Atmospheric black carbon makes an important but poorly quantified contribution to the warming of the global atmosphere. Laboratory and modelling studies have shown that the addition of non-black-carbon materials to black-carbon particles may enhance the particles' light absorption by 50 to 60% by refracting and reflecting light. Real-world experimental evidence for this â € lensing' effect is scant and conflicting, showing that absorption enhancements can be less than 5% or as large as 140%. Here we present simultaneous quantifications of the composition and optical properties of individual atmospheric black-carbon particles. We show that particles with a mass ratio of non-black carbon to black carbon of less than 1.5, which is typical of fresh traffic sources, are best represented as having no absorption enhancement. In contrast, black-carbon particles with a ratio greater than 3, which is typical of biomass-burning emissions, are best described assuming optical lensing leading to an absorption enhancement. We introduce a generalized hybrid model approach for estimating scattering and absorption enhancements based on laboratory and atmospheric observations. We conclude that the occurrence of the absorption enhancement of black-carbon particles is determined by the particles' mass ratio of non-black carbon to black carbon.
Centre for Atmospheric Sciences, School of Earth and Environmental Sciences, University of Manchester, Manchester, United Kingdom; National Centre for Atmospheric Science, Manchester, United Kingdom; Institute for Climate and Atmospheric Science, School of Earth and Environment, University of Leeds, Leeds, United Kingdom; School of Atmospheric Physics, Nanjing University of Information Science and Technology, Nanjing, China; School of Environmental Studies, China University of Geosciences (Wuhan), Wuhan, China
Recommended Citation:
Liu D.,Whitehead J.,Alfarra M.R.,et al. Black-carbon absorption enhancement in the atmosphere determined by particle mixing state[J]. Nature Geoscience,2017-01-01,10(3)