Statistical Characteristics of Extreme Flash Rain and Environmental Parameters in Xiaogan City

Luo Jinfang; Wang Ziyao; Jiang Min; Hao Yinghui; Chen Yidan; Bao Zhongxiu; Wu Juntao

doi:10.16765/j.cnki.1673-7148.2026.01.010

Abstract：Based on ERA5 reanalysis data and the hourly precipitation data of 107 ground meteoro-logical observation stations in Xiaogan City from 2016 to 2022,the weather classification of extreme flash rain(EFR)in Xiaogan City is carried out,and the environmental circulation parameters and their anom-aly characteristics are analyzed.The results show that:(1)The EFR events in Xiaogan City occurred from May to August,most in June,followed by July and August.The average number of stations and rainfall intensity of EFR events increased with time.EFR in Xiaogan City is prone to occur at 06-12 and 23-01 the next day.The windward slope of Dabie Mountain and Dahong Mountain,the transition zone between the two mountains,and the dense area of lakes and rivers are densely populated with EFR sta-tions.(2)There are four weather types of EFR events in Xiaogan City EFR event:vortex shear type,frontal cyclone type,upper trough front type and weak forcing type.The favorable weather situation of EFR in Xiaogan City is that the upper air is a divergence area,the southwest jet around the strong sub-tropical high is in the convergence of wind speed in Xiaogan City,the east or north cold airflow forms a stable shear line with the southwest warm and humid jet,and the mesoscale low vortex moves to the vicin-ity of Xiaogan City or the cold shear is located in Suizhou City.(3)Xiaogan City EFR is closely related to water vapor content,water vapor convergence and low-level convergence,high-level divergence,and low-level vertical velocity anomalies.Abnormally abundant water vapor content and water vapor saturation in the boundary layer are necessary conditions for the generation of large-scale EFR.(4)The average PW of EFR events in Xiaogan City is 68 mm,and PW<54 mm is not conducive to the occurrence of EFR events.The average specific humidity at 850 hPa is 16 g·kg-1.The average LCL is 960 hPa,the aver-age CAPE is 2300 J·kg-1,the average K index,LI index and △T85 are 38,-4 and 23℃,and the av-erage vertical wind shear of 0-6 km is 9 m·s-1,which are favorable environmental parameters of EFR in Xiaogan City.