Changes of the absorption properties of aerosol from Siberian wildfires due to atmospheric aging: analysis of satellite observations

Abstract

Carbonaceous aerosol originating from forest fires and other types of open biomass burning (BB) is known to have a strong impact on the radiative balance of the atmosphere but available model estimates of the corresponding climate effects are characterized by large uncertainties due to insufficient knowledge of its sources and atmospheric transformations (aging). Here we study the atmospheric aging of BB aerosol by analyzing data of satellite measurements of the absorption and extinction aerosol optical depths (AAOD and AOD) in BB plumes from wildfires in Siberia. Along with the aerosol measurements, our analysis involves satellite data for CO column amounts as well as the simulations of the BB aerosol photochemical age using a chemistry transport model. The analysis includes the two main stages. First, we study the BB aerosol evolution as a function of its photochemical age by using the observations over Siberia in the period from May to September of 2012. Second, we examine changes in the BB aerosol optical characteristics in the smoke plumes that had been transported from Siberia into the European part of Russia in July of 2016. The results indicate that photochemical aging strongly affects the behavior of both AAOD and AOD. The results also show that aged BB aerosol becomes less absorptive at the near UV wavelength range, indicating a depletion of brown carbon in particles. The BB aerosol aging effects detected at the both stages of the analysis are found to be consistent.