In this study, the scenario for a numerical modeling of the fine grid scale air dispersion phenomena was proposed and an analysis of the special event which was occurred on September 3, 2002 was performed using by a coarse grid prognostic meteorological model, a fine grid diagnostic meteorological model and a fine grid air dispersion model. Based on the results, we found that the local circulations, like as land-sea breeze, should be seriously considered for evaluating the high PM10 concentration event and for making the reduction policy of the major air pollutant emissions in Ansan area.