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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。
Through the census of 24 major floods in the upper reaches of the Yangtze River from 1981 to 2012, it is found that the weather systems affecting the heavy rainfall in the upper reaches of the Yangtze River mainly include the eastward shift of the Bahu Lake, the stable of the Bayhu Channel, and the cold trough of the Northeast China. The statistical, diagnostic and synthetic methods are used to study the large-scale circulation background of three different types of weather, mainly affecting the system and the mechanism of flood-induced precipitation, and summarizing the characteristics and differences. The results show that the flood characteristics and precipitation characteristics of the three flood types are different, and the background of large-scale circulation and the weather system are also different. The anomalies of the subtropical high and the circulation at mid-high latitudes at 500hPa are the direct causes of heavy rainfall. The southwest vortex, the warm and cold shear line and cold air play different roles in different types of flood precipitation. The anomalous cyclonic circulation and water vapor transport The direction and the convergence of water vapor flux and the location of heavy precipitation are closely related.