title: Vertical distribution of ambient aerosol extinctive properties during haze and haze-free periods based on the Micro-Pulse Lidar observation in Shanghai.
abstract: Ambient aerosols make a significant contribution to the environment and climate through their optical properties. In this study, the aerosol extinction coefficient and Aerosol optical depth (AOD) retrieved using the Fernald Method from the ground-based Micro-Pulse Lidar (MPL) were used to investigate the characteristics of aerosols during haze and haze-free periods in Shanghai. There were 216 haze days including 145 dry haze days, 39 damp haze days and 32days of both dry and damp haze in Shanghai from March 2009 to February 2010. During the haze periods, aerosols were concentrated mainly below 600m resulting in the most severe pollution layer in Shanghai. In contrast to the aerosol optical properties during haze-free periods, aerosol extinction coefficients and AOD were larger in the lower altitude (below 1km) during haze periods. The lowest 1km contributed 53-72% of the Aerosol optical depth (AOD) below 6km for the haze periods and <41% of that for the haze-free periods except summer. According to the analysis of influencing factors, although atmospheric convection was strong in summer which led to reduce the extinction, the highest occurrence of haze with relatively low aerosol extinction most of time was in summer, which resulted from the factors such as higher relative humidity, temperature and more solar radiation causing hygroscopic growth of particles and formation of secondary aerosols; in spring and autumn, there was less haze occurrences because the boundary layer was relatively higher, which allowed pollutants to diffuse more easily, but spring was the second most frequency season of haze due to frequent dust transport from the north; in winter high concentrations of particles and low boundary layer height were not beneficial to the diffusion of pollutants near the surface and caused haze occurrence rather high with high aerosol extinction.
authors: Environmental Science and Engineering College, Donghua University, Shanghai, China; Shanghai Key Laboratory of Atmospheric Particle Pollution and Prevention (LAP3), Department of Environmental Science and Engineering, Fudan University, Shanghai, China.
authors: Qiong
authors: Q
authors: Liu
authors: Environmental Science and Engineering College, Donghua University, Shanghai, China; Shanghai Meteorological Bureau, Shanghai, China. Electronic address: oxeye75@163.com.
authors: Qianshan
authors: Q
authors: He
authors: Baruch College, City University of New York, New York, USA.
authors: Sihua
authors: S
authors: Fang
authors: Environmental Science and Engineering College, Donghua University, Shanghai, China.
authors: Ying
authors: Y
authors: Guang
authors: Environmental Science and Engineering College, Donghua University, Shanghai, China.
authors: Chengyu
authors: C
authors: Ma
authors: Environmental Science and Engineering College, Donghua University, Shanghai, China. Electronic address: yonghangchen@dhu.edu.cn.
authors: Yonghang
authors: Y
authors: Chen
authors: Environmental Science and Engineering College, Donghua University, Shanghai, China.
authors: Yanming
authors: Y
authors: Kang
authors: Environmental Science and Engineering College, Donghua University, Shanghai, China.
authors: Hu
authors: H
authors: Pan
authors: National Climate Center of China Meteorological Administration, Beijing, China.
authors: Hua
authors: H
authors: Zhang
authors: Environmental Science and Engineering College, Donghua University, Shanghai, China.
authors: Yifeng
authors: Y
authors: Yao
keywords: AOD; Extinction; Haze; Haze-free; Influencing factors; Micro-Pulse Lidar