Abstract: The temporal and spatial distribution characteristics of meteorological elements and aerosol in Dalian in December of 2015 when some air pollution events occurred were analyzed using the conventional meteorological observation data and air pollution indices from the Ministry of Environmental Protection of China as well as the simulation results from the regional air quality WRF-CMAQ (Weather Research and Forecasting-Community Multi-scale Air Quality) model.Under the air pollution weather conditions,how to carry out precipitation/snow enhancement operation was discussed as well.The results show that there are five air pollution events during December of 2015 in Dalian city,with a persistent time of 13 days,which is 41.94% of the total number of days in this month.The daily mean lowest visibility is 2.27 km.When the air pollution events occur,the temperature near surface increases slightly,and the atmospheric stratification is stable.Thus,it is suitable to choose aircraft or rocket to carry out the precipitation/snow enhancement operations in order to guarantee the catalyst to be sowed to the nucleation layer with the temperature of -15℃~-10℃.A certain amount of fine particles can reach up to the height of more than 3.00 km under the air pollution weather conditions.Therefore,the amount of catalyst should be properly reduced on the basis of the normal level when operating on the cold cloud target.Based on the analysis of a serious air pollution cases occurring in Dalian in December,it reveals that nitrate,ammonium,and sulfate are the main pollutant components,and the percentage of nitrate is the highest among these components,reaching 51.27%;it suggests that,except industrial sources and coal emissions,car emissions are also responsible for the pollution in Dalian city.