北京城区夏季静稳天气下大气边界层与大气污染的关系

Relationship between Atmospheric Boundary Layer and Air Pollution in Summer Stable Weather in the Beijing Urban Area

利用ALS300激光雷达系统测量的信号,根据Fernald方法反演的气溶胶消光系数的最大突变即最大递减率的高度确定大气边界层高度.结果表明:在夏季静稳天气下,大气边界层平均高度为600 m,其中晴天为1 000 m,雾天为700 m,阴雨天在200～300 m之间.静稳天气下的大气边界层不容易被有效突破,故不利于大气污染物扩散.大气边界层高度对污染物浓度影响显著,没有降雨时,大气边界层降低(400 m),大气污染加重,在城区宝联站监测的ρ(PM2.5)近200μg/m3,在大气本底站———上甸子站近150μg/m3;如果伴有降水,大气边界层高度升至600 m,大气污染则减轻,2个站点观测的ρ(PM2.5)均降至50μg/m3以下.静稳天气下的大气污染呈现区域性特点.

Abstract： Aerosol extinction coefficients were retrieved from a signal obtained by the ALS300 lidar system and application of the Fernald method. The atmospheric boundary layer （ABL） height was determined according to the maximum inflection point of the inversed aerosol extinction coefficient （i. e. the height of the maximum rate of decline）. The results showed that during stable weather in summer in Beijing, the average ABL height was 600 m. On sunny, foggy and cloudy days, the heights of the ABL were 1000 m, 700 m and 200-300 m, respectively. When stable weather occurs, it is very difficult for the pollutants to be diffused from the atmospheric boundary layer. The height of the atmospheric boundary layer significantly affects the pollutant concentration in the air; the higher the ABL lifts, the lighter the pollutant concentrations are. When there was no rain, the air pollution increased with decrease of the ABL down to 400 m. The concentration of PM2.6 was up to 200 μg/m3at Baolian （urban） station and 150 μg/m3 at Shangdianzi （background） station. On rainy days, the atmospheric boundary layer increased to 600 m. As a result, the air pollution decreased and PM2.5was only 50 μg/m3. Air pollution exhibited a regional distribution during stable weather days.