an overview of new developments with the ncep climate forecast system suranjana saha environmental...
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An Overview of New Developments with the NCEP Climate Forecast System
SURANJANA SAHAEnvironmental Modeling Center
NCEP/NWS/NOAA
20th Annual Climate Diagnostics and Prediction WorkshopState College, PA24 October 2005
ACKNOWLEDGEMENTS
SCIENTISTS AND STAFF OF THE :
THE GLOBAL CLIMATE AND WEATHER MODELING BRANCH
ENVIRONMENTAL MODELING CENTER (EMC)
AND THE CONSIDERABLE HELP AND SUPPORT OF
CLIMATE PREDICTION CENTER (CPC)
AND
GEOPHYSICAL FLUID DYNAMICS LABORATORY (GFDL)
• The NCEP Climate Forecast System (CFS) was made operational in August 2004
• Currently, two fully-coupled nine-month forecasts are made every day
• The present CFS operational system at T62L64 resolution is frozen
• Development work is underway at EMC to improve the CFS
• We anticipate a new CFS implementation will take place in a few years
For a new CFS implementation :
• New upgrades to the CFS must lead to better performance
Retrospective forecasts with the new CFS, covering a period of nearly 30 years, will then have to be made
A global reanalysis of the atmosphere, land and ocean will have to be made, prior to that, to provide the initial conditions consistent with the new version of the CFS
This is indeed an enormous challenge !!!
TESTING CHANGES IN THE OCEAN PART OF THE CFS
NEW OCEAN MODEL MOM4 (GFDL)
Jiande Wang
Ocean-Only Simulation Run with MOM4
1981-2004 R-2 Daily Forcing (heat flux, E-P). Same Resolution as operational MOM3, which has the following configuration :
1/3 degree at equator, gradually decreasing to 1 degree at 30N and 30S. Northern boundary is at 65N and southern boundary is at 75S
40 Vertical layers, 10 meter interval in the top 220 m Depth to 5.5 Km
• Indonesian through flow is completely open in a larger area and the surrounding marginal seas are fully resolved as ocean (not land) points
• Use runoff data from NCAR (Dai and Trenberth)
• Use real fresh water flux, instead of “virtual salt flux”. This method gives more accuracy in the simulation of sea surface height
The bias everywhere is considerably less than with MOM3
NEW SEA ICE MODEL
Xingren Wu
1. Thermodynamics : 3-layer (Winton, 2000)
2. Dynamics : EVP Model (Hunke and Dukowicz, 1997)
3. The sea ice model was coupled to MOM4.
4. The model was forced using R-2 climatology
Sample results was for Year-20, March
Modeled sea ice thickness (Year-20, March)
The simulated sea ice distribution is reasonable,
but sea ice thickness may be not thick enough
Sea ice concentration (Year-20, March)
Sea ice concentration is just a little bit too high relative to the satellite observations
Model Simulation Observations
Ocean Developmental work for the future
MOM4
1. Test higher horizontal resolution everywhere for MOM4 (¼ degree globally, or ¼ degree in the tropics decreasing to ½ degree at 30N and 30S)
2. Increased number of vertical levels in the ocean mixed layer, from 40 to 50
3. Use new, more efficient, coupler, with more frequent coupling to the ocean (than the present once a day)
4. Include river (fresh water) runoff from climatology or NOAH land model
Global Ocean Data Assimilation (GODAS) :
• Explicit bias correction
• Geostrophic balance in the assimilation
• Altimetry and Argo salinity added to GODAS
TESTING CHANGES IN ATMOSPHERIC PART OF THE CFS
• NOAH Land Model : 4 soil levels. Improved treatment of snow and frozen soil
• Sea Ice Model : Prediction of ice concentration and ice fraction
• Sub grid scale mountain blocking
• Reduced vertical diffusion
• RRTM long wave radiation
TEST THE CURRENT OPERATIONAL VERSION OF THE GFS (USED FOR WEATHER PREDICTION)
UPGRADES
GFS Developmental work for the future
1. Test higher horizontal resolution (T126)
2. Test new convection scheme (RAS)
3. Test hybrid vertical coordinate (sigma-pressure, sigma-theta)
4. Test improved boundary layer physics
5. Test convectively forced gravity wave drag
6. Test new short wave radiation parameterization
TWO KINDS OF STUDIES
CFS MONTHLY RETROSPECTIVE FORECASTS
CFS FREE COUPLED SIMULATIONS (CMIP)
CFS WEEKLY AND MONTHLY FORECASTS
Higher resolution, both spatial and temporal.
Spatial : T126L64 GFS Atmospheric model (as in operational CFS) coupled to MOM3 Ocean Model
Temporal : 4 CFS runs daily : from 0Z,6Z,12Z and 18Z Atmospheric R2 initial conditions coupled to the same Ocean GODAS initial condition
Period : 2000 – 2004 (5 years)Summer : 7 May – 15 July (70 days)Winter : 7 Nov – 15 Jan (70 days)
Integrations out to 65 days or more (covers the last full calendar month)
POSTER OF AUGUSTIN VINTZILEOS :
WEDNESDAY, 9-10:30 AM
THE CFS 126 : A DYNAMICAL SYSTEM FOR SUBSEASONAL FORECASTS – CHALLENGES
IN PREDICTION THE MJO
U200 hPa forecasts averaged 20°S-20°N and projected to the MJO EOFs obtained from R2
SUMMER
WINTER
13 days
25 days
Conclusions: Good skill and for the reasons that is shown in the poster, we expect improvements....
POSTER OF HUA-LU PAN :
MONDAY, 9-10:30 AM
CLIMATE MODEL DIAGNOSES FROM A WEATHER MODELER’S POINT OF VIEW
V850 hPa forecasts and PRECIPITATION in the tropics from CFS retrospective forecasts and free coupled runs are examined
Conclusions: Episodic nature of easterly waves are well captured. Tropical disturbances in the T126 are better simulated
POSTER OF ÅKE JOHANSSON :
TUESDAY, 9-10:30 AM
PREDICTION SKILL OF NAO AND PNA FROM DAILY TO SEASONAL TIME SCALES
Skill in predicting NAO and PNA indices (as deduced from geopotential at 500 hPa) from daily T126 and T62 retrospective forecasts for 5 winters (DJF 2000-2004) are examined, as well as the 24 winters of operational T62 CFS
Conclusions: There is lingering skill in both NAO and PNA out to 45 days, albeit small. PNA has higher skill than NAO in the short/medium range while NAO has higher skill than PNA in the intraseasonal time range
PNA
NAO
POSTER OF CATHERINE THIAW :
MONDAY, 9-10:30 AM
INDIAN SUMMER MONSOON PREDICTION IN THE NCEP CLIMATE MODEL
Using retrospective forecasts from 9-13 May, the CFS prediction of the onset of the Indian
summer monsoon is examined, using the wind at 850 hPa, Precipitation and SST.
SOMALI JET AREA BAY OF BENGAL
WIND 850 hPa (m/s) CLIMATOLOGY (1981-2004)
15 DAYS (3 Pentads)
ALL INDIA RAINFALL (mm/day) CLIMATOLOGY
Conclusions: The overall prediction of the Indian monsoon rainfall is reasonable. The onset is a little late and the rainfall is a little weak. Higher horizontal resolution and better physics may lead to improvements
PRECIPITATION (mm/day) JULY 2000-2004
XIE-ARKIN CMAP
DIFF T126 - CMAP DIFF T62 - CMAP
FREE COUPLED [CMIP] RUNS
ATMOSPHERIC MODEL
1. T62L64 CURRENT OPERATIONAL CFS
49 years (2002-2050)
2. T126L64 CFS OPERATIONAL VERSION
85 years (2002-2084)
3. T126L64 GFS OPERATIONAL VERSION
30 years (2002-2031)
OCEAN MODEL
CFS OPERATIONAL MOM3 VERSION
T62 very regular ; T126 better variability, weaker amplitude
POSTER OF CÉCILE PENLAND :
MONDAY, 9-10:30 AM
EL NIÑO IN THE CLIMATE FORECAST SYSTEM :
T62 vs T126
Prepare CFS output as we do COADS data : project SSTs onto a 4° x 10° grid, subject to a 3-month running mean, and then project onto 20 leading EOFs
Conclusions: The resolution of the atmospheric component of the model matters a lot! The T126 does get the El Niño spectrum about right
Good variability ; Good amplitude
Good variability ; Good amplitude
CDAS2
Amplitude
CHI 200 hPa
[107 m2/s]
T62 too strong
T126 better
Phase Speed
CHI 200 hPa [m/s]
Eastward speed : T62 too slow T126 better
Westward speed :T62 too strongT126 better
CDAS2Westward propagating Easterly waves
MJO
CDAS2
Phase Speed
CHI 200 hPa [m/s]
At the Equator
Eastward speed : T62 too slow T126 better
Westward speed :T62 too strongT126 better
Semi-annual cycle in the observations not well simulated in any run
Anomalies Climatology
T126new has much reduced bias
Illinois 2m column soil moisture from CMIP runs [ Courtesy: Fan and van den Dool, Thursday 10.30 AM ]
POSTER OF SUDHIR NADIGA :
MONDAY, 9-10:30 AM
ENSO-RELATED SALINITY VARIABILITY IN CFS
Salinity simulation from a free coupled run of the T62L64 operational CFS is compared to salinity estimates from GODAS as well as synthetic salinity dataset (Maes, 2000)
RED = WARM EVENTS
BLUE = COLD EVENTS
Different water masses, caused by zonal advection
Conclusions: Salinity contributes significantly to the density variability in the global oceans. The sub surface salinity shows a strong ENSO-related signal in the western equatorial Pacific Ocean
LAYOUTSEASONAL MEANS AVERAGED OVER 24 YEARS
[2007-2031]
CFS T126 CFS T126 NEW
CFS T62 OBS
PRATE [mm/day] JJA
PRATE [mm/day] BIAS JJA
PRATE [mm/day] DJF
PRATE [mm/day] BIAS DJF
PRATE [mm/day] BIAS JJA
PRATE [mm/day] BIAS DJF
PRATE [mm/day] BIAS JJA
PRATE [mm/day] BIAS DJF
PRATE [mm/day] BIAS JJA
PRATE [mm/day] BIAS DJF
CONCLUSIONS
A LOT MORE WORK NEEDS TO BE DONE TO IMPROVE THE CFS. ACTIVITIES ARE IN PROGRESS IN THE FOLLOWING AREAS :
INCREASED HORIZONTAL RESOLUTION OF THE ATMOSPHERIC MODEL
IMPROVED PHYSICS AND NUMERICS IN THE ATMOSPHERIC MODEL
NEW OCEAN MODEL WITH INCREASED HORIZONTAL AND VERTICAL RESOLUTION
NEW COUPLER
NEW LAND SURFACE MODEL
NEW ICE MODEL
ESMF COMPATIBLE
GLOBAL ATMOSPHERE-LAND-OCEAN COUPLED REANALYSIS