Impact of the Atmospheric Photochemical Evolution of the Organic Component of Biomass Burning Aerosol on Its Radiative Forcing Efficiency: A Box Model Analysis

Abstract

We present the first box model simulation results aimed at identification of possible effects of the atmospheric photochemical evolution of the organic component of biomass burning (BB) aerosol on the aerosol radiative forcing (ARF) and its efficiency (ARFE). The simulations of the dynamics of the optical characteristics of the organic aerosol (OA) were performed using a simple parameterization developed within the volatility basis set framework and adapted to simulate the multiday BB aerosol evolution in idealized isolated smoke plumes from Siberian fires (without dilution). Our results indicate that the aerosol optical depth can be used as a good proxy for studying the effect of the OA evolution on the ARF, but variations in the scattering and absorbing properties of BB aerosol can also affect its radiative effects, as evidenced by variations in the ARFE. Changes in the single scattering albedo (SSA) and asymmetry factor, which occur as a result of the BB OA photochemical evolution, may either reduce or enhance the ARFE as a result of their competing effects, depending on the initial concentration OA, the ratio of black carbon to OA mass concentrations and the aerosol photochemical age in a complex way. Our simulation results also reveal that (1) the ARFE at the top of the atmosphere is not significantly affected by the OA oxidation processes compared to the ARFE at the bottom of the atmosphere, and (2) the dependence of ARFE in the atmospheric column and on the BB aerosol photochemical ages almost mirrors the corresponding dependence of SSA.

Phase Behavior and Viscosity in Biomass Burning Organic Aerosol and Climatic Impacts

“…Previous studies have investigated the phase behavior of some types of atmospheric aerosol particles, such as mixtures of secondary organic aerosol with inorganic salts and mixtures of secondary organic aerosol with hydrocarbon-like organic aerosol. − However, the phase behavior of primary BBOA remains understudied and unresolved. Models simulating the microphysics, chemical evolution, concentration, or radiative properties of wildfire smoke typically assume that BBOA comprises only a single phase. ,− On the other hand, Jahn et al identified that some sampled BBOA particles exhibited an organic shell coating an organic core using transmission electron microscopy images, with the caveat that the vacuum conditions required for this type of microscopy may affect the particle morphology. In addition, bulk-phase liquid tar condensates generated from high-temperature wood distillation were reported to have separated into a water-soluble and nonsoluble oily phase, , although it is not known whether phase separation would occur in particles containing this material after equilibration with ambient relative humidity (RH).…”

Microphysical parameters of smoke aerosols based on the results of inversion of aerosol scattering and extinction coefficients in a big aerosol chamber of IAO SB RAS

“…As an integral part of atmospheric aerosol, smoke particles significantly affect the environment and human health 1,[9][10][11][12][13][14][15][16][17][18][19] . Scattering and absorbing optical radiation, smoke aerosol participates in the formation of the radiation budget of the atmosphere and the Earth's surface, affects the state of the weather and climatic processes [20][21][22][23][24][25][26][27] .…”

Biomass burning organic aerosol (BBOA) from wildfires has multiple phases and is more viscous than laboratory generated BBOA

“…44 Hettiyadura et al and Li et al have both shown that tar condensates from both burning and O2-free pyrolysis of wood separate into immiscible aqueous and oily liquid phases. 45,46 Despite the above, models simulating the chemistry, transport, and climatic impacts of wildfire BBOA typically assume that BBOA comprises only a single phase. 37,[47][48][49] Our understanding of the viscosity and phase behaviour of BBOA remains incomplete, in part, because previous studies have focused on samples generated in the laboratory and not collected from the real atmosphere.…”