中国主要河流流域极端降水变化特征

利用中国1956-2008年逐日降水量资料，以全国主要河流流域为研究区域，分析了年最大日降水量、年暴雨（日降水量≥50.0 mm）日数的多年平均状况及长期变化趋势。分析表明，近53年，全国平均年最大日降水量没有明显的线性变化趋势，但全国范围内多数气象站点年最大日降水量呈现出增加趋势，并存在南方流域增加、北方流域减少的变化趋势，这种变化特征在2001年以来表现更加突出。全国平均年暴雨日数呈不显著的增多趋势，20世纪90年代最多，70年代最少。空间上，我国南北方流域年暴雨日数呈现相反的变化特征，南方流域多呈上升趋势，北方流域呈减少趋势。

Variation of Extreme Precipitation over Large River Basins in China

In this study, we chose ten major river basins in China as the study area, and defined southern and northern river-basin regions. The northern region includes the Songhua River, Liaohe River, Haihe River, Yellow River and Northwest China rivers, and the southern region contains the Huaihe River, Yangtze River, Pearl River, Southeast China rivers and Southwest China rivers. Variation characteristics of the nationwide-averaged maximum daily rainfall amount and heavy rain (daily rainfall amount≥50.0 mm) frequency over each river basin and the northern and southern regions were analyzed by using the daily precipitation data over China for the last 53 years of 1956-2008. Results indicate that maximum daily rainfall amount averaged over the entire country showed no obvious trend, but there were some differences between southern and northern river basins, with increasing trends over southern river basins but decreasing trends over northern river basins especially after 2001. The frequency of heavy rain displayed an indistinct increasing trend over the whole China, but exhibited an increasing trend in the southern river basins and a decreasing trend in the northern river basins. On the whole, more heavy rain occurred in the 1990s than in other decades, with the least heavy rain in the 1970s.