北京地区大气温湿廓线对气溶胶垂直分布的影响

目的分析北京地区大气温湿廓线对气溶胶垂直分布的影响。方法利用北京地区2017年9月至2018年8月每日两次(08时和20时)的气象探空、地面PM_(2.5)浓度和气溶胶激光雷达消光系数资料,分析不同污染条件下大气温湿廓线与气溶胶消光系数廓线的关系。结果地面PM_(2.5)浓度和210m气溶胶消光系数的相关系数达到0.77。春季、秋季和冬季污染条件下的近地面消光系数约是清洁条件下的5倍,夏季污染条件下的近地面消光系数约是清洁条件下的3倍。相比清洁条件下,污染条件下各季节的大气温度垂直递减率偏小,并且低层大气相对湿度偏大。结论大气温度廓线代表大气层结稳定性,影响气溶胶的扩散高度,而相对湿度廓线与气溶胶吸湿增长密切相关,两者对气溶胶消光系数的垂直分布都有重要影响。

Effects of Atmospheric Temperature and Humidity Profiles on Vertical Distribution of Aerosols in Beijing

Objective To analyze effects of atmospheric temperature and humidity profiles on the vertical distribution of aerosols in Beijing. Methods The relationship between atmospheric temperature and humidity profiles and aerosol extinction coefficient profiles under different pollution conditions was analyzed with meteorological sounding, ground PM2.5 concentration and aerosol lidar extinction coefficient data twice (08:00 and 20:00) a day from September 2017 to August 2018 in Beijing. Results The correlation coefficients of ground PM2.5 concentration and aerosol extinction coefficient at 210 m was 0.77. The extinction coefficient of near ground in spring, autumn and winter was about 5 times of that under clean conditions; and that under summer pollution was about 3 times of that under clean conditions. Compared with the clean conditions, the vertical decline rate of atmospheric temperature in each season under the pollution conditions was smaller; and the relative humidity in the lower atmosphere was larger. Conclusion The atmospheric temperature profile represents the stability of atmospheric stratification and affects the height of aerosol diffusion. The relative humidity profile is closely related to the aerosol hygroscopicity growth. Both have important effects on the vertical distribution of aerosol extinction coefficient.