Inthisstudy,evolutionofthemesoscaleconvectivesystems(MCSs)withinaMeiyufrontduringaparticularlyheavyrainfalleventon22June1999inEastChinawassimulatedbyusinganonhydrostaticnumericalmodelARPS(AdvancedRegionalPredictionSystem).Investigationswereconductedwithemphasisontheimpactoftheinteractionamongmulti-scaleweathersystems(MWSs)onthedevelopmentofMCSsintheMeiyufrontalenvironment.Forthiscase,thedevelopmentofMCSsexperiencedthreedifferentstages.(1)TheconvectionsassociatedwithMCSswerefirstlytriggeredbytheeastward-movingSouthwestVortex(SWV)fromtheSichuanBasin,accompanyingtheintensificationoftheupper-leveljet(ULJ)andthelow-leveljet(LLJ)thatwereapproachingtheMeiyufront.(2)Next,alow-levelshearline(LSL)formed,whichstrengthenedandorganizedtheMCSsaftertheSWVdecayed.Meanwhile,theULJandLLJenhancedandproducedfavorableconditionsfortheMCSsdevelopment.(3)Finally,astheMCSsgotintensified,amesoscaleconvectivevortex(MCV),amesoscaleLLJandamesoscaleULJwereestablished.Thenacoupled-developmentofMWSswasachievedthroughtheverticalfrontalcirculations,whichfurtherenhancedtheMCVandresultedintheheavyrainfall.ThisisanewphysicalmechanismfortheformationofMeiyuheavyrainfallrelatedtotheSWVduringthewarmseasoninEastChina.Inthethreestagesoftheheavyrainfall,theverticalfrontalcirculationsexhibiteddistinguishedstructuresandplayedadynamicrole,andtheyenhancedtheinteractionamongtheMWSs.AfurtherexaminationontheformationandevolutionoftheMCVshowedthattheMCVwasmainlycausedbythelatentheatreleaseoftheMCSs,andthepositivefeedbackbetweentheMCSsandMCVwasakeycharacteristicofthescaleinteractioninthiscase.
