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Forecast Sensitivity - ObservationImpact(FSOI)Inter-comparison Experiment
RolfLangland,NavalResearchLaboratory(NRL)TomAuligné,JointCenterforSatelliteDataAssimilation(JCSDA)RonGelaro,NASA,GlobalModelingandAssimilationOffice(GMAO)RahulMahajan,DavidGroff,NOAA,NationalWeatherService(NWS)JianjunLiu,NOAA’sSatelliteandInformationService(NESDIS)JamesCotton,LarryMorgan,UKMetOfficeYoichiro Ota,JapanMeterological Agency(JMA)
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FSOIComparisonStudyMotivation
• SeveralNWPcenterscomputeFSOIroutinelytomonitor/understand/tunetheirDAsystem.OpportunitytocompareimpactsinsystemswithdifferentDAmethodsanddifferentmixofassimilatedobservations.
• ImpactofAMVsandotherwindobservationdata.• Satellitevs.in-situdata,TLM/ADJvsensembleDA.• Arerelativeimpactofvariousobservationtypescomparable?• Canwelearnfromsimilarities/differencestoimproveNWPsystems
andDAprocedures?
• NWPCentersthatparticipated:NRL,GMAO,EMC,MetOffice,JMA
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• FSOIquantifiesimpactofallassimilatedobservationsonaselectedforecastmetric…showsifanyobservation[orsetofobservations]decreasesorincreasesforecasterror…
• OSEshowsimpactofoneselectedchangetotheobservationsystemonallaspectsofforecast…notabletopartitionimpactofvariousobservationtypes
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FSOIvs.data-denial(OSE)experiments
Observations ForecastMetricsFSOIOSE
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ExperimentalDesign
• Timeperiod:3-monthDJF2014-15,00UTC&06UTCanalysistimes
• Verification: 24hforecastagainstself-analysis• Metric:globaltotaldryenergy(surface-100hPa)• Adjoint: dryplusmoistphysics,asavailable• Ensemble: flow-followinglocalization
Resultsshownherearepreliminary[onlyglobalsummaryplotsofimpactat00UTCwillbeshown]
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NWPCenters
NRL GMAO Met Office JMAAdjoint
JMAEnsemble
EMC
AnalysisSystem
4DVar InObservationSpace
Hybrid3DVar 4DVar 4DVar LETKFre-centeredvia4DVar
EnKFre-centeredvia4DEnVar
FSOITechnique Adjoint Adjoint Adjoint Adjoint Ensemble Ensemble
ExperimentResolution
Model:T425L60Adjoint:T119L60
Model:25km
DA:50km
Ens: 100km
Model:N320(40km)
Adjoint:N216 (60km)
Model:TL959L100
Adjoint:TL319L100
Ensemble:(x50)TL319L100
Ensemble:(x80)T254
SpecificConsiderations
Super-obbingforAMVs
QC=channelselection +dynamicalobservationerror
~30%cyclesdiscarded duetospuriousimpacts
Additionalthinning ofobservationsexceptforaircraftdata
ParticipatingNWPCenters
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ObservationCountat00UTC
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FractionalOb-Impact
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EnsembleDAMethods
EnsembleDAMethodsNavy
FractionalObImpact:SatelliteRadiances
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EnsembleDAMethods
FractionofNeutralImpact-Observations
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EnsembleDAMethods
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FSOIInter-comparisonSummary
• LargestAMVimpactsinNavyGlobalsystem• SmallestAMVimpactsinEMC&JMAensemble-DAsystems
• ImpactsdependonamountofAMVandotherobservationdatathatisassimilated
• Thinningorsuper-ob procedures• Assimilationmethod:TLM/ADJvs.ensemble• Ensemblemethodsappearless-accurateatquantifyingsensitivityforobservationswithsmallindividualimpacts(e.g.,satelliteobs)…
QuestionsabouttheFSOIinter-comparisonstudy?
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ObservationImpactat00UTC:ObservationCount
Radiances OtherObservations
muchthinningofobservations
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Largeimpact-per-ob…
TOTAL TOTAL
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ObservationImpactat00UTC:ImpactperObservation
10-3 10-2
Radiances OtherObservations
PERCENT PERCENT
Impact<0à BeneficialImpact>0à Detrimental
ε=10-10Impact<-ε à BeneficialImpact>ε à Detrimental-ε <Impact<εà Neutral
ObservationImpactat00UTC:FractionofBeneficialObservations
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Observationimpactwithensemblemethod isartificiallychangedbyensemble“inflationfactors.”
Only~20%oftheforecasterrormetricprojectsontoensemblestructures,soobservationsensitivitymaybenotwell-representedwithensemblemethods [Problemswithensemble localization,inflationfactorsandotherissues].ImplicationsforFSOIwithensemblemethods, andalsoforensembleDAitself,suchas4dENS-Var,asopposed to4DVARwithTLM/ADJ.
FSOITLM/ADJvs.Ensemblemethods