长江上游和中下游地区空中水汽资源气候特征对比分析

利用ERA 40再分析资料通过多种统计诊断方法对比分析了长江流域上、中下游空中水汽资源的气候变化特征。研究表明：1958～2001年以来长江流域上游以及中下游地区年平均大气可降水量均呈显著减少趋势，减少率分别为025和026 kg/(m2·10 a)；年平均状态下，长江流域上中下游地区均为水汽汇，上游地区年平均收入水汽226×105 kg/s，中下游地区收入124×105 kg/s；1958～2001年长江上游地区的年平均总水汽收入呈显著减少趋势，每10 a减少98×105 kg/s；中下游地区则呈显著增加趋势，每10 a增加115×105 kg/s。夏季水汽收入变化是影响长江流域水汽收支的重要因素，44 a来，长江上游地区水汽总收入减少和该区域夏季南边界上输入的水汽减少密切相关；而中下游地区水汽总收入的增加则主要是由夏季北边界上输出的水汽显著减少所导致；1958～2001年长江流域上、中下游地区水汽收支的变化和该时期夏季风北扩强度的变化有密切关系，其携带的南来水汽扩展变化则是最直接的影响因子。

A COMPARATIVE ANALYSIS OF THE CLIMATE FEATURES FOR THE WATER VAPOR RESOURCE BETWEEN THE UPPER REACHE ANDTHE MIDDLE AND LOWER REACHES OF THE YANGTZE RIVER

Based on the monthly reanalysis data provided by the European Center for Medium range Weather Forecasts (ECMWF), a comparative analysis of the climate features for the water vapor resource between the upper reach and the middle and lower reaches of the the Yangtze River was studied. In need of comparative analysis, the monthly reanalysis data provided by the National Centers for Environmental Prediction (NCEP/NCAR) was also used. The main results are as follows: from the year of 1958 to 2001, the regional average of yearly atmospheric precipitable water of the upper reach,and the middle and lower reaches of the Yangtze River had both shown a significant decreasing trend, with the reduced rate of 025 and 026 kg/(m2·10) arespectively. Under the yearly average condition, the upper reach and the middle and lower reaches of the Yangtze River both are moisture sinks, and the annual mean water vapor income is 226×105 kg/s and 124×105 kg/s respectively. For the 44 years, the yearly moisture income of the upper reaches had a significant decreased trend, with an average decreasing rate of 98×105 kg/(s·10 a);While that of the middle and lower reaches had a significant increased trend, with an average increasing rate of 115×105 kg/（s·10 a）. Among four seasons, the summer moisture budget has the most important influence on the total yearly moistuare. In the 44 years, the decrease of the moisture budget over the upper reaches had been closely related to the reduced income through its south border, and the increase over the middle and lower reaches had been main caused by the significant decreasing output through its north boundary. The changes of the water vapor resource over the Yangzte River had a close relationship with the expansions vatiation of summer moonsoon, and the expansion changes of the southerly water vapor with moon is the direct impact factor.〖