中文摘要：

随着工业化发展,近十年来珠江三角洲地区空气质量有恶化的趋势.在冷锋过境前常常由于地面受低压控制,近地面出现静小风的情况导致污染物在这一区域的滞留加剧.本文选取这样的天气背景来模拟珠江三角洲地区的环流形势和污染物扩散,模拟试验应用加入扩散方程的MM5模式进行.模式模拟时间（北京时）从2008年10月21日08时到2008年10月23日08时.共设计两个模拟试验,控制试验和敏感性试验.两个试验中置入污染点源资料,包含珠三角地区的3179个污染点源的源高和源强.两个试验的区别在于设计了不同的区域网格距,控制试验最细2 km,而敏感性试验最细1 km.模拟结果表明提高模式分辨率主要明显优化风场的模拟效果,而气象要素模拟效果的提高又间接影响着污染物的传输与扩散.综合各方面因素说明高精度的分辨率是有利于提高模式模拟效果的.

英文摘要：

In the past decade,the air quality of the Pearl River Delta（PRD）became worse due to industrialization. Before cold front the surface is controlled by the low pressure,which causes small wind speed near the ground and air pollutant accumulation.In this paper,the weather environment before cold front was simulated by the MM5 that a diffusion equation was added to model the air circulation and air pollutant diffusion in the PRD.The simulation time is 48 hours from 21/10/2008 08：00 to 23/10/2008 08：00 （the Beijing local solar time）.There were 3179 pollutant point sources including the height and the intensity of pollutant source taken into account in the finer domain.Two simulation experiments were conducted,the control experiment use the fine mesh scale 2 km,the sensitive experiment is 1 km.The simulation results show that the wind field and the air pollutant distribtion are op-timized when the model resolution is changed to be fine,which suggeets that the high resolution mesh scale is in favor of improving the simulation of pollutant diffusion.