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Contribution of brown carbon and lensing to the direct radiative effect of carbonaceous aerosols from biomass and biofuel burning emissions
Author(s) -
Saleh Rawad,
Marks Marguerite,
Heo Jinhyok,
Adams Peter J.,
Donahue Neil M.,
Robinson Allen L.
Publication year - 2015
Publication title -
journal of geophysical research: atmospheres
Language(s) - English
Resource type - Journals
eISSN - 2169-8996
pISSN - 2169-897X
DOI - 10.1002/2015jd023697
Subject(s) - biofuel , radiative transfer , absorption (acoustics) , biomass (ecology) , aerosol , biomass burning , atmospheric sciences , carbon fibers , chemistry , environmental science , physics , optics , materials science , ecology , organic chemistry , composite number , composite material , biology
Abstract We present global direct radiative effect (DRE) calculations of carbonaceous aerosols emitted from biomass/biofuel burning addressing the interplay between two poorly constrained contributions to DRE: mixing state of black carbon (lensing) and light absorption by organic aerosol (OA) due to the presence of brown carbon (BrC). We use the parameterization of Saleh et al. (2014) which captures the variability in biomass/biofuel OA absorption. The global mean effect of OA absorption is +0.22 W/m 2 and +0.12 W/m 2 for externally and internally mixed cases, while the effect of lensing is +0.39 W/m 2 and +0.29 W/m 2 for nonabsorbing and absorbing OA cases, signifying the nonlinear interplay between OA absorption and lensing. These two effects can be overestimated if not treated simultaneously in radiative transfer calculations. The combined effect of OA absorption and lensing increases the global mean DRE of biomass/biofuel aerosols from −0.46 W/m 2 to +0.05 W/m 2 and appears to reduce the gap between existing model‐based and observationally constrained DRE estimates. We observed a strong sensitivity to these parameters in key regions, where DRE shifts from strongly negative (< −1 W/m 2 ) to strongly positive (> +1 W/m 2 ) when accounting for lensing and OA absorption.