1960—2005年长江上游水文循环变化特征

对长江上游水汽含量以及各边界水汽通量、水汽收支的变化特征进行分析,建立了长江上游水文循环概念模型,并通过分析水循环参数的变化特征讨论水文循环的陆面分支与大气分支之间的相互作用和变化过程.结果表明:长江上游为水汽汇区,净水汽收支为23 790 t/s;纬向为水汽输出向,纬向水汽通量减小趋势显著.整个上游地区水汽收支变化趋势不显著,水汽输入总体呈微弱减小趋势.尽管当地蒸散发形成的降水在区域总降水量中的贡献尚不足10%,但蒸散发量对当地水文循环的作用正逐年增加.

Variation of water cycle in upper reaches of Yangtze River from 1960 to 2005

Variations of the water vapor content,water vapor flux,and water vapor budget in the upper reaches of the Yangtze River were analyzed,and a conceptual model of the water cycle was established in this study.Through analysis of the variation of water cycle parameters,the interaction and change process of the land surface branch and the atmosphere branch of the water cycle were studied.The results show that the water vapor was concentrated in the upper reaches of the Yangtze River,and the net water vapor input was 23 790 t/s.Water vapor flowed out in the latitudinal direction,and there was a significant declining trend of the water vapor flux in this direction.There was a slight variation in the water vapor budget in the upper reaches of the Yangtze River and a slightly decreasing trend of the water vapor input.Although the precipitation caused by the local evapotranspiration accounts for less than 10% of the total regional precipitation,it has an increasing effect on the local water cycle year by year.