An Approach to Simulate the Effects of Antenna Patterns on Polarimetric Variable Estimates

One of the main challenges to the use of phased array radar for weather observations is implementation of dual-polarization with acceptable errors of polarimetric variable estimates. This is because the differences between the copolar antenna patterns at the horizontal and vertical polarizations as well as cross-polar fields can introduce unacceptable measurement biases. For example, to achieve acceptable differential reflectivity (Z_DR) bias (i.e., less than 0.1 dB) using simultaneous transmission and reception of H and V polarized waves, the isolation between coaxial cross-polar and copolar beams needs to be in excess of 50 dB. Because such isolation cannot be achieved at an affordable price by antenna hardware and the copolar patterns inevitably vary with each beam position it is crucial to properly evaluate errors of estimates due to radiation patterns. Herein a novel approach to evaluating antenna pattern induced polarimetric variable biases by combining the measured or simulated radiation patterns and simulated time series will be presented.