Abstract: The effects of air pollution prevention and control and the role of meteorological conditions during the APEC meeting in Hohhot were analyzed,based on the upper and surface meteorological conventional observations over the Eurasian region,the NCEP (National Centers for Environmental Prediction) reanalysis data,and the monitoring data of pollutant concentration and daily AQI (Air Quality Index) from the environmental monitoring central station of Inner Mongolia Autonomous Region from October 14 to November 13,2014.The results show that before air pollution prevention and control measures were carried out in Inner Mongolia Autonomous Region,the number of days with the light and upper levels of air pollution in Hohhot during October 14-25,2014 is 37.5% higher than that during the same period of 2013.With the measures taken on October 26,the concentrations of contamination particulate matter decrease significantly,and the number of days with the light and upper levels of air pollution in Hohhot decreases by 100.0% in 2014 than that in the same period of 2013.There are four times of obvious cold air activities in North China during the period of air pollution prevention and control.Strong cold advection flows intrude to the ground from the middle and upper levels,and wind speed increases in Hohhot,resulting in favorable meteorological conditions for the diffusion of air pollutants.The four times of cold air activities all correspond to the smallest values of AQI in Hohhot.Therefore,the air quality in Hohhot achieved excellent level during the APEC meeting,which is probably due to the significant effects of government prevention and control measures based on meteorological conditions.

Key words: APEC meeting, Atmospheric pollution, Air Quality Index (AQI), Prevention and control, Cold air