Abstract: A simulation study of a heavy fog process over Beijing metropolitan area in November,1999,was conducted by use of a1-D boundary layer model considering the soil plant atmosphere interaction with high vertical resolution.Comparative analysis between the simulation results and the corresponding field observation data,for the heavy fog lasting from 21:00,November 22 to 09:00,November 23,shows that the charact eristics of the boundary layer structure associated with the fog can be reproduced by the model basically,as well as the occurrence,dissipation and sustainable time.The results also reveal some common features for the heavy fog,for example,the temperature is almost the same in vertical in fog,and the inversion is over the top of the fog,where the relative humidity is decreasing very rapid verticaly,a relative maximum wind velocity appears whereas the wind speed is smal in fog,and there exists the greater gradient for most physical variables.Further more,the results suggest that the fog was caused jointly by advection and radiation processes since those processes were included in the model.It ought to be pointed out that there are some limitations in the fog simulation,since the aerosol effect and the collision between the cloud particles were not considered in the model,as well as the radiation ef fects of rain droplet,water vapor and CO2,and the dynamic forcing is unchanged in simulation period,which causes the discrepancies between the simulation results and the observation,especially with the much denser isograms for temperature,relative humidity,and so on,which should be improved in our future research.