IMPACT OF AIR-SEA INTERACTION ON THE GENESIS OF TROPICAL INCIPIENT VORTEX OVER SOUTH CHINA SEA: A CASE STUDY

(整期优先)网络出版时间:2016-03-13
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Basedon6-hourlysensibleheatfluxandlatentheatfluxfromtheNCEPClimateForecastSystemReanalysis(CFSR)andcirculationdatafromtheJapanese25-yearReanalysis(JRA-25),theinitialdevelopingprocessoftropicalcycloneMindulle(1005)in2010hasbeendiagnosedtorevealtheimpactofair-seainteractionovertheSouthChinaSea(SCS)onthegenesisofitsincipientvortex.TheresultsshowthattheincipientvortexfirstoccurredeastoftheLuzonIslandon0000UTC20August,suggestingthatthetopographicforcingoftheLuzonIslandforeasterlywindsoverthewesternPacificmightbeoneofthefactorsresponsiblefortheformationoftheincipientvortex.Duringtheformationstageoftheincipientvortex,strongsoutheasterliesovertheSCScausedwarmwaterofthemiddleandeasternSCStoflowtowardtheLuzonIslandduetoEkmantransportresultingfromwindstress,leadingtoanincreaseoftheseasurfacetemperatureandsensibleheatfluxintotheatmosphere.Althoughtheanomaloussensibleheatingfavoredsurfacepressuretoreduce,itwasnotconducivetotheincreaseoflocalvorticityassociatedwiththevortexabovetheheatingareabecause,accordingtotheatmosphericthermaladaptationtheory,theanticyclonicvorticitywouldbecreatedinthelowertroposphereduetothedecreasedverticalgradientofthesensibleheating.However,theascendingmotionsoccurredovertheeasternareaoftheanomaloussensibleheatingduetotheaugmentationofthevorticityadvectionwithincreasingheight,causingwatervaportocondenseinthemiddleanduppertroposphere.Inturn,cyclonicvorticitywasgeneratedinthelowertroposphereduetotheincreasedverticalgradientofthecondensationlatentheating,resultingintheformationandfurthergrowthoftheincipientvortex.Therefore,thevorticitycreationduetothecondensationheatingplayedadominantroleduringthesubsequentenhancingstageoftheincipientvortex.