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GFS/GDAS CHANGES SINCE 1991
History of recent modifications to the global forecast/analysis system
Many of the more recent changes (TPB > 442) are documented in
Global Modeling Branch Technical Procedures Bulletins(TPB)
Another source of information is the
Parallel run home page
- Pre-1991
- 08/80: R30L12
- 10/83: R40L12
- 04/85: MRF85 R40L18 - GFDL physics
- 06/86: MRF86 R40L18 - convection to tropopause
- 08/87: MRF87 T80L18 - diurnal cycle, moisture all layers
- 01/88: MRF88 T80L18 - interactive clouds
- 03/91: T80L18 to T126L18, silhouette to mean orog, new SST,
marine stratus, reduced horizontal diffusion
- 06/91: SSI analysis
- 08/93: Arakawa-Schubert convection, 28 layers
- 01/95: SSM/I PW over sea; analysis changes; various physics changes (TPB 417 (not on Web))
- 10/95: Satellite radiances instead of T retrievals; ERS-1 winds; physics changes (TPB 428 (not on Web))
- 06/96: Adjustments to PBL and convection
- 02/97: SSM/I water vapor discontinued
- 11/97: Elimination of "valley snow" and other small changes
(TPB 443)
- 01/98: TOVS-1b radiances; vertical diffusion inc in free atmosphere
(TPB 445)
- 06/15/98: T170L42 to day 3.5; physics changes; 3D ozone; analysis changes
(See TPB 449)
- 07/22/98: First emergency implementation: fix to convection, horizontal diffus,
plant evap: see last section of TPB 449 above.
- 10/06/98: Second emergency implementation: Back to T126L28, better fits to data, more
iterations in analysis, physics changes
(TPB 450)
- 12/01/98: Snow resolution increased from 2.0 to 0.5 degrees; snow depth field added;
snow depth no longer estimated by model
- 01/08/99: Use of VAD winds eliminated due to problems with light wind speeds
- 03/08/99: Introduction of high-resolution data from the
NOAA-15 satellite.
The data are radiances from the AMSU-A and HIRS-3 intruments.
The NOAA-11 Satellite is no longer providing AMSU data and will
soon be unable to provide HIRS data.
- 01/24/2000: Resolution upgraded from T126L28 to T170L42, restoring the resolution
used from June 15 through Oct 5, 1998. No other changes in the
forecast/analysis system. The MRF is run at T170L42 through day 7,
then at T62L28 through day 16. The AVN is run at T170L42 out to 84
hours four times a day.
(See TPB 452)
- 05/17/2000: AVN available out to 126h at full (T170) resolution at 00Z and 12Z.
- 06/27/2000: Resolution of ensemble members increased from T62 to T126 for first 60 hours of forecast.
- 07/06/2000: Hurricanes and tropical storms in the model's guess field
are relocated to the official Tropical Prediction Center position in each
6-hour analysis cycle.
( TPB 472)
- 08/29/2000 18Z: Data cutoff time for the 06Z and 18Z final analysis (FNL)
extended from 4 hours to 6 hours.
- 10/01/2000 06Z: Package of minor changes:
Observations and analysis:
New obs error diagnosis,rawinsonde radiation correction,
effects of balloon drift in time and space included
Forecast and post processing:
Improved orography, reduced gaussian grid over polar regions, new surface albedo
climatology, single scattering albedo adjusted
- 11/01/2000 12Z: ERA wind data erratic; turned off.
- 02/13/2001 12Z: Satellite radiance and moisture analysis changes plus smoothed output MSLP.
- 05/15/01 12Z:
(See TPB 484).
- Inclusion of cloud condensate as a history variable
- Use of the cloud condensate in the calculation of radiative transfer
- Stronger quality control for AMSU radiances
- Momentum mixing included in deep convection
- Refinement of hurricane relocation algorithm
- SST anomaly damped toward climatology during forecast, with 90-day relaxation time
- 06/27/01 12Z: Minor increase in vegetation fraction.
- 07/24/01 12Z: The data source for the daily 1-degree sea surface
temperature analysis is changed from NOAA-14 to NOAA-16
due to instrument drift.
- 08/15/2001 06Z: Package of minor changes:
Observations and analysis:
Higher resolution sea ice mask
Forecast and post processing:
Bug corrections in gravity wave drag, randomization of convective cloud tops,
land surface evaporation with trace snow cover; minor adjustments in
effective radius for ice crystals, autoconversion rate for ice, evaporation
of falling precip, and critical RH for condensation
- 10/09/2001: Snow depth is updated daily at 00Z from observations;
at 06Z, 12Z and 18Z the model guess is used. Formerly the same
00Z update was reinserted in each of the day's cycles.
- 01/15/2002 12Z: Quikscat surface winds included.
- 03/05/2002 : AVN runs four times a day out to 384 hours.
Resolution is T170L42 to 180h, thereafter T62L28.
- 04/23/2002 00Z: MRF is replaced by the 00Z AVN. Look-alike MRF
grids will still be available daily for several months on th
ftp server at
ftp://ftpprd.ncep.noaa.gov/pub/data/nccf/com/mrf/para/
- Sept-Oct 2002: Name changes:
The AVN will be referred to as the Global Forecast System model (GFS).
- 10/29/02 12Z:(See draft TPB)
- Resolution change
old: T170L42 to 180h, T62L28 to 384h
new: T254L64 to 84h, T170L42 to 180h, T126L28 to 384h
- Analysis and observation changes: background error recomputed,
AMSU-A channels 12 and 13 from NOAA-15 and NOAA-16 and HIRS from NOAA-16 used,
METAR surface pressure observations used, divergence tendency constraint
in tropics turned off.
- 03/11/03 12Z: NOAA 17 1B radiances assimilated, NOAA-16 AMSU-A radiances
restored, QuikSCAT winds superobbed at 0.5 degrees.
- 08/28/03 12Z: RRTM longwave radiation from AER installed:
More trace gases (CH4, N2O, CFC's)
and better tropospheric water vapor absorption.
- 10/28/03 12Z: NOAA-17 AMSU-A radiances turned off
- 11/20/03 12Z: Package of minor analysis changes
(see description)
- 12/09/03 12Z: Vertical diffusion added to ozone
- 02/24/04 12Z: Mountain blocking: Parameterization of the separation of
airflow in the vertical with passage over mountainous terrain.
- 03/09/04 12Z: Ensemble run 4 times daily. Resolution T126 0-180 h,
then T62 to 384 h.
- 05/25/04 12Z: Turn off NOAA-16 HIRS/3 observations
- 05/31/05 12Z:(See TPB
- includes changes made 06/14/05 and 07/07/05)
- Resolution change:
old: T254L64 to 84h, T170L42 to 180h, T126L28 to 384h
new: T382L64 to 180h, T190L64 to 384h
- Increase mountain blocking, decrease vertical diffusion and modify sea ice.
- Land Surface Model: Upgraded from OSU 2-L LSM to 4-L NOHA LSM.
- 06/14/05 12Z: Increase canopy resistance of vegetation
- 07/07/05 12Z: Correct error in temperature near top of model
- 01/31/05 18Z: Radiation code corrected to prevent blowups in ensemble forecasts
- 05/30/06 12Z: GFS Ensembles now have 14 members, 4 times daily. Each cycle now
has its own control member. Resolution is T126L28 through 384 h. New ensemble
transform method used to generate members.
- 08/22/06 12Z:(See Briefing Notes):
- New orography&land-sea mask, improved snow analysis, and new ozone physics.
- New glacial ice and fix error in downward LW radiation at earth's surface.
- Infrastructure changes (e.g. Full ESMF compliance).
- 05/01/07 12Z:(See Briefing Notes):
- Change vertical coordinate to hybrid sigma-pressure, reducing some upper air model errors.
- Unify the NCEP 3DVAR assimilation system under the GSI, improving some performance metrics without affecting others and preparing for future analysis improvements.
- Add new observing systems.
- Modernize the radiation package.
- Increase output particularly for hydrology.
- 09/25/07 12Z: GSI Upgrade
- Modify GSI code to permit assimilation of SBUV-8 and JMA wind data.
- Upgrade to latest version of GSI. Incremental improvement due to addition of new data types.
- 12/04/07 12Z: Use of Unified Post Processor in GFS
- 12/04/07 12Z: GFS Ensemble (NAEFS/TIGGE) UPGRADE
- GFS deterministic model bias corrected (bc) output through F180
- GFS bc output used in GEFS processing
- Combine NCEP/GEFS (20 member) and CMC/GEFS (20 member) to produce:
Ensemble mean and anomaly, ensemble spread and mode along with 10%,50%,90%
probability forecast at 1x1 degree resolution.
- Statistical downscaling by using RTMA as a reference: a. At NDGD (5km) resolution
(CONUS), generate mean and mode along with 10%, 50% and 90% probability forecast
- 12/09/08 12Z: Post Change
- Formulation change in freezing level calculation
- Adding several new parameters to output files
- A fix to the calculation of precipitation type
- 02/24/09 12Z: GSI Upgrade
- Inclusion of METOP IASI data
- Use of variational qc
- Change in land/snow/ice skin temperature variance
- Flow dependent reweighting of background error variances
- Addition of background error covariance input file
- Reduction of number of airs water vapor changels used
- Use of new version and coefficients for community radiative transfer model
- Modification of height assignment for height based wind observations
- Modification of surface land use file to remove a few
permanent (~12) glacial points to improve surface temperature forecasts over those points.