中文摘要：

／论文采用EEMD分解方法分析了南京气象站1951-2009年降水序列的多时间尺度，发现南京市年降水序列存在2a、6～7a、14～15a和20a的准周期变化，降水在20世纪70年代之前较小，70年代之后降水较大，整个时间尺度上呈现先减小后升高的平均变化趋势。综合运用Hurst指数及降水距平分析降水的趋势变化结果与EEMD分析结论基本吻合，未来南京市降水可能呈现减少趋势。另外用小波分析对EEMD提取的周期进行验证，小波分析表明南京市降水序列包含2a、7～9a和15～16a的准周期，与EEMI）的结果基本一致，说明EEMI）的结果具有一定的可信度，可以为该地区的降水预测提供依据。

英文摘要：

Based on the precipitation time series from 1951 to 2009 in Nanjing Weather Observation, ensemble empirical mode decom position is used to analyze temporal scales and trend of the annual precipitation. The results show that the annual precipitation with short periods that last 2 years, and 6～7 years, as well as 20 years of long-term oscillation. Hurst index and the precipitation anoma ly analysis reveal that the precipitation has a decrease trend before 1970, and then precipitation began to increase, lightly. Further more, the wavelet method was employed to analyze the precipitation period, it can be found that the annual precipitation has periods that last 2 years, 7～9 years and 15～ 16 years, which are basically consistent with the EEMD results.