怀化三次西南涡暴雨天气过程对比分析

利用常规观测资料、地面区域气象自动站加密资料、卫星以及NCEP再分析资料,对2010年6月、2012年6月、2015年6月3次发生在湖南怀化的暴雨天气过程进行对比分析。结果表明:(1)3次过程均是典型的低涡冷槽型暴雨过程,降雨分布在低涡东南侧及其向东伸展出的切变线附近,对于低涡沿切变线东移的暴雨过程,降雨分布在低涡移动的路径上。(2)中低层中尺度低涡或辐合中心是直接造成暴雨的系统,其发展演变和移动直接影响降雨的落区和持续时间,在卫星云图上反应为中尺度云团的生消。(3)孟湾、南海是怀化暴雨的水汽源地,暴雨发生在高温高湿的不稳定层结和强水汽辐合区域,强降雨是整层水汽通量和水汽辐合共同作用的结果,当两者同步增强并达到极值时,降雨也同步增强,当两者不同步时,不能使用单一要素判断降雨,而要综合考虑。(4)3次暴雨过程都是发生在低层正涡度、负散度和高层负涡度、正散度的高低空耦合结构下。

Contrastive analysis of three southwest China vortex weather processes in Huaihua

Based on the conventional observation data, surface regional auto weather station data, satellite data and the NCEP reanalysis data, three heavy rainfall weather processes were analyzed which happened in June, 2010, June, 2012 and June, 2015 in Huaihua, Hunan Province. The results are shown: 1. Three processes were all typical vortex and cold trough heavy rainfall, the precipitation distribution was around the vortex southeast side and its eastward wind shear, and for those processes whose vortex is moving eastwards along wind shear, the rainfall distribution is on the vortex moving path. 2. Meso-scale vortex or convergence center in the lower level is the direct system causing heavy rainfall, and its development and movement have an influence on the precipitation area and duration which reflect on the satellite is the growing and decaying of meso-scale cloud. 3. Bay of Bengal and South Chian Sea is the vapor source of heavy rainfall in Huaihua. Heavy rainfall happened in the unstable stratification of high temperature and high moisture and the area of strong vapor convergence. Heavy precipitation is the result of whole layer water vapor flux and vapor convergence, when both of them enhanced to extreme values, precipitation increased too, when the their enhancements are not synchronized, we cannot use single factor to estimate the precipitation, but with comprehensive consideration. 4. Three processes all happened under the coupling structure of positive vorticity, negative divergence in the lower layer and negative vorticity, positive divergence in the upper layer.