Patricia Sawamura¹, Eduardo Landulfo¹

¹IPEN - Instituto de Pesquisas Energeticas e Nucleares

 

The angstrom exponent α is often used to provide information about the aerosol size distribution. Variations of the latter are a result of dynamic processes that occur from the moment aerosols are formed and they influence the aerosols radiative properties (aerosol optical thickness, phase function, single-scattering albedo). In the context of biomass burning events, a decrease of α might be due to particles aging and size increasing processes. The single-scattering albedo ω₀ can be seen as a parameter which characterizes absorption: the higher is the absorption the lowest is ω₀. Furthermore, literature shows that as the particles grow by coagulation and as the smoke gets old, ω₀ increases. The lidar ratio S is the ratio between the aerosol extinction coefficient and the aerosol backscatter coefficient and is needed to determine the backscatter lidar equation. Its behavior is not obvious since it depends on the wavelength of the incident light, the refractive index, the aerosol size distribution and the relative humidity; however the higher values of S are supposed to be linked to coarse mode events and the lowest values to higher concentrations of fine mode particles. S is also found to increase with relative humidity for continental aerosols. In this paper we analyze the temporal evolution of these optical parameters obtained from AERONET (Aerosol Robotic Network) data and compare them to 2005 lidar data in attempt to find patterns as those mentioned above and signatures of smoke transports from regions where biomass burning occur (during the latter half of the Brazilian dry season) to São Paulo.