Abstract: This study were carried out based on the daily air quality data, ground meteorological data, NCEP / NCAR reanalysis data and Lband radar sounding data of Wuhan city in November, 2013. The WRF model was used to simulate the change of local meteorological conditions in the air pollution process, and the influence of boundary layer structure and local flow in the whole process of pollutant generation and elimination were also discussed. The results show that: (1) when the background largescale circulation is strong, the influence of the local flow caused by the terrain on pollutant diffusion will be weak in Wuhan; on the contrary, when the background largescale circulation field is weak, the local flow caused by the topography is found to have a large contribution to the diffusion of pollutants in Wuhan. Since Wuhan is surrounded by mountains on three sides, the impact of the topography on the flow field is obvious. When the background circulation field is weak, wind field is dominated by mountain wind at night and by valley wind in the daytime. At night, mountain winds, northwest airflow and easterly airflow converge in Wuhan and the surrounding areas, forming a convergence zone of airflow, which has been continually contaminating Wuhan. (2) When air pollution occurs in Wuhan, the humidity of earth surface is high, and the boundary layer is dry in the high altitude and wet in the low altitude. Moreover, the boundary structure features warm and dry air with easterly breeze which contributes a lot to the continuous accumulation of pollutants and the formation of heavy pollution process.

Key words: local flow, boundary layer structure, numerical simulation