Analysis on Environmental Characteristics of Hail Weather in the Midsummer Season in Shanghai

Zhao Yuanming; Qi Liangbo; Chen Saihua

doi:10.16765/j.cnki.1673-7148.2026.02.003

Abstract：Based on the surface and upper-air observations from July to August of 2003-2022 as well as the ERA5 reanalysis data,the environmental characteristics of midsummer hail cases in Shanghai are analyzed.The results demonstrate that,in midsummer season,the atmosphere always shows moist and unstable stratification,and the occurrence of deep moist convections(DMCs)mainly depend on the triggering of meso-scale convergence lines.Although the three typical hail situations(subtropical high edge type,subtropical high control type and upper-air trough type)are different from each other,their common features are the large-value combination of CAPE and 0-6 km vertical wind shear(SHR6),the cold advection or cold tongue at 500 hPa,and the warm center or warm-wet advection at lower levels.In midsummer season,when hail occurs in Shanghai,the median WBZ is 4343 m,which is significantly higher than the median WBZ height threshold in other regions of China.The median temperature differ-ence between 850 hPa and 500 hPa is 26℃,and the 0-6 km vertical wind shear is weak.The Signifi-cant Hail Index(SHIP)has certain indicative value for hail forecasting,but the threshold applicable to the Shanghai area is significantly lower than the commonly used threshold,approximately 0.2.Compared with other convective weather conditions(thunderstorms and short-time severe precipitation)in the same period,the sounding of hail weather shows the characteristics of drier and colder middle layer,and larger potential instability.