中文摘要：

利用1960-2000年全国436个地面测站的逐日降水量资料,将中国雨季分为江南春雨期（3月16日-5月15日）、夏季风主汛期（5月16-7月15日）、夏季风后汛期（7月16日-9月15日）3个时段,应用S-EOF（Season-reliant Empirical Orthogonal Function）分解的方法研究了中国雨季旱涝型主模态季节演变的空间分布及其时间变化特征。主要分析了前3个主模态的时空分布特征,第一模态（S-EOF1）的旱涝分布为江南初夏旱涝型,主要显示出江南地区在夏季风主汛期以整个长江以南地区的旱或涝为主要特征,具有20-30 a的年代际振荡周期。第二模态（S-EOF2）空间向量集中体现了夏季风主汛期长江中下游流域和华南地区形成南北相反的旱涝分布,为南北跷跷板型,且这种分布在夏季风后汛期发生转变,这种南北旱涝急转型以2-4 a的年际变化为主。第三模态（S-EOF3）主要体现了夏季风后汛期长江中下游地区与华北和华南地区降水异常呈负相关关系,即自南向北呈现三明治夹心型的旱涝分布,以低频年际振荡为主,显著周期为6-8a,同时还具有准30 a的年代际变化。

英文摘要：

The observed daily rainfall data（from 2000 are used to analyze the spatial and temporal March to September） at 436 stations in China from 1960 to distribution of variations of dominant drought/flood patterns in rainy seasons over China. The present paper divides the rainy seasons in China from spring to autumn into three major periods; the first period is termed as spring rainy season of the South China from mid-March to mid-May, before the summer monsoon onset; the second period is termed as pre-flooding of the monsoonal rainy season from mid-May to mid-July, including the pre-summer season in South China and the Meiyu rainy season in the Yangtze and Huaihe valley; the third period is called post-flooding（or typhoon-induced-flooding） period of the monsoonal rainy season from mid-July to mid-September, including the rainy season in North and Northeast China and the post-flooding season in South China. By using Season-reliant Empirical Orthogonal Function（S-EOF） analysis, three major modes of the drought/flood patterns of rainy seasons in China are identified. The first spatial mode exhibits the lasting drought/flood pattern over the entire area of the south of the Yangtze River throughout the three major periods, most significant in the pre-flooding of the monsoonal rainy season. And this mode shows a strong interdecadal variability with a 20-30 years period oscillation. The second spatial mode shows a north-south seesaw pattern with negative correlation between the precipitation anoma- ly over the middle and lower reaches of the Yangtze River and Huaihe River valley and over the South China in the pre-flooding of the monsoonal rainy season; and the transition of this drought/flood pattern over the two areas above occurs in the post-flooding period. Therefore, this pattern shows a sharp change in flood/drought pat- tern during a summer monsoonal rainy season. This mode exhibits a prominent 2-4 years interannual oscillation. The third spatial mode is termed as sandwich pattern with negative-positive-ne