长江上游流域大洪水天气分型特征分析

通过对1981~2012年24例长江上游流域大洪水过程进行普查,发现影响长江上游大洪水强降水过程的天气系统主要为:巴湖槽东移型、贝湖槽稳定型和东北冷槽型。采用统计、诊断及合成分析方法,对3种不同天气类型的大尺度环流背景、主要影响系统及致洪降水发生机理进行研究,并总结其特点及差异。结果表明:3种类型大洪水的洪水特征及降水特征各不相同,大尺度环流背景及天气系统也有所差异。副高及500hPa中高纬环流形势异常是导致强降水发生的直接因素,西南涡、冷暖式切变线及冷空气在不同的类型洪水降水中作用各不相同,异常气旋性环流场、水汽输送方向及水汽通量辐合区与强降水的位置密切相关。

CHARACTERISTICS OF VARIOUS WEATHER SYSTEM TYPES DURING BIG FLOOD IN THE UPPER REACHES OF YANGTZE RIVER

Through the 24 cases in 1981-2012 census on the big flood process in the upper reaches of the Yangtze River, it was found that the influencing heavy precipitation weather systems are mainly: the moving eastward trough in balkhash lake, the stable trough in Baikal Lake and the cold trough in northeast. By using the method of statistics, diagnosis and synthetic analysis, the large-scale circulation background, the main influencing system and the mechanism to flood-causing precipitation were analyzed for these three weather types and their characteristics and differences were also summarized. The results showed that the characteristics of three types of flood and precipitation in each were not identical and the large-scale circulation background and the weather systems are also different. The subtropical high and middle-high latitude circulation anomaly on 500 hPa are the direct factors of heavy precipitation. Southwest vortex, cold front shear line and warm front shear line and cold air in different types of rainfall flood effect each are not identical, anomaly cyclonic wind field, water vapor transport direction and the vapor flux divergence convergence zone is closely related to the position of the heavy rain.