Nonlinear Enhancement of Radiative Absorption by Black Carbon in Response to Particle Mixing Structure

Black carbon (BC) strongly absorbs solar radiation, contributing to global warming. Absorption enhancement of BC particles is difficult to quantify due to an inadequate representation of their complex morphology and mixing structures, as well as interaction with radiation. Here, we apply a 3D method accounting for detailed BC mixing structures to predict the absorption enhancement of individual BC particles (E_abs) and the total BC particle population (E_{abs, bulk}). The diverse range of mixing structures in individual BC particles leads to variable E_abs that could hardly be predicted by empirical approximations. We find that the volume proportion of the BC embedded in coating (F) determines E_abs when the particle to BC core diameter ratio (D_p/D_c) is larger than 2.0. Our findings reveal the potential mechanism behind the differences in observed and modeled E_{abs, bulk}. The framework builds a bridge connecting the microscopic mixing structure of individual BC particle with E_{abs, bulk}.