Key Laboratory of Meteorological Disaster, Ministry of Education, Joint International Research Laboratory of Climate and Environment Change, Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, Nanjing University of Information Science and Technology, Nanjing 210044, China
The purpose of this study is to investigate the optical properties of aerosols during spring in Beijing. A comparison of aerosol optical properties was performed between spring and dusty days from Aerosol Robotic Network (AERONET) measurements during 2010~2014. The extinction of coarse particles (r > 0.6μm) accounted for 28% and 59% of that of total particle in spring and dusty days respectively. Average absorption percent out of extinction for total particles were 11.4% during dusty days. This result indicated that aerosol extinction was dominated by coarse particles. The aerosol optical depth showed high values in dusty days with the average value was 1.7 times higher than that of spring. Angstrom exponents during dusty days were higher than those of spring, and about 85% of them less than 0.6 during dusty days. The aerosol volume size distributions presented abimodal structure (fine and coarse modes), and the coarse mode was dominant in spring. The volume concentrations of coarse mode in spring were evidently lower than those of dusty days. The single scattering albedo showed an increasing trend with wavelengths during dusty days in Beijing. The averaged single scattering albedos were about 0.92 for dusty days and 0.89 for spring during 440~1020nm. The real parts of the refractive index at 440nm were 1.48 during spring and 1.51 during dusty days, suggested the aerosol particles from dust source regions were involved in a stronger scattering. The imaginary parts of refractive index showed a decreasing trend with wavelength sand the average value in dusty days were higher than that of spring. The averaged aerosol radiative forcing in dusty days was higher than that of in spring and in clean days in Beijing.
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