Impacts of Internally and Externally Mixed Anthropogenic Sulfate and Carbonaceous Aerosols on East Asian Climate |
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Authors: | Li Zhang Hongnian Liu Ning Zhang |
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Institution: | School of Atmospheric Sciences, Nanjing University, Nanjing 210093;School of Atmospheric Sciences, Nanjing University, Nanjing 210093;School of Atmospheric Sciences, Nanjing University, Nanjing 210093 |
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Abstract: | A coupled regional climate and aerosol-chemistry model, RIEMS 2.0 (Regional Integrated Environmental Model System for Asia),
in which anthropogenic sulfate, black carbon, and organic carbon were assumed to be externally mixed (EM), internally mixed
(IM) or partially internally mixed (IEM), was used to simulate the impacts of these anthropogenic aerosols on East Asian climate
for the entire year of 2006. The distributions of aerosol mass concentration, radiative forcing and hence the surface air
temperature and precipitation variations under three mixing assumptions of aerosols were analyzed. The results indicated that
the mass concentration of sulfate was sensitive to mixing assumptions, but carbonaceous aerosols were much less sensitive
to the mixing types. Modeled results were compared with observations in a variety of sites in East Asia. It was found that
the simulated concentrations of sulfate and carbonaceous aerosols were in accord with the observations in terms of magnitude.
The simulated aerosol concentrations in IM case were closest to observation results. The regional average column burdens of
sulfate, black carbon, and organic carbon, if internally mixed, were 11.49, 0.47, and 2.17 mg m−2, respectively. The radiative forcing of anthropogenic aerosols at the top of the atmosphere increased from −1.27 (EM) to
−1.97 W m−2 (IM) while the normalized radiative forcing (NRF) decreased from −0.145 (EM) to −0.139 W mg−1 (IM). The radiative forcing and NRF were −1.82 W m−2 and −0.141 W mg−1 for IEM, respectively. The surface air temperature changes over the domain due to the anthropogenic sulfate and carbonaceous
aerosols were −0.067, −0.078, and −0.072 K, with maxima of −0.47, −0.50, and −0.49 K, for EM, IM, and IEM, respectively. Meanwhile,
the annual precipitation variations were −8.0 (EM), −20.6 (IM), and −21.9 mm (IEM), with maxima of 148, 122, and 102 mm, respectively,
indicating that the climate effects were stronger if the sulfate and carbonaceous aerosols were internally mixed. |
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Keywords: | anthropogenic aerosols externally mixed internally mixed climate e?ects |
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