简介：Mesoscaleconvectivesystems(MCSs)areseveredisaster-producingweathersystems.PreviousattemptsofMCScensusaremadebyexamininginfraredsatelliteimageriesartificially,withsubjectivityinvolvedintheprocessunavoidably.Thismethodisalsoinefficientandtime-consuming.ThedisadvantagesmakeitimpossibletodoMCScensusoverAsiaandwesternPacificregion(AWPR)withanextendedspanoftime,whichisnotfavorableforgainingadeeperinsightintothesesystems.Inthispaper,afire-newautomaticMCSidentification(AMI)methodisusedtocapturefourcategoriesofMCSswithdifferentsizesandshapesfromnumericalsatelliteinfrareddata.47,468MCSsareidentifiedoverAsiaandwesternPacificregionduringthewarmseason(MaytoOctober)from1995to2008.Basedonthisdatabase,MCScharacteristicssuchasshape,size,duration,velocity,geographicaldistribution,intermonthlyvariation,andlifecyclearestudied.ResultsindicatethatthenumberoflinearMCSsis2.5timesthatofcircularMCSs.Theformerisofalargersizewhilethelatterisofalongerduration.The500hPasteeringflowplaysanimportantroleintheMCSmovement.MCSstendtomovefasteraftertheyreachthemaximumextent.FourcategoriesofMCShavesimilarcharacteristicsofgeographicaldistributionandintermonthlyvariation.Basically,MCSsarezonallydistributed,withthreezonesweakeningfromsouthtonorth.TheintermonthlyvariationofMCSsisrelatedtotheseasonaladjustmentofthelarge-scalecirculation.AstotheMCSsoverChina,theyhavedifferentlifecyclecharacteristicsoverdifferentareas.MCSsoverplateausandhillareas,withonlyonepeakintheirlifecyclecurves,tendtoformintheafternoon,matureatnightfall,anddissipateatnight.Ontheotherhand,MCSsoverplains,whichhaveseveralpeaksintheirlifecyclecurves,mayformeitherintheafternoonoratnight,whereasMCSsovertheoceanstendtoformatmidnight.Affectedbythesea-landbreezecirculation,MCSsoverc

简介：Usingreal-timedataandtheWRFmesoscalemodel,aheavyraineventintheprocessofMesoscaleConvectiveComplex(MCC)turningintobandedMesoscaleConvectiveSystems(MCSs)during18-19June2010issimulatedandanalyzedinthispaper.Theresultsindicatedthattheformationandmaintenanceofasouthwestvortexandshearlineat850hPawasthemesoscalesystemthataffectedtheproductionofthisheavyrain.Thelow-vortexheavyrainmainlyhappenedinthedevelopmentstageofMCC,andthecircularMCCturnedintobandedMCSsinthelatestagewithmainlyshearlineprecipitation.Inthevicinityofrainfallarea,theintensehorizontalvorticityduetotheverticalshearofuandvcausedtherotation,andincorrespondence,theascendingbranchoftheverticalcirculationtriggeredtheformationofheavyrain.Thedifferentdistributionsofuandvintheverticaldirectionproducedvaryingverticalcirculations.Thehorizontalvorticitynearthelow-vortexandshearlinehadobviousdifferenceswhichledtovaryingreasonsforheavyrainformation.Thelow-vortexheavyrainwasmainlycausedbytheverticalshearofv,andtheshearlinerainfallformedowingtotheverticalshearofbothuandv.Inthisprocess,theverticalshearofvconstitutedtheEW-trendingrainbandalongtheshearline,andthelatitudinalnon-uniformityoftheverticalshearinucausedtheverticalmotion,whichwascloselyrelatedtothegenerationanddevelopmentofMCSsattheshearlineandtheformationofmultiplerainclusters.Therewasalsoasimilardifferenceinthepositively-tiltingterm(conversionfromhorizontalvorticitytoverticalpositivevorticity)neartherainfallcenterbetweenthelow-vortexandtheshearline.Theconversioninthelowvortexwasmainlydeterminedbyбv/бp<0,whilethatoftheshearlinebyбu/бp<0.Thescaleoftheconversionfromthehorizontalvorticitytoverticalvorticitywasrelativelysmall,anditwaseasilyignoredintheaveragedstate.Thetwistingtermwasmainlyconducivetothereinfor

简介：对1995年7月25-28日高原上连续数日出现MCSs的现象进行了红外云图特征及其演变、大尺度环境背景场和对流有效位能的分析.可以发现,所有这些MCSs有着相似的日变化演变过程;它们的初始对流在中午由于日射加热开始活跃,之后迅速发展,这些MCSs在后下午形成,在傍晚达到最强,之后逐渐减弱.其中26日MCS最为强大,它是在单一的强大的近于圆形的高原反气旋高压背景下受强的低层热力强迫和条件不稳定的驱动而发生的.这些发生条件都与高原本身的热力作用紧密相关,所以它的发生发展主要与高原特有的较为纯粹的热力因子相联系.28日MCS是另一个很强的MCS,它明显地受到中纬度西风槽的斜压区的影响,这二个很强的MCS有着不同的发展机制和显著不同的表现特征.