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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
-40
-20
0
20
40
60
80
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
GeometricsOpticsGalaxyModel,allwinds
0 50 100 150 200 250 300 350
-80
-60
-40
-20
0
20
40
60
80
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
GalaxyModelderivedfromSMAP,allwinds
0 50 100 150 200 250 300 350
-80
-60
-40
-20
0
20
40
60
80
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
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
40
60
80
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
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).