1998年夏季长江上游暴雨过程的水汽输送特征

应用ECMWF再分析资料,分析了1998年夏季长江上游9次暴雨过程的水汽输送特征.结果表明:长江上游暴雨的水汽主要来源于孟加拉湾、南海和西太平洋,也存在由阿拉伯海北部经印度半岛北部再经青藏高原东南部进入长江上游的水汽路径;不同暴雨过程其水汽来源差别较大;长江上游的复杂地形和水汽输送形式的共同作用是决定长江上游暴雨发生的一个重要因素;当西太平洋副热带高压偏南、偏西、偏强,印度季风低压偏弱时,有利于长江上游暴雨的水汽输送;长江上游水汽输送的特征决定了其暴雨过程发生发展的复杂性.

Characteristics of Water Vapor Transportation During Summer Heavy Rainfall at the Upper Reaches of Yangtze River in 1998

Using the ECMWF reanalysis data in summer of 1998, we analyzed the characteristics of water vapor transportation in the nine heavy rains taken place at the upper reaches of Yangtze River. The result shows that the water vapor of heavy rains at the upper reaches of Yangtze River mainly originates from Bay of Bengal, South China Sea and West Pacific, and sometimes the water vapor from north part of Arabian Sea can transport through the north part of India and southeast part of Tibetan Plateau which can contribute to the heavy rains. The source regions of the water vapor have an obvious difference between different heavy rains. Both the complex topography and the water vapor transportation ways at the upper reaches of Yangtze River are an important factor to determine the heavy rains. When the West Pacific Subtropical High is strong and shifts both to south and to west, and the Indian Monsoon Low Pressure is weak, there is a favor condition of water vapor transportation for the occurrence of heavy rains at the upper reaches of Yangtze River. The characteristics of the water vapor transportation also resuh in the complexity of the occurrence and development of heavy rains at the upper reaches of Yangtze River.