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