Aerosol optical properties during the typical haze/fog event in Nanjing

The aerosol optical properties during haze/fog event were analyzed in the north suburb of Nanjing in the winter of 2010 by using direct solar irradiance and sky radiance of CE318 sun-photometer.Under the influence of haze/fog,the aerosol optical depth(AOD) showed a higher value.The values of AOD at 440,675,870 and 1020 nm varied from 0.16 to 0.43 before the haze and fog episodes,increased to 0.31~0.84 during the haze/fog influencing periods and reduced to 0.19~0.48 after the haze/fog process.The higher single scattering albedo(SSA) occurred in haze/fog influencing periods with value of 0.89~0.91.The imaginary part of complex refractive index decreased after the fog/haze days.These results suggests that the enhancement of scattering ability and the decrease of absorption ability of local aerosols.During the haze/fog episodes,the aerosol size distribution come from the addition of coarse aerosol particles and the contribution of the anthropogenic fine particles.The volume concentration of coarse mode increased by 2.5 times,with the lower value of 0.033 μm3/μm2 before the outbreak of the fog/haze process and 0.082 μm3/μm2 during the fog/haze influencing periods.The volume concentration of fine mode also increased by 90% compared to the before the events.