Theradiancesscatteredoremittedbycloudsdemonstratepersefeaturesatdifferentwavelengthsduetodifferentcloudphysicalstructures.Thispaperpresentsamethod(thesmallest-radiance-distancemethod,SRaDM)ofrevealingthephysicalstructuresofclouds.Themethodisbasedonmulti-spectralradiancesmeasuredbytheModerateResolutionImagingSpectroradiometer(MODIS)onboardAqua.TheprincipleandmethodologyofSRaDMisdeducedandprovidedinthispaper.CorrelationanalysisbasedondatafromMODISandCloudProfilingRadar(onboardCloudSat),collectedfromJanuary2007toDecember2010overanoceanarea(15°N–45°N,145°E–165°E),ledtoselectionofradiancesat13wavebandsofMODISthatdemonstratedhighsensitivitytocloudphysicalstructures;radiancesattheselectedwavebandsweresubjectedtoSRaDM.TheStandardizedEuclideandistanceisintroducedtoquantifythedegreeofchangesinmulti-spectralradiances(termedDrd)andinphysicalstructures(termedDst)betweencloudprofiles.StatisticsbasedonnumerouscloudprofilesshowthatDrddecreasesmonotonicallywithadecreaseinDst,whichimpliesthatsmallDrdalwaysaccompaniessmallDst.AccordingtothelawofDrdandDst,thenewmethod,SRaDM,forrevealingphysicalstructuresofcloudsfromthecollocationofcloudprofilesofsimilarmulti-spectralradiances,ispresented.Then,twosuccessfulexperimentsarepresentedinwhichcloudphysicalstructuresarecapturedusingmulti-spectralradiances.SRaDMprovidesawaytoobtainknowledgeofthephysicalstructuresofcloudsoverrelativelylargerareas,andisanewapproachtoobtaining3Dcloudfields.
