为了解北京地区2013年1月严重灰霾污染过程中大气气溶胶特性,基于地基太阳-天空辐射计CE318观测数据,反演了气溶胶光学和微物理参数,并据此对1月份第2次严重污染过程进行了详细分析。研究表明:(1)2013年1月北京地区灰霾污染天气下,气溶胶光学厚度比同时期清洁天气有所增大,在440 nm处均值达到0.87,在个别严重污染天气下高达3左右;(2)气溶胶光学参数与灰霾过程密切相关,Ångström指数由清洁大气时的1.3降到灰霾污染时的0.95,复折射指数虚部均值由污染前的0.04下降为污染过程中的0.01,单次散射反照率均值则由0.73增大到0.92,同时不对称因子均值从0.58增大到0.67;(3)灰霾污染过程中细模态气溶胶比例较高,占总体积比例平均达到73.0%,最高达90.5%,在灰霾污染中气溶胶细模态平均峰值半径随光学厚度增大而增大,清楚表明了灰霾过程中颗粒物的吸湿增长效应,粗模态平均峰值半径随光学厚度的增加而减小,在污染最严重时,粒子谱分布峰值半径约为0.43 μm。

Aerosol optical and microphysical parameters retrieved from ground-based sun-sky photometer (CE318) measurements are used to investigate aerosol properties during heavy haze days. The heavy haze episode in January 2013 is analyzed, and we find that: (1) Aerosol Optical Depth (AOD) in haze days (an average of 0.87 at 440 nm), is much higher than that of clean days, and can reach up to about 3 in some seriously polluted conditions. (2) Aerosol properties are well related to the haze pollution levels. For example, the averaged Ångström exponent, imaginary part of refractive index, single scattering albedo and asymmetry factor under clean condition are 1.3, 0.04, 0.73 and 0.58, respectively, while the corresponding values in polluted days change to 0.95, 0.01, 0.92 and 0.67, respectively. (3) The volume proportion of fine mode aerosol is higher than that of coarse mode during the haze episode. The average volume ratio of fine mode to total aerosol is 73%, with the maximum of 90.5%. The fine mode radius peak increases with the increase of AOD, indicating clearly hygroscopic growth effects, while that of coarse mode aerosol decreases accordingly. Moreover, the peak radius of size distribution is 0.43 μm when the heaviest haze pollution during January 2013 occurs.