三峡库区洪涝特征及其与大尺度环流的联系

利用三峡库区降水观测资料和NCEP/NCAR再分析资料,分析了1980—2007年三峡库区洪涝年际变化特征,研究了三峡库区洪涝典型年份大尺度环流合成特征,进一步讨论了水汽输送特征。近年来,三峡库区年均洪涝、区域洪涝强度变化趋势不明显,而区域性洪涝较为频繁;乌拉尔山高压脊加强,经向环流增强,引导冷空气南下,与低纬北上暖湿气流交汇,三峡库区在以上环流背景下,易于产生洪涝灾害;蒙古高原,以及我国东北地区的环流背景合成有差异,三峡库区建库前典型洪涝年份较建库后环流异常更有利于降水;水汽输送异常在三峡地区均有汇合,建库前指示特征比三峡建库后大;典型洪涝年2004、2007年以及典型洪涝事件中,各个关键区水汽输送强度较弱。

Features of Floods in the Three Gorges Reservoir Region and Its Relationship with Large Scale Circulation

Based on the observed precipitation data in the Three Gorges Reservoir Region and the NCEP/NCAR reanalysis data, the interannual variation features of the floods in this area during 1980-- 2007 were investigated and the large scale circulation in typical flood years were studied. The water va- por transportation features were further discussed. In recent years, there was no notable variation tenden- cy in the annual mean flood intensity or the regional flood intensity but regional floods often occurred. It was apt to flood when the high pressure ridge over Ural strengthened and the meridional circulation was enhanced, which caused the cold air moving southward and the warm air moving northward con- verged in the Three Gorges Reservoir area. The large scale circulation composites were different in the Mongolia plateau and Northeast China. The circumfluence anomalies before the construction of the Three Gorges Reservoir were prone to cause rainfall. The water vapor transportation anomalies con- verged in the Three Gorges Reservoir region, but the amount of water vapor after the construction of the Three Gorges Reservoir was less than that in historical flood years （1980 and 1984）. The water vapor transportations in the key areas were weak during the typical flood years （2004 and 2007 ）.