| With the rapid development of urbanization, the urban population and building density is increasing, and the business district buildings accompanied has become an integral part of city life. Due to the irrational architectural design and increased traffic, road traffic has become a major pollution source of modern city. Besides, the city ventilation is getting worse, which brings inconvenience to people’s travel.The heat and mass transfer between the ground and the atmospheric boundary layer directly affect the balance and uniformity of urban air system, which decides the outdoor thermal environment and air quality. Turbulence enables uniform distribution of contaminants within the mixed layer. Atmospheric mixing layer has deep relationship with the air pollution, for it can characterize the diffusion of pollutants in the vertical direction. this paper analyses the relationship between the near-ground meteorological data from 2011 to 2013 in Chongqing and the atmospheric mixing layer height from the angle of meteorological condition.Then it points out the dominant factors, and uses linear regression model to predict the mixed layer height.As a mountain city, Chongqing’s complex terrain is the talk of the crowd. For the planners, it adds a certain degree of difficulty. This article takes a commercial district buildings of Chongqing as research subjects, analyzes how the meteorological data at the average daily different times and seasons affect ventilation of the buildings and pollutant diffusion in the horizontal and vertical directions, then analyzes the relation between ventilation and pollutant concentration and atmospheric mixed layers height, at last proposes measures to improve air quality.The result of this study shows that:(1) In Chongqing, The atmospheric mixing layer height has a typical rising trend, with significant seasonal variation and day variation characteristic. Generally in spring and summer the height is significantly larger than that in autumn and winter, mixing layer height variation has relatively large fluctuations during the day, while in the evening it is stabilized, maintaining at about 100 meters. The atmospheric mixing layer height has positive correlation with the intensity of solar radiation and temperature, it has negative correlation with the relative humidity and pressure. At night, atmospheric mixing layer height and intensity of solar radiation and wind speed are positively correlated,it has little relationship with other meteorological parameters.(2) The capacity of urban ventilation has a significant seasonal variation and day variation characteristic in the commercial district buildings. horizontally, the spread of pollutant ventilation capacity and speed have a significant positive correlation with the wind speed, vertically, the spread of pollutant has positive correlation with the mixing layer height.(3) The pollutant diffusion has a significant seasonal variation and day variation characteristic in the commercial district buildings. Horizontally, winds play a leading role in the spread of pollutants. Vertically, the concentration of pollutants and the atmospheric mixing layer height has a negative correlation. When the atmospheric mixing layer height is large, it is conducive to the spread of pollutants,and the concentrations of pollutants is lower; When the atmospheric mixing layer height is small, such weather conditions will restrain the dilution and diffusion of pollutants, which lead to relatively high concentrations of pollutants on the ground.Given the rapid development of the commercial district, urban ventilation and pollutant dispersion is very important to people, This study suggests that we should unify the nearly ground meteorological parameters, increase the atmospheric mixing layer height to improve urban air circulation, reduce the concentration of contaminants in the surrounding buildings, and provide the suitable business plan for operator. |
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