Multipath EM scattering from breaking ocean waves at grazing incidence外文

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1、RadioScience,Volume32,Number4,Pages1455-1467,July-August1997MultipathEMscatteringfrombreakingoceanwavesatgrazingincidenceJ•mesC.WestElectricalandComputerEngineering,OklahomaStateUniversity,StillwaterMarkA.SlettenNavalResearchLaboratory,Washington,D.C..Abstract.Theelectromagneticscatteringfromabre

2、akingwaterwavewithneargrazingilluminationhasbeenexaminedusingbothexperimentalmeasurementandnumericalcalculation.Thescatteringfromametalmodelofabreakingwaveof1.2mwavelengthwascharacterizedatgrazinganglesrangingfrom0øto25oandatfrequenciesrangingfrom6GHzto12GHz.Strongmultipathinterferenceisobservedi

3、ntheverticalpolarization(VV)backscatterandmuchweakerinterferenceisseeninthehorizontalpolarization(HH)backscatter.Scatteringfromthewaveprofilebothwithandwithoutthebreakingplumeshowsthattheplumeisthedominantscatteringfeature.Numericalcalculationofthescatteringfrommodifiedsurfaceprofilesshowsthatthe

4、interferenceisduetomultipathscatteringfromtheplumeandfrontfaceofthewave.HHinterferenceissubstantiallysmallerthanthatofVVbecausethescatterfromtheplumeinthemultipathdirection(towardthefrontface)isgreatlyreducedowingtotheconductingsurfaceboundaryconditions.Therelativelevelsoftheplumeandexpecteddistr

5、ibuted-surfacescatteringareconsistentwiththewave-tankmeasurementofhorizontallypolarizedseaspikesfrombreakingwavesofthisscale.1.Introductionpolarization(VV)andcanlastforperiodsofuptoElectromagneticscatteringfromtheoceansurface1s.StrongHHseaspikescanraisethebackscatterisnotwellunderstoodwhentheillu

6、minationgrazingtoabovethatatVV,behaviorthatisnotpredictedangleissmall(lessthanabout20ø).Scatteringmod-bytheBragg-resonancemechanismthatisthebasisofthetwo-scalemodel.elssuchasthetwo-scalemodelValenzuela[1968]thataccuratelypredictthescatteringatmoderategraz-Severalmechanismshavebeensuggestedtoex-in

7、ganglesfailatsmalleranglesGuinardandDaleyplainthesmall-grazingscattering,includingwedge[1970].Infact,itappearsthattheprimaryscatter-diffraction[Lyzengaetal.,1983;KalmykovandPust-ingmechanismsareentirelydifferentatmoder