Abstract
Abstract. The particle mixing state plays a significant yet poorly quantified role in aerosol radiative forcing, especially for the mixing of dust (mineral absorbing) and anthropogenic pollution (black carbon absorbing) over East Asia. We have investigated the absorption enhancement of mixed-type aerosols over East Asia by using the Aerosol Robotic Network observations and radiative transfer model calculations. The mixed-type aerosols exhibit significantly enhanced absorbing ability than the corresponding unmixed dust and anthropogenic aerosols, as revealed in the spectral behavior of absorbing aerosol optical depth, single scattering albedo, and imaginary refractive index. The aerosol radiative efficiencies for the dust, mixed-type, and anthropogenic aerosols are −101.0, −112.9, and −98.3 Wm-2τ-1 at the bottom of the atmosphere (BOA); −42.3, −22.5, and −39.8 Wm-2τ-1 at the top of the atmosphere (TOA); and 58.7, 90.3, and 58.5 Wm-2τ-1 in the atmosphere (ATM), respectively. The BOA cooling and ATM heating efficiencies of the mixed-type aerosols are significantly higher than those of the unmixed aerosol types over the East Asia region, resulting in atmospheric stabilization. In addition, the mixed-type aerosols correspond to a lower TOA cooling efficiency, indicating that the cooling effect by the corresponding individual aerosol components is partially counteracted. We conclude that the interaction between dust and anthropogenic pollution not only represents a viable aerosol formation pathway but also results in unfavorable dispersion conditions, both exacerbating the regional air pollution in East Asia. Our results highlight the necessity to accurately account for the mixing state of aerosols in atmospheric models over East Asia in order to better understand the formation mechanism for regional air pollution and to assess its impacts on human health, weather, and climate.
Highlights
Atmospheric aerosols or particulate matter (PM) profoundly affect the energy budget of the Earth–atmosphere system directly by interfering with the radiative transfer and indirectly by modifying cloud formation (Twomey, 1977; Charlson et al, 1992; Fan et al, 2007; Wang et al, 2011)
The mixing of dust with anthropogenic aerosols exerts a significant influence on aerosol absorption and radiative efficiency
We present an extensive investigation of the radiative effects of the East Asian aerosol mixtures
Summary
Atmospheric aerosols or particulate matter (PM) profoundly affect the energy budget of the Earth–atmosphere system directly by interfering with the radiative transfer and indirectly by modifying cloud formation (Twomey, 1977; Charlson et al, 1992; Fan et al, 2007; Wang et al, 2011). The mixing state of dust and anthropogenic aerosols considerably affects aerosol radiative effects, further studies are urgently required to better understand the key role that the East Asian aerosol mixtures play in the formation mechanism of regional air pollution. In this present work, we have extensively investigated the radiative absorption enhancement by the East Asian aerosol mixtures on the basis of long-term AERONET observations and Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model simulations. Our results suggest that the East Asian aerosol mixtures result in a more stable atmosphere that is unfavorable for diffusion and dispersion of the atmospheric pollutants
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