Differential phase calibration of linearly polarized weather radars with simultaneous transmission/reception for estimation of circular depolarization ratio

The circular depolarization ratio (CDR) measurement recently regained great interest among radar meteorologists because of its significant potential for detection and quantification of hydrometeors above the melting layer. An innovative CDR estimator has recently been proposed by Ryzhkov et al. for a linearly polarized weather radar (LPWR) with simultaneous transmission and reception of the waves with horizontal and vertical polarizations (SHV), a popular operational radar configuration for most national weather radar networks. The key for efficient implementation of CDR estimator in LPWR is the accurate calibration of the system differential phase upon transmission in the SHV mode of operation. The Enterprise Electronics Corporation (EEC) recently has proposed a novel calibration method, which facilitates the implementation of the CDR measurement in LPWR. The paper addresses the details of the proposed calibration method. The measurements by the EEC C-band in-house polarimetric radar illustrate reliable performance of the proposed calibration method for CDR measurement, paving the way for a wide use of CDR to reveal important microphysical features of the storms.