The temporal and spatial variation characters of local flow fields in Shanghai are simulated and investigated in this paper by using the 0800 BST observed meteorological element fields as the initial fields and by employing a 3-D terrain-following coordinate atmospheric meso-β scale hydrostatic model,in which some physical processes are considered in detail such as turbulent excharge,long-and short-wave radiation,condensation,evaporation and surface heat energy budget.Then the Eulerian advection-diffusion equation solved by the finite element method is used to simulate the distribution of sulphur dioxide concentration.The results show that the local flow fields exhibit a distinct diurnal variation,and are obviously affected by the sea-land temperature differences;the wind velocity in day time is greater than that at night and the wind rotates clockwisely from daytime to night;under the condition of unstable stratification the air pollutants from elevated point source can be transported to the ground leading to an increase in the surface SO₂ concentration.