87th AMS Annual Meeting

Monday, 15 January 2007
Asian dust - pollution interactions inducing more solar radiation absorption: Results from ground-based sky radiation measurements
Exhibit Hall C (Henry B. Gonzalez Convention Center)
B. J. Sohn, Seoul National University, Seoul, South Korea; and T. Nakajima, H. W. Chun, and K. Aoki
In this paper we present evidences that Asian dusts can become more absorbing when mixed with polluted aerosols. Spectral direct/diffuse solar radiation and black carbon (BC) concentrations were measured on April 7, 2000 at Anmyeon-Do Korea, when a narrow and heavy dust band moved through the Anmyeon site. It was found that the BC concentration was significantly elevated when dust was present; the BC density of about 0.4 g m-3 over the non-dust area before the arrival of the dust band increased to1.4 g m-3 within the dust area, and then reduced to about 0.5 g m-3 after the passage of the dust band. Consistent with the behavior of BC concentrations, the retrieved single scattering albedo (SSA) showed lowest value (about 0.91) within the dust band while comparatively high values (up to 0.97) are found over a non-dust area at about 300 km away from the dust band. Results strongly suggest that there may be significant interactions between air pollutants and mineral dust aerosols, leading to the decreased SSA and thus to more solar absorption by dust/black carbon aerosols. In other words, Asian dusts tend to become darkened after mixing with soot particles produced over the industrial/urban area of China. This is important because black carbon's direct effect on absorbing incoming solar radiation and its heating contribution to the lower troposphere may be bigger than previously surmised for the black carbon alone. Consequently, physico-chemical interactions for dust and pollution emissions should be incorporated if regional or large-scale climate effects are modeled correctly.

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