WRFAtmosphericDataAssimila3on:lessonslearnedfromASR
NCAR/MMM:ZhiquanLiu,Hui‐ChuanLin
UCAR/COSMIC:Ying‐HwaKuo,Tae‐KwonWee
OSU/BPRC:DaveBromwich,LeshengBai,KeithHines,Sheng‐HungWang
WCRP/ICR4‐May9,2012 1
Outline
• IntroductionofWRFDASystem
• SeasonalvariationofWRFmodelerroratstratosphere
• RadiancebiascorrectionstrategyforregionalDA
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3
WRFDA(formerlyWRF‐Var):AcommunityfacilityBarkeretal.2012,BAMS
• DevelopedandsupportedbyNCAR/MMMwithcontributionsfromresearchcommunity
• Includeoptionsfor3DVAR,4DVAR,andhybridVar/Ensemble– 3DVARusedforASR
• Canassimilateconventionaldata,GPSRO(refractivity),satelliteradiances,radar,precipitation(4DVARonly)
– Variationalbiascorrection(VarBC)forradianceDA
• Controlvariables– Streamfunction,unbalanced(velocitypotential,T,Ps),andpseudoRH
• NotdirectlyanalyzeT2m/Q2m/U10/V10– ThoseareWRFmodeldiagnosticvariables,notprognosticvariables.– T2m/Q2m/U10/V10obsusedtoanalyzethelowestmodellevels’state.
WCRP/ICR4‐May9,2012
Observa3onsusedinASR• Surface
– U/V,T,Q,P:SYNOP,METAR,SHIPS,BUOY,SONDE_SFC,– U/V:QuikSCAToverocean
• Upperair– SOUND(U/V,T,Q),AIREP(U/V,T),PROFILER(U/V),
PolarAMV,GeoAMV(U/V)
• GPSRadioOccultation(refractivity)
• Microwaveradiancesfrompolarsatellites
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NCEP BUFR/PrepBufr data provided by Jack Woollen
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synop + metar ship buoy * sound gpsref profiler airep quikscat SatWind
More than 4000 surface stations
Around 300 sounding stations
observa3oncoveragesnapshotat2007120100with3‐h3mewindow
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Seasonalvaria3onofmodelforecasterrorsatstratosphere(standardderiva3onsta3s3csfrom24hFC‐12hFCvalidatsame3me)
This is the basis for the background error covariance statistics.
100 hPa
Discon3nuitycausedbyBECchange
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Compare to ERA-Interim.
One of reasons to use grid-nudging near the top.
SatelliteMWradiancedataused(2000~)
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AMSU‐A AMSU‐B MHS
NOAA‐15 X X
NOAA‐16 X X
NOAA‐17 X
NOAA‐18 X X
NOAA‐19 X X
METOP‐2 X X
EOS‐2(Aqua) X
AMSU-A: assimilate channels 5~9. AMSU-B/MHS: assimilate channels 3~5.
Total 12 sensors from 7 satellites
DataAvailability
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LTAN(localtimeofascendingnode)
Launchdate availabledateforASR
NOAA‐15 16:38:14 1998/05/13 Sincethebeginning
NOAA‐16 20:00:43 2000/09/21 2001/01/24
EOS‐2(Aqua) PMorbit 2002/05/04 2004/04/13
NOAA‐17 19:45:41 2002/06/24 2002/09/11
NOAA‐18 14:31:03 2005/05/20 2005/08/23
METOP‐2 21:31:00 2006/10/19 2007/04/24
NOAA‐19 13:31:47 2009/02/06 ??
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Radiance Monitoring against ERA-Interim over ASR domain
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METOP-2
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RadianceMonitoringagainstERA‐InterimGlobalvs.Regionalsta3s3cs
spin-up 6-h cycling exps
BC statistical different over globe & sub-regions
Bias correction coefficients: “offset” evolution from global, ASR-domain, South-Pole domain.
Global statistics
Statistics over ASR-domain Statistics over south-pole domain
Biascorrec3onsensi3vityexperiments
• Reducedresolution– 60km/57L/10hPatop,nogrid‐nudgingontop,singledomain
• 4experiments– gts:Non‐radiancedataassimilated
expswithconventionaldataandAMSU‐Aradiancesassimilated– varbc_cs:uses“cold‐start”VarBCcoeffsatthebeginningof
cycles,i.e.,noknowledgeofcoeffs.
– varbc_ws:uses“warm‐start”VarBCcoeffsatthebeginningofcycles,i.e.,regionalspun‐upcoefffsfromMay~July.
– glb_freez:turn‐offVarBC,butupdateBCcoeffseachcyclefromglobalstatistics
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ComparetoASCOSsoundingAug.3~Sep.7,2008
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T/QAnalysisvs.ASCOS
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Bias Bias
RMSE RMSE
T/Q24hFCvs.ASCOS
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Bias Bias
RMSE RMSE
Planfor10‐kmASRproduc3on• Diagnose30kmASR‐Interimandidentify/fixtheissues
• ImplementinWRFDAradianceblacklisttableusedbyERA‐Interim– AlsorefertoNESDISinstrumentmonitoringandNCEPradianceblacklisttable– http://www.star.nesdis.noaa.gov/smcd/spb/icvs/– http://www.emc.ncep.noaa.gov/mmb/data_processing/
Satellite_Historical_Documentation.htm
• Conservativeusageofsurface‐sensitivechannels– e.g.,useAMSU‐Ach5,AMSU‐B/MHSch5onlyoverwater.
• PerformradiancemonitoringrungloballypriortoASRproduction– Pre‐computeglobalBCcoefficientsstatisticsusingERA‐Interim(ina1°x1°grid)
overthewhole11‐yearperiod.
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