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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

GFS Upgrade Implementationscheduled May 1, 2007Scientific Decision Briefing

Mark Iredell

Global Climate and Weather Modeling Branch

April 23, 2007

outline
Outline
  • Scientific Approach
    • Motivation
    • Details of changes
    • Test strategy
  • Retrospective Evaluation
  • Real-time Evaluation
goals of this gfs implementation
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
gfs implementation changes
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
observation changes
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
analysis changes
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
physics changes
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
dynamics changes
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
post processing and product changes
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]
final testing set
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
outline12
Outline
  • Scientific Approach
    • Motivation
    • Details of changes
    • Test strategy
  • Retrospective Evaluation
  • Real-time Evaluation
overview of objective scores summer 2005 and 2006
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

slide14

500 hpa height anomaly correlations

July 1-Nov. 5, 2005

Tropical rms vector wind error

slide15

500 hpa height anomaly correlations

Aug. 15-Nov. 6, 2006

Tropical rms vector wind error

2005 2006 atlantic season average track error using the current operational and new gfs
2005-2006 Atlantic Season Average Track Error Using The Current Operational and New GFS

GFS

GFDL

120h track error comparing gfdl and gfs model with current operational gfs and new hybrid gfs
120h Track Error Comparing GFDL and GFS Model With Current Operational GFS and New HYBRID GFS

GFDL

GFS

much improved tracks of ophelia
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

degraded philippe track but improved intensity forecast
Degraded Philippe Track but Improved Intensity Forecast

OLD GFDL (2)

NEW GFDL (4)

OLD GFS (1)

NEW GFS (3)

WINDSPEED

HYBRID GFDL

84 HOURS

early and later forecasts of wilma improved
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)

overview of objective scores winter 2006 2007 pryc vs op
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

slide35

500 hpa height anomaly correlations

Nov.1 2006-Feb. 05 2007

Tropical rms vector wind error

outline47
Outline
  • Scientific Approach
    • Motivation
    • Details of changes
    • Test strategy
  • Retrospective Evaluation
  • Real-time Evaluation
slide58

~5 day forecasts from the operational GFS (top left) and the hybrid/GSI GFS (top right) and verifying analysis (bottom) on 1 April 1200 UTC