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1、JOURNALOFGEOPHYSICALRESEARCH,VOL.116,D16206,doi:10.1029/2010JD015344,2011Verticalvelocitystructureofmarineboundarylayertradewindcumulusclouds111VirendraP.Ghate,MarkA.Miller,andLynneDiPretoreReceived16November2010;revised16May2011;accepted25May2011;published27August2011.[1]Oceanictradewind
2、cumuluscloudsnotonlyimpacttheEarth’sradiationbudgetbutalsoaffecttheboundarylayer(BL)structure.DatafromthedeploymentofAtmosphericRadiationMeasurements(ARM)’sMobileFacilityattheislandofGraciosaintheAzoresisusedtostudytheverticalvelocitystructureoftheseclouds.ThesurfacefluxesasreportedbytheE
3、uropeanCentreforMedium‐RangeWeatherForecasting(ECMWF)analysismodelwereusedtocharacterizethedynamicstructureoftheBL.Cloudradardatafromninecasestotalingto114hoursandcontaining557cumuluscloudelementsareanalyzedtoreporthourlyvaluesofmeanreflectivity,meanverticalvelocity,cloudfraction,andcloud
4、massflux.Thehourlyaveragedin‐cloudverticalvelocitywasconstant−1(∼0.35ms)withheight,whiletheaveragevelocityofupdraftsandverticallycoherentupdraftsincreasedfromcloudbasetocloudtop.Thereflectivitydidnotexhibitanysignificantchangesbetweenall,updraftandcoherentupdraftsamples.Thecloudfractionan
5、dmassfluxshowedsimilarverticalprofileswithbothhavingapeaknearcloudbase.Themassfluxcontributionofverticallycoherentupdraftsspanningthroughtheentirecloudlayertotheaverageupdraftmassfluxwas∼62%.Thehourlyvalueswereclassifiedbasedonthesurfaceconvectivevelocityscale(w*)asreportedbytheECMWFmodel
6、.−1Thecloudfractionnearcloudbaseduringhourswithw*lessthan0.2mswas∼6%−1whilethatduringhourswithw*greaterthan0.6mswas∼9%.Thecloudbasemassflux−1duringhourswithw*greaterthan0.6mswasalmostdoublethatduringhourswithw*−1lessthan0.2ms.Citation:Ghate,V.P.,M.A.Miller,andL.DiPretore(2011),Verticalvel
7、ocitystructureofmarineboundarylayertradewindcumulusclouds,J.Geophys.Res.,116,D16206,doi:10.1029/2010JD015344.1.IntroductionshallowcumulusconvectionplaysanimportantroleindeterminingthestrengthandwidthoftheIntertropical[2]Boundarylayer(BL)fairweathercumuluscloudsorCon