Black-carbon absorption enhancement in the atmosphere determined by pjournal article mixing state
Journal
Nature Geoscience
Journal Volume
10
Journal Issue
3
Pages
184-188
Date Issued
2017
Author(s)
Liu, D.
Whitehead, J.
Alfarra, M.R.
Reyes-Villegas, E.
Spracklen, D.V.
Reddington, C.L.
Kong, S.
Williams, P.I.
Ting, Y.-C.
Haslett, S.
Taylor, J.W.
Flynn, M.J.
Morgan, W.T.
McFiggans, G.
Coe, H.
Allan, J.D.
Abstract
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.
Type
journal article