Dynamical and Thermodynamic Process of Thunderstorms Triggered and Merged by Sea-Breeze Convergence Lines Based on VDRAS Data

VDRAS(Variational Doppler Radar Analysis System) data whose temporal resolution is 12min,horizontal and vertical resolutions are respectively 3km and 1km or so.Using radar ,intensive AWS(automatic meteorological stations) data as well as VDRAS data,the dynamical and thermodynamic processes of thunderstorm systems that are impacted by sea-breeze convergence lines are investigated by analyzing the two cases triggered by pure sea breeze convergence line and by the merged sea breeze convergence line and existing thunderstorm system. The results showed that: 1) When the environmental wind system is very weak, the moving sea-breeze of Tianjin coastal sea breeze into the inland is about 15-18km.h^-1 and after the leaving of sea breeze, temperature there decreases and humidity increases. 2) The sea-breeze convergence lines cooperates with the surface highly unstable region, triggering and strengthening the thunderstorm system, so that developed moisture and cold sea breeze convergence line in local instable region on ground the thunderstorm warning can be 2h in advance. 3)Thunderstorm cell forms near the sea-breeze convergence line, which corresponds to the mesoscale vertical circulation in the frontal surface(to the sea side)of the tilting sea breeze front.4)After sea-breeze convergence line mergers with the thunderstorm, the severely development of the thunderstorm is attributed to the accumulated water vapor near the sea breeze and the large zone of convergent updraft.