Advanced Polarimetric Measurements and Analysis with the CSD-CHILL Weather Radar

This AFOSR grant played an important role in the validation of polarimetric signatures in severe storms obtained with advanced CSU-CHILL fully polarimetric radar system. Two field programs during the summers of 95 and 96 were conducted involving instrumented chase vehicles for hydrometeor measurements. An unusual flood event in Fort Collins was also captured by radar and these data were analyzed to show the power of polarimetric-based techniques of measuring rainfall. Equipment purchased with this grant enabled the evaluation of transmitting slant 45 deg135 deg and RHCLHC polarizations on a pulse-to-pulse basis. A simplified variant of this technique is likely to be adopted for the polarimetric upgrade of the WSR-88D system in the future. Thus, this grant played a key role in the evaluation of future NEXRAD modifications in which the DoD has a heavy investment. We also evaluated random phase and polarization coding of the transmitted waveform via simulations and time series analysis for suppressing second-trip echoes, a known problem for the WSR-88D system. The final results from this grant show conclusive evidence that polarimetric techniques are vital to the remote sensing of storm microphysics. The results of this grant are also applicable to the Theatre Weather Radar TWR planned by the DoD to provide tactical weather support.