Circularly polarized waves are most sensitive to the influence of the propagation medium factors such as differential phase shift and differential attenuation. The reason of that is a feature of the wave polarization transformation. Such circumstances require consideration during designing radars working with circularly polarized waves. The aim of the study is to develop of approach for estimating the effect of the wave polarization transformation on a value of one of the most informative parameters based on the use of Jones vector component functional dependence on a polarization ellipse orientation angle and ellipticity angle. The task of this work is obtaining the analytical equation for the determination of that polarimetric radar informative parameter. As a result, the solution for the case of wave backscatter by the propagation medium was obtained when the medium basis orientation differs from the radar basis orientation. The estimation of the circular depolarization ratio providing the determination of regions with its raised value was obtained.