“18.8”粤东暴雨中心极端强降水“列车效应”分析

The analysis of train effect features of a record-breaking severe rainfall in eastern region of Guangdong in August 2018

2018年8月30-31日广东出现一次超历史记录的极端强降水过程,惠东高潭24 h雨量达1 056.7 mm,采用广东省区域雷达拼图产品、MICAPS实况、CFSR逐6 h再分析资料(水平分辨率0.5°×0.5°),以及广东省国家级地面气象观测站和区域自动站资料,着重分析了此次过程中"列车效应"的演变特征。结果表明:"列车效应"发生在缓慢移动的季风低压诱发的有利大气环流背景下,最显著的特点是水汽通量散度和假相当位温大值区主要存在于925 hPa及其以下的边界层中,且在强降水发生时段汕尾附近地区边界层风向由西南风逐渐逆时针转为偏南风,在汕尾中部附近地区形成气流辐合上升;MβCS中多单体对流风暴沿西南季风和莲花山山脉走势自西南向东北方向传播;地面中尺度辐合线以及低空西南-偏南暖湿气流的脉冲,以及惠东高潭附近的特殊地形分布触发了此次过程中"列车效应"的发生发展,从而引发了高潭创历史记录的极端强降水过程。

Using data of regional radar mosaic products, MICAPS, 6-hourly reanalysis data of CFSR with horizontal resolution of 0.5°×0.5°,and data of national meteorological observatories and regional automatic stations in Guangdong Province, the train effect features of an extremely severe rainfall event in Guangdong with a record-breaking rainfall of 1 056.7 mm within 24 hours in Gaotan of Huidong from 30 to 31 August 2018 is analyzed. The result is shown as follows. The train effect took place in the environment of a favorable atmospheric circulation induced by slowly moving monsoon depression. The most remarkable characteristic was that the high value of vapor flux divergence and potential pseudo-equivalent temperature mainly appeared in the boundary layer below 925 h Pa. The wind direction in the boundary layer near Shanwei gradually shifts from southwest to south. The air current produced an upward movement of convergence around the central region of Shanwei.The storm cells of the severe rainfall moved along with southwest monsoon and the Lianhua Moutain from southwest to northeast. Surface mesoscale convergence line, the pulses of southwest-south airflows and the special terrain distribution triggered the generation and development of the train effect. The conditions presented above have resulted in the extremely severe precipitation breaking historical records in Gaotan.