Abstract
Aerosol particles are the major contributor to the deterioration of air quality in China’s capital, Beijing. Using ground-based sun photometer observations from 2005 to 2014, the long-term variations in optical properties and microphysical properties of aerosol in and around Beijing were investigated in this study. The results indicated little inter-annual variations in aerosol optic depth (AOD) but an increase in the fine mode AODs both in and outside Beijing. Furthermore, the single scattering albedo in urban Beijing is larger, while observations at the site that is southeast of Beijing suggested that the aerosol there has become more absorbing. The intra-annual aspects were as follow: The largest AOD and high amount of fine mode aerosols are observed in the summer. However, the result of air pollution index (API) that mainly affected by the dry density of near-surface aerosol indicated that the air quality has been improving since 2006. Winter and spring were the most polluted seasons considering only the API values. The inconsistency between AOD and API suggested that fine aerosol particles may have a more important role in the deterioration of air quality and that neglecting particulate matter with aerodynamic diameter less than 2.5 μm (PM2.5) in the calculation of API might not be appropriate in air quality evaluation. Through analysis of the aerosol properties in high API days, the results suggested that the fine mode aerosol, especially PM2.5 has become a major contributor to the aerosol pollution in Beijing.
Highlights
Aerosol is an important component of the atmosphere that affects the environment [1,2,3], weather [4], climate [5] and even human health [6,7,8]
The temporal trends for both the fine mode fraction and Ångström exponent have been similar in the past decade, indicating that these two parameters were similar in describing the sizes of aerosol particles
2014, we present the optical and microphysical properties of aerosol from Beijing, including aerosol optic depth (AOD), Ångström
Summary
Aerosol is an important component of the atmosphere that affects the environment [1,2,3], weather [4], climate [5] and even human health [6,7,8]. Monitoring aerosol properties via both ground-based observations and satellite observations has become important [4,9,10]. Monitoring aerosol properties, including aerosol optic depth (AOD), size distributions, and single scattering albedo (SSA), is a difficult task as remote sensing techniques obtain aerosol properties through measuring direct solar radiance and sky scattering signals [11]. For ground-based observations, AOD can be measured with high accuracy, while the accuracies of size distribution and single scattering albedo are not as high quality as AOD. Satellite observations provide unique tools for monitoring wide-range aerosol properties considering the available wide coverage of the earth surface, and various satellite-based sensors such as the Moderate Resolution Imaging Spectroradiometer (MODIS), Multi-angle Imaging
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