GeophysicalModelFunctionoftheAquariusV5.0SalinityRetrievals

FrankWentzandThomasMeissnerRemoteSensingSystems

NASAOSSTMeetingCrystalCity

September18,2017

Aquarius

Sun

SolarReflection QuasiSpecular

0– 10psu

SolarBackscatter

Galaxy&Cosmic0– 6psu

Moon

OceanSurface

IonosphereAtmosphere

Land/Ice RFI

Needstobedoneat0.2psu=0.1Kelvinaccuracy

Antenna

Challenge:RemovalofManyLargeSpuriousSignals

ForwardModel:OceanScene->TAPhysicalRadiativeTransferModel

AquariusAntennaTemperatures(TA)

Spacecontributions:galaxy,sun,moon,coldspace

TopoftheIonosphereBrightnessTemperatures

FaradayRotationinEarthIonosphere(3rd Stokes)

TopoftheAtmosphereBrightnessTemperatures

Atmosphericattenuation(O2,cloud,andrainabsorption)

Sea-SurfaceBrightnessTemperatures

SurfaceRoughnessEffects(Wind,SST)

SpecularBrightnessTemperatures

EmissionformspecularseasurfaceMeissner-Wentz2012dielectricmodel

OceanSceneSSS,SST

Antennaeffects(x-polcontamination)

AquariusSalinityRetrievalInversionofForwardModel

AquariusAntennaTemperaturesRFIfiltered

Removespacecontributions:galaxy,sun,moon,coldspace

TopoftheIonosphereBrightnessTemperatures

CorrectforFaradayRotationinEarthIonosphere(3rd Stokes)

TopoftheAtmosphereBrightnessTemperatures

Removeatmosphericattenuation(O2,cloudandH2OAbsorption)

Sea-SurfaceBrightnessTemperatures

RemoveSurfaceRoughnessEffects(Wind)

SpecularBrightnessTemperatures

FindSalinityforwhichemissivityofMeissner-Wentz2012dielectricmodel

matchesspecularTB

AquariusSalinity

Removeantennaeffects(x-pol)

Sea-SurfaceEmissivity

DielectricConstantModelMeissner+Wentz2004,2012,IEEETGRSpapers

• DeterminesemissivityofspecularoceansurfacethroughFresnelreflection.• DoubleDebyerelaxationlaw:

• TheDebyeparametersdependonSST(T)and,SSS(S)• Physicalmechanismthatconnectsemissivitiesatdifferentfrequencies.• Theconductivityσ istakenformStogryn's etal.laboratorymeasurements.• TheDebyerelaxationparametersεandν werefittedbasedonoldermodelsthatused

variouslaboratorymeasurements(Hoetal.,1970's)andonmorerecentW-band(Guillou etal.,1998).

• Allparameterswerecarefullytunedbasedonsatelliteobservations(SSMI,WindSat).• ThemodelisusedinallRSSpassivemicrowaveoceanretrievals(L– Kaband).• Klein-Swiftmodel(singleDebye)breaksdown>10GHzandincoldwater.

( ) ( ) ( ) ( ) ( )

( )1 1

1 2 0

,( , ) ( , ) ( , ) ( , ), ,1 , 1 , 2S T ST S T S T S T ST S T S ii v v T S i v v T S v

se e e ee epe

¥¥

- -= + + -

+ +

1 1 2, , , , ,Se e e n n s¥

SurfaceRoughnessModel

0 WE E E= + D

specular

Emissivity

rough

( ) ( ) ( ),,0 1 0 , , , , S SW WW VVrelE E W T E W T E Wj j sD = D + D + D ¢isotropic wind-directionsignal higherorderterm

VV-polscatterometer

• Meissner,T.,F.Wentz,andL.Ricciardulli, TheemissionandscatteringofL-bandmicrowaveradiation fromrough oceansurfacesandwindspeedmeasurementsfromAquarius,JGROceans,vol.119,doi:10.1002/2014JC009837,2014.

• UseAquariuswindspeed(HH-polscatterometer+H-polradiometer).• DerivedfromEmeas – E0 (S,TS)usinganexternalreferencesalinityS(HYCOM).• EditedforVersion5release:

§ switchedtoARGO(Scripps)asreferenceSSSfield§ includeallothermodelfunctionupdatesintheanalysis

SSTdependencewindspeeddependence

RoughnessModelUpdatesinV5Release

WindDirectionSignal

HigherOrderCorrectionΔEW,1 (W,σ'0VV)characterizesroughnesseffects"orthogonal"towindspeed

look-uptable

AtmosphericAbsorption

OxygenAbsorptionModel

TheO2 absorptionatL-bandisalmostentirelyduetonon-resonantcontinuum.

§ Farfromabsorptionline.Littleknown.

( ) 0.8, 0.0056 1.1O nr p eg q= +

p:dryairpressuree:watervaporpressureθ=300K/Tair

Liebeetal.1992

Wentz+Meissner2016 ( ) 1.5, 0.0056 1.1O nr p eg q¢ = +

• UptoV4theAquariussalinityalgorithmhasusedtheWentz+Meissner2016absorptionmodel.

• ForV5wegobacktotheLiebe1992modelwhichhasweakerdependenceonTair.

• ThishelpstomitigatesomeofthebiaseswehaveseeninV4.• FurtherreducingtheTair dependencedidnothelp.

AtmosphericCorrection:TBTOA – TBSURDifferencebetweenLiebe1992(V5)andMW2016(V4)

Galaxy

GalacticRadiationatL-Band

• Aquariusfrequency(1.4GHz)liesinprotectedband– Usedbyradio-astronomersasitoccursingalacticprocesses(e.g.:

molecularH2)

– Unwantedconsequence:GalacticradiationisasignificantnoisesourceforL-bandradiometers

• Theintrusioncanoccur– Directlyintotheantenna:small,easytocalculate– ThroughreflectionfromtheEarthsurface:canexceed3K(6psu),if

uncorrected.

BasicComponentforCorrectingReflectedGalaxy:GeometricOptics(GO)Model

• PhysicalModel• ModelingGalacticRadiation:ATiltedFacet(GeometricOptics)Model.

• Green arrows fromGalaxytoOcean:Red arrowsfromOceantoAquarius• Slopevariance∆S2:25%ofCox-Munkvalue.

• FacetintegrationmustbedoneforeveryoceanpixelseenbyAquariusantenna.

• Computationisa4-foldintegraloverroughsurface(tiltedfacets)andantennapattern.

• Overalleffectisasmoothingofthegalaxymapaswindsincrease.

( ) ( )( ) ( )( )( )

2 ,, z u c

B u c B

P z zT dz dz Tt= × ¡

× ×òòs s i ss

k P k k nk z n z

AdjustingGeometricOpticstoAgreewithSMAPUsingResultsfromSMAPFore– AftLook

Summary

1. Effectiveincreaseinroughness:W->W+2m/s,whicheffectivelyincreasestheslopevariance∆S2 oftheGOmodel.

2. Scalingofthestronggalacticsourcesbyabout10%.

ThisprescriptionisderivedformtheSMAPandhasthenbeenimplementedinthederivationofthegalactictablesforall3Aquariushorns.

MethodforFindingGalaxyTAfromSMAPDualLooks

( ) ( ) ( )0 , , ,A A A galaxy A rough w A sunT T T T Tf f f f= + + - +

( ) ( ) ( ) ( ) ( ) ( ), , , ,A galaxy fore A galaxy aft A fore A aft A rough w fore A rough w aftT T T T T Tf f f f f f f fé ù- = - - - - -ë û

Avoidareaswheresuncontributionmaybesignificant

IfthegalaxymodelsaysTAaft issmall(<2K),thenassumeitiscorrect

( ) ( ) ( ) ( ) ( ) ( ), , , ,A galaxy fore A fore A aft A rough w fore A rough w aft A galaxy aftT T T T T Tf f f f f f f fé ù= - - - - - +ë û

LikewiseifthegalaxymodelsaysTAfore issmall(<2K),thenassumeitiscorrect

( ) ( ) ( ) ( ) ( ) ( ), , , ,A galaxy aft A aft A fore A rough w aft A rough w fore A galaxy foreT T T T T Tf f f f f f f fé ù= - - - - - +ë û

0 50 100 150 200 250 300 350

-80

-60

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-20

0

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60

80

0

0.5

1

1.5

2

2.5

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3.5

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4.5

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GeometricsOpticsGalaxyModel,allwinds

0 50 100 150 200 250 300 350

-80

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-40

-20

0

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60

80

0

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GalaxyModelderivedfromSMAP,allwinds

0 50 100 150 200 250 300 350

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-60

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-20

0

20

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80

0

0.5

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1.5

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4.5

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GOGalaxyModel,2m/saddedtowindspeed,10%increasetopeak

0 50 100 150 200 250 300 350

-80

-60

-40

-20

0

20

40

60

80

-1

-0.8

-0.6

-0.4

-0.2

0

0.2

0.4

0.6

0.8

1

SMAP-derivedModelminusGOGalaxyModel

0 50 100 150 200 250 300 350

-80

-60

-40

-20

0

20

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60

80

-1

-0.8

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-0.4

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0

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1

SMAP-derivedModelminusGalaxyModelwith2m/saddedandpeakisscaled

Fine-Tuning2:ZonalSymmetrizationAscending– Descending

GeometricOpticsGalaxy

SMAPfor- aftGalaxy

improvesasc- dscbiasesbutdoesnoteliminatethem

DerivationofZonalSymmetrizationΔ(z)BasicAssumptions:1. Therearenozonal asc/dscbiasesinoceansalinityonatimescale>1week.2. Allremainingzonal asc/dscbiasesweseearecausedbythegalaxy.3. Theerrorisproportionaltothestrengthofthereflectedgalacticradiation.

( ) ( ) ( ) ( )( ) ( ) ( ) ( ) ( ) ( )

( )( )

( ) ( )

( )( )

( ) ( )( ) ( )

,

, ,

,

, ,

1 : zonal average z:orbital angle

B B B

B B B

A gal

A gal A gal

A gal

A gal A gal

T z T z T z z

z p z T z q z T z T z

T zp z

T z T z

T zq z

T z T z

p z q z

¢® º + D

é ùD = × + × - -ë û

-=

+ -

=+ -

+ =

( ) ( )B BT z T z¢ ¢= -

( ) ( ) ( ) ( )B B B BT z T z T z T z¢ ¢+ - = + -

( ) ( ) ( ) 0B BT z T z z= - Þ D =

EffectofZonalSymmetrizationrequiresnoancillaryfield(ARGO,HYCOM)

asc– dscbiasesusingGO+SMAPfore/aftmodel

asc– dscafterincludingzonalsymmetrizationcorrection

AntennaPatterns

AntennaPatternCorrection(APC):TB =A·TA

horn111.0300-0.0350+0.050020.00011.0641+0.030030.0000-0.02581.0755

horn211.0337-0.03040.000020.00271.0435-0.01443-0.0006+0.02111.0555

horn311.0420-0.0326+0.025020.00111.0328+0.021530.0000-0.01481.0489

A-matrixV3,V4,V5

horn111.04484-0.03827-0.003872-0.002971.078600.030893-0.00009-0.025821.07551

horn211.04967-0.03432-0.007372-0.000631.05936-0.015583-0.002720.011121.05553

horn311.05800-0.03435-0.011572-0.000361.048480.007083-0.00324-0.014801.04885

A-matrix(I,Q,U)GRASP2012orbitsimulator

A-matrixusinghybridpatterns

horn111.03009-0.03410-0.0006120.000281.061660.023573-0.00011-0.025901.07779

horn211.03465-0.02829-0.0073920.002841.04475-0.016063-0.003730.010311.06918

horn311.04505-0.03028-0.0065520.001621.038350.003063-0.00321-0.014131.05891

• GRASPpatternsresultedintoolargespilloverandthushighTBoverland(Amazon).• V5APCisbasedonhybridpatterns(E.Dinnat)thatmovepowerfromthebacklobe

tothemainandnear-sidelobes.• TuningofAIU andAQUtominimizeobservedcross-couplings.

Far-Sidelobe CorrectionbasedonSimulatorMitigateLandContamination

, , ,ˆ

toa toa toaD = -BE BE BET T T

"observed"TBcalculatedfromorbitsimulator

integratingoverantennapatterns

TBatboresight(averagedover3dBfootprint)

Tableisstratifiedaccordingtothespacecraftnadirlongitude(1440elementsin0.25° increment),thespacecraftpositioninorbit(1440elementsin0.25° increment),month(12elements),polarization(v-pol,h-pol),andhorn(inner,middle,andouter)andtakestheformTb_land_correction(1440,1440,12,2,3).

LandCorrectionBIASSSSAquarius– HYCOMasfunctionoflog(gland)

nolandcorrectionlandcorrectionV3.0

landcorrectionhybridAP

LandCorrectionStdDevSSSAquarius– HYCOMasfunctionoflog(gland)

nolandcorrectionlandcorrectionV3.0

landcorrectionhybridAP

Summary• TheAquariusV5GMFisacomplexmodelconsistingof

SpeculardielectricmodelSurfaceroughnessmodelAbsorptionofatmosphericoxygenReflectedgalacticradiation(modifiedgeometricoptics)FaradayrotationintheionosphereHybridantennapatterns(GRASPwithS.O.adjustment)

• Limitedempiricaladjustments• Therearenopost-hocempiricaladjustments(SSTbias

correction,…)asinpreviousversions.• TheV5GMFisphysicallybasedwithinthecontextofthe

standardformulationfortheMWOceanRadiativeTransferModel(MWO-RTM).