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Light Absorption Properties and Radiative Effects of Primary Organic Aerosol Emissions
Citation:
Lu, Z., D. Streets, E. Winijkul, F. Yan, Y. Chen, T. Bond, Y. Feng, M. Dubey, S. Liu, J. Pinto, AND G. Carmichael. Light Absorption Properties and Radiative Effects of Primary Organic Aerosol Emissions. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 49(8):4868-4877, (2015).
Impact/Purpose:
Article assimilates available information on the optical properties of organic aerosols and estimates absorption of solar radiation by brown carbon.
Description:
Organic aerosols (OA) in the atmosphere affect Earth’s energy budget by not only scattering but also absorbing solar radiation due to the presence of the so-called “brown carbon” (BrC) component. However, the absorptivities of OA are not or poorly represented in current climate models. In this study, we provide a method to address the BrC issue at the emission inventory level. We review available measurements of the light-absorbing primary OA (POA), and quantify the wavelength-dependent imaginary refractive indices (kOA, the fundamental optical parameter determining the particle’s absorptivity) and their uncertainties of the bulk POA emitted from biomass/biofuel, lignite, propane, and oil combustion sources. In particular, we parameterize the kOA of biomass/biofuel combustion sources as a function of the black carbon (BC)-to-OA ratio, implying that the absorptive properties of POA depend strongly on burning conditions. The derived fuel-type-based kOA profiles are incorporated into a global carbonaceous aerosol emission inventory and the integrated kOA values of sectoral and total POA emissions are presented. Results of a simple radiative transfer model show that the POA absorptivity warms the atmosphere significantly and leads to ~27% reduction in the amount of the negative global average POA radiative forcing compared to results using the non-absorbing assumption.
