长江流域水汽收支与高原水汽输送分量“转换”特征

WHOLE LAYER WATER VAPOR BUDGET OF YANGTZE RIVER VALLEY AND MOISTURE FLUX COMPONENTS TRANSFORM IN THE KEY AREAS OF THE PLATEAU

中文关键词:  青藏高原，水汽输送分量，区域洪涝

英文关键词:Tibetan Plateau, Moisture flux component, Regional flooding.

中文摘要:

      文中采用“箱体”模型边界的整层水汽输送特征描述长江流域梅雨带水汽收支总体效应，发现长江流域夏季降水与“箱体”模型整层水汽输送收支总量呈显著相关；青藏高原动力、热力强迫构成周边水汽输送特殊流型结构，大地形动力强迫导致高原周边水汽输送在高原南侧与东侧存在经向或纬向不同分量的水汽流型，且它们分别对长江流域梅雨带“箱体”模型水汽收支具有重要的影响。研究还发现高原南侧经向水汽输送与高原东侧纬向水汽输送分量之间呈显著相关特征，此研究揭示了长江流域洪涝过程上游高原周边关键区水汽输送不同分量间的“转换”特征，且此类水汽输送流型对夏季长江全流域各区域降水具有不同程度影响。上述高原周边水汽输送经向 纬向分量间的相互“转换”效应，是认识长江流域异常洪涝过程形成的关键环节之一。高原周边水汽输送分量相关结构及区域边界水汽收支问题将为长江流域洪涝预报提供科学依据。

英文摘要:

      One of key scientific issues in Yangtze River flood forecasts is the persistent water vapor transport to maintain the rain belt and its mechanism. Therefore the moisture source and its transfer sensitive region are the clues to the flood forecast in China. Some studies show that the dynamic and thermal effects of the Tibetan Plateau play an important role to the Asian monsoon activities, and they are also the key factors for water vapor transport mechanism for the Meiyu rain belt in the Yangtze River valley. The region in the south of Plateau exist a distinct warm/wet airflow from the Indian Ocean, the South China Sea and the tropical West Pacific. Under the dynamic and thermal effects of the plateau, the southerly water vapor flow from the lower latitudes turns right to Yangtze River valley at the southeast of Tibetan Plateau during its northward transit. Which form the specific water cycle process in the plateau peripheral areas. This is the conception of water vapor transport “forwarding station”, put forward by Prof. Xu xiangde. In this paper, a “box” model is adopted to discuss the whole layer water vaporbudget feature at the edges of middle and lower reaches of Yangtze River valley. The results show that the main input part of water vapor transport in summer is from south and west edges with the main output part at the east edge. Of course, the composite water vapor budget of the region has close relationship with the regional rainfall. Moisture flux components are analyzed in the key areas south and east to the Plateau. It's found that the northward water vapor component in the south of the Plateau is correlated significantly to the eastward in the east of the Plateau. Furthermore, the influencing areas of these two kinds of moisture flux components are discussed. The results show that they can both affect on different degree the summer rainfall, as well as the composite water vapor budget of downstream regions. These results not only verify further the opinion of water vapor transport “forwarding station”, but also reveal that the moisture flux components transform effect possesses influence on the summer rainfall of Yangtze River valley. This is one of the key factors to understand the causes of regional flood and will provide some scientific proof for flood forecast of Yangtze River valley.