Assessment of column aerosol optical properties using ground-based sun-photometer at urban Harbin, Northeast China

Aerosol plays a key role in determining radiative balance, regional climate and human health. Severe air pollution over Northeast China in recent years urges more comprehensive studies to figure out the adverse effects caused by excessive aerosols. In this study, column aerosol measurements over urban Harbin, a metropolis located at the highest latitude in Northeast China, during May 2016 to March 2017 were conducted using a CIMEL sun-photometer to analyze local aerosol properties and its variation from different aspects. According to the observations, aerosol optical depth at 440nm (AOD₄₄₀) ranges from 0.07 up to 1.54, and the large variability in both AOD₄₄₀ and Angstrom Exponent (AE_440-870) indicates the frequent change of aerosol types due of different emission sources. Coarse mode particles dominated Harbin during the studying period because of the long-range transported dust and probably the suspended snow crystals in winter. As the wavelength increases, relatively consistent decrease trends of single scattering albedo (SSA) and asymmetry factor (ASY) were observed in spring, autumn, and winter, indicating the presence of absorbing polluted aerosols. Mixed type (MIX) aerosol dominated the study region with a total percentage of 34%, and biomass burning and urban industry (BB/UI), clean continental (CC), and desert dust (DD) aerosols were found to be 31%, 27%, and 8%, respectively. The current work fills up the optical characteristics of aerosols in Harbin, and will contribute to the in-depth understanding of local aerosol variation and regional climate change over Northeast China.