陕甘宁半干旱区特大降水的环流特征

分析陕甘宁半干旱区特大降水的环流特征及其与一般大、暴雨的环流差异，指出中低纬系统相互作用和下游系统阻挡是产生特大降水的重要条件。热带气旋北上时，存在第二类间接作用，不仅在东风急流下游能出现倒槽暴雨，还有利于热带气旋下游的副热带高压另一侧产生特大降水。

Circulation Features of Catastrophic Precipitation in Shan Gan Ning Semi Dry Region

The analysis of Circalation features of Catastrophic precipitation and circulationdifferences between its and ordinary heavy rainfall are made in shan Gan Ning Semi DryRegion. The Results show that both interaction of mid low latitude systems and inhibitionof downstream systems are important conditions of produced catastrophic precipitation. Sec-ond indirect effect is existed when tropical cyclone moves toward the north. The heavy rain-fall of inversion trough has not only arisen in downstream of easterly jet, but a catastrophicprecipitation has also produced on the other side of subtropical high pressure downstream oftropical cyclone.