长江上游地区盛夏季节的水分循环

根据1955—1961年的材料,研究了每年盛夏长江上游地区的水分循环,给出了本区四个边界上各年各层的水汽输送量及各年的水分循环各要素值,并与其它几个地区的水分循环情况进行了比较。文中也简略讨论了本区水汽输送与夏季环流形势间的关系。 本区的水分循环,与其它地区相比较,有一些独特之处:水分循环系数K及水分循环强度均较大(K=1.094)。蒸发与降水量之比值较小。水汽输送最大的层次较高(在850—700毫巴间)。造成这些特点的原因主要在于本区的特殊自然地理条件(是群山环抱,海拔较高的盆地)。可见自然地理条件对水分循环情况有重要影响。 可以推论,在本地区采取增加内部蒸发量的措施,对于降水量之增加,效果似乎应该较在平原地区显著。

AN INVESTIGATION ON THE WATER CYCLE IN THE BASIN OF THE UP-YANGTZE RIVER IN SUMMER

From the serological data of 1955-1961 in West China, the water cycle in the basin of the Up-Yangtze river in summer is investigated for each year, and the mean of six years is obtained.The water vapour transfer is closely related to the circulation pattern over this area in summer. The inflow of water vapour from the south is on the average over 85 per cent of the total inflow, and the inflow from the west is about 10 per cent. About 98 per cent of the total outflow passes through the eastern and northern boundaries, so that there is a high negative correlation between the outflow through the east and north. The intensity of inflow from the south does not change significantly, while the outflow through the eastern and northern boundary is quite different, from year to year.When the inflow of water vapour is large (or small), the outflow from this area is also large (or small), hence the net inflow or runoff of the basin are not determined solely by the inflow of water vapour.In this region the coefficient of water cycle K (K=1.094) and the intensity of the water cycle are larger than in other regions of the world. The ratio of evapotranspiration to precipitation is relatively small and the maximum layer of water vapour transfer is situated between 850 and 700 mb. It is found that the orographic condition is an important factor for these characteristics of the water cycle in this region. We conclude that the possibility of the increase of the precipitation by increasing the internal evapotranspiration in this region is larger than in plain areas.