Analysis of Hailstone and Thunderstorm Characteristics in Tianjin during Recent Years

Based on the hailstorm and thunderstorm data from 13 meteorological observation stations, this article analyzes the spatial and temporal distribution characteristics of hailstorms and thunderstorms in Tianjin. Three main conclusions are reached from the results of this study: (1) During the last 20 years the annual mean hailstorm days of 13 meteorological station in Tianjin is 13. The total number of hail days in Jixian district is the most (105 days). The hailstorm weather often appears in spring, summer and autumn, from March to September mostly. (2) Jixian, Jinghai and Hangu districts have more thunderstorms than other regions in Tianjin. The thunderstorms which form in the northwest have the highest frequency. The influence of southwest thunderstorms has increased gradually in recent years. (3) There are four kinds of synoptic systems which can cause the formation of hailstorms and thunderstorms in Tianjin. They are high level vortex, upper trough, shear line and northwest air current.