Quantifying the sensitivity of black carbon absorption to model representations of particle mixing

Abstract:

Atmospheric black carbon is distributed across diverse aerosol populations, with individual particles exhibiting tremendous variation in their chemical composition and internal morphology. Absorption by an individual particle depends on both its constituent aerosol species and the arrangement of those species within the particle, but this particle-scale complexity cannot be tracked in global-scale simulations. Instead, large-scale aerosol models assume simple representations of particle composition, referred to here as inter-particle mixing, and simple representations of particle’s internal morphology, referred to here as intra-particle mixing. This study quantifies the sensitivity of absorption by black carbon to these model approximations of particle mixing. A particle-resolved model was used to simulate the evolution of diverse aerosol populations and, as the simulations proceeded, absorption by black carbon was modeled using different representations of inter-particle mixing and intra-particle mixing. Although absorption by black carbon at the particle level is sensitive to the treatment of particles’ internal morphology, at the population level absorption is only weakly sensitive to the treatment of intra-particle but depends strongly on model representations of inter-particle mixing.