Analyses of aerosol optical properties and direct radiative forcing over urban and industrial regions in Northeast China

The aerosol optical depth (AOD), Angstrom exponent (Alpha), single scattering albedo (SSA), and volumes of aerosol size distributions were all retrieved from measurements made by a CE318 sunphotometer at four urban and industrial sites (Shenyang, Anshan, Benxi and Fushun) in Northeast China from 2009 to 2013. Values for direct radiative forcing (DRF) were then estimated using these measurements. For all four sites, the mean AOD appeared higher in the spring and summer, with the minimum occurring in the autumn. Conversely, the Alpha was lower in the spring but higher in the autumn and winter. The mean 440 nm SSA at the four sites varied from 0.81 to 0.87, indicating the highly spatial variability of aerosol optical properties. Frequent dust events resulted in a dominant contribution by coarse particles in spring, while fine particles were predominant during the summer. Mixtures of fine and coarse particles influenced aerosol optical properties in the autumn and winter. Results from this study provide useful information for the further understanding of retrieved aerosol optical properties and DRF in Northeast China.