Research On Characteristics Of Sea-land Breeze Along Coastal Jiangsu Province And Its Strong Convective Process Related To Sea Breeze Front

Using conventional observation data, ECMWF Era-interim dataset, observed data of three wind towers in Jiangsu Province, assimilated precipitation data and the results of numerical simulation, sea/land breezes(SLB) and sea-breeze fronts(SBF) in Jiangsu coastal regions are studied and analyzed. Then sea-breeze front events are divided into two categories:one is caused by the westward extending of subtropical high from sea; the other is caused by continental high systems entering the sea from inland. There are more strong convective systems occurring for the second type of SBF. The research results show that:1) According to wind data from observatory stations, the occurrence frequency of sea/land breezes (SLBs) increases with the distance closing to the coast. The appearance of SLBs is more often during summer compared to other seasons, and sea breezes are usually stronger than land breezes.2) Sea breeze fronts (SBF) are characterized with remarkable wind velocity gradient, big temperature gradient and strong vertical ascending motion. Wind from the sea surface reduces its speed immediately after landing on the coasts, and companied with temperature increasing rapidly and the pressure gradient along coast line. So around the SBF there is a strong vertical ascending motion area due to convergence of horizontal wind. Sometimes the thickness of the strong ascending motion can be higher than 3 km. Analysis of wind tower data shows that the sea breezes are more concentrated in wind direction than land breezes.3) The difference between SBF Type 1 and SBF Type 2 is not only the difference in circulation background, but also in the possibility of triggering strong convection. The type I SBF is with less strong convection as the subtropical high is strong, and the type II SBF is easier with strong convective systems as the continental high flowing by baro-clinic systems.4) WRF model shows that two types of SBFs can be simulated in details for their spatio-temporal evolution with hourly output. During the type II case with strong convection occurs, the environmental CAPE is released in two hours, while the other type I case without strong convection, the environmental CAPE shows very small decrease. In both cases, radar echoes and vertical ascending motion are all small areas, which indicate that the strong convective rainfalls are local events.