Light Absorption Enhancement of Black Carbon Aerosol Constrained by Particle Morphology.

The radiative forcing of black carbon aerosol (BC) is one of the largest sources of uncertainty in climate change assessments. Contrasting results of BC absorption enhancement ( Eabs) after aging are estimated by field measurements and modeling studies, causing ambiguous parametrizations of BC solar absorption in climate models. Here we quantify Eabs using a theoretical model parametrized by the complex particle morphology of BC in different aging scales. We show that Eabs continuously increases with aging and stabilizes with a maximum of ∼3.5, suggesting that previous seemingly contrast results of Eabs can be explicitly described by BC aging with corresponding particle morphology. We also report that current climate models using Mie Core-Shell model may overestimate Eabs at a certain aging stage with a rapid rise of Eabs, which is commonly observed in the ambient. A correction coefficient for this overestimation is suggested to improve model predictions of BC climate impact.