Simulation Study On The Characteristics Of Air Boundary Layer In Le Shan City

As the urbanization and industry progresses, environment protection has become the prior consideration in construction. In different weather condition, the land pollution concentration caused by the same pollution source can range from tens of times to hundreds of times, the reason of which is the dispersing and diluting ability of air would change greatly as to different weather conditions. The dispersion of air pollutants happens mainly in the boundary layer of air, therefore, the relative characteristics of air boundary layer has determined the dispersion ability of air pollutants. Currently, the study of air boundary has turned into the uneven or complex underlaying surface, like the underlaying surface boundary layer with unevenly distributed characteristics, the air boundary layer of modern urbans.The city is the centre of human activities, the studied region has dense population and construction, where the underlaying surface of air is very active and complex. With the concentration of industry and business, and busy transportation, the consuming amount of onflow is the biggest. Besides, there are a lot of heat and steam released by human, and a lot of dust and various trace gases and air pollutants are released into the air, therefore, the transportation and dispersion of air above the city land is a typical multi-dimensional, multiscale dispersion problem.As to a certain region, the distribution pattern of air pollutants through lifting, cleaning and transportation by weather factors not only has a direct relationship with the pollution source and scale, but also has a certain relationship with the weather field. As the boundary layer is strongly affected by underlaying surface, a special wind field and temperature field are caused horizontally and vertically, plus, the boundary layer is affected by bottom architectures and water body, the pollutant dispersion pattern is very complex.This thesis chose Le Shan city group which has an underlaying surface with complex parameters as a represent, and the MM5 model is adapted to simulate the air dispersion factors. Through the distribution pattern of weather field, the dispersion pattern of pollutants was analyzed, which provided a reference and suggestion for environment planning decision-making and air pollution controlling.