Constructing shapes and mixing structures of black carbon particles with applications to optical calculations

Black carbon (BC) is a kind of ubiquitous atmospheric aerosol with strong optical absorption in the atmosphere. BC can influence the regional and global climate by disturbing the energy balance of the earth and atmosphere. At present, it is challenging to precisely estimate the BC optical properties using instruments and numerical models because of its complex morphology and mixing structures in individual particles. This study for the first time presents a novel tool (named as EMBS) to construct realistic 3D shape models based on real BC particles from observed electron microscopic images for their optical calculation. We found that the commonly used spherical shape models may underestimate the absorption enhancement (E_abs) of BC particles. The mixing structures between BC and non-BC materials in individual particles can significantly influence their E_abs. The study highlights that the BC core morphology, coating shape, coating thickness, and mixing structures influence their optical properties and should be considered as important variables in climate models. The novel EMBS builds a bridge between microscopic observation and BC optical calculation, which has strong implications for reducing the bias of optical calculation and providing important variables in estimating BC climate effects in the future.

Figure 1. 3D models of black carbon individual particles