Abstract
During aging processing, black carbon (also called soot) particles may tend to be mixed with other aerosols, and highly influence their radiative forcing. In this study, freshly emitted soot particles were simulated as fractal aggregates composed of small spherical primary monomers. After aging in the atmosphere, soot monomers were coated by a thinly layer of sulfate as thinly coated soot particles. These soot particles were entirely embedded into large sulfate particle by further aging, and becoming heavily coated soot particles. In clear-sky conditions, black carbon radiative forcing with different aging states were investigated for the bottom and top of atmosphere (BOA and TOA). The simulations showed that black carbon radiative forcing increased at BOA and decreased at TOA after their aging processes. Thinly and heavily coated states increased up to ~12% and ~35% black carbon radiative forcing at BOA, and black carbon radiative forcing at TOA can reach to ~20% and ~100% smaller for thinly and heavily coated states than those of freshly emitted states, respectively. The effect of aging states of black carbon radiative forcing was varied with surface albedo, aerosol optical depth and solar zenith angles. These findings would be helpful for the assessments of climate change.
Highlights
Other aerosol components in the atmosphere through the coagulation and condensation of secondary aerosol compounds[28]
Emitted soot particles consist of small spherical primary particles combined into branched aggregates, the soot monomers are coated by a thin layer of other aerosol components as thinly coated soot particles, and the soot particles are entirely embedded into other aerosol components in heavily coated soot particles
Compared with freshly emitted soot particles, each monomer of thinly coated soot particles can be assumed as having structures of a concentric core containing black carbon particles with high light absorption and a shell containing weakly absorbing particles[49]
Summary
Other aerosol components in the atmosphere through the coagulation and condensation of secondary aerosol compounds[28]. The differences of black carbon radiative forcing between different aging states decrease at BOA and increase at TOA with higher surface albedo.
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