Aerosol optical properties and the mixing state of black carbon at a background mountainous site in Eastern China  

作　　者：Liang Yuan Yan Yin Hui Xiao Jian Hao Kui Chen Xingna Yu Xiaoling Zhang 

机构地区：[1]Key Laboratory for Aerosol-Cloud-Precipitation of China Meteorological Administration, School of Atmospheric Physics, Nanjing University cf Information Science and Technology, Nanjing 210044, China [2]Plateau Atmosphere and Environment Key Laboratory of Sichuan Province, College of Atmospheric Science, Chengdu University of Information Technology, Chengdu 610225, China [3]Guangzhou Institute of Tropical and Marine Meteorology, CMA, Guangzhou 510641, China [4]Tianjin Institute of Meteorological Science, Tianjin 300074, China

出　　处：《Journal of Environmental Sciences》2019年第9期21-38,共18页环境科学学报（英文版）

基　　金：supported by the National Key Research and Development Program of China(2016YFC0203500,Task#1 and2016YFA0602004);the National Science Foundation of China(NSFC)(Nos.41590873,41030962)

摘　　要：In-situ measurements of aerosol optical properties were conducted at Mt. Huang from September 23 to October 28, 2012. Low averages of 82.2, 10.9, and 14.1 Mm-1 for scattering coefficient(σsp, neph, 550), hemispheric backscattering coefficient(σhbsp, neph, 550), and absorption coefficient(σap, 550), respectively, were obtained. Atmospheric aging process resulted in the increase of σap, 550 but the decrease of the single scattering albedo(ω550) at constant aerosol concentration. However, the proportion of non-light-absorbing components(non-BCs) was getting higher during the aging process, resulting in the increase of aerosol diameter, which also contributed to relatively higher σsp, neph, 550 and ω550. Diurnal cycles of σsp, neph, 550 and σap, 550 with high values in the morning and low values in the afternoon were observed closely related to the development of the planetary boundary layer and the mountain-valley breeze. BC mixing state, represented by the volume fraction of externally mixed BC to total BC(r), was retrieved by using the modified Mie model.The results showed r reduced from about 70% to 50% when the externally mixed non-BCs were considered. The periodical change and different diurnal patterns of r were due to the atmospheric aging and different air sources under different synoptic systems. Local biomass burning emissions were also one of the influencing factors on r. Aerosol radiative forcing for different mixing state were evaluated by a "two-layer-single-wavelength" model,showing the cooling effect of aerosols weakened with BC mixing state changing from external to core-shell mixture.In-situ measurements of aerosol optical properties were conducted at Mt. Huang from September 23 to October 28, 2012. Low averages of 82.2, 10.9, and 14.1 Mm-1 for scattering coefficient(σsp, neph, 550), hemispheric backscattering coefficient(σhbsp, neph, 550), and absorption coefficient(σap, 550), respectively, were obtained. Atmospheric aging process resulted in the increase of σap, 550 but the decrease of the single scattering albedo(ω550) at constant aerosol concentration. However, the proportion of non-light-absorbing components（non-BCs） was getting higher during the aging process, resulting in the increase of aerosol diameter, which also contributed to relatively higher σsp, neph, 550 and ω550. Diurnal cycles of σsp, neph, 550 and σap, 550 with high values in the morning and low values in the afternoon were observed closely related to the development of the planetary boundary layer and the mountain-valley breeze. BC mixing state, represented by the volume fraction of externally mixed BC to total BC（r）, was retrieved by using the modified Mie model.The results showed r reduced from about 70% to 50% when the externally mixed non-BCs were considered. The periodical change and different diurnal patterns of r were due to the atmospheric aging and different air sources under different synoptic systems. Local biomass burning emissions were also one of the influencing factors on r. Aerosol radiative forcing for different mixing state were evaluated by a "two-layer-single-wavelength" model,showing the cooling effect of aerosols weakened with BC mixing state changing from external to core-shell mixture.

关 键 词：AEROSOL optical properties Mixing state Direct RADIATIVE FORCING BACKGROUND mountainous SITE Mt.Huang 

分 类 号：X[环境科学与工程]