宜昌一次致灾极端短时强降水成因分析

Causal analysis of an extreme short-range heavy precipitation in Yichang

利用常规气象观测资料、地面加密自动站资料、NCEP 1°×1°再分析资料、卫星及风廓线雷达和多普勒雷达资料,对2016年7月7日夜间湖北宜昌地区一次致灾极端短时强降水过程,从大尺度环流背景、中尺度特征以及地形等方面进行分析。结果表明:这次局地强降水产生于副热带高压边缘的西南暖湿气流中,表现出中低层中尺度动力抬升强、降水效率高、地形作用明显等特点。峡谷入口处地面中尺度涡旋与强垂直风切变相互作用造成强上升运动为强降水提供了充足的动力条件,较弱的引导气流和山体阻挡作用使得局地降水维持时间长,共同造成了此次极端短时强降水的发生。回波的低质心结构提高了降水效率,降水过程中单体的后向传播也使局地累计雨量增大。

By using the conventional meteorological observations,data of automatic ground stations,NCEP 1°×1°reanalysis data,wind profile radar data,satellite and Doppler radar data,an extreme short-range heavy precipitation process in Yichang of Hubei Province at night of July 7,2016 was analyzed from large-scale circulation background,meso-scale characteristics and topography.According to the results,the heavy precipitation in local areas is generated from the southwest warm and moist airflow at the edge of the subtropical anticyclone,showing the characteristics of strong meso-scale dynamic uplift in the middle-lower layer,high precipitation efficiency,and obvious topographic effect.The intensive ascending motion caused by the interaction of meso-scale vortex and strong vertical wind shear on the ground at the entrance of the canyon provides sufficient dynamic conditions.The weak guiding airflow and the blocking effect of mountains prolong the duration of precipitation in local areas.The two conditions jointly lead to this extreme short-range heavy precipitation.Furthermore,the low centroid structure of the echo improves the precipitation efficiency,and the backward propagation of the MCS also increases the cumulative precipitation in local areas.