Correlation analysis between environmental factors and microphysical variables during the “Suizhou 812” heavy precipitation process in Suizhou City, Hubei Province of China

Abstract

Based on numerical simulation, this study investigates the relationship between environmental factors and microphysical variables of a heavy precipitation event in Suizhou on August 12, 2021, aiming to provide a reference for studying the interaction mechanisms of physical processes involved at different scales. The results demonstrate that environmental instability factors give an early indication of heavy precipitation occurrence and play a crucial role in connecting microphysical processes in the middle/upper layers with water vapor uplift in the lower layers before and during heavy precipitation events. Most of the peak/valley values of both environmental factors and microphysical variables occur simultaneously with those of precipitation on the hourly time series. The vertical profile reveals that, before the occurrence of heavy precipitation, there is an initial strengthening of ascending movement in the middle to upper troposphere, leading to an increase in ice‐phase particles and cloud water within these layers. Additionally, gravity sedimentation and melting significantly contribute to increased rainwater content within the lower to middle layers. When heavy precipitation occurs, intensified vertical velocity, vorticity, and water vapor convergence results in a decrease in cloud/rain particles' peak height and an increase in graupel particles' peak height. This leads to a prolonged collision process and heightened rainfall intensity. Furthermore, enhanced water vapor convergence promotes raindrops formation through colliding and coalescing with cloud droplets. By comparing variables/factors between extreme hourly heavy precipitation and general hourly heavy precipitation, it is suggested that the strengthened self‐feedback mechanism between microphysical latent heat release and vorticity may be one of the reasons for the occurrence of extreme hourly heavy rainfall.