采用EOF法对中国东部季风区夏季（6月-8月）降水场进行分解，得到三种主要的降水空间分布型，即“总体一致型”、“南北涝（旱）中间旱（涝）型”以及“南涝（旱）北旱（涝）型”。利用Mann-Kendall检验和功率谱对时间系数做进一步处理，分析各空间分布型的时间演变特征，结果表明：第一、第二时间系数均未检测出突变的发生，第三时间系数存在一次突变，时间开始于20世纪70年代初期，由之前的“南旱北涝型”转变为“南涝北旱型”；第一时间系数存在50年左右的显著周期，第二时间系数存在2年左右的显著周期，第三时间系数存在50年左右的主周期和2～3 a左右的次周期。对季风指数和时间系数进行相关分析，发现第二时间系数与东亚、南海季风指数存在正相关关系，揭示了季风强弱对夏季主要降水场的指示作用。

EOF method was applied to analyze the summer precipitation field (June- August) in the monsoon region of eastern China. Three main spatial distribution types of precipitation were obtained, including the even distribution of flood and drought type, flood (drought) in the north and south while drought (flood) in the center type, and flood (drought) in the south while drought (flood) in the north type. The Mann-Kendall test and power spectrum analysis were used to analyze the temporal characteristics of each above type of spatial distribution. The results showed that (1) no mutations are detected for the first and second time coefficients but there is a mutation for the third time coefficient. The mutation occurred in the early 1970s with the type of spatial distribution varying from “southern drought and northern flood” to the opposite; and (2) a cycle of 50 years exists in the first time coefficient, a cycle of two years in the second time coefficient, and two cycles with a main cycle of 50 years and a sub-cycle of 2 to 3 years in the third time coefficient. The correlation analysis between monsoon indices and time coefficients showed that there are positive correlations between the second time coefficients and monsoon indices of East Asia and South China Sea, which indicated the intensity of monsoon on summer precipitation.