简介：ThisstudyexaminestheseasonalvariationsoftropicalcyclogenesisovertheSouthChinaSea(SCS)usingagenesispotential(GP)indexdevelopedbyEmanuelandNolan.Howdifferentenvironmentalfactors(includinglow-levelvorticity,mid-levelrelativehumidity,verticalwindshear,andpotentialintensity)contributetothesevariationsisinvestigated.CompositeanomaliesoftheGPindexareproducedforthesummerandwintermonsoonsseparately.ThesecompositesreplicatetheobservedseasonalvariationsoftheobservedfrequencyandlocationoftropicalcyclogenesisovertheSCS.Thedegreeofcontributionbyeachfactorindifferentregionsisdeterminedquantitativelybyproducingcompositesofmodifiedindicesinwhichonlyoneofthecontributingfactorsvaries,withtheotherssettoclimatology.OverthenorthernSCS,potentialintensitymakesthelargestcontributionstotheseasonalvariationsintropicalcyclogenesis.OverthesouthernSCS,thelow-levelrelativevorticityplaystheprimaryroleintheseasonalmodulationoftropicalcyclone(TC)genesisfrequency,andtheverticalwindshearplaysthesecondaryrole.ThermodynamicfactorsplaymoreimportantrolesfortheseasonalvariationsintropicalcyclogenesisoverthenorthernSCS,whiledynamicfactorsaremoreimportantintheseasonalmodulationofTCgenesisfrequencyoverthesouthernSCS.