Abstract
Spectral and angular distributions of the intensity of solar aureole were evaluated accurately for several realistic models of the turbid atmosphere. Three cases of the size distribution, two cases of the imaginary part of the index of refraction and four cases of the columnar amount were assumed for aerosol models. The reflection of light from the ground surface was taken into account by assuming a Lambertian surface. Computations were carried out by means of the matrix-doubling method, but evaluating the intensities of singly and multiply scattered radiations separately. An advantage of this algorithm is to provide accurate solutions without consuming large computation time, because the intensity of singly scattered radiation can be evaluated exactly and only ten or twenty terms are necessary for the Fourier expansion of the phase function to evaluate the intensity of multiply scattered radiation with sufficient accuracy.
Results of computation show that the effect of multiple scattering is so significant as compared with the multiple scattering due to air molecules that the single scattering theory for aerosols breaks down for almost all wavelengths and turbidity conditions. The contribution of light reflected from the ground surface is also significant. The effect of absorbing aerosols becomes noticeable for scattering angles larger than 10°, as a result of multiple scattering.
