Characteristics of the Interdecadal Variations of Heavy Rain over China in the Last 40 Years
近40年我国暴雨的年代际变化特征

Serious flooding disasters owing to heavy rain occur frequently in summer in China,especially in the middle and lower reaches of the Yangtze River.Previous many studies about heavy rain in China have been conducted on the synoptic scale,but few on the climatology.Tao and Ding(1981) studied heavy rain in China with the data during 1953-1977 and found there are three zones in which heavy rain occurs frequently.Matsmoto and Takahashi(1999) studied heavy rain in East Asia and pointed out that a heavy rain zone exists from the Yangtze River basin in China to the southern parts of Japan.Recently,Zhai et al.(2005) researched the trend of heavy rain in China.The characteristics of the interdecadal variations of heavy rain in China are analyzed by using the daily precipitation data at 610 stations in China for the Last 40 years of 1961-2000.The results indicate that heavy rain mostly occurs in the middle and lower reaches of the Yangtze River,South China,the central and eastern parts of Sichuan Province,the area between the Yellow River and the Huaihe River and the eastern part of North China in summer.The occurrence frequency of the summertime heavy rain has an obvious interdecadal variability,but there are some differences among these areas.More heavy rain occurred in the 1980s than 1970s followed by a step-up increase in the 1990s in the middle and lower reaches of the Yangtze River.Whereas the decrease of heavy rain in the eastern part of North China has happened since the late 1970s.In the boreal spring and autumn,the interdecadal variations in the southern China are not obvious.Moreover,the analyzed results also show that there is a close relationship between heavy rain and flooding disasters in the monsoon region of eastern China,especially,heavy rain greatly contributed to flooding disasters in the Yangtze River and Huaihe River valleys in the 1990s.Furthermore,the climatic background of interdecadal variability of the occurring frequency of the summer heavy rain is also discussed preliminarily.The interdecadal decrease of heavy rain in North China from the late 1970s may be related to the interdecadal variation of SST in the equatorial central and eastern Pacific,and the interdecadal increase of heavy rain to the south of the Yangtze River in the 1990s may be associated with the thermal convective activities over the eastern part of the tropical northwestern Pacific.The interdecadal variation of outgoing longwave radiation(OLR) over the eastern part of the tropical northwestern Pacific induces the interdecadal variation of the subtropical anticyclone at the lower layer over the northwestern Pacific,which has an impact on the interdecadal variation of heavy rain to the south of the Yangtze River in the 1990s.