贵州夜间大暴雨主要影响系统初步统计特征

Preliminary Statistical Cha-racteristics of Main Impact Systems of Nighttime Heavy Rain in Guizhou

本文分析了贵州夜间大暴雨的10年资料。结果表明:贵州4—9月均有夜间大暴雨出现,主要集中在春末和初夏;500 hPa上影响贵州夜间大暴雨天气系统的有主要两大类,一类是大(深)槽型,另一类是小槽型,大槽型占40.8%,小槽型占53.9%;对贵州大暴雨影响较大的孟加拉湾低槽位于90°E附近,20°N以南,有77.6%个例中存在孟加拉湾低槽;夜间大暴雨的地面影响系统可分为以下5种类型:冷锋型(含弱冷空气抬升、静止锋型、梅雨锋型、雷暴外流触发型、低压槽辐合型)。

The statistical characteristics of 10-year data of night heavy rain in Guizhou show that night heavy rain occurs from April to September in Guizhou,mainly in late spring and early summer.The spatial distribution of heavy rain at night is uneven.There are five obvious heavy rain distribution centers.The most obvious heavy rain centers at night are Qinglong County,Wangmo county and Zhijin Pingba area.The distribution of heavy rain days is roughly northeast southwest.Almost every heavy rain is accompanied by a low-level shear line or vortex,and the middle-level low trough is helpful to trigger convection,and 76.3%of cases have low-level jet.There are two types of heavy rainstorm weather systems affecting Guizhou at night on 500hPa,one is large(deep)trough type,and the other is small trough type,with large trough type accounting for 40.8%and small trough type accounting for 53.9%.The bay of Bengal trough,which has a great impact on the rainstorm in Guizhou,is located near 90°E and to the south of 20°N.77.6%of the cases have the bay of Bengal trough.The ground impact system of heavy rainstorm at night can be divided into the following five types:(1)cold front type including weak cold air uplift;(2)Static frontal type;(3)Meiyu front type;(4)Thunderstorm outflow trigger;(5)Low pressure trough convergence type.