NUMERICAL EXPERIMENT ON THE EFFECT OF URBANIZATION UPON SUMMER LAND-SEA BREEZES IN THE COASTLAND OF GUANGXI

The 2003-006 observations were utilized to analyze the surface characteristics of summer land-sea breezes along the coastland of Guangxi and the Weather Research and Forecast model was applied to simulate the breeze structure on August 1-2, 2006. Results show that 1） the intensity and distributions of the breezes reproduced from improved urban underlying surface were close to observations. In the daytime the coastwise urban band was a convergent belt of sea breeze, corresponding to the centers of torrential rains; in the nighttime hours the surface of the Gulf of Tonkin （the Vietnamese name） or the Northern Bay （the Chinese name） acted as a convergent zone of land breezes, likely to produce convective cloud cluster; 2） the experiment on urbanization showed the heat island effect enhancing （weakening） the sea （land） breeze development. Furthermore, the heat island effect mitigated the atmospheric cooling via radiation over the cities in the night, weakening sinking motion correspondingly, thereby suppressing the dominant factor responsible for the steady development of temperature inversion. As a result, the inversion vigor was reduced greatly, but nevertheless no strong effect of the decreased subsidence was found upon the inversion height.

The 2003–2006 observations were utilized to analyze the surface characteristics of summer land-sea breezes along the coastland of Guangxi and the Weather Research and Forecast model was applied to simulate the breeze structure on August 1–2,2006.Results show that 1) the intensity and distributions of the breezes reproduced from improved urban underlying surface were close to observations.In the daytime the coastwise urban band was a convergent belt of sea breeze,corresponding to the centers of torrential rains;in the nighttime hours the surface of the Gulf of Tonkin (the Vietnamese name) or the Northern Bay (the Chinese name) acted as a convergent zone of land breezes,likely to produce convective cloud cluster;2) the experiment on urbanization showed the heat island effect enhancing (weakening) the sea (land) breeze development.Furthermore,the heat island effect mitigated the atmospheric cooling via radiation over the cities in the night,weakening sinking motion correspondingly,thereby suppressing the dominant factor responsible for the steady development of temperature inversion.As a result,the inversion vigor was reduced greatly,but nevertheless no strong effect of the decreased subsidence was found upon the inversion height.