Wind errors in the GFS

Glenn.White@noaa.gov

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Fang-Lin Yang

GFS .033 behind ECMWF, .006 behind Met Office

GFS .019 ahead of ECMWF

Fang-Lin Yang

GFS .051 behind ECMWF, .037 behind Met Office

GFS .078 behind ECMWF

GFS slightly better than ECMWF;GFS 6-10 day forecasts explain 50% of variance

CPC

CPC

GFS poor precip forecasts, large bias

MMB

Jan. 2000 T170 L42

May 2001 cloud liquid water, momentum mixing, stonger QC AMSU

Oct. 2002 T254 L64, analysis changes

May 2005 T382 L64, increased mountain blocking, decreased vertical diffusion

May 2007 GSI, hybrid vertical coordinate

Note increase in numberOf observations

Improvement has leveled offLast 2 years

Little improvement last 5 years

GSI improved agreement with analyses, not with raobs

GFS analysesCloser to rawinsondes

ECMWFforecastsCloser toRawinsondes

GFS Day 1 problemGFS day 1 and day2 problem

In NH extratropics, fall behind ECMWF first 24 hoursIn tropics fall behind ECMWF day 2

Wind errors not just a tropical problem.

Zonal mean RMS difference in wind analyses

Analyses most different at equatorAbove 700 hPaGFS most like ECMWFMost different from FNMOC

EC more similar to Met Office Than GFS except above 150hPa atequator

RMS difference in wind analyses at equator

Biggest differences in analyses 200 hPa and aboveAnd in ePacific 800-400 hPa

GFS stronger trades than other centers

GFS more variability in forecasts than other centersFNMOC less variability

Transient eddy kinetic energy (1/2(u’2+v’2))

GFS tends to have larger rms wind errors than ECMWF, Met Office

Not just a tropical problem

Analysis differences quite large near equator

GFS stronger trade winds western hemisphere

FNMOC less variability than other centersGFS more variability in forecasts

Initially GFS error grows more slowly near equator than other centers, more rapidly than other centers in midlatitudes.