Enhancing sensitivity on the polarimetric WSR-88D

A polarimetric configuration with simultaneous transmission and reception of horizontally and vertically polarized electromagnetic waves has been implemented with the WSR-88D KOUN in Norman, Oklahoma. The transmitted power in each polarimetric channel is two times or 3 dB lower than in the “legacy” single polarization channel. This makes the polarimetric WSR-88D less sensitive than the legacy system, which means the weakest signals just above the noise level are lost in the polarimetric system relative to the legacy system. Some of the important weather features in weak signal may become less visible with the polarimetric radar. Among those are total echo coverage, the thin lines associated with low-level boundaries, distant echoes, tops of clouds.

Two signal processing techniques to enhance sensitivity of polarimetric weather radar are discussed in the paper.

1. Removal of noise speckles allows reducing signal-to-noise threshold in calculations of the radar moments and adds 3-4 dB to sensitivity.

2. Coherent summation of voltages in the horizontal and vertical channels adds an additional 1 to 3 dB to sensitivity.

Combining the above techniques, sensitivity of the polarimetric WSR-88D can be restored to the level of the “legacy” system. The techniques are demonstrated on data collected with the dual-polarization prototype KOUN. The results are compared against data collected with the single-polarization WSR-88D testbed KCRI which is nearly co-located to KOUN.