东莞地区冬季大气边界层结构对PM_(2.5)影响的观测研究

The Influence of Atmospheric Boundary Layer Structure on PM_(2.5) Concentration Over Dongguan Region

利用2013年12月在东莞地区开展大气边界层观测试验得到的垂直风温资料和逐时PM2.5质量浓度资料,研究了东莞地区大气边界层结构对PM2.5质量浓度的影响的。结果表明:在大陆冷高压控制下,东莞地区的边界层结构演化非常典型,而东莞地区冬季PM2.5污染事件通常由冷气团南下的天气形势引起。在PM2.5污染过程中,日平均边界层高度往往不足600 m,较低的大气边界层高度使得PM2.5持续累积,夜间稳定边界层高度约为100 m使得夜间出现PM2.5质量浓度峰值。东莞地区的垂直风场存在显著的三层结构,较小的底层风速有利于PM2.5聚集在边界层内难以扩散,而高度较低的小风中层使得PM2.5污染物进一步被压缩在大气底层,加剧了地表的PM2.5污染程度。在冬季大陆冷高压控制下,在PM2.5污染过程中,东莞逆温结构多发,低空逆温层底约在700m,而且厚度和强度都较大,夜间常见贴地逆温,且厚度约为100 m,持续稳定存在的较低的逆温层导致的稳定层结是造成PM2.5污染的重要原因。

Based on the observational wind profile data,temperature sounding data and the hourly PM2. 5concentration data from the boundary layer observation experiment in Dongguan region during December2013,the influence of atmospheric boundary layer structure on PM2. 5concentration in Dongguan region has been discussed. It was found that the PM2. 5air pollution weather occurred in winter of Dongguan region was mostly influenced by the weather system of weak southward moving cold air. Under the control of continental cold high,the evolution of atmospheric boundary layer structure was very typical. During the PM2. 5air pollution situation,the daily mean height of mixing layer in daytime was lower than 600 m sometimes,the pollutants accumulated persistently and its concentration increased gradually with the low atmospheric boundary layer height. The height of stable boundary layer in nighttime was about 100 m. By reason of the law height of stable boundary layer in nighttime,the peak PM2. 5concentration occurred in nighttime. The vertical wind field of Dongguan region had obvious three layer construction. The lower layer with slow wind speed made the pollutants accumulate inside atmospheric boundary layer and hard to diffuse. The middle layer which appeared in a very low height with slow wind speed gave rise to the pollutants be compression inside lower layer further. Under the control of continental cold high in winter,the inversion layer appeared frequently in Dongguan region during PM2. 5air pollution situation. The height of low altitude inversion base was about 700 m with a large thickness and intensity; the surface inversion occurred in nighttime frequently with a thickness of about 100 m.