A4-daypersistentrainstormresultinginseriousfloodingdisastersoccurredinthenorthofFujianProvinceundertheinfluencesofaquasi-stationaryMeiyufrontduring5-8June2006.With1~x1~latitudeandlongitudeNCEPreanalysisdataandthegroundsurfacerainfall,usingthepotentialvorticity(PV)analysisandPVinversionmethod,theevolutionofmainsynopticsystems,andthecorrespondingPVandPVperturbation(orPVanomalies)andtheirrelationshipwithheavyrainfallalongtheMeiyufrontareanalyzedinordertoinvestigatethephysicalmechanismoftheformation,development,andmaintenanceoftheMeiyufront.Furthermore,thePVperturbationsrelatedtodifferentphysicsareseparatedtoinvestigatetheirdifferentrolesintheformationanddevelopmentoftheMeiyufront.Theresultsshow:theformationandpersistenceoftheMeiyufrontinaquasi-WEorientationaremainlyduetothemaintenanceofthehigh-pressuresystemsinitssouth/northsides(theWestPacificsubtropicalhigh/thehighpressurebandextendingfromtheKoreanPeninsulatoeastofNorthChina).TheMeiyufrontiscloselyassociatedwiththePVinthelowertroposphere.ThelocationofthepositivePVperturbationontheMeiyufrontmatcheswellwiththemainheavyrainfallareaalongtheMeiyufront.ThePVinversionrevealsthatthebalancedwindssatisfyingthenonlinearbalancedassumptionrepresenttoalargeextenttherealatmosphericflowanditsevolutionbasicallyreflectsthevariationofstreamflowassociatedwiththeMeiyufront.TheunbalancedflowformstheconvergencebandoftheMeiyufrontanditmainlycomesfromthehigh-pressuresysteminthenorthsideoftheMeiyufront.ThepositivePVperturbationrelatedtolatentheatreleaseinthemiddle-lowertroposphereisoneofthemainfactorsinfluencingtheformationanddevelopmentoftheMeiyufront.ThepositivevorticitybandfromthetotalbalancedwindsisinaccordancewiththeMeiyufrontbandandthemagnitudeofthepositivevorticityfromthebalan
