Atmospheric Chemistry and Physics Spectral dependence of aerosol light absorption over the Amazon Basin

Abstract. In this study, we examine the spectral depen-dence of aerosol absorption at different sites and seasons in the Amazon Basin. The analysis is based on measurements performed during three intensive field experiments at a pas-ture site (Fazenda Nossa Senhora, Rondônia) and at a pri-mary forest site (Cuieiras Reserve, Amazonas), from 1999 to 2004. Aerosol absorption spectra were measured using two Aethalometers: a 7-wavelength Aethalometer (AE30) that covers the visible (VIS) to near-infrared (NIR) spectral range, and a 2-wavelength Aethalometer (AE20) that mea-sures absorption in the UV and in the NIR. As a consequence of biomass burning emissions, about 10 times greater absorp-tion values were observed in the dry season in comparison to the wet season. Power law expressions were fitted to the measurements in order to derive the absorption Ångström ex