Measurements of surface aerosol optical properties in winter of Shanghai

Aerosol optical properties were continuously measured at an urban site in Shanghai of China from December 2010 to March 2011, and aerosol scattering (sigma(scat)) and absorption (sigma(abs)) coefficients and single scattering albedo (SSA) were examined. During the entire period, mean sigma(scat), sigma(abs), SSA were 293 Mm(-1), 66 Mm(-1) and 0.81, respectively. Higher sigma(scat) and sigma(abs) occurred in December while relatively lower values were observed in March, and SSA was just opposite to them. sigma(scat) and sigma(abs) coefficients behaved an apparent bi-peak pattern in diurnal variation: maxima of 319, 76 Mm(-1) at 8:00 LT during traffic rush hours and sub-maxima of 280, 71 Mm(-1) at 20:00 LT. SSA also behaved a bi-peak diurnal cycle with maximum 0.85 at 13:00 LT and sub-maximum 0.82 at 4:00 LT. sigma(scat) and sigma(abs) coefficients showed a clear negative correlation with atmospheric visibility. PM2.5 and black carbon were major contributors to large optical parameters because their concentrations were 2 times higher during haze episode than in clean days. sigma(scat) and sigma(abs) were low in magnitude when northeasterly winds bring clean air from the China Yellow Sea arriving the observation site, and were relatively high when air masses from the north or northwest pass through continental areas or/and industrial regions, indicating impacts of various aerosol origins on aerosol optical properties. (C) 2012 Elsevier B.V. All rights reserved.