ERA-CLIM2GeneralAssembly,UniversityofBern12-15December2017
CERA-SAToceancomponentandfurtherdevelopments
EricdeBoisséson,DinandSchepers,PatrickLaloyaux,PerDahlgren,YukiKosaka,GiovannaDeChiara,MarcinChrust,MagdalenaBalmaseda,PhilBrowne,PatriciadeRosnay,MichaelMayer,RobertoBuizza
CERA-20C CERA-SAT
ResoluQon ORCA1_Z42 ORCA025_Z75
OceanIC 10ensemblemembersfromORA-20C 2x5ensemblemembersfromORAS5
AssimilaQon EN4.0.2T/Sprofiles EN4.1T/SprofilesAVISOalong-trackSLA(usingORAS5MDT)OSTIAsea-ice
SSTrelaxaQon HadISST2.1.1¼degreemonthly OSTIA1/20degreedaily
Period 1901-2010 2008-2016
IntroducQon
• FromCERA-20CoceantoCERA-SATocean:
• CERA-SAToceanhasbeenproducedin4separatestreams(6-monthoverlap)thatcover2008-2016:
CourtesyofD.Schepers
• Thesea-iceissuesinCERA-20Cwere“solved”inCERA-SAT:problemswithsefngsforsea-icealbedoandtemperatureincoupledmode.
ArcQcicethickness
March2002icethick.CERA-20C March2014icethick.CERA-SAT March2014icethick.ORA-S5
• Driginsea-icethicknessseeninCERA-20Ccontained.Nosignsofsea-iceaccumulaQonintheArcQc.CERA-SATsea-icesimilartoORAS5sea-ice.
CERA-SAToceanvsORAS5
• CERA-SATstreamsrestartfromORA-S5ICs.LikeinCERA-20C,CERA-SATisdrigingfromitsbaseline.
CERA-SAToceanvsORAS5
Temp.CERA-20CminusORA-20C-Global Temp.CERA-SATminusORA-S5-Global
• CERA-20CwasgainingheatwrtORA-20Cfromthestartofeachstream.InCERA-SAT,differencesaresmaller,butthingsarelessstraighiorward.DifferencesassociatedwithstraQficaQonbutalsoAMOCadjustment.
Temp.CERA-SATminusORA-S5-Tropics NextraTropics SextraTropics
CERA-SAToceanvsORAS5
• OceanheatbudgetanalysisinCERA-SATandORA-S5
CERA-SATOceanHeatBudget-Global ORA-S5OceanHeatBudget-Global
• InCERA-SAT,fluxesandincrementstendstoaddheattotheocean.TheSSTrelaxaQoniscoolingtostayclosetoOSTIASSTanalysis.
• HeatfluxeshaveoppositesignsinCERA-SATandORA-S5.ThecontribuQonofthebiascorrecQonschemeinORA-S5isthelargestandcompensatesforthelargenegaQveflux.
• Conclusionsunclear.SSTrelaxaQonappropriate?BiascorrecQonneededinCERA?(SeeXiangbo’sreport)
CERA-SAToceanvsORAS5
• FittoobservaQons:
RMSTempvsprofiles2011-2014-Global
RMSSSHvssatellite-Global
ORAS5CERASAT
• CERA-SATdoesnotfitprofilesaswellasORAS5intheupperocean.BiascorrecQonneededinCERA?OceanassimilaQonsefngstoberevisedincoupledmode?
• ThefittoalQmeterisalsoslightlyworseinCERA-SAT.DuetotheuseofuncoupledMDTforcoupledrun?Theerrorisnotgrowingthough.
• TheoceanassimilaQonincoupledmodeneedsrevisionwhendevelopingthenextreanalysisbasedonCERAifwewanttomatchocean-onlyperformances.
Coupledvsuncoupledspread
• InanuncoupledatmosphericreanalysissuchasERA5,thespreadattheair-seainterfaceisgeneratedbytheschemedevelopedbyHiraharaetal.(2016)thatappliesperturbaQonstoSSTandsea-iceusinginformaQonfromdifferentreanalysisproducts.ThespreadisstaQc.
• InCERA,thespreadattheair-seainterfaceisflow-dependentresulQngfromtheatmosphericEDAandtheperturbaQonsappliedtotheocean.
SSTspread5S-5N–UncoupledCERA-SAT SSTspread5S-5N–CERA-SAT
• Thespreadislargerintheuncoupledreanalysis.ButtheCERA-SATspreadisabletocapturefinephysicalfeaturesassociatedtoENSOvariabilityandTIWs
Coupledvsuncoupledspread
• TheSSTspreaddirectlyimpactstheatmosphericvariablethatarecloselyassociatedSKTspread5S-5N
Uncoupled CERA-SAT2Tspread5S-5N
Uncoupled CERA-SAT
Uncoupled CERA-SATEvaporaQonspread5S-5N
• TheextenttowhichthisimpactshigheratmosphericlevelsandwindsremainstobeinvesQgatedasnodirectimpactisasobviousasfortheparametersshownhere...
Impactofscaqerometerdataontheocean
• CasestudyontheimpactofassimilaQngscaqerometerdatainCERA-SAT:
• Directimpactonthemomentumforcingovertheocean.Oceancurrentsresponse.
CourtesyofG.DeChiara
Impactonsurfacewinds
Impactonsurfacecurrents
Impactofscaqerometerdataontheocean
• CasestudyontheimpactofassimilaQngscaqerometerdatainCERA-SAT:NWPacific
SCATNoSCAT
NWAtlanQc
Nino3.4
SCATNoSCAT
NWPacific
Impactonoceantemperature
Impactonoceansalinity
CourtesyofG.DeChiara
SSS
E-P
Impactofscaqerometerdataontheocean
• CasestudyontheimpactofassimilaQngscaqerometerdatainCERA-SAT:
SCATNoSCAT
ImpactonsealevelFittoalQmeter–50S-50N
• AssimilaQngornotscaqerometerimpactsoceanparametersandtheabilityofthesystemtofitobservaQons.ScaqerometerdatahelpswiththeassimilaQonofT/SprofilesandalQmeterSLA
• On-goingstudythatwillfurtherinvesQgatetheimpactofscaqerometerobservaQonsinthe
coupledsystem.
CourtesyofG.DeChiara
Futuredevelopments:SSTassimilaQon
• ImplementaQonofdevelopmentsfromprojectpartnersintothereanalysissystem
• AssimilaQonofSST:usingUKMOframeworktoreplacethecurrentSSTrelaxaQonscheme
• TestdatasetprovidedbyUKMO:oneyearofbias-correctedSSTin-situandsatelliteobservaQons
• DatafromAMSRE,NOAA-AVHRR,AATSR,METOP-AVHRR,AMSR2,ships,drigersandmooredbuoys~8e5obs/day(3e4fortheprofiles)
Futuredevelopments:SSTassimilaQon
• TesQngoftheMLDparameterisaQonfortheverQcalcorrelaQonlengthscaletopropagatetheincrementduetoSSTobservaQonsdowntothethermocline
• SensiQvitytestswithSSTobservaQonerrorsdvandthinning
SSTrelaxaQon-stdvert.lengthscales SSTassim-stdvert.lengthscales
SSTrelaxaQon–MLDparam SSTassim–MLDparam
SSTassim–thinning SSTassim–thin+OEincrease
• MLDparamallowsthepropagaQonoftheTincr.downtothethermocline
• FurtherthinningandincreasedSSTOEreducetheweightgiventoSSTobs.wrttoprofiles
FittoprofileobservaQonsJan-May2010–50S-50N
SSTrelaxaQon-stdvert.lengthscalesvsMLDparamBKGRMSE(solid),ANRMSE(dashed)
SSTassim–MLDparamBKGRMSE(solid),ANRMSE(dashed)
• SSTrelaxaQon:fittoprofilesgreatlyimprovedwithMLDparam.Butmuchmoreexpensive.
• SSTassimwithMLDparam:assimilaQngallthedataimprovesthebkginthefirstlevelsbutdegradesthefitinthethermoclineandatdepth.ThinningandincreasingtheOEsdvforSSThelpreducingthedegradaQonatdepthbutfirstlevelssQllworse.
Futuredevelopments:SSTassimilaQon
• Firstresultsencouraging.WorksQllongoingtofindthebestconfiguraQon:convergence,MLDparam,OE,biascorrecQon…
Conclusion
• CERA-SATprovidesa¼degree10-memberensembleofoceanreanalysisproducedbyacoupledsystemover2008-2016
• CERA-SATisbeingrouQnelycomparedtotheORA-S5ocean-onlyreanalysisintermsofoceanparametersandfittoobservaQons.
• InsightsonpotenQalimprovements,impactofcoupled/forcedapproaches
• TheCERA-SATframeworkisbeingusedatECMWFforobservaQonstudiesinacoupledanalysissystem:exampleofscaqerometerdata
• CERA-SATisonlyamilestoneinthedevelopmentofanEarthsystemapproachtoNWPandreanalysis:coupledsystemadaptedforhigh-resoluQonNWP,baselineforERA6…
• CrucialdevelopmentssuchastheassimilaQonofSSTdataarebeingtestedforfutureimplementaQon