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