USING THE MULTIPLE SCATTERING THEORY FOR CALCULATION OF THE RADIATION FLUXES FROM EXPERIMENTAL AEROSOL DATA

Abstract

The ground-based measurements of the spectral direct solar radiation fluxes and spectral sky radiances were basis for obtaining the aerosol characteristics such as columnar distribution function and effective refractive index, respectively. These characteristics were retrieved by a numerical solution of the inverse problem. The particle columnar size distribution function was chosen in the form of modified gamma distribution. The obtained aerosol parameters were utilized as input data for the multiple radiation scattering model (MRSM) to calculate the radiation fluxes. The dependence of calculation error of individual radiation characteristics (sky radiance, global and diffuse radiation) on a given number of terms NT (scattering orders) in the MRSM is studied. The NT necessary for successful calculation of radiation characteristics (for chosen accuracy) for actual atmospheric conditions is shown (aerosol optical properties were characterized, e.g., by spectral optical thickness). The approximate formulae for calculating the total sky radiances and total radiation fluxes, are find. Applying these formulae the value NT′ smaller than NT can be used for calculating radiation characteristics with the same accuracy. The scattering orders higher than NT′ are calculated on the basis of a known structure of previous scattering orders (1→NT′).