Intensity and Polarization of the Radiation Emerging from an Optically Thick Rayleigh Atmosphere

Abstract

The intensity and degree of polarization of the radiation diffusely transmitted and reflected by a plane-parallel, homogeneous Rayleigh atmosphere were computed for scattering optical thicknesses τ1 from 1.0 to 10.0. The results show that the distribution of the intensity of the radiation diffusely reflected by an atmosphere of τ1 = 10.0 is similar to that reflected by an atmosphere of infinite optical depth. The distributions of the degree of polarization are identical for τ1 = 10.0 and ∞ when the sun is at the zenith; otherwise, they are significantly different. Except for the magnitude of the intensity which decreases with increasing solar zenith distance, the distributions of the intensity and polarization of the diffusely transmitted radiation are independent of the sun’s position when τ1 ~ 10.0 or greater. An interesting feature displayed by the polarization of the transmitted radiation for 1.0≤τ1≤2.0 is the simultaneous appearance of four neutral points at low elevations of the sun. For higher values of τ1, neutral points are nonexistent.