Radiative forcing of smoke aerosol taking into account the photochemical evolution of its organic component: influence of illumination condtions and underlying surface albedo
T.B. Zhuravleva1, I.M. Nasrtdinov1, I.B. Konovalov2, N.A. Golovushkin2
1V.E. Zuev Institute of Atmospheric Optics of Siberian Branch of the Russian Academy of Science, Tomsk, Russia
2Institute of Applied Physics of the Russian Academy of Sciences (IAP RAS), Nizhny Novgorod, Russia
Keywords: organic aerosol, microphysical model, evolution of optical characteristics, numerical simulation, solar radiation, aerosol radiative forcing
Abstract
The simulation results the radiative forcing of smoke aerosol (RFA) at the boundaries of the atmosphere are considered depending on the photochemical evolution of its organic component, illumination conditions, and underlying surface types (water, mixed forest, and snow/ice). An increase in the albedo of the underlying surface and a decrease in the aerosol optical depth can lead to the transformation of the cooling effect into heating at the top of the atmosphere. An increase in the absorbency of aerosol particles is the cause of an increase in RFA at the top of the atmosphere, which is most significant over snow/ice surfaces, while at the bottom of the atmosphere, RFA decreases. As the solar zenith angle increases, the absolute value of RFA decreases as the smoke plume propagates over weakly reflecting surfaces, but with an increase in the albedo of the underlying surface, this dependence transforms into a nonmonotonic one. It is shown that neglecting the transformations of the optical characteristics of organic aerosol can lead to overestimation or underestimation of the radiative forcing of the aerosol at the top of the atmosphere by several times (by several tens of W/m2), and also cause an error in determining the RFA sign.
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