Publication Date:
2015-09-05
Description:
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 non-absorbing 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.
Print ISSN:
0148-0227
Topics:
Geosciences
,
Physics
