Estimation of seasonal variability of aerosol radiative forcing based on measurements of atmospheric aerosol optical properties at ZOTTO station
S.S. Vlasenko, A.S. Mikhailova, E.F. Mikhailov, E.Yu. Nebosko
Saint Petersburg State University, St. Petersburg, Russia
Keywords: atmospheric aerosol, radiative forcing, single scattering albedo, aerosol scattering coefficient, aerosol absorption coefficient, smoke aerosol
Abstract
Atmospheric aerosols are a significant factor of variations in the radiative balance, particularly for such regions as Central Siberia, where there are many anthropogenic and biogenic aerosol sources. However, the parameters and seasonal dynamics of aerosol radiative forcing in this region remain understudied. The aim of this work is to estimate the efficiency of aerosol radiative forcing ( RFE ) for the atmosphere of Central Siberia based on measurements of aerosol scattering and absorption coefficients at background ZOTTO station in 2007-2024. The atmospheric and underlying surface characteristics required for calculating RFE were taken from MERRA-2 reanalysis data. The resulting time series of RFЕ for ZOTTO station show strong day-to-day variability and a clearly pronounced seasonal cycle. Although the maximal concentrations of absorbing (soot) aerosol and, consequently, the maximal values of the aerosol absorption coefficient are observed in summer, the efficiency of aerosol forcing during this period is negative, with the characteristic RFЕ = -30 W/m2. In winter, when aerosol concentrations and aerosol optical coefficients are substantially lower, the efficiency of aerosol forcing is positive and amounts to approximately +25 W/m2; the measurement-period mean RFE = -5 W/m2. The change in the sign of aerosol forcing from positive to negative occurs in early May, and vice versa, in late October, which is primarily due to the seasonal change in the albedo of the underlying surface. The results can be used to refine predictions of regional climate changes in Siberia.
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