Monday, 10 February 2003: 11:15 AM
Evaluation of polarimetric Capability on the Research WSR-88D
Several years of effort devoted to the NOAAs Research WSR-88D radar culminated in generation and display of dual polarization data. For expediency the system was configured from several autonomous subsystems, most of which were designed for other purposes. We document integration of the various components needed to operate radar in the dual polarization mode. The proposed polarization scheme uses simultaneous transmission and reception of horizontally and vertically polarized echoes. Because it has not been tested, we have devoted much time to engineering evaluation and calibration. We report on the overall stability of the system, and ways to calibrate the radar. Particularly challenging is calibration of differential reflectivity because unlike other research radars the WSR-88D can not point its beam vertically. We believe that combining sun scans, ground clutter returns, and self consistency of polarimetric data from precipitation can provide accuracy of few tenths of dB in differential reflectivity. The implied limit for depolarization is about - 30 dB. Meteorological data have high co to cross-polar correlation and therefore small error in estimates of differential phase. Therefore for rain measurement and classification of hydrometeor in warm regimes existing WSR-88D scanning strategies should suffice. Nonetheless, for measurements in various winter storms, slowing the antenna rotation or more complex data processing are needed to insure that the error in differential reflectivity is smaller than about 0.2 dB.