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