A hybrid method for modeling polarized radiative transfer in a spherical-shell planetary atmosphere

The Markov chain method is developed for polarized radiative transfer in a pseudospherical atmosphere with solar illumination. This solution is then used as an initial guess of the radiation field for a spherical atmosphere. By use of the short characteristic method, a convergent radiation field throughout the atmosphere is achieved after a few Picard iterations. We verified this hybrid method by comparing numerical results to those obtained by a backward Monte Carlo calculation. We carried out a demonstration calculation by simulating the Titan haze reflected intensity I and Stokes parameter Q, and degree of linear polarization at 934.8 nm wavelength. Comparison of the I and Q images to those measured by the Imaging Science Subsystem instrument on the Cassini spacecraft shows the hybrid method to be useful for radiative transfer analyses for (both optically and physically) thick spherical atmospheres.