发生短时强降雨的对流云合并作用分析

Analysis of the merger of convective clouds in short-time strong rainfall event

利用静止气象卫星、新一代多普勒天气雷达、地面、wrf数值模拟和LAPS再分析资料,对2013年6月30日皖南山区一次短时强降雨过程中的对流云合并现象进行了观测和分析。综合观测显示,这是一次由三个强弱不同的对流云先后发生合并的过程;强弱不同或强度相当的两对流云合并后的新对流云系统短时间内强度是增强的。分析认为,山区夏季对流云合并发生在水平垂直风切变及垂直涡度增大的湿斜压不稳定增强的环境中;对流云合并过程中伴有中气旋、地形涡等中γ系统形成,中气旋与地形涡系统内的强烈垂直运动导致低层形成辐合的垂直环流是山区短时强降雨触发机制。

Using geostationary meteorological satellite, a new Doppler weather radar, ground, WRF numerical simulation and LAPS reanaly- sis data, we analyzed a short-time strong rainfall convective cloud merger case on 30 June 2013 in the mountain area in south of Anhui. Results show that this was a merging event of three different convective systems occurred successively. The strength of the newly developed convective system merged from the two older convective clouds is enhanced in a short time. According to the analysis, in the mountain area, summer merger of convective clouds occurred in the environment where the horizontal and vertical wind shear and vertical vorticity are in- creasing and the wet baroclinic instably is enhancing. The merging process of convective clouds is accompanied with meso-＇y-scale system such as a mesoscale cyclone, or atopographic eddy. Strong vertical motion within the cyclone and topographic eddy systems leads to low- level convergence, which is the triggering mechanism for a short-time strong rainfall in mountainous areas.