GFS/GDAS CHANGES SINCE 1991

History of recent modifications to the global forecast/analysis system

• 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; Addition of background error covariance input file; Reduction of number of airs water vapor changels used
  • Change in land/snow/ice skin temperature variance
  • Flow dependent reweighting of background error variances
  • 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.
• 12/15/09 12Z: GFS, GSI and Post upgrades, see NWS TIN for the detail.
  • GFS: Upgrading ESMF to Version 3.1.0rp2. Changing output definition of low cloud to combine the previously separately defined boundary-layer cloud and low cloud. Establishing a baseline/housekeeping version of the GFS for future implementations.
  • GSI: new data sources and improved numerical techniques are included in GSI. The analysis changes include:
    • Assimilating tropical storm pseudo sea-level pressure observations, NOAA-19 HIRS/4 and AMSU-a brightness temperature, RARS 1b data, NOAA-18 SBUV/2 and AURA OMI ozone, EUMETSAT-9 atmospheric motion vectors.
    • Using uniform thinning mesh for brightness temperature data.
    • Improving assimilation of GPs radial occultation data. RE-tuned observation errors.
    • Adding dry mass pressure constraint.
    • Using goddard modeling and assimilation office/emc merged code including hooks for 4dvar and observation sensitivity.
    • Updating background error covariance file.
  • Post: the post processors used for GFS and GDAS are unified and two minor changes are introduced into the GFS. Unification of the post processing codes results in slightly less smooth fields in the gdas. A number of diagnostic variables are improved and additional parameters aree added to the model output files.