Implementation of a Phase-Spin Dual-Polarized Weather Radar

The University of Massachusetts Microwave Remote Sensing Laboratory, as part of the CASA Engineering Research Center, developed the Phase-Tilt Weather Radar (PTWR) as a low-cost means to develop and evaluate phased-array technology for weather applications. The PTWR scanned electronically in azimuth and mechanically in elevation. As a consequence of the mechanical tilting, the horizontal and vertical polarizations are known to rotate as one scans in azimuth away from boresight. The rotation can result in bias of polarimetric products. Though the effect is negligible for low elevation angles (less than 10 degrees), it is more pronounced for higher elevations. This polarization rotation effect is eliminated by rotation of the aperture such that the electronic scan is perfomed in elevation with mechanical scan in azimuth. We refer to this configuration as Phase-Spin. The PSWR has been deployed atop a tower on Orchard Hill on the UMass campus. It scans electronically in elevation with 11 beams, from 0 degrees to 45 degrees and rotates mechanically over 360 degrees in azimuth. Observations by the radar in this configuration are presented, and plans for a mobile deployment are presented.