Thewintersof1997/1998and1998/1999,correspondingtoElNi(?)oandLaNi(?)aepisodes,respectively,weretwotypicalrain-abundantand-scarceseasonsforthesouthernChina.Inordertounderstandthecauseoftheanomalousprecipitationduringthetwowinters,acomparativeanalysistechniquehasbeenemployedtoinvestigatethedifferencesingeneralcirculationandmoisturetransportationbetweenthetwoseasons.Theresultsshowthattheabundantrainfallduringthewinterof1997/1998wasassociatedwiththeENSOwarmepisodeevent,eastwardshiftedweakwesterlytrough/ridge,weakenedEastAsianwintermonsoon(EAWM),strengthenedsubtropicalhigh,andpresentedtwoanti-cycloniccirculationsoverHokkaidoandthePhilippineSea,respectively,aswellasonecycloniccirculationovertheYangtzeRiverBasinintheanomalouswindfieldsofthelowertroposphere.Duringtherain-scarcewinter,however,thepatternsofequatorialseasurfacetemperatureanomaliesandthecirculationsystemsbothinupperandlowerlevelswerenearlytheoppositeofthoseduringtherain-abundantwinter.IthasalsobeendiscoveredthatthewatervaporoversouthernChinaduringthewinterscamemainlyfromthesouthwesterlyflowaheadoftroughsinthesouthernbranchofwesterliesandtheturningflowovertheSouthChinaSea-Indo-ChinaPeninsulaarea;andthemoisturetransportationchannelsvariedsignificantlywithregardtoheight.Theintensifiedflowinthesouthernbranchofwesterliesandtheanti-cycloniccirculationanomalyoverthePhilippineSeaduringthewinterof1997/1998werefavorableformoisturetransportationtomainlandChina,howeverthetwomoisturetransportationstreamsweredramaticallyweakenedduringthewinterof1998/1999duetoweakwesterlyflowandthedominanceofacoldhighsysteminthelowerleveloverthesoutheastcoastofChina.Suchasignificantinter-annualchangeofmoisturetransportationisakeyfactorresultingintheobviousdifferenceinprecipitationbetweenthetwowinters.
