近53 a来长江流域极端降水指数特征

Analyses on Characteristics of Extreme Precipitation Indices in the Yangtze River Basin in the Past 53 Years

利用1963~2015年长江流域115个气象站点逐日降水数据,分析了不同极端降水指标的空间变化特点和时间变化趋势。结果表明,近53 a来,长江流域多年平均年极端降水量与年降水量从下游到上游逐渐递减,两者变化趋势大致呈现"增-减-增"的空间分布格局。年极端降水量对年降水量贡献(PEP)存在明显的空间分布差异,但贡献比例在流域内普遍呈现增加的趋势。持续1 d的极端降水事件的降水量分布及其变化趋势与年极端降水量的分布特征类似,其对年极端降水量的贡献比例高达65%以上,说明长江流域极端降水以持续1 d的极端降水事件为主。持续2 d及以上的极端降水事件主要集在中皖苏赣局部地区和四川中部地区,但其降水量对年极端降水量的贡献比例较小。从上游到下游,年最大日降水量(MDP)逐渐增大。其中,上游源头地区的沱沱河、曲麻莱和玉树3个站点MDP主要集中在0~25 mm之间,其他站点均以25~50 mm量级为主;长江流域中部地区的MDP大部分以50~100 mm的量级为主,处于100~150 mm之间的次之;长江流域东部地区主要以100~150 mm量级的MDP为主。

Based on the daily precipitation data at 115 meteorological stations in the Yangtze River Basin during1963 - 2015,the spatial distributions and temporal change trends of some important extreme precipitation indices were analyzed. The results show that multi-year mean annual extreme precipitation and mean annual precipitation decrease from lower to upper reaches in the past 53 years,with the spatial distributions of their change trends as＂increase-decrease-increase＂from lower and middle to the upper reaches. The proportions of annual extreme precipitation accounting for annual precipitation have significant difference although the contribution ratios show increasing trend in the whole basin in general. The spatial distribution and the change tread of precipitation amount of extreme rainfall events lasting one day are similar to those of annual extreme precipitation amount,with the ratios of them more than 65%,indicating that extreme rainfall events lasting one day are dominated in the Yangtze River Basin. The extreme rainfall events lasting two or more days,with the relative low contribution to annual extreme precipitation amount,appear mainly in regions of Anhui,Jiangsu and Jiangxi provinces,as well as central Sichuan. Annual maximum daily precipitation（ MDP） increases from the lower to the upper reaches of the Yangtze River Basin. In the upper reach,MDP varies from 0 to 25 mm at Tuotuohe,Qumalai and Yushu stations,but from 25 to 50 mm at other stations; in the middle reach,MDP varies from 50 to 100 mm mostly,and from 100 to 150 mm secondly; in the low reach,the MDP from 100 to 150 mm is dominated.