Effects of atmospheric transformations of the organic fraction of biomass burning aerosol on the radiative forcing: a box model analysis

We present the first results of our numerical study aimed at identifying the possible effects of the atmospheric evolution of biomass burning (BB) aerosol on the aerosol direct radiative forcing (DRF). We used a microphysical box model, which implements different parameterizations of the organic aerosol evolution within the volatility basis set framework, along with the Mie theory and radiative transfer calculations to simulate the dynamics of the physical, optical and radiative properties of polydisperse carbonaceous aerosol in an isolated BB smoke plume. We found that atmospheric transformations of the organic fraction of BB aerosol can result in major changes in the BB aerosol DRF. These changes are related to the underlying variations in the aerosol optical depth and single scattering albedo in a nonlinear manner and are especially strong in optically dense plumes.