长江流域不同区域暴雨发生机理的比较研究

对发生于1998年7月21日长江流域不同区域同时次的两个暴雨个例发生的机理进行了比较研究。结果表明：长江上游的贵州思南暴雨受西南涡、低空急流及南亚高压的影响，雨区位于低空急流的左中侧，水汽主要来源于孟加拉湾。而长江中游的武汉暴雨不受西南涡的影响，主要是边界层偏南风急流、低空西风急流、高空西风急流三者上下耦合的结果，其水汽来源主要是南海，暴雨区上空低层为非热成风的对流不稳定，高层为非热成风的对称不稳定。

Mechanism on Torrential Rain in Different Places of the Yangtze River Valley

Mechanism is compared for two rainstorm processes in different places of the Yangtze River valley in Jul. 21,1998. The torrential rain in Sinan area of Guizhou Province in the upper valleys of the Yangtze River is under the influence of southwest vortex,low-level westerly jet and south Asia high. Rainbelt locates on the left-mid-hand side of the low level jet and the main vapour source is from the Bay of Bengal. But the torrential rain in Wuhan in the mid valleys of the Yangtze River is principally resulted from the coupling of boundary-layer southerly jet,low-level westerly jet and high level westerly jet. Its major vapour source is from South China Sea. Non-thermal wind convective instability at low level and non-thermal wind symmetric instability at high level are the mechanism of torrential rain.