Temporalandspatialevolutioncharacteristicsofthe30-60dayoscillation(intraseasonaloscillation,ISO)ofsummerrainfallinChinaandtheeffectsofEastAsianmonsoonontherainfallISOareanalyzedinthispaper.Resultsshowthattheannualanddecadalvariationsoftheoscillationexistbetween1960and2008,andtheintensityisweakestinthelate1970sandearly1980s.InthetypicalstrongyearsoftherainfallISOobtainedfromempiricalorthogonalfunctions(EOFmode1),ananticycloneisinnorthwesternPacificandacycloneisintheeastofChina.Inthetypicalweakyears,thewindISOismuchweaker.Thelow-frequencyzonalwindandwatervaportransportfromthelowlatitudestomid-latitudesinthetypicalstrongyears,andtheoscillationstrengthofdiabaticheatingismuchstrongerthanthatintheweakyearsoftherainfallISO.TheanomalycharacteristicsoftherainfallISOshowanti-phasesbetweentheYangtzeRiverbasinandsouthofChina.AsforthetypicalstrongyearsoftherainfallISOintheYangtzeRiverbasin(EOFmode2),themainoscillationcenterofwatervaporisintheeastofChina(20-30°N,110-130°E).Inthepeak(break)phaseoftherainfalloscillation,alow-frequencycyclone(anticyclone)isintheYangtzeRiverbasinandananticyclone(cyclone)isnearTaiwanIsland.Inaddition,thepeakrainfallcorrespondstotheheatsourceintheYangtzeRiverbasinandtheheatsinkintheQinghai-TibetPlateau.AsforthetypicalstrongyearsoftherainfallISOinthesouthofChina,themainoscillationcenterofwatervaporissouthof20°N.Inthepeak(break)phaseoftherainfallISO,alow-frequencycyclone(anticyclone)isinthesouthofChinaandananticyclone(cyclone)isinthePhilippines.ThepeakrainfallcorrespondstotheheatsourceinthesouthofChinaandtheSouthChinaSea,andtheheatsinkinthewestofIndochina.
