NUMERICAL SIMULATION OF THE 3-D STRUCTURE OF SEA BREEZES OVER THE HAINAN ISLAND
WANG Yu-hui;MIAO Jun-feng;CAI Qin-bo;College of Atmospheric Sciences,Nanjing University of Information Science and Technology;Hainan Meteorological Observatory;
To study the three-dimensional structure of sea breezes and its diurnal evolution,a non-hydrostatic mesoscale model WRF,version 3.5,is used to simulate a typical case of sea breeze day on April 12,2012 over the Hainan Island.Compared with observational data,the results show that the evolution and characteristics of sea breezes can be reasonably simulated by WRF.Sea breezes over the Hainan Island begin later than other regions in China.Sea breezes occur in the afternoon,develop intensely during 15:00—18:00 LST and change into land breezes at about 21:00 LST.Sea breezes in the north and south stay longer and develop stronger than those in the east and west.At 18:00 LST,two significant convergence lines are located in the north and northwest to the island which is the urban area,with a large convergence zone in the centre.As the convergence lines are mainly distributed in urban areas over the islands,it is easy to gather pollutants and cause hazy weather.Horizontally,owing to the effect of an onshore background flow,sea breezes in the south penetrate approximately 80 km,which is far more than those in other parts of the island.Vertically,the mountains in the southwest play a role in lifting and intensifying sea breezes and the dynamic effect of topography contributes to the development of land breezes in the evening as well.In addition,the return current is weakened by the effect of topography and the onshore background flow and can be shown clearly only in the north and east.Therefore,the structure of sea breezes is the most complete in the eastern and northern plain areas.Sea breezes in the east can reach the height of 1.8 km,and that in the north can extend as far as 2.5 km.The potential temperature over Hainan Island enhances significantly since 12:00 LST,and the gradient near the coastline increases substantially,which generates sea breezes.The gradient reaches the maximum at 15:00 LST in the vicinity of a sea breeze front and sea breezes develop intensely.The water vapor mixing ratio increases sharply during 15:00-18:00LST,and the accumulation of ample amount of water vapor is at the back of SBF.Severe convective weather tends to occur in the south of the mountain and northeast to the island.
【CateGory Index】： P732.1
【CateGory Index】： P732.1