Initiation, organizational modes and environmental conditions of severe convective wind events during the warm season over North China

Abstract

Based on the significant weather report, CG lightning, composite radar reflectivity, and ERA5 reanalysis data, we first studied the spatiotemporal distribution characteristics of four types (only severe convective wind (SCW); SCW and hail; SCW and short-duration heavy rainfall (SDHR); and SCW, hail, and SDHR) of convective weather events related to SCW during the warm season (May to September) from 2011 to 2018 in North China. Second, severe convective cases producing SCW were selected to statistically analyze the initiation, decay, lifetime, and organizational characteristics of convective systems. Finally, using ERA5 reanalysis data and conventional surface observation data, preconvective soundings were constructed to explore the differences in environmental conditions for initiating convective systems between SCW and non-SCW. The results indicate that mixed-type of SCW and SDHR events occur more frequently over plains, while other types of convective weather occur more frequently over mountains. The frequency peak of SCW occurs in June, while mixed convective weather peaks in July. The initiation time of convective systems is concentrated between 1000 and 1300 BST, with apeak at 1200 BST. Over mountains, the daily peaks of ordinary and significant SCW generally occur at 1700–1800 BST and 1600–1700 BST, respectively, while over plains, the peak of ordinary SCW typically lags behind that of mountains by 1–2 hours. Additionally, SCW systems are mainly initiated over mountains, with most lifetimes lasting 7–13 hours. Nonlinear convective systems produce the most SCW events, followed by trailing-stratiform convective systems. The convective available potential energy (CAPE), downdraft convective available potential energy, and the temperature difference between 850 and 500 hPa can all distinguish between SCW systems and non-SCW systems occurring over plains. Compared to non-SCW convective systems, SCW convective systems over mountains are more likely to occur in environments with less precipitable water, while SCW convective systems over plains are more likely to occur in environments with higher CAPE and stronger deep-layer wind shear.