北京城区污染过程气溶胶光学特性观测分析

Observation and analysis of aerosol optical properties during pollution episodes in Beijing

基于激光雷达连续观测数据反演得到的多种气溶胶光学参数,包括气溶胶后向散射系数(355/532/1064nm)、消光系数(532/607nm)、退偏比(532p/532s)、激光雷达比(532nm)及波长指数(355/532nm和532/1064nm),分析了2019年10月北京城区三种不同污染事件(空气污染/污染沙尘/纯沙尘)的气溶胶光学特性。结果表明,空气污染气溶胶退偏比(波长指数)为0.10±0.02(1.2±0.19),激光雷达比(43±7sr)相比典型城市污染气溶胶偏低,可能与硝酸盐等水溶性气溶胶吸湿增长或二次有机气溶胶的生成有关;污染沙尘退偏比(波长指数)为0.19±0.03(1.0±0.35),激光雷达比为51±7sr;纯沙尘相比前者退偏比(0.25±0.03)较大,波长指数(0.11±0.44)较小,激光雷达比为40±4sr。

Based on the continuous observation data of lidar,the aerosol backscattering coefficient(355/532/1064 nm),extinction coefficient(532/607 nm),depolarization ratio(532 p/532 s),lidar ratio(532 nm)and backscatter-related?ngstr?m exponent(355/532 nm and 532/1064 nm)are retieved.Then,the aerosol optical properties of three different pollution episodes(air pollution/polluted dust/pure dust)in Beijing in October 2019 are analyzed.Results show that the air pollution aerosol depolarization ratio at 532 nm(?ngstr?m exponent between 355 and 532 nm)is 0.10±0.02(1.2±0.19),and the lidar ratio at 532 nm(43±7 sr)is lower than that of typical urban pollution aerosol,which is probably affected by hygroscopic growth of water-soluble aerosolssuch as nitrate or the formation of secondary organic aerosols.In the polluted dust episode,the depolarization ratio(?ngstr?m exponent)is 0.19±0.03(1.0±0.35),and the lidar ratio is 51±7 sr.In the pure dust episode,compared with the former,the depolarization ratio(0.25±0.03)is larger,the?ngstr?m exponent(0.11±0.44)is smaller,and the lidar ratio is 40±4 sr.