Dr. Jordan G. Powers!!

Mesoscale and Microscale Meteorology Division!NCAR Earth System Laboratory!

National Center for Atmospheric Research!Boulder, Colorado!

! Polar Prediction Project Meeting !

Boulder, Colorado!October 2, 2013 !

Mesoscale NWP Over Antarctica

Real-Time NWP Over Antarctica!!

!• Operational Global Models (examples)!!

! ! !ECMWF Global (16 km)!!

! ! !UKMO Unified Model (25 km)!!

! ! !NCEP GFS (28 km)!!

! ! !JMA GSM (20 km)!!

! !– Resolution inadequate in key areas!!

! !– Physics not necessarily tuned for high latitudes!!

!• Mesoscale NWP over Antarctica: AMPS!!

! !– High resolution!!

! !– Polar physics !!

! !– Products and coverages tailored for users!

!• Tuned NWP system for Antarctica!!

! !Ø WRF (Weather Research and Forecasting) Model!!

! !Ø Variable resolution to 1.1-km!!

!• Priority mission: U.S. Antarctic Program (USAP) weather ! ! ! ! ! ! ! ! !support !

!!• Collaborators: NCAR and The Ohio State University !! ! ! ! ! (Byrd Polar Research Center) !

AMPS— The Antarctic Mesoscale Prediction System !

http://www.mmm.ucar.edu/rt/amps

Powers et al., 2012: A decade of Antarctic science support through AMPS. Bull. Amer. Meteor. Soc., 93, 1699–1712

Motivations for Mesoscale NWP Program for the USAP: ! ! !Forecasting Needs!

!

!• Weaknesses seen in the NWP available to the !! !McMurdo forecasters !

!

! !The Antarctic Weather Forecasting Workshop !! ! !(May 2000, Byrd Polar Research Center, The Ohio State Univ.)!

!!

! !1) Inadequate resolution!!

! ! !* To capture mesoscale weather features!!

! ! !* To capture local topography!!

! !2) Need to improve high-latitude model performance!!

! ! !* Better physics and schemes needed!! ! ! !for the Antarctic PBL and troposphere!

!!⇒ Proposed: A real-time mesoscale modeling system !tailored for ! ! ! ! ! !the USAP forecasters!

User Groups— AMPS Antarctic NWP!!

!1) USAP Forecasters (SPAWAR– Space and Naval Warfare Systems Center)! ! ! ! ! • Station forecasting !!

! ! ! ! ◊ McMurdo, South Pole, Palmer!!

! ! ! ! ◊ Field camps across Ice!!

! ! ! ! • Air operations forecasting !! ! ! ! !◊ US Air Force, New York Air !! ! ! ! ! !National Guard!

!

! ! ! ! !◊ Kenn Borek Air & PHI!!

! ! ! ! • Marine forecasting !!

! ! ! ! !R/V Nathaniel B. Palmer !!

! ! ! ! !R/V Laurence M. Gould!!2) Field Campaigns !! !(Ex: Pine Island Glacier; GIMBLE— Geophysical Investigations !! ! ! !of Marie Byrd Land Lithospheric Evolution)!

!

!3) International Forecasters and Efforts!!

!4) Researchers and Students!

USAF C-17 Ice Runway, McMurdo

AMPS Model Configuration— WRF!

South Pole

● ●

Primary air route: CHC–MCM

Topography shaded

MCM

CHC • Forecast domains!!

– 5 primary grids!! – Grid sizes!!

!30 km!!

!10 km!!

!3.3 km!!

!1.1 km !!• 2-way nesting!

AMPS WRF Domains!

Topography shaded

Antarctic Peninsula grid

Ross Sea / South Pole grid

Ross Is. grid

Ross Sea / South Pole grid

Ross Is. grid

AMPS WRF Configuration Model: WRF V3.3.1 with polar modifications!!Forecasts: !30 km— 120 h ! !10 km— 120 h!!

! !3.3 km— 39 h ! !1.1 km— 39 h!!

Vertical: !Top: 10 mb !Levels: 61!!First-guess/Boundary conditions: GFS!!Data assimilation: WRFDA system— 3DVAR

Observations Ø Standard: AWS, radiosonde, SYNOP, METAR, ship, buoy, aircraft

ØSATOB, SATEM, COSMIC (GPSRO), GOES AMV, MODIS AMV, AMSU radiance

Frequency: 0000 & 1200 UTC initializations

WRF— Polar Modifications Modifications: Changes in physics packages to better capture conditions !

! !over the high latitudes and extensive ice sheets!!Primary developer: Polar Meteorology Group, BPRC, The Ohio State Univ.!!Examples!!

!– Variable sea ice thickness!!– Modified surface emissivity, thermal conductivity (ice sheets)!!– Variable snow depth over sea ice!!– Variable sea ice albedo!!– Albedo of snow over Antarctica!!– Fractional sea ice in grid cells!

!Testing: Arctic and Antarctic!!

!Bromwich et al. (2013): Comprehensive Evaluation of Polar WRF Performance in !! !the Antarctic. JGR, 118, 274– 292.!

!!Wilson et al. (2011): Evaluation of Polar WRF Forecasts over the Arctic System !! !Reanalysis Domain: Surface and Upper-air Analysis. JGR, 116, D11112.!

AMPS Forecast Products 7 Apr 2011 00 UTC Hr 48

Sea Level Pressure/Precipitation (3 hr)

500 mb GHT, Winds Pseudosat Image

L  

L  L  

Pseudosat: Model-based satellite cloud depiction

High Resolution: Impact in Katabatic and Complex Flows

Ex: McMurdo region

AMPS (1.1 km)

AMPS 12-h forecast: 10-m wind (ms-1) (1200 UTC 17 June 2013)

Ross Island

m/s GFS

Lee vortex

Byrd Gl. outflow

�  Common occurrence during summer forecasting season

�  Brings low cloud and precip affecting aviation operations

�  Shallow, transient, mesoscale feature

�  Example: Forecast by AMPS, but not global models

AMPS Sfc Winds

(0600 UTC 22 Jan 2013)

Mesolow near Amery Ice Shelf

Resolution: Impact in Antarctic Mesolow

Simulation Ex: Prydz Bay Mesolow

Davis

Mawson

Amery Ice Shelf

AMPS 1-km RH 0600 UTC 22 Jan 2013 – Low-level moisture wrapping around

mesolow

– Low cloud consistent with AMPS 1-km RH but not fully with cloud base

MODIS 0415 UTC 22 Jan 2013

Cloud base

RH

AMPS cloud base 0600 UTC 22 Jan 2013 – Low cloud associated with mesolow seen

AMPS— Forecast and Model Improvement Areas!!

!• Investigation of stable boundary layer simulation!

– WRF schemes used/tested (MYJ, MYNN) found to promote too much vertical mixing in the stable PBL

• Positive biases in near-surface

temperatures, wind speeds (esp. winter)

• Sites / obs to be used: Alexander Tall

Tower, Halley, Dome C

!!!

AMPS— Forecast and Model Improvement Areas (cont’d)!!

!• Forecast cloud bias (underforecast)!!

! !– Less-than-observed cover over Southern Ocean and ! ! ! ! ! ! ! ! ! ! ! ! !continent!

!

! !– Comparison vs. obs: McMurdo, Pole, Davis!!

! !– Comparison of WRF microphysics schemes in case tests!

Monthly Mean Cloud Fraction Feb. 2011 (Nicolas and Bromwich 2011)

AMPS CloudSat / CALIPSO satellites

Advancing Mesoscale Polar NWP: Modeling Issues!!

!1) Development of Polar Modifications !!

! !– Certain high-latitude conditions may not be accurately ! ! ! !represented in standard physics schemes!

!! !– Datasets from polar field campaigns very helpful for ! ! ! !polar code development (e.g., SHEBA)!

!!

! 2) Subsurface Temperature Initialization (Antarctica)!!

! !– Forecast sensitivities to source of ground temperatures ! ! ! !have been seen in AMPS !

!! ! !Ø Currently cycled temps in AMPS!

!

Advancing Mesoscale Polar NWP (cont’d)!!

!3) Sea Ice and Ocean Model Coupling!!

! ! – Important for short-term Arctic mesoscale prediction?!!!!4) Improved High-latitude Cloud Representation!

!

! ! – What are the needs in our basic understanding of !! ! !clouds in polar environments?!

!! ! – How can model microphysics schemes be improved !!

!!5) Blowing Snow Parameterization!

!

! !– Blowing snow an operational forecasting issue!!

! !– Possibilities for a parameterization or diagnostic? !!

Advancing Mesoscale Polar NWP (cont’d)!!!

!6) Diamond Dust / Clear Sky Precip! !

! !– Significant source of precip over Antarctic plateau!!

! !– Development of a parameterization or an algorithm ! ! ! ! ! !for forecasting possible?!

General Considerations: Improving Polar Mesoscale ! ! ! ! ! ! ! ! !Prediction!

!!• Addressing the key issues in mesoscale modeling!

!! !– Can a list general list be compiled, or are areas of ! ! ! ! !weakness model-specific?!

!! !– Determining target areas for improvement!

!

! ! !i) Better simulation of certain meteorological conditions? !!

! ! ! !Ex: Fog, stable PBL, polar clouds!!

! ! !ii) Reduction of errors for specific weather forecast ! ! ! ! ! !applications? !

!

! ! ! !Ex: Ceiling, blowing snow, sea ice movement!

General Considerations (cont’d)!!!!• What physics areas are easiest to improve for!! ! model advancement (i.e., low-hanging fruit)?!

!

! !– Does this vary from model to model?!!

!• Are there pole-specific model deficiencies? !!

! !– What are the sensitivities of the modeling questions !! ! !and needed improvements to the Arctic vs. Antarctic ! ! !application? !

!!• Role of mesoscale data assimilation?!

!!!!End