Aerosol characteristics during summer haze episodes from different source regions over the coast city of North China Plain

摘要

Haze episodes in the North China Plain (NCP) have attracted intensive attentions due to their significant impacts on the regional and global climate. Surface measurements of aerosol microphysical and optical properties in Tanggu, a coast city in NCP from June 12 to July 8, 2011 were carried out. The aim of this study was to evaluate the summertime haze episodes from different source regions identified by the air-mass back-trajectories. A highest percentage of coarse particles (diameter larger than 1. μm), consistent with lowest scattering Angstrom exponent were observed in haze episodes with pollutions from only local areas. The up-scatter fraction and asymmetry parameter were similar for all haze episodes with the median values of 0.24 and 0.66, respectively, since hemispherical backscatter ratio reached the limit of ~0.10. The haze episode with the air masses from eastern coast seems to have a more effective heating effect on the atmosphere, which also exhibited significant enhancements in aerosol concentrations and optical parameters. The larger median single scattering albedos of 0.85 and 0.87 were found for haze episodes with air masses from oceanic regions and eastern coast of China, respectively. The median single scattering albedo for haze episodes with air masses from northeast China was lowest among all haze episodes. Our study indicates that the long-range transport aids the formation of haze episodes.