我国南方暴雨一些气候特征的统计分析

Climatic Features of Rainstorm Days in South China

根据我国南方59个气象观测站1958～1995年月暴雨日数资料,应用三维经验正交函数分解(EOF3)和小波分析方法,研究了暴雨的主要分布类型、季节变化特征、年际变化和年代际变化规律。结果表明:我国南方暴雨的总趋势是略有增加,但幅度很小;年际变化存在32年、10年、5年和2～3年左右的周期震荡;年代际变化规律是:20世纪50年代末～60年代约10年周期较为清楚,70年代5年周期最强,80～90年代中期10年左右周期最明显,而且比50～60年代要强得多,此外80年代3年左右周期也较明显。我国南方暴雨季节变化显著,4～10月为多暴雨季节,最多的月份出现在6月。暴雨最活跃区域的年变化不大,均位于华南地区,虽然长江流域和黄淮地区是分别对应于梅雨和华北雨季中的多暴雨区域,但是其最大中心值没有超过华南地区。我国南方暴雨、雷暴和冰雹的气候特征,在总趋势、空间分布、季节变化、年际变化和年代际变化方面均存在明显的差异,表明了这3类对流性天气形成物理机制的复杂性。

With data of the rainstorm days of 59 stations in South China in the period of 1958-1995, by three dimensional EOF and wavelet analysis, we investigated climatic features of the rainstorm days in South China, e.g., their spatial distributions, seasonal, interannual and interdecadal variations. The results show that the annual mean rainstorm days has small ascending tendency in the period of 1958 -1995. There are 32-, 10-, 5-, and 2- 3-year periods in the rainstorm days. These oscillations have interdecadal changes with 10-year period in the 1950- 1960s, 5-year period in the 1970s, 10- and 3-year periods in the 1980s, and 10-year period in the 1990s. Rainstorm days have obvious seasonal variations. More rainstorm days are during April- October and the maximum is in June. The maximum values appears in South China. There are obvious differences on climatic features among rainstorm days, hail days, and thunderstorm days in South China. This implies that the cause of the three kinds of weather phenomena is very complex.