AssessingArgocontribu.onontheMercator-OceansystemforanIntegratedandMoreSustainableAtlan.cOceanObservingSystem

F.Gasparin,E.Rémy,M.HamonandP-YLeTraonMercator-Ocean,fgasparin@mercator-ocean.fr

6thEuro-ArgoUsersMee.ng

(AtlantOS)

OUTLINE

1. Whyimpactstudiesareneeded?

2. ObservingSystemSimulaGonExperiment

3. ThedoublingofArgoinWBCandalongtheequator

4. TheDeepArgonetwork

5. Conclusion/Discussion

1.WhyobservaGonsimpactstudiesareneeded?

• Obs.impactstudieswerelimitedbythedevelopmentofmodelsanddataassimilaGonsystems

• ForsupporGngtheevoluGonofanintegraGveglobaloceanobservingsystem

• ForimprovingdataassimilaGonschemesinoceanreanalysesandmonitoringsystems

• ForcombiningexperGsesofresearchlabsandoperaGonalcentrestodefinenewmetricsrelatedtonewscienGficquesGons

Targeted Global core-Argo DesignAtlantic Ocean Observing System (2015)

ThenumberofobservaGonsimpactstudiesislimited

ObservingSystemExperiment(OSE)=ImpactofexisGngobservaGons,with/withoutdataassimilaGon.

ObservingSystemSimula7onExperiment(OSSE)=ImpactofnewobservaGonspriortodevelopment,with/withoutsyntheGcdataassimilaGonsampledinarealisGcsimulaGon

(i) RigorousOSSEmethodology,withspecificsteps(ii) Standardmetricsbutalsofocusingonspecific

phenomena,GmeandspaGalscales(iii) Jointexperimentsforrobustnessofresults

OSE/OSSEareexpensiveando]enhardlyconclusive,dueto:- thesystemaGcerrorsinmodelsand- thedependenceonthedetailsofthemodelandassimilaGonsystem.

(Turpin et al., 2016)

TemperatureRMSdiff“withArgominuswithoutArgo”

0-300 m

700-2000 m

°C

°C

(Jul-Dec2012)

TowardanintegraGveAtlanGcOceanObservingSystem(AtlantOS)

CommonSyntheGcobservaGonsfromtheMercator-Oceansystem

Synthetic-observations

- ARMOR3D (CLS)- PSY3, NEMO+SAM2 (Mercator)- Ensemble NEMO simulations

(CMCC)- NEMO+NEMOVAR (MetOffice )

Task1.3-H2020AtlantOS:ObservingSystemDesignStudies

➔MulG-models/mulG-approachesexerciceonthemid-2008/mid-2010period➔SamesyntheGcobservaGonsassimilatedindifferentsystems

- Whatistheadded-valueofXBTlinesforAMOCtransport?- WhatistheimpactofdoublingArgoinWBCandalongequatorialregions?- HowdeepArgo(downto6000m)willimproveoceanstateesImate?- Howsparsehigh-frequencymooringsimpactonoceananalysisandforecasIngsystems?- WhatisthepotenIalimpactofanextensionto150mofdriNersthermistorchain?etc…

Inthecontextofanintegratedoceanobservingsystem…

AssimilaGonindifferentsystems

includingCore-Argo+BGC-Argo(PosterGerminaudetal.)

CombiningexperGseofresearchlabsandoperaGonalcentres

MODELING ASSIMILATION OBSERVATIONS

• OSSEhavebeeninlongeruseandaremoreadvancedfortheatmosphere• OSSEneedtofollowthecompletesetofdesignstrategiesandrigorousvalidaGontechniques(GODAE-OSEvalTT,Halliwelletal.,2014,Okeetal.,2015)

• OSSEsystemincludesseveraldomainsofoceanography

• ExplainingthestrengthsandlimitaGons• DemonstraGngthatcredibleresultscanbeobtained• ProvidingquanGtaGveimpactsunderstandablefortheenGreoceanographycommunity

CONCLUSIVE INTERPRETATION

OSSE

2.ObservingSystemSimulaGonExperiment

OSSEisacomplexsystem

• Amodel(NatureRun,NR),closelyreflecGngthereality=CMEMSoperaIonalsystem(1/12°,noassimilaIon)

• ConstrucGonofsynthe.cdatasetfromtheNR+ Physicalparameters(T/S,SSH)+ IntroducGonofrealisGcerrors

• AnoceandataassimilaGonsystem(DAS),withcalibraGonsothatexisGngobservaGonimpactandsimulatedoceanissimilar=Mercator-Oceansystem1/4°,withsubstanIaldifferenceswithNR(iniIalisaIon,forcings,resoluIon)

NR

DAS

Synthetic dataset

NatureRun,closelyreflecGngthereality(phenomenaofinterest)- RealisGcmeanclimatologyandvariability- Canbeusedforprocessstudies- Availabletothecommunity

NATURE RUNOBSERVATIONS (AVISO)

NATURE RUNOBSERVATIONS (AVISO)

SST variability (stand. dev.) SSH intraseasonal variability (stand. dev.)

ConstrucGonofsyntheGcoriginalArgodesign(Backbonenetwork)

Zonal average of Argo / 3ºx3º box

Argo number / 3ºx3º box

Global

Atlantic

Argo

num

ber /

3ºx

3º b

ox

Temporal homogeneity (South Atlantic) of 1 float / 3ºx3º box

AtlanticGlobal

3-yr average Argo number / 3ºx3º box- NotarGficiallygridded,exisGngArgoposiGons- Period2008-2012- LowsamplingSouthAtlanGc,Highsamplingin

Kuroshioregion

➔SubtracGonoffloatsintheKuroshio+AddiGonintheSouthAtlanGc(followingyear)togetaquitehomogeneousdistribuGonwith1float/3°x3°box

Existing sampling Synthetic sampling

ConstrucGonofsyntheGcArgodoubleddesignandDeepArgodesign

Argodoubleddesign=AddiGonofArgoprofiles(followingyear)inmagenta/orangeregions

DeepArgodesign=Deepextensiononmodellevelsof1/3floatsfromtheOriginalArgodesign

Zonal average Argo / 5ºx5º box

3-yraverageprofilesnumberin3x3box/10daysforeachareaofthemaskanditstemporalstandarddeviaGon

Global

Atlantic

IntroducGonofrealisGcerrorsonsyntheGcobservaGons

1.RandominstrumenterrorsareaddedasaGaussianwhitenoisewithastandarddeviaGonof0.01°Cfortemperature,0.01psuforsalinity(Cabanesetal.,2013)

2.RepresentaGonerrorsarespaGalandtemporalscalesaswellasphysicalprocessesthatarenotrepresentedbythedataassimilaGonmodel(OkeandSakov,2008)

(i)SyntheGcobservaGonsareextractedfromahigherresoluGonmodel(1/12°)tothatofthemodelincludedinthedataassimilaGonsystem(1/4°).

However,thiserrorisnotsufficienttorealisGcallyrepresenterrors.

(ii)WeaddmorerepresentaGvityerrorbyrandomlyshi]ingNatureRunmodelby±3days.ThisintroduceshorizontalandverGcallycorrelatederrors.

AllerrorspresentinexisGngobservaGonsmustbeaddedtosyntheGcobservaGons.FailuretorealisGcallyaddallerrorswillleadtoinaccurateimpactassessments.

Stand.dev.ofSSTnoisecomparedtostand.dev.oftheCMEMSGlobalMul.-ProductEnsemble.

SystemcalibraGonforrealisGcexperiments

IntroducingdifferenceswiththeNR,consideredaserrors,whichmimicthedifferencesexisGngbetweentheactualoceanandoperaGonaloceanmodelsimulaGons,andwhicharetobecorrectedthroughtheassimilaGon.

OSSE BACKBONEOPERATIONAL SYSTEM

OSSE BACKBONEOPERATIONAL SYSTEM

SimilarRMSdifferencebetween“Exis.ngobsminusopera.onalsystem”with“Synthe.cobs.minusOSSEsystem”

Global RMS Temp. diff with assimilated obs.Global RMS SSH diff with assimilated obs.

Global RMS SST diff with assimilated obs.

01-MAR-2008

3.ThedoublingofArgoinWBCandalongtheequator

➔Improvingthe2-yrmeanposi.onoftheGulfStream

RMS (zone) = 0.08 ºC

-Air-seainteracGon-WBCVsbasinwidevariability-ImpactofWBConmid-laGtudeclimatevariabilityandpredictability

RMS (zone) = 0.04 ºC

RMS (zone) = 0.30 ºC

➔DecreasingoftheRMSdiff.comparedtoNRwhencore-Argoisdoubled

3.ThedoublingofArgoinWBCandalongtheequator

RMS (zone) = 0.25 ºC

4.TheDeepArgonetwork

NO DEEP FLOATS WITH DEEP FLOATS

➔Unbiasingthedeepocean

- HowmuchGmeforfilteringvariability(eddies,interannual)?Short-termvariabilityisexpectedtobemuchlargerthanlonger-term

Regionaldisparity:NorthernH.VsSouthernH.Temporaldisparity:>75%ofprofilesa]er2004Ver7caldisparity:0-3000dbarprofiles=1/100-2000profiles

T/S profiles going to 2000 m

T/S profiles going to 3000 m~ 1 000 000 profiles

~ 100 000 profiles

(World Ocean Database)

RMS diff

➔Recoveringlong-termsignaloftheNRintheAtlan.c

4.TheDeepArgonetwork

-Long-termvariabilityoftheNRhassimilaramplitudethanliterature(around1x10-3/decade)-5°x5°deepArgowouldcapturelong-termvariability

(i) Noshort-termvariabilityintheNRforthedeepocean(addedbyerrors)

(ii) NeedmoreobservaGonsforbeqercalibraGonofdeepoceanOSSE

NATURE RUNBACKBONE (NO DEEP FLOATS)BACKBONE + DEEP FLOATS

3-month running mean of 2000-4000m layer temperature

North Atlantic

South Atlantic

(Kouketsu et al., 2011))

SUMMARY

1. ObservaGonimpactstudiesareneededtosupporttheevoluGonofglobaloceanobservingsystem,butalsorefinedataassimilaGonschemesinoperaGonalsystems(e.g.,DeepArgo).

2. ObservingSystemSimulaGonExperiment(OSSE)dedicatedtoinsituobservaGonsareperformed,andarigorousframeworkhasbeenrecentlyundertakenbyGODAE.

3. MulG-approachOSSEareunderwayfortheArgonetworkinAtlantOSprojectanddiscussionsareinprogressfordefiningimpactmetrics.Communityinputisneeded.

4. FirstOSSEresultsfromMercator-Oceanareencouragingandsuggestthat:- DoublingArgoinWBCandalongtheequatorwouldimprovethemeaninWBC,butalsoimproverepresentaGonofspecificGmescales(intraseasonal,interannual).

- TheimplementaGonofaDeepArgoarraywouldcapturelong-termvariabilityinthedeepocean.

5. Nextsteps:(i) DiscussionsonimpactmetricswithotherOSSEgroups(CLS,MetOffice,CMCC)(ii) Robustnessofresultswillbedonebycomparingsimilarexperimentsresultsusing

otherssystems(MetOffice/CLS/CMCC)-OSSEmeeGng(3rdGAAtlantOS,Canaryislands)(iii) Specificmetricshavetobecarefullydefineddependingoncomponents(e.g.,moorings,

dri]ers,XBT).