A Study on Beijing Aerosol Optical Properties in Spring 2006 by Skyradiometer Measurements

A ground-based skyradiometer was used to measure the direct and diffuse solar irradiances, as well as aureole radiances, from Mar to May 2006 over Beijing. The aerosol optical depth (AOD), Angstr?m exponent (α), Single Scattering Albedo(SSA), and volume size distributions of aerosols were retrieved. The results indicated that the mean aerosol optical depth at 0.5 μm ［AOD(0.5 μm)］, Angsrom exponent, and SSA(0.5 μm) in spring over Beijing were 0.67, 0.536, and 0.876, respectively. The aerosol volume size distributions presented a bimodal structure: A coarse mode with a radius of about 7.7 μm and a fine mode with a radius of about 0.17 μm, and the latter volume concentration is higher. Compare with the results of 2004, the volume of coarse particles was higher which caused by frequently dust storm in 2006 and the SSA was lower which meant higher percentage of absorptive particles. The diurnal variability of AOD was controled by human avtivity and air turbulence which reaced the peak value from 1100 LST to 1400 LST. The single scattering and Angstr?m exponent was decrease with time, which indicated that the anthropologic aerosol was weak scattering and the coarse mode paricle number was growing in day time. The difference between skyradiometer and CE-318 was less than 7% for the AOD.