Aerosol Optical Properties over Mount Song, a Rural Site in Central China

Lunche Wang,Xiangao Xia,Hong Lin,Ramesh P Singh,Wei Gong,Huizheng Che,Ming Zhang

doi:10.4209/aaqr.2014.12.0335

Abstract

Seasonal variations of aerosol optical depth (AOD), Angstrom exponent (α), single scattering albedo (SSA), water vapor content (WVC), aerosol size distribution and refractive index at Mount Song, a rural site in Central China are analyzed using ground-based sunphotometer data for the period April 2012 to May 2014 for the first time. The results show that the area is highly polluted even the major anthropogenic emission sources are far away. Seasonal mean AOD is high (0.72 ± 0.52) during summer (June–August) season and low (0.51 ± 0.38) during autumn (September–November) season. The monthly mean α is very low (0.81 ± 0.30) in the month of April and very high (1.32 ± 0.23) in the month of September with annual average value 1.1. Analysis of the frequency distributions of AOD and α in each season indicates presence of fine-mode particles. Strong seasonal variations in SSA is likely due to local biomass burning and regional transport of anthropogenic aerosol particles, Seasonal mean SSA at 440 nm wavelength are 0.89 ± 0.04, 0.91 ± 0.06, 0.89 ± 0.07 and 0.92 ± 0.05, respectively during spring, summer, autumn and winter seasons. It is also shown that the scattering capacity of the fine-mode particles is relatively higher during summer compared to other seasons. The aerosol volume size distributions show pronounced seasonal variations in volume concentration, peak radius and the fine-mode particles are evidently dominant during summer season due to the hygroscopic growth. A distinct seasonal variations in aerosol parameters confirm the transport of polluted air mass at Mount Song.

Highlights

Aerosols are solid or liquid particles in the atmosphere, their concentrations and type of particles influence the global and regional climates, directly through the interaction with solar radiation and indirectly modifying cloud microphysics (Albrecht, 1989)
The annual mean AOD500nm at Mount Song during the period 2012–2014 is about 0.60, which is lower than those observed at Beijing (0.841, annual mean AOD500nm during 2002–2007) (Xia et al, 2006; Yu et al, 2009a)
The annual mean aerosol optical depth (AOD) 500nm at Xianghe, Taihu and Yanting are 0.82 (Li et al, 2007), 0.77 (Li et al, 2007) and 0.79 (Wang et al, 2011), which indicate that aerosol loading at Mount Song in Central China is lower compared to Beijing, Xianghe, Taihu and other sites in China

Summary

Introduction

Aerosols are solid or liquid particles in the atmosphere, their concentrations and type of particles influence the global and regional climates, directly through the interaction with solar radiation and indirectly modifying cloud microphysics (Albrecht, 1989). Seasonal variations of aerosol optical depth (AOD), Ångström exponent (α), single scattering albedo (SSA), water vapor content (WVC), aerosol size distribution and refractive index at Mount Song, a rural site in Central China are analyzed using ground-based sunphotometer data for the period April 2012 to May 2014 for the first time.

Results

Conclusion