边界层低空急流导致北京PM_(2.5)迅速下降及其形成机制的个例分析  

A Case Study on the Rapid Cleaned Away of PM_(2.5) Pollution in Beijing Related with BL Jet and Its Mechanism

作　　者：廖晓农[1,2] 孙兆彬[2] 何娜[3] 赵普生[2] 马志强[2] 

机构地区：[1]中国气象局北京城市气象研究所,北京100089 [2]中国气象局京津冀环境气象预报预警中心,北京100089 [3]北京市气象台,北京100089

出　　处：《环境科学》2016年第1期51-59,共9页Environmental Science

基　　金：国家科技支撑计划项目(2014BAC16B04);国家级雾霾监测与预报团队项目

摘　　要：2015年3月17日18：00-23：00北京地区的PM2.5质量浓度快速下降,在此期间并未出现与冷空气活动相伴的强偏北风.本研究分析了导致空气质量迅速改善的原因,结果表明边界层急流起着关键的作用.随着边界层内偏南风速增大,大气的通风量增大,污染物浓度降低.急流发展也加大了边界层内水平风的垂直切变,从而导致湍流增强和混合层增厚.此外,3月17日20：00在混合层顶附近出现气旋性地转涡度,Ekman抽吸的方向为垂直向上,于是底层的污染物就被带到高空并随强劲的西南风输送到下游.边界层急流的发展与惯性振荡和大气的斜压性有关.The concentration of PM2.5 decreased very rapidly from 18：00 to 23：00 on 17^th Mar.2015 in Beijing area.No cold air bringing strong north wind influenced Beijing.The reason leading to the clean away of PM2.5 was discussed.The results showed that a boundary layer jet played a key role.The ventilation in the boundary layer went up with the enhancement of southwesterly wind speed,which was favorable to the dilution of pollution.Besides,the development of jet also caused the increase of vertical wind shear.As a result,the turbulence in the boundary layer became more obvious and the mixing layer height rose.Furthermore,the geostrophic vorticity at the top of mixing layer was positive at 20：00 on 17 Mar.It means that the direction of Ekman-Pumping was upward.So,the pollution near the surface was brought to upper levels and transported downstream by the jet.The development of boundary layer jet attributed to inertial oscillation and atmospheric baroclinicity.

关 键 词：PM2.5 污染 快速清除 边界层急流 惯性振荡 大气斜压性 

分 类 号：X513[环境科学与工程—环境工程]