  In this article we propose a numerical algorithm to compute the intensity and
polarization of a polychromatic electromagnetic radiation crossing a medium
with graded refractive index and modeled by the Vector Radiative Refractive
Transfer Equations (VRRTE). Special attention is given to the case where the
refractive index has a discontinuity for which the Fresnel conditions are
necessary. We assume that the only spatial variable of interest is the altitude
(stratified medium). An algorithm based on iterations of the sources is shown
to be monotone and convergent. Numerical examples are given with highly varying
absorption coefficient kappa and Rayleigh scattering as in the Earth
atmosphere. To study the effect of CO2 in the atmosphere kappa is changed in
the frequency ranges where CO2 is absorbing.
