珠江三角洲秋季典型气溶胶污染的过程分析

为了解大气中各物理和化学过程对气溶胶浓度的贡献情况,利用Models-3/CMAQ模式系统对珠江三角洲(以下简称珠三角)秋季典型气溶胶污染进行研究.模拟时间是2012年10月,期间珠三角主要受高压系统的控制,在17日冷锋过境前后高压天气形势发生转变,风向从东北风转为偏东风.结果表明,珠三角秋季PM2.5浓度呈现西高东低的水平分布特征,随着高度的上升浓度高值中心也向西南方向偏移;受大气边界层高度的影响,陆地上PM2.5输送高度呈现白天高夜晚低的变化特征;过程分析结果表明源排放,水平输送和垂直输送是影响近地面PM2.5浓度变化的主要过程;本地污染物排放是城市中心(广州站)PM2.5浓度升高的主要原因,而在下风向位置(江门站)外来污染物的水平输送过程是PM2.5的最主要来源.

Process analysis of typical aerosol pollution in autumn over Pearl River Delta,China

For the purpose of discerning the contributions of various physical and chemical processes to the aerosol concentration in the atmosphere, Models-3/CMAQ modeling system has been used to study the typical aerosol pollution in autumn over Pearl River Delta (PRD), China. The simulated period was October 2012, when PRD was under the control of a high-pressure system. The wind direction switched from north-east to east when a cold font passed PRD on October 17th. It was found that PM2.5 concentration in the western part of PRD was higher than that in the eastern part, and the region of the highest concentration extended southwestward with increase in height. Influenced by planetary boundary layer height, PM2.5 was transported to higher altitudes in the daytime than in the nighttime on land. The results of process analysis showed that emission, horizontal transportation and vertical transportation were the most important processes in the variations of PM2.5 concentration near land surface. Local pollutants emission was the most important factor of rising concentration in city center (Guangzhou site), while horizontal transportation of non-local pollutants was the major source of PM2.5 in the downwind area (Jiangmen site).