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GFS Upgrade Implementation scheduled May 1, 2007 Scientific Decision Briefing

GFS Upgrade Implementation scheduled May 1, 2007 Scientific Decision Briefing. Mark Iredell Global Climate and Weather Modeling Branch April 23, 2007. Outline. Scientific Approach Motivation Details of changes Test strategy Retrospective Evaluation Real-time Evaluation.

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GFS Upgrade Implementation scheduled May 1, 2007 Scientific Decision Briefing

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  1. GFS Upgrade Implementationscheduled May 1, 2007Scientific Decision Briefing Mark Iredell Global Climate and Weather Modeling Branch April 23, 2007

  2. Outline • Scientific Approach • Motivation • Details of changes • Test strategy • Retrospective Evaluation • Real-time Evaluation

  3. Goals of this GFS implementation • Unify the NCEP 3DVAR assimilation system under the GSI, improving some performance metrics without affecting others and preparing for future analysis improvements • Change vertical coordinate to hybrid sigma-pressure, reducing some upper air model errors • Add new observing systems • Modernize the radiation package • Increase output particularly for hydrology

  4. GFS Implementation changes • Observation changes • Full resolution AIRS • COSMIC GPSRO • Analysis changes • GSI (Gridpoint Statistical Interpolation) • Forcing changes • None • Physics changes • Modularized radiation package • Dynamics changes • Hybrid sigma-pressure vertical coordinate • Infrastructure changes • None • Resolution changes • None • Post processing and product changes • Output hourly GDAS files • Change to internal model history file • More fields output in model flux file

  5. Observation changes • Inclusion of COSMIC GPS-RO refractivities • Data available to retrospective runs starting November 2006 • Inclusion of every field of view AIRS • Data available to retrospective runs starting September 2006 • Modifications to quality control other radiances

  6. Analysis changes • GSI (Gridpoint Statistical Interpolation) unifies global 3DVAR with the mesoscale system • Grid point definition of background error • Use of recursive filters • More appropriate background errors in the tropics • Improved code design • Inclusion of improved balance constraints • Modified to use hybrid coordinates • Many future options included but not exercised in this version

  7. Physics changes • Modularized radiation package • Overall restructuring of radiation related programs to help future development and upgrade. • In RRTM1-LW, minor upgrade of emissivity coefficient. Rare gas absorption effect turned on. • In aerosol calculation, vertical sigma based structure changed to pressure based structure • Minor bug correction in cloud related calculation • Performance of new radiation very close to operational model

  8. Dynamics changes • Hybrid sigma-pressure vertical coordinate • Model surface remain terrain-following in the lower troposphere but become pure pressure surfaces in the stratosphere • Reduces vertical advection errors and pressure-gradient calculation errors in the upper part of the model • Data assimilation and physics done on hybrid sigma-pressure coordinate as well

  9. Vertical coordinate comparison across North America

  10. Post processing and product changes • Output hourly GDAS files • Supports hydrology and other needs • May be useful in data assimilation • Change to internal model history file • Hybrid sigma-pressure vertical coordinate • Affects downstream codes • More fields output in model flux file • Supports hydrology needs • No effect on downstream codes • [website here]

  11. Final testing set • Retrospective testing • 15 June 2005 to 5 November 2005http://wwwt.emc.ncep.noaa.gov/gmb/para/paralog.2005tropics_retro_gsihybrid.html • 31 July 2006 to 5 November 2006 http://wwwt.emc.ncep.noaa.gov/gmb/para/paralog.2006tropics_retro_gsihybrid.html • 24 October 2006 to 5 February 2007 http://wwwt.emc.ncep.noaa.gov/gmb/para/paralog.200607winter_retro_gsihybrid.html • Real-time parallel • NCO started January 2007; in fairly final form about March 1, 2007 to presenthttp://wwwt.emc.ncep.noaa.gov/gmb/para/paralog.gsihybrid.html

  12. Outline • Scientific Approach • Motivation • Details of changes • Test strategy • Retrospective Evaluation • Real-time Evaluation

  13. Overview of objective scores: Summer 2005 and 2006 500 hPa heights neutral in both Northern Hemisphere and Southern Hemisphere rms vector wind error in pry at 200 and 850 hPa in tropics reduced GSI hybrid precipitation over continental US less positive bias, more skill compared to radiosondes, GSI hybrid temperatures warmer, temperature forecasts improved in lower troposphere in Southern Hemisphere and tropics, improved in upper troposphere tropics forecast heights fit radiosondes significantly better bias of 200 hPa winds over East Asia substantially reduced in GSI hybrid GSI hybrid analysed moisture closer to radiosondes

  14. 500 hpa height anomaly correlations July 1-Nov. 5, 2005 Tropical rms vector wind error

  15. 500 hpa height anomaly correlations Aug. 15-Nov. 6, 2006 Tropical rms vector wind error

  16. Precipitation skill CONUS

  17. Precipitation skill CONUS

  18. 2005-2006 Atlantic Season Average Track Error Using The Current Operational and New GFS GFS GFDL

  19. 120h Track Error Comparing GFDL and GFS Model With Current Operational GFS and New HYBRID GFS GFDL GFS

  20. Much Improved Tracks of Ophelia OLD GFDL (2) NEW GFDL (4) OLD GFS (1) NEW GFS (3) OLD GFDL (2) NEW GFDL (4) OLD GFS (1) NEW GFS (3) OLD GFDL (2) NEW GFDL (4) OLD GFS (1) NEW GFS (3

  21. Degraded Philippe Track but Improved Intensity Forecast OLD GFDL (2) NEW GFDL (4) OLD GFS (1) NEW GFS (3) WINDSPEED HYBRID GFDL 84 HOURS

  22. Early and Later Forecasts of Wilma Improved OLD GFDL (2) NEW GFDL (4) OLD GFS (1) NEW GFS (3) OLD GFDL (2) NEW GFDL (4) OLD GFS (1) NEW GFS (3) OLD GFDL (2) NEW GFDL (4) OLD GFS (1) NEW GFS (3)

  23. 2005-2006 Eastern Pacific Average Track Error GFDL GFS

  24. Overview of objective scores: Winter 2006-2007 PRYC vs OP 500 hPa heights slightly better in GSI hybrid in NH (.012 anomaly correlation day 5), slightly worse in SH (.004 anomaly correlation day 5) rms vector wind error in pry at 200 and 850 hPa in tropics reduced; large improvement in 850 hPa tropical winds GSI hybrid precip over continental US slightly more skill than operational GSI hybrid analysed tropical winds closer to radiosondes; forecast tropospheric winds closer to radiosondes than operational Bias, rms vector error of 200 hPa winds over East Asia substantially reduced in GSI hybrid GSI analysed and forecast extratropical temperatures closer to radiosondes than operational, stratospheric temperatures closer to radiosondes forecast heights fit radiosondes significantly better in GSI hybrid GSI hybrid analysed moisture closer to radiosondes

  25. 500 hpa height anomaly correlations Nov.1 2006-Feb. 05 2007 Tropical rms vector wind error

  26. Precipitation skill CONUS

  27. Winter retro: Precip and 2m Temp (East CONUS)

  28. Outline • Scientific Approach • Motivation • Details of changes • Test strategy • Retrospective Evaluation • Real-time Evaluation

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