, McGill University (MacDonald Campus), 805 Sherbrooke Street West, Ste Anne de Bellevue, Montr�al, Qu�bec, H9X 3V9, Tel: 514-398-3719, Fax: 514-398-6115, E-mail: [email protected]

Zawadski, Istzar, J.S. Marshall Radar Observatory, P.O. Box 198, MacDonald College, Ste Anne de Bellevue, Montr�al, Qu�bec, H9X 3V9, E-mail: [email protected]

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