一次华南飑线的观测分析和数值模拟研究OACSTPCD

Based on meteorological observation data and high-resolution numerical simulation results,the evolution and mechanism of convective organization and modes in a squall line over South China on May 11,2020,were analyzed in four stages:nascent stage,enhanced stage,mature stage,and decay stage.The results show that the squall line occurred in the strong divergence zone of the upper jet stream.With the deepening and eastward moving of the south branch of the trough,the warm and wet advection in the low layer and mesoscale convergence line on the ground provided favorable conditions of water vapor,heat,and uplift triggering.In the nascent stage,the squall developed in a manner of Bro-ken Lines with medium to strong convective available potential energy and maximum convective inhibi-tion,in the environment of the maximum thermal condition.In the mature stage,a trailing stratiform squall was formed,and the low-level wind shear and cold pool intensity gradually reached a balanced state.During the decay stage,the phase mode of the squall line changed,mainly affected by the thermal condition caused Back Building mode convective cells,and also by different water vapor and wind shear conditions in the lower layer.In South China,it requires high convective effective potential energy to generate a squall line of stratiform cloud mode with trailing tail strong thermal conditions to maintain the squall line.The convective available potential energy,convective inhibition,Bulk Richardson num-ber,and storm-relative helicity can indicate the type and structure mode of convective monomer forma-tion.