Surface and Column-Integrated Aerosol Properties of Heavy Haze Events in January 2013 over the North China Plain

Heavy haze events were recorded over the North China Plain (NCP) during January 2013. The meteorological condition, in-situ measurement, and ground remote sensing of aerosol size distributions and aerosol optical properties were analyzed to study the meteorological effects on surface and column-integrated aerosol loading. Besides special terrain, analysis of meteorological parameters showed that such a long-standing pollution event was attributable to stagnant weather with high humidity, frequent inversion and low wind speed. The monthly average mass concentration of particulate matter smaller than 1.0 µm (PM1), 2.5 µm (PM2.5), and 10 µm (PM10) was 169, 190, and 233 µg/m3, respectively. High mass fraction of PM1 (73%) and PM2.5 (82%) in PM10 indicated the domination of fine mode particles. Increase of the fraction of PM1–2.5 during haze events was attributed to the increase of secondary aerosol under high humidity. Two polluted aerosol types (A1, A3) and one background aerosol (A2) were classified based on aerosol optical depth at 440 nm (AOD440) and column-integrated size distributions. The AOD440 of cloud/fog processed aerosol (1.43) was about two and seven times larger than that of A1 and A2, respectively. The single scattering albedo at 675 nm (SSA675) of A3 was ~0.93, which was larger than that of A1 (0.85) and A2 (0.80) due to hygroscopic growth under humid environment.