中国十大流域近40多年降水量时空变化特征

利用中国1956～2000年月降水量资料,按流域将全国划分为10个区域,分析了各流域年、季降水量的多年平均状况和年代际变化特征以及长期变化趋势。分析结果进一步证实,中国北方流域降水量少,年际变化大,水资源缺乏且不稳定;南方流域降水较多,年际变化较小,水资源相对充足且比较稳定。分析结果还表明,近45年来,北方外流河流域年降水量一般趋于减少,特别是20世纪90年代以来降水明显减少;南方流域以降水增加为主,90年代降水均较80年代增多,特别是长江流域以南地区更为明显。季节降水减少主要出现在夏秋季,冬春季降水有微弱增加趋势。近20年来,中国绝大多数流域降水的增减趋势与近45年长序列的变化趋势基本一致。北方大部分外流河流域年降水量减少,南方流域多为增加。夏、秋季,大部流域降水较前20年减少,冬春季则相反。中国西北诸河流域是十大流域中惟一四季降水均有增加的流域。

Spatial and Temporal Variation of Precipitation over Ten Major Basins in China between 1956 and 2000

In the context of 1956～2000 monthly rainfall data at 743 stations over China,regional normal mean condition,inter-decadal change and trends of annual and seasonal precipitation are analyzed at drainage basins scale.The changes of mean precipitation between 1956～1979 and 1980～2000 periods were compared for 10 drainage basins.The results show that the preci-pitations are less with larger variability and water resources are insufficient and more instable in river basins of northern China.As for basins in southern China,precipitation is abundant with small variability and water resources are relatively sufficient and stable.In the recent 45 years,the trends of annual precipitations for the northern basins have been generally negative,with the decrease of the 1990s being the most remarkable.On the other hand,the increasing tendency of precipitation is a major feature for the southern basins.In the 1990s,the mean annual precipitations of the southern basins exceed mostly those of the 1980s,particularly in the areas south of the Yangtze River.For seasonal precipitation,obvious decreasing tendencies mainly occurred in summer and autumn,while winter and spring experienced a slight increasing tendency for most of the basins.In the last 20 years,the tendencies of precipitations in most of the basins are similar with those for the 1956～2000 period.The river basins in Northwest China are the only basins among the ten where precipitation of the four seasons all experienced an increasing trend.