Investigating the aerosol optical and radiative characteristics of heavy haze episodes in Beijing during January of 2013

Abstract

Abstract Several heavy atmospheric haze pollution episodes occurred over eastern and northern China during January of 2013. The pollution covered more than 100 km 2 and caused serious impacts on environmental quality, human health, and transportation. In this study, we characterize aerosol microphysical, optical, and radiative characteristics using a combination of ground‐based Sun/sky radiometer retrievals and a radiative transfer model. Our results show that during about half of the total number of days, daily PM 2.5 and PM 10 concentrations are larger than 100 µg/m 3 , with maxima of 462 and 433 µg/m 3 , respectively, during the haze events. Fine‐mode (PM 2.5 ) particles dominated the aerosol size during the episodes. The volume size distribution and median radius of fine‐mode particles generally increase as aerosol optical depth at 440 nm (AOD 440 ) increases. The median effective radius of fine‐mode particles increases from 0.15 µm at low AOD value (AOD 440 ~ 0.3) to a radius of 0.25–0.30 µm at high AOD value (AOD 440 ≥ 1.0). The daily mean single‐scattering albedo (SSA), imaginary part of refractive index (RI), and asymmetry factor display pronounced spectral behaviors. The overall mean SSA 440 and SSA 675 are 0.892 and 0.905, respectively. The corresponding RI 440 and RI 675 are 0.016 and 0.011, respectively. This indicates that a significant amount of absorption occurred under the haze event in Beijing during January 2013. Approximately half of the incident solar radiation energy went into heating the atmosphere as a result of strong aerosol loading and absorption. The daily averaged heating rate in the haze particle layer (0–3.2 km) varies from 0.12 to 0.81 K/day in Beijing, which might exert profound impact on the atmospheric thermodynamic and dynamical structures and cloud development, which should be further studied.