Single-scattering albedo of smoke retrieved from the sky radiance and solar transmittance measured from ground

A method of aerosol single-scattering albedo retrieval from diffuse radianc e measured in the solar almucantar and direct solar measurements is propose d, The aerosol scattering optical thickness is derived from the diffuse rad iance by applying a radiative transfer model driven by aerosol microstructu re parameters and Mie theory. To improve the accuracy of the scattering opt ical thickness, the inversion results are acceptable only if the radiance i s measured across the total almucantar and is accurately fitted by a theore tical model. The aerosol is assumed as an external mixture of purely scatte ring particles and soot particles, with the soot approximated as a pure abs orber. The criterion for the acceptance of fit is determined from the analy sis of the effects of random and systematic errors on the single-scattering albedo retrieval. The method was applied to measurements conducted during the Smoke, Clouds, and Radiation - Brazil (SCAR-B) campaign in August and S eptember 1995. Aerosol radiance data were extensively collected by the Aero sol Robotic Network (AERONET) of ground-based Sun/sky radiometers. The anal ysis focuses on the studies of the time variability of the biomass burning aerosol in the local Cuiaba area, supplemented by measurements collected in Cuiaba in 1993-1994. The results show reasonable ranges of the aerosol sin gle-scattering albedo variability (for example, single-scattering albedo av erages 0.87 +/-0.08 at 670 nm). The spectral dependence of the single-scatt ering albedo has both tendencies: decreasing and increasing with wavelength . The potential reasons causing different spectral behavior are analyzed th eoretically.