Effects of meteorological factors on air quality above the third grade pollution in Beijing

The relationship between mean daily pollution indices of SO2,NO2,PM10 issued by Beijing municipal environmental protection bureau during 2001—2007 and synchronous meteorological factors such as ground and radiosonde data from Beijing observatory were analyzed by statistic method based on air pollution day of the third grade or that above the third grade in Beijing.At the same time,pollution sources of serious pollution day that mean daily air pollution indices of SO2,NO2,PM10 are the forth grade or above were discussed by backward trajectory analysis method(Hysplit-4 model).The results indicate that wind direction is one of main reasons leading to serious pollution of three pollutants.There are two layers or multi-layers inversion layer in pollution day.Inversion layer is lower and deeper,vertical convection,horizontal diffusion and wet deposition are very weak,so pollutants are difficult to be diffused and transported.They are accumulated on the ground,which comes into being serious pollution.The main source locations of heavy pollution weather are located in the southwest and southeast of Beijing,in Inner Mongolia and in the north of Hebei province.The results could provide scientific basis for heavy pollution alarm and forecast and integrated control systems in Beijing.