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Atmospheric radiative transfer simulation for atmospheric correction of remote sensing data

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Atmospheric radiative transfer simulation for atmospheric correction of remote sensing data

    Atmospheric radiative transfer simulation

    for atmospheric correction of remote

    sensing data

    GlobalGeology,9(1):100.108(2006)

    ArticleID:1008.0503(2006)01010009

    Atmosphericradiativetransfersimulationfor

    atmosphericcorrectionofremotesensingdata

    YunfeiBao,ShengboChen,

    i.CollegeofGeo-ExplorationScienceandTechnology,JilinUniversity,Changchun130026,Jilin,China

    2.StateKeyLaboratoryofRemoteSensingScience,InstituteofRemoteSensingApplicationsofCAS,BeijingNormal

    University,Beijing100101,China

    Abstract:Theradlancelcavingtheearth

    atmospheresystemwhichcanbesensedbyasatellitebornetadiome.

    teristhesumofradiationemissionfromtheearthsurfaceandeachatmosphericlevelthataretransmittedtothe

    topoftheatmosphere.Theradiationemissionfromtheearthsurfaceandtheradianceofeachatmosphericlevel

    canbeseparatedfromtheradlanceatthetoptheatmospheric1eve1measuredbyasatelliteborneradiometer.

    However,itisverydifficulttomeasuretheatmosphericradiance,especiallythesynchronousmeasurementwith

    thesatellite.Thussomeatmosphericradiativetransfermodelshavebeendevelopedtoprovidemanyoptionsfor

    modclingatmosphericradiationtransport,suchasLOWTRAN,MODTRAN,6S,FAS?

DE,LBLRTM,

    SHARC,andSAMM.Meanwhile,thesemodelscansupportthedetaileddetectorsystemdesign.theopti.

    mizationandevaluationofsatellitemissionparameters,andthedataprocessingprocedures.Asanexample,the

    newlyatmosphetictadiativetransfermodels,MODTRANwillbecomparedwithothermodelsaftertheatmo.

    sphericradiativetransferisdescribed.Andtheatmosphericradiativetransfersimulationproceduresandtheir

    applicationstoatmospherictransmittance,retrievalofatmosphericelements,andsurfaceparameters,willalso

    bepresented.

    Keywords:atmosphericradiativetransfermodel(ARTM);atmosphericcorrection;atmosphericradiatve

    transfersimulation;remotesensing;MODTRAN

    Introduction

    Theradianceleavingtheearth..atmospheresys

    ternwhichcanbesensedbyasatellitebornera

    diometeristhesumofradiationemissionfromthe

    earthsurfaceandeachatmosphericlevelthatare

    transmittedtothetopoftheatmosphere.Theradia

    tionemissionfromtheearthsurfaceandtheradiance

    ofeachatmosphericlevelcanbeseparatedfromthe

    ReceivedlMarch,2006;receivedinrevisedform28May,2006

    radianceatthetoptheatmosphericlevelasatellite

    measured.Thus,theearthsurfaceparameterswill

    beretrievedfromthesurfaceradianceafteratmo

    sphericcorrection.Also,theatmosphericcompo.

    nentsandparameterswillberetrievedfromtheradi

    anceofeachatmosphericleve1.However,itisso

    difficulttomeasuretheatmosphericradiance,espe. ciallythesynchronousmeasurementwithsatellite O

    ,

    ntheotherhand,aremotesensingmission

Atmosphericradiativetransfersimulationforatmosphericcorrectionofremotesensingdata

    requirestheadaptationofindividualhardwarepa

    rametersofasensorsystem,observationconditions, andretrievalalgorithmstocertainscientificorcom

    mercialgoals.Theconsistentendtoendsimulation

    ofdataofoptoelectronicremotesensingsystemshas significantimportancefordevelopment,optimiza tion,calibration,test,andapplicationofsuchin

    strumentsandtheinterpretationoftheirdataprod

    ucts.Therefore,thephysicalsimulationapproachis usuallyappliedwhenthereisastraightrelationship betweeninputandoutputquantities.

    Agoodmanyofstudyontheatmosphericcor

    rectionweredonesince1960s,andmanymodelsand algorithmsareproposed,suchasHITRAN(High ResolutionTransmissionMolecularAbsorption Database),LOWTRAN(LowerResolutionTrans

    mittance).MODTRAN(ModerateResolution

    Transmittance)FASCODE(FastAtmosphericSig

    natureCode),6S(SecondSimulationoftheSatellite SignalintheSolarSpectrum)LBLRTM(LineBy

    LineRadiativeTransferMode1),SHARC(Synthet

    icHighAltitudeRadianceCode),SAMM(SHARC

andMODTRANMerged),andsoon.Aftertheat

    mosphericradiativetransferisdescribed,thenewly atmosphericradiativetransfermodels,MODTRAN willbecomparedwithothermodels.AndtheMOD

    TRANistakenasanexampleforintroducethesim ulationproceduresofatmosphericradiativetransfer. Finally,theapplicationstoatmospherictransmit

    tance.retrievalofatmosphericelementsandthe Earthsurfaceparametersbyatmosphericradiative transfersimulationwillalsobepresented. 1Atmosphericradiativetransfereq-

    uation(ARTE)

    Radiationtransferservesasamechanismforex

    changingenergybetweentheatmosphereandunder

    lyingsurfaceandbetweendifferentlayersoftheat

    mosphere.Theradiancescanbemeasuredbyasen

    sotonboardthesatellitesincludingtheemissionradi-- ationfromtheearthsurfaceandtheatmosphericra

    diationatthetopofatmosphere.Theradiation transferprocessandthecomponentsoftheradiances sensedbyatsatellitedetectorsareillustratedinFig 1.DifferentcOntribuLionstotheatsensorradiance

    aredenotedindifferentnumbers.Thus,thespectral radianceJatviewingangle(0,)atsatellitelevel isexpressedwithanequationas

    J^(0,)=R^(0,)(0,)

    +R,

    (0,)+Rs(0,)(1)

    whereR^(0,)isthespectralradianceobservedat

groundlevel(denotedinnumber?),R.(0,)is

    thethermalpathatmosphericradiance(denotedin number@),Rs(0,)isthepathradianceresult

    ingfromscatteringofsolarradiation(denotedin number@),r(0,)isthetotaltransmissionofat

    mosphere.AndR^(0,)ismadeupoftheradiance emitteddirectlybysurface(denotedinnumber?),

    thedownwardatmosphericthermalradiation(denot

    edinnumber?),.solardiffusionradiation(denoted innumber@),andthedirectsolarradiationreflect

    edbysurface(denotedinnumber?).ThusR(0,

    ),isexpressedas

    R^(0,)=(^(0,)B^(1)+

    (1_))+

    ,o)Eacos()(0,)(2)

    Where^(0,)isthesurfacespectralemissivity,Ba (Ts)istheradianceemittedbyablackbodyatsur

    facetemperatureTs,Rfisthedownwardatmo

    sphericthermalradiance,andR,isthedownward solardiffusionradiation,p6isthebidirectionalsur

    facespectralreflectivity,E^isthesolarirradianceat thetopoftheatmosphere.Therefore,theatsensors

    radiancesnotonlyincludetheground??emittedradil. anceanddirectlyreflectedradiance,buttheradiance reflectedandscatteredfromthesurroundingofob

    ectandatmosphere.TheinfluenceoftheEarth's atmosphereonthesolarirradiancecanbeestimated

102Y.F.Bao.S.B.Sheng

    approximatelybytheradiationtransfermodels

    Fig.1Sketchmapofatmosphericradiativetransfer Contfibutiomstotheat.sensorradianceindifferentmumber

    2Atmosphericradiativetransfer

    model(ARTM)

    ItiSaproblemforcalibrationofremote

    sensingplatformsbecauseoftheamountofunknown variablesthatmustbeaccountforintheatmospheric radiativetransferequation.Inaddition,thelarge numberofgeometricalpathssolarilluminationcan reachatargetthereisalsotheatmospherictransmis

    sionlosses,andscatteringofenergyintotheobserv

    er'Sfieldofview.Thus,someatmosphericradiative transfermodels(ARTM)havebeendevelopedand improvedtOsimulateapproximatelytheatmospheric radiativetransfer.Themaincharacteristicsofthese ARTMareshowninTable1.

    Table1Atmosphericradiativetransfermoddsandtheircharacteristics

    notes

    AFRL:TheAirForceResearchLaboratory;AER:AtmosphericandEnvironmentalResearc

    hInc;LOA:LaboratoryofOp-

    ticAtmosphere

    TheeffectofatmosphericmoleculesiSfirstly consideredbytheoriginalHITRANdatabase. LOWTRANisthefirstalgorithmforatmospheric transmission,anditsabsorptionbandmodeliSim. plementeduntilHITRAN86iSinvolvedinLOW

    TRAN7.Owingtothelowerspectralresolutionof LOWTRAN.itisnecessarytobeimprovedto

    MODTRAN.astandardmoderatespectralresolution radiancetransportmodelwiththeenhancedspectral

resolutionextendingfron1ultraviolettothermalin

    flared(O.2to10,000.0m).Atthesametime,

    theatmosphericheightforsimulationbecomeshigh

    erfrom30kilometersofLOWTRANto60kilome. tersofMODTRAN.Andtheabsorptioncoefficient. linedensity.averagedlinewidthareusedinMOD?

    TRAN.whileonlythesingleparameterisusedin thebandmodelofLOWTRAN.Moreover.the

    newlyreleasedMODTRAN4canoffermoreoptions foratmosphericradiativetransfersimulation.ACor

    related_kalgorithmhasbeenintroducedintoMOD. TRANbandmodel.andtheDISORTdiscreteordi

    natemultiplescattering(MS)modelhasbeenmodi

Atmosphericradiativetransfersimulationforatmosphericcorrectionofremotesensingdata

    103

    fiedtoincludeazimuthdependenceinthesolarMS formoreaccuratescatteringalgorithms.Thesurface BRDFs(BidirectionalReflectanceDistributionFunc

    tions)arecoupledwiththeatmosphericradiation transport,andsurfaceadjacencyeffectsareincluded forupgradingthegroundsurfacemodeling.Inaddi

    tion,whenthehigherspectralresolutionisunneces. sary,anoptimized,reducedspectralresolution(15 cm)bandmodelcanbeanalternativetothestan+ dardMODTRANbandmodel(1cm)forhigher

    speed.

     FASC0DEisthefirstline_byline(LBL)atmo

    sphericradianceandtransmittancecodesatlowalti

    tudeswithbetteraccuracyofabsorption(optical

    depth)calculationsperlayer.Specially,theradiance transportandabsorptionbetweendifferentlayersat nonequalheightcanbesimulatedbyFASC0DE. whereasothercodes,likeL0WTRANandMOD

    TRAN.cannotdoit.Althoughthespectraltrans

    mittancesandradiancesinthethermalinfraredre

    gionareallcalculatedaccuratelybyM0DTRANand FASC0DE.MODTRAN4canofferanoptionfor

    thefluxandatmospherescatteredsolarradianceca1. culationinthevisibleandnearinfraredspectralre. gion,whichisnotreadilyimplementedbytheLBL models.LBLRTMisanaccurateandefficientline

    bylineradiancetransfermodelderivedfromFAS

    C0DEmode1.whichhasbeenvalidatedfromtheu1 traviolettothesubmillimeterregions.Thepressure shiftcoefficient,thehalfwidthtemperaturedepen

    dence,andtheselfbroadeningcoefficientofwater vaporintheHITRANlinedatabaseareusedtoopti

    mizetheradiate,scattering,andweighedfunctions. TheSecondSimulationoftheSatelliteSignalin theSolarSpectrum(6S)isasinglescatteringmod? e1.whichisdifferentfromthebandmodelandline bylinemode1.ThesurfacealtitudeandnonLambert

    areconsideredforsimulations.TheSHARCisthe DoDstandardfortheradianceandtransmittance simulationintheinfraredspectralregion(2to40 m)foranylinesof.sight(LOS)pathsathigheralti

    tude(between30and300km).Andthechemistry andradiationtransportmodelsarecoupledin

SHARCcodetocalculatetheNoLocalThermody

    namicEquilibrium(NLTE)statefortheenhance

    mentsofopticalradiance.TheNLTEalgorithmand differentaltitudescopesfromtheSHARC,andthe M0DTRANareintegratedintotheSAMMmode1. whichissatisfiedtosimulatetheatmosphericradi

    ancetransportatdifferentaltitudes. 3Atmosphericradiativetransfersi- mulation(ARTS)

    Afterthedeterminationofthegeometricprop

    erties,theatsensorradianceiscalculatedforeach pixelofeachremotesensingimagelineineachspec

    tralband.Theradiativetransferdescribestheinflu

    enceoftheEarth'satmosphereonthesolarirradi

    ance.MODTRAN4,thelatestpubliclyreleased versionofMODTRAN,providestheaccuracyre

    quiredforprocessingspectralimageryandincludes majormodelenhancements,whichistakenasanex

    ampletodepicthowtomodelatmosphericradiation transportforatmospher.

    icabsorptionandradiance

    simulation.

    MODTRANiscontrolledbyasingleinput file,'tape5'or'rootname.tp5',whichmostlycon

    sistsoffourCARDS:CARD1,CARD2,CARD3, andCARD4(Fig2).AndeveryCARDhasseveral subCARDS.

    CARD1ismainradiationtransportdriverand controlstherunningoftheotherthreeCARDS. MODTRANselectsthebandmodelalgorithmused

    fortheradiativetransport.eitherthemoderatespec? tralresolutionMODTRANbandmodelorthelOW spectralresolutionLOWTRANbandmodelinCARD 1.TheM0DTRANbandmodelmaybeselectedei

    therwithorwithouttheCorrelatedktreatment.

    Oneofthesixgeographicalseasonalmodelatmo

    spheres(TropicalAtmosphere,MidLatitudeSum

104Y.F.Bao.S.B.Sheng

    met,Mid,LatitudeWinter,Sub.ArcticSummer, Sub-ArcticWinterand1976USStandardAtmo. sphere)isselectedwithMODELin(,ARD1oruser. definedmeteorologicalorradiosondedataaretobe input.Additionally,thetypeofatmospheric1ineof-

    sight(L0S)path,themodeofexecutionofthepro- gramandthescatteringandtheboundarytempera- turearesetupinCARD1.WhenIEMSCTiSsetto 0,MODTRAlNprogramexecutesinspectraltrans- mittancemode,anditiSsetto1or2,MODTRAN executesinspectralradiancemode,whileitiSsetto 3,programcalculatesdirectlytransmittedspectral solar/lunarirradiance.IEMSCTmustbe1or2to executewithmultiplescattering(IMULT=1).The parametersinCARD1Aarenotonlyused.togovern themultiplestreamDISORTalgorithm,thesolarir- radiance,andthecchmixingratio,butdefinewa

    tervaporandozonecolumnamounts,triggerspeeifi- cationofdatafiles,andenablescalingofthesolar conStant.

    Flg.2RelationofCARDSinMOAN4

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