The Circulation And Boundary Layer Characteristics Of Air Pollution In Wuhan, China

It is concerned for the atmospheric environmental issues because of the rapid development of the city. In this paper, the pollutant concentration data in Wuhan, NCEP/NCAR reanalysis data, L-band radar data and ground observations in 2004-2013 are used to classify circulation types, and analyze the spatial and temporal characteristics and structural features of the boundary layer of the haze in Wuhan by the Lamb-Jenkinson atmospheric circulation classification scheme. It is explored to the changes of the boundary layer and the effects of local circulation in the process of haze pollution by WRF model.It’s explored to the major types, their catalogues and the relationship between the atmospheric circulation and the concentration of pollutants from 2004 to 2013 in Wuhan by Lamb-Jenkinson scheme and subjective analysis.The results show that the major types are A, AE, E, SE, C and NE in haze day and it’s different in every season. The four major types(A, SE, E, AE)are relevant to severe air pollution in Wuhan. The severe air pollution occurred easily on the control of anticyclone or easterly. The impact of the circulation types on the concentration of air pollutants is different.In this study of air pollution and extinction process, we used WRF model. Because of Wuhan and the surrounding areas surrounded by mountains and the terrain significantly affecting the circulation, heat difference in the underlying surface is one of the reasons for formation of local circulation. The wind from the mountains to the plains in the night and the northeasterly and southeasterly mountain wind converge with the northwesterly and easterly wind in Wuhan and the surrounding areas. The formation of air convergence and vertex makes continuous accumulation of pollutants and cause the air pollution. Local circulation and air convergence zone change over time and disappeared during the day. The location of local circulation and air convergence is different because of the strength of the mountain and valley winds, northerly and easterly winds. When the northerly wind is stronger and cold air is coming, local circulation and air convergence disappear. They have the certain regularity and the life-cycle changes in the stable atmospheric boundary layer. When the haze pollution occurs, combined with model results and observations, there are the more stable atmosphere, stronger and thicker inversion layer, and thin mixed layer thickness. The top is dry, the bottom is wet in the vertical humidity and the humidity increases with height above 1km. The lower surface wind speed or calm wind, less vertical wind shear near the ground and above all cause pollutants to accumulate easily.