The Study On Numerical Simulation Of A Persistent Pollution Event In Beijing And Its Surrounding Regions

The air pollutant of the first importance in China is PMI0 at present instead of SO₂ in the past, and the quality of the atmospheric environment has appeared to be of the territorial feature. Presently in order to develop the cities, the main problem facing is that the concentration of PM 10 is steady and high, and it has typically regional and complex characteristic in Beijing and its surrounding regions. As a city holding Olympic Summer Games in 2008, the concentration of PM10 in Beijing is correlative with Green Olympic Games. So based on the consecutive monitor to the air pollutant, the regional air pollution is studied by means of numerical model in Beijing and its surrounding regions, and consequently provides instructor to the government.In this paper, the Fifth-Generation Mesoscale Model (MM5) and the air quality model Models- /CMAQ were combined to simulate and analyze an air pollution event occurring in Beijing and its Surrounding Regions from October 7th to 13th, 2002. Firstly an analysis was made of the developing feature of this air pollution event by means of the daily air pollution index. The results indicate that the air pollution event had a regional characteristic. Secondly, based on the MICAPS meteorology data and the Fifth-Generation Mesoscale Model (MM5), the weather conditions during the event were analyzed and simulated. The results show the formulation mechanism and development process, and indicate that the pollution event was resulted from combined influences of local pollution sources and emissions out of Beijing in special weather conditions. Meanwhile, using the backward trajectory model (HYSPLIT) in NOAA, the location and movement routes of pollution which affected Beijing were analyzed. The analyses based on the HYSPLIT trajectory model indicated that the air pollution of regions surrounding Beijing could have an obvious effect on Beijing, and the emissions from south surrounding cities were important factors which gave birth to pollution in Beijing. Lastly using the combination of the MM5 and Models-3/CMAQ, the variation of surface PM10 was calculated and compared with the observations during the period in Beijing and its surrounding regions. Model results indicate that the simulated concentration levels and their daily variation are in good agreement with the observations in the period. Further the source contributions of PM10 from the regions surrounding Beijing are studied. Meanwhile, analyzes and discusses the source contribution ratio of PM 10 from the different emissions and the ratio of local pollution sources and emissions out of Beijing. The results show that besides the influence of the Beijing local emissions, the emissions out of Beijing also have a great effect on the surface concentration of Beijing. During the pollution event, the local emissions from Beijing give about 58.4% of contributions, and the sources from the surrounding regions contribute about 41.2%.