Size distribution of atmospheric aerosols and radiative properties

In the modeling of aerosols effects in the energy budget, radiative forcing, two parameters are mainly used: the asymmetry parameter, g and the back scattering parameter, R. These parameters have been evaluated with the aerosols distributions obtained by King´s inversion method. The aerosol optical thickness obtained from the direct radiance measurements, made by a solar photometer at the wavelengths of 368, 500 and 778 nm, have been used as input variables to this method. The temporal behavior showed during 1994 by the asymmetric and the back scattering parameters can be explained as a function of the evolution in the particles concentration. Thus, it is observed that the evolution toward an atmosphere with Mie behavior for the wavelengths of the solar spectrum is related to the relative increase of particles concentration with a ratio bigger than 0.8 μm. The relation between the distribution function and the temporal behavior of the parameters g and R shows for small values of Angstrom parameter, α, scattered values of both parameters. On the other hand, when the Angstrom parameter increases both parameters g and R also increase tending to an average value of 0.8 and 0.6 respectively.