Depolarization of radar signals due to multiple scattering in rain

The linear depolarization ratio (LDR) of radar returns from rain is studied. Pulse intensities of copolarized and cross polarized components are calculated by using the second-order solution of the time-dependent radiative transfer equation for a finite rain layer composed of spherical raindrops. Theoretical results show significant differences in LDR values between X and Ka bands for light to moderate rainfall rates and a rapid increase in the LDR reaching a level of about -8.5 dB at radar ranges near the rear edge of the rain layer. These characteristics of the LDR are in good agreement with observations from an air-borne dual-frequency, dual-polarized radar and suggest that a part of the depolarized radar power is caused by second-order multiple scattering effects