北京地区夏末秋初气象要素对PM_(2.5)污染的影响  

Effect of Meteorological Factors on PM_(2.5) in Late Summer and Early Autumn of Beijing

作　　者：蒲维维[1] 赵秀娟[1] 张小玲[1] 

机构地区：[1]中国气象局北京城市气象研究所,北京100089

出　　处：《应用气象学报》2011年第6期716-723,共8页Journal of Applied Meteorological Science

基　　金：城市气象科学研究基金项目(UMRF200805);北京市自然科学基金项目(8092010);公益性行业(气象)科研专项(GYHY200806027)

摘　　要：利用北京宝联站及北京上甸子大气本底站2006—2008年的7—9月PM_(2.5)连续观测资料以及北京市观象台的探空数据、海淀气象站的风廓线雷达和降水量等资料,对北京地区夏末秋初PM_(2.5)的质量浓度特征及其与气象要素的关系进行了统计分析。结果表明:城区站各月平均PM_(2.5)质量浓度明显高于郊区站,高空偏南气流的输送是造成城区及本底地区出现细颗粒物污染的主要原因。从地面风速来看,城区当北风和南风分别达到2 m·s^(-1)和3.5 m·s^(-)以上时能起到扩散作用;郊区在低风速的北风条件下也能起到扩散和稀释作用,而南风基本上对郊区的颗粒物无扩散作用。PM_(2.5)质量浓度在降水前后的清除量与降水量、初始质量浓度均呈正相关关系,城区及郊区的云下清除过程更多取决于降水前污染物的浓度,降水量作用较弱。当混合层高度突破1500 m时,垂直扩散对污染物的稀释扩散效果明显。The characteristics of PM2.5 concentration of Beijing and the relationship with meteorological factors are investigated,using the PM2.5 data of Baolian,Shangdianzi stations,sounding data,wind profiling radar data and precipitation data during July,August and September from 2006 to 2008.The results show that the average PM2.5 concentration of late summer and early autumn at urban station（Baolian） are significantly higher than that of rural station（Shangdianzi）.The prevailing southerly air flow of July to September of Beijing can transport the pollutants that generated in Tianjin,Hebei and Shanxi to Beijing.Due to the mountains blocking in the north,the pollutants are very likely to accumulate and form particle pollution. So the wind direction at 1500 m level has significant influence on PM2.5 concentration.The transport of pollutants by the southerly flow not only enhances the pollution level of urban,but also contributes to the fine particle pollution in regional background areas.The northerly flow is clean,and plays the important role of effective dilution and diffusion of PM2.5 in Beijing area.The ground wind speed plays different roles in urban and rural areas.The southerly and northerly wind could diffuse PM2.5 in urban area when the wind speed exceeds 2 m ？ s^（-1） and 3.5 m ？ s^（-1）,respectively.In rural area,the northerly wind could dilute and diffuse PM2.5 effectively,but the southerly wind has no effect of diffusion.The variation of PM2.5 concentration has positive correlation with precipitation amount and PM2.5 initial concentration.The precipitation amount and PM2.5 initial concentration in the process of below-cloud scavenging in urban and rural areas are different.As the most critical factor in the below-cloud scavenging process,the capture coefficient depends on the raindrop size,particle size and the raindrop falling speed.Owing to high PM2.5 concentrations in urban area,the capture efficiency of PM2.5 per unit time is greater than that of rural area under the same precipitation

关 键 词：PM2.5 风向 风速 降水 混合层高度 

分 类 号：X513[环境科学与工程—环境工程]