Interpretation of the Sun's Aureole Based on Atmospheric Aerosol Models

Theoretical calculations of forward scattered sunlight are carried out assuming single scattering. Analytic models for the altitude-size distribution of atmospheric aerosols are used of the separable form eta(y,r) = rho(y)n(r), where rho(y) is a vertical density profile and n(r) is the differential aerosol size distribution. The functions considered for n(r) include the models of Junge, Deirmendjian, a generalized distribution function, and a mathematical spline model. For rho(y), we use an exponential model, a mixing height model involving a step function profile, and a two-term generalized distribution function. The theory is set up so that optimum fits to the experimental data at several wavelengths can be achieved by adjusting the parameters of the aerosol model. Both photoelectric and photographic measurements of daytime sky brightness are made, and the data are analyzed with several different aerosol models.