A POLARIMETRIC RAIN BACKSCATTER MODEL DEVELOPED FOR COHERENT POLARIZATION DIVERSITY RADAR APPLICATIONS

The electromagnetic direct and inverse scattering problem of plane wave backscattering from distributed fluctuating scatterers, such as hydrometeors in rain, is analyzed for the monostatic case for which coherent dual polarization pulsed radar measurements are made available. Based on a critical assessment of the existing literature on polarimetric radar meteorology, it was found necessary to relate the polarimetric doppler signatures of such distributed fluctuating scatterers in terms of the Kennaugh target characteristic radar polarization theory and its extensions. Using the resulting co/cross-polarization null/max approach expressed in a linear (HV) polarization state basis in order to recover more useful information from such polarimetric L-to-W band radar data, the rain backscatter model of Stapor and Pratt is further developed. Using polarimetric scattering matrix pulse compression radar data in the X- and Q-bands, the derived polarimetric rain backscatter model is verified. The computer assisted data evaluation resulted in the findings that the simultaneous use of the co/cross-pol nul and of the scattering matrix element spectral plots measured in the linear (HV) basis provide very useful information on identifying dynamic phase changes of fluctuating hydrometeors within moving sheets of rain showers. It was observed that the polarimetric doppler signatures of the various scattering element plots {dollar}vert{dollar}S{dollar}sb{lcub}rm HH{rcub}{dollar}(f){dollar}vertsp{lcub}2{rcub}{dollar}, {dollar}vert{dollar}S{dollar}sb{lcub}rm HV{rcub}{dollar}(f){dollar}vertsp{lcub}2{rcub}{dollar} and {dollar}vert{dollar}S{dollar}sb{lcub}rm VV{rcub}{dollar}(f){dollar}vertsp{lcub}2{rcub}{dollar} are identical only for a moving compact (single) scatterer whereas for non-uniformly moving distributed scatterers those may be rather different and may provide a means of discriminating between slowly moving compact objects such as ground-based vehicles, amphibious carriers, naval vessels and/or low altitude aircraft against dynamic meteorologic and marine background clutter.