Abstract
Abstract. Temporal variations in aerosol optical properties were investigated at a coastal station in Hong Kong based on the field observation from February 2012 to February 2015. At 550 nm, the average light-scattering (151 ± 100 Mm−1) and absorption coefficients (8.3 ± 6.1 Mm−1) were lower than most of other rural sites in eastern China, while the single-scattering albedo (SSA = 0.93 ± 0.05) was relatively higher compared with other rural sites in the Pearl River Delta (PRD) region. Correlation analysis confirmed that the darkest aerosols were smaller in particle size and showed strong scattering wavelength dependencies, indicating possible sources from fresh emissions close to the measurement site. Particles with Dp of 200–800 nm were less in number, yet contributed the most to the light-scattering coefficients among submicron particles. In summer, both ΔBC / ΔCO and SO2 / BC peaked, indicating the impact of nearby combustion sources on this site. Multi-year backward Lagrangian particle dispersion modeling (LPDM) and potential source contribution (PSC) analysis revealed that these particles were mainly from the air masses that moved southward over Shenzhen and urban Hong Kong and the polluted marine air containing ship exhausts. These fresh emission sources led to low SSA during summer months. For winter and autumn months, contrarily, ΔBC / ΔCO and SO2 / BC were relatively low, showing that the site was more under influence of well-mixed air masses from long-range transport including from South China, East China coastal regions, and aged aerosol transported over the Pacific Ocean and Taiwan, causing stronger abilities of light extinction and larger variability of aerosol optical properties. Our results showed that ship emissions in the vicinity of Hong Kong could have visible impact on the light-scattering and absorption abilities as well as SSA at Hok Tsui.
Highlights
Atmospheric aerosol strongly affects the earth’s radiative balance by scattering and absorbing incoming solar radiation, which, is still a large source of uncertainties in global climate forcing assessment (Stocker et al, 2013)
Compared to the other rural sites in South China, black carbon (BC) levels in Hok Tsui station were lower than the concentrawww.atmos-chem-phys.net/17/2653/2017/
Based on aerosol optical properties, relevant species and aerosol size measured at Hok Tsui station in Hong Kong, we studied the temporal variations and investigated the potential sources by using correlation analysis and Lagrangian dispersion modeling
Summary
Atmospheric aerosol strongly affects the earth’s radiative balance by scattering and absorbing incoming solar radiation, which, is still a large source of uncertainties in global climate forcing assessment (Stocker et al, 2013). The aerosol optical properties are responsible for the direct aerosol radiative forcing, depending on aerosol chemical composition and microphysical properties. Relative to another major component of radiative forcing, greenhouse gases, the shorter atmospheric lifetime of aerosols leads to more localized effects and regional differences in aerosol optical properties. J. Wang et al.: Observations of aerosol optical properties of aerosol optical properties caused by the complex distribution of tropospheric aerosols, field monitoring of aerosol optical properties in different regions around the world is critical for exploring the variations in aerosol radiative forcing. Absorbing aerosols, like black carbon (BC), can strongly absorb visible light, enhancing the warming effect of the atmosphere (Jacobson, 2001; Babu and Moorthy, 2001; Ding et al, 2016)
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