Operational GSI Changes

History of recent modifications to the operational GSI system

Note some changes prior to 2012 may be missing. Please notify the webmaster of any missing information.

GSI was introduced in regional on 6/20/06
RTMA first operational implementation using GSI on 8/6/2006
GSI was introduced in global on 5/1/07
Rapid Refresh (RAP) introduced with GSI on 5/2/12

Information prior to these dates used earlier analysis systems.


  • Global and Regional 07/03/2013 18Z
    • HIRS4 radiances on NOAA-19 removed from operations due to increased noise

  • Global 05/22/2012 12Z: GSI/GFS Q3FY2012.
    • GSI Changes
      * EnKF hybrid system
      * GPS RO bending angle rather than refractivity
      * Inclusion of compressibility factors for atmosphere
      * Retune SBUV ob errors . fix bug at top
      * Update radiance usage flags
      * Prepare for monitoring NPP and Metop-B
      * Add GOES-13 and GOES-15 data
      * Add Severi CSBT radiance product
      * Satellite monitoring stats code included in Ops.
      * New Sat wind data and QC
      * Add NPP ATMS data - modify to monitor NPP CrIS and METOP-B
      * Update to current version of trunk
      * Several small updates to moisture fields (modify minimum value and supersat clipping)
      * New version of Forecast model
      * Updated postprocessor
  • Rapid Refresh 05/02/12 Initial Rapid Refresh Implementation using GSI (r9374 + GSD changes)

  • Regional 10/18/11 Regional analysis Updates
    • Upgrade to latest version (March 2011) of Grid-point Statistical Interpolation (GSI) analysis code
    • Add GSI analysis job for all 5 NAM nests
    • Begin use of dynamic reject list (from RTMA) for mesonet data
    • New observation types:
      • ACARS humidity
      • WDSATR : superob'ed Scatterometer winds over oceans
      • HIRS and AMSU-A radiances from NOAA-19,
      • IASI radiances from METOP
      • AMSU-A radiances from AQUA
      • RASS virtual temperatures
      • MAP winds
      • ASCAT winds
      • Improved assimilation of GPS radio occultation (COSMIC) data
    • Analysis will now update the first guess 2-m temperature/specific humidity and 10-m wind (12 km NAM domain only)
  • Global 05/09/2011 12Z: GSI/GFS Q2FY2011.
    • GSI Changes
      * Improved OMI QC
      * Removal of redundant SBUV/2 total ozone
      * Retune SBUV/2 ozone ob errors
      * Relax AMSU-A Channel 5 QC
      * New version of CRTM 2.0.2
      * Inclusion of Field of View Size/Shape/Power for Radiative transfer
      * Inclusion of GPS RO data from SAC-C, C/NOFS and TerraSAR-X satellites
      * Remove down weighting of collocated radiances
      * Limit moisture >= 1.e-10 in each outer iteration and at end of analysis
      * Inclusion of uniform (higher resolution) thinning for satellite radiances
      * Improve location of Buoys in vertical (move from 20 to 10m)
      * Improved GSI code with optimization and additional options
      * Recomputed background errors
      * Inclusion of SBUV and MHS from NOAA-19 รข removal of AMSU-A NOAA-15
      * Ambiguous vector quality control for ASCAT (type 290) data
  • RTMA 9/28-29/10 RTMA Analysis Updates
    • Add 2.5 km RTMA for Guam; use downscaled GFS for first guess
    • Extended assimilation time window (+/-30 min; 5 km RTMA uses +/-12 min)
    • Use First Guess at the Appropriate Time (FGAT)
    • Apply sequential bias-correcton algorithm for background temperature
    • Improved quality control
    • Add ocean surface WindSat and ASCAT winds and low-level satellite drift winds
    • Slight realignment of the Hawaii 2.5 km RTMA grid
  • Global 12/15/09 12Z: GFS, GSI and Post upgrades, see NWS TIN for the detail.
    • 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 radio 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.
  • Global 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.
  • Regional 12/16/08 Regional updates
    • Use latest (1Q 2008) version of the GSI analysis code
    • Assimilate METOP radiance data
    • Assimilate TAMDAR/AMDAR aircraft data
    • New version of Communitity Radiative Transfer Model
  • RTMA 10/7/08 Initial implementation of RTMA over Hawaii and Puerto Rico

  • RTMA 4/15/08 Initial implementation of RTMA over Alaska

  • Regional 3/31/08 Regional updates
    • New (August 2007) version of GSI code.
    • Retuned background errors (gives improved obs fit to first guess)
    • Use AIRS radiance data (not updated until 31 March 2008)
    • Use GOES 1X1 radiance data
    • New SATWND data (eumetsat and modis)
    • MESONET uv (winds with uselist)
  • Global 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.
  • RTMA 6/26/07 RTMA changes

  • Global 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.
  • Regional 6/20/06 Initial Regional implementation with GSI

  • RTMA 8/6/06 RTMA initial implementation

  • Regional 6/20/06 Initial Regional implementation with GSI

  • Global 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
  • Global 05/25/04 12Z: Turn off NOAA-16 HIRS/3 observations

  • Global 11/20/03 12Z: Package of analysis changes (see description)

  • Global 10/28/03 12Z: NOAA-17 AMSU-A radiances turned off

  • Global 03/11/03 12Z: NOAA 17 1B radiances assimilated, NOAA-16 AMSU-A radiances restored, QuikSCAT winds superobbed at 0.5 degrees.

  • Global 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.
  • Global 01/15/2002 12Z: Quikscat surface winds included.

  • Global 05/15/01 12Z: (See TPB 484).
    • Stronger quality control for AMSU radiances
    • Refinement of hurricane relocation algorithm
  • Global 02/13/2001 12Z: Satellite radiance and moisture analysis changes plus smoothed output MSLP.

  • Global 11/01/2000 12Z: ERA wind data erratic; turned off.

  • Global 10/01/2000 06Z: Package of changes:
    Observations and analysis:     
    • New obs error diagnosis,
    • rawinsonde radiation correction,
    • effects of balloon drift in time and space included
  • Global 08/29/2000 18Z: Data cutoff time for the 06Z and 18Z final analysis (FNL) extended from 4 hours to 6 hours.

  • Global 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)

  • Global 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.

  • Global 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.

  • Global 01/08/99: Use of VAD winds eliminated due to problems with light wind speeds

  • Global 10/06/98: Emergency implementation: Back to T126L28, better fits to data, more iterations in analysis, physics changes (TPB 450)

  • Global 06/15/98: T170L42 to day 3.5;3D ozone; other analysis changes (See TPB 449)

  • Global 01/98: TOVS-1b radiances (TPB 445)

  • Global 02/97: SSM/I water vapor discontinued (TPB 443)

  • Global 10/95: Satellite radiances instead of T retrievals; ERS-1 winds; physics changes (TPB 428 (not on Web))

  • Global 01/95: SSM/I PW over sea; analysis changes; various physics changes (TPB 417 (not on Web))

  • Global 06/91: SSI analysis introduced into operations