2016年冬季北京地区一次重污染天气过程边界层特征

利用中国气象局地面常规观测资料、微脉冲激光雷达（MINI-MPL）、风廓线雷达资料、生态环境部大气成分等资料，对2016年12月16~21日京津冀多地污染过程的生消特征、与气象条件的关系以及边界层的结构特点进行了分析.结果表明：大气处于静稳状态，低层大气盛行偏南气流，大气湿度持续增加，加之北京三面环山不利于污染物扩散的特殊地形是造成北京此次严重空气污染的重要因素.重污染期间，污染物主要聚集在800m高度以下，严重污染时，污染物高度甚至仅有400m左右.风廓线雷达反演风场显示：2次PM_2.5浓度快速上升阶段低层伴随持续偏南风或偏东风.污染过程期间，逆温结构明显，两次污染快速发展阶段恰好出现在两次逆温最强时段.此次污染天气过程，激光雷达退偏振比总体小于0.25，反映污染主要是人类活动产生气溶胶，前期以一次排放颗粒物为主，后期以二次转化颗粒物为主.退偏振比污染过程前期呈明显日变化特征，且白天退偏比比夜间高.

Analysis of boundary layer characteristics of a heavily polluted weather process in Beijing in winter 2016

The characteristics of the pollution process occurred in Beijing, Tianjin and Hebe province during 16~21 December 2016, the relationship between the pollution process and meteorological conditions were studied by using the data of routine ground observation, Micropulse Lidar (MINI-MPL), wind profiler radar, and atmospheric composition of the Ministry of Ecology, etc. of China Meteorological Administration. The static state of the atmosphere, the prevailing southerly airflow in the lower atmosphere, the continuous increase of atmospheric humidity, and the special terrain surrounding the mountains on three sides of Beijing which was not conducive to the diffusion of pollutants were the important factors causing the serious air pollution in Beijing. During the period of heavy pollution, the pollutants mainly accumulated below 800 meters. When the pollution was serious, the height of pollutants was only about 400 meters. Wind profiler radar retrieved wind field showed that the low level of PM_2.5 concentration rose rapidly during two periods, accompanied by persistent southerly or easterly winds. During the pollution process, the inversion structure was obvious, and the rapid development of two pollution stages occured in the two periods of the strongest inversion. In this polluted weather process, the depolarization ratio of lidar was less than 0.25, reflecting that the pollution was mainly caused by human activities. In the early stage, primary particulate matter was the main pollutant, and in the later stage, secondary transformed particulate matter was the main. The depolarization ratio showed obvious daily change in the early stage of pollution process, and the depolarization ratio was higher in daytime than at night.