Interdecadal Variation Of The Relationship Between ENSO/IOD And East-China Summer Rainfall

By using Hadley Centre monthly sea surface temperature data、 NCEP/NCAR reanalysis data and daily rainfall of 753 stations over China, it is found that different subdivisions of summer rainfall in East China are independent, which differs from three types of summer rainfall pattern of eastern China, as that represent the connection of summer rainfall in East China. Based on that, interdecadal variation of the relationship between ENSO / IOD and independent subdivisions of summer rainfall in East China is analysed by using rotated empirical orthogonal function(REOF) 、moving correlation、composite analysis etc. The main conclutions are summerized as follows:(1) Eleven subdivisions of summer rainfall in East China is found by using rotated empirical orthogonal function(REOF). And the Eleven subdivisions of summer rainfall are independent from each other by statistical methods.(2) Based on the interdecadal variation of the relationship between ENSO and eleven subdivisions of summer rainfall,3 categories of the correlation between SSTA in the Nino3 region and summer rainfall are defined: the first type is that the correlation is always very week in the long term, as Northeast China, the middle and lower reaches of the Yangtze River, South of Yangtze River, Fujian-Jiangxi and Qiongzhou Rim strait represent. The second one is that the significant correlation is fairly stable, as Hetao area and the middle and lower reaches of the Yellow River show. The third type is that the relationship has noticeable change, as Liaoning-Jilin, Yellow River- Huaihe River, Huaihe River and Guangdong-Guangxi represent.(3) Based on the interdecadal variation of the relationship between IOD and eleven subdivisions of summer rainfall, 2 categories of the correlation between IOD and summer rainfall are defined: the first type is that the correlation is always very week in the long term, as Northeast China, the middle and lower reaches of the Yellow River, Huaihe River and South of Yangtze River show. The second one is that the relationship has noticeable change, as Liaoning-Jilin, Hetao area, Yellow River- Huaihe River, the middle and lower reaches of the Yangtze River, Guangdong-Guangxi, Fujian-Jiangxi and Qiongzhou Rim strait represent.