Model Analysis of Origination of Semidirect Radiative Effect of Siberian Biomass Burning Aerosol in the Arctic

The effects of atmospheric aerosol, including smoke, on cloudiness are of great interest for understanding the current climate changes. However, the radiative effect of Siberian biomass burning aerosol (SBBA) on clouds in the Arctic has been little studied. Based on simulation with the CHIMERE chemistry transport model and WRF meteorological model, we analyze the processes responsible for origination of the semidirect radiative effect (SDRE) of smoke from Siberian wildfires over snow–ice surfaces in the Arctic, including time- and space-averaged changes in the radiative fluxes, cloud parameters in different cloud levels, and some meteorological characteristics associated with cloud generation due to the radiative effect of (SBBA). The results show that solar radiation scattering by SBBA particles increases the static stability of the atmosphere at altitudes of 2–4 km and suppresses vertical turbulent motions, which decreases the rate of water condensation, the optical thickness of clouds, and the mixing ratio in the medium- and partly lower-level clouds. The decrease in the optical thickness of clouds, in turn, causes origination of positive SDRE of SBBA at the top and bottom of the atmosphere. Radiation absorption by SBBA particles does not play an essential role in these processes, although additionally changes meteorological characteristics. Our results expand fundamental knowledge of aerosol–cloud interactions in the Arctic and can be used for improving climate models.