Radiance and Polarization of the Earth's Atmosphere with Haze and Clouds

Abstract

The radiance and polarization of the earth's atmosphere with haze and clouds has been calculated for a realistic model which includes Rayleigh scattering from the atmospheric molecules, Mie scattering from aerosols which are distributed with height according to the Elterman model, and Mie scattering from water droplets in clouds. Two different size distributions are used for the water droplets: one for the haze C model and the other from the nimbostratus model. Multiple scattering from the atmosphere and planetary surface is included to all orders by a Monte Carlo technique. The exact scattering matrix for the aerosol haze C and nimbostratus models is calculated from the Mie theory. Solar radiation is assumed to be unpolarized and incident from the zenith. The radiance and polarization are calculated at λ = 0.4 and 0.7 μ for a model of a cloud in the real atmosphere and the results are compared to those for the cloud alone and for the atmosphere alone. Relatively large polarization values are obtained except for viewing angles near the zenith or nadir or for photons transmitted through optically thick clouds. The polarization is typically larger at λ = 0.4 μ than at λ = 0.7 μ, because of the greater contribution from Rayleigh scattering at the former wavelength.