Diagnostic Analysis And Numerical Experiments Of The Sea-land Breeze Associated With Rainstorm

Firstly, by using 5 years (2005-2009) hourly observation data including air surface temperature, sea-level pressure and surface wind field of 5 stations in the area of Qinhuangdao, the statistical analysis of the sea-land breeze in Qinhuangdao is investigated. We get sea-land breeze direction, and the diurnal variation characteristics of air surface temperature, sea-level pressure, sea-land breeze velocity and direction. Based on these works, with the precipitation data in 2009 summer of Qinhuangdao and Funing station, the diagnostic analysis of sea-land breeze and rainstorm is carried out. Finally, using the two-dimensional non-hydrostatic equation model including the latent heat of condensation of water vapor, we carry out experimental series by changing 5 different heating field of sea-land surface and 5 different coefficient of latent heat of condensation. The main conclusions are as follows:1. The appearance time of the maximum value of sea breeze field and the minimum value of sea level pressure field lag behind that of the highest surface air temperature 0 and 0～4 hours respectively, in addition, the latter still lag behind the former 0～4 hours. Both of the strongest sea breeze and the low sea level pressure are caused by the high surface air temperature field, and sea level pressure field adapt to the surface wind field.2. The maximum values of sea breeze occur in spring, while land breeze in winter or spring, and the latter is weaker than the former.3. Before the rainstorm appeared relatively high temperature sustaining 1～3 days, sea breeze with biggish speed maintaining for 1～4 days and low pressure lasting 1～4 days.4. Whether the centre position of sea and land surface heating become closer and farther, or land and sea-land surface heating filed with two centre, sea-land breeze circulation always occurs. (1)When the centre of sea and land surface heating field near and away from the coast, the centre of sea-land breeze circulation is also near and away from the coast accordingly, besides, surface wind as well as vertical velocity increase and decrease simultaneously, the sea-land breeze circulation also strengthen and weaken, respectively.(2)When land and sea-land surface heating field with two centre, sea(land) breeze circulation extends to the land(sea) surface, neither surface wind and vertical velocity corresponding to the former or the latter decreases, and the latter is weaker, so dose sea-land breeze circulation.The study provides the solid foundation to formation and development of rainstorms and sea-land breeze in Qinhuangdao, and supplies its forecasting with modified clues. Besides, the research deepens the knowledge of sea-land breeze circulation over the group of coastal cities and high-urbanized areas, has high significance to forecast of sea-land breeze circulation.