I. Introduction
The Weather Surveillance Radar–1988 Doppler (WSR-88D) has been operational for over 30 years and continues to be the primary mission-critical instrument supporting national weather service (NWS) forecasters in issuing hazardous weather warnings in the United States. The WSR-88D provides measurements through simultaneous transmission and reception of electromagnetic waves in both horizontal () and vertical () polarizations, which are used to estimate spectral moments and polarimetric variables. The WSR-88Ds have exceeded their engineering design lifespan and are projected to reach the end of their operational lifetime by 2040. Considering the limitations of reflector-antenna radars, it is unlikely that the WSR-88D will be capable of meeting the radar functional requirements outlined by the National Oceanic and Atmospheric Administration (NOAA) [1]. Demanding optimal requirements include the capability to produce 1-min volume scans with a spatial resolution of 1° in azimuth and elevation (as defined by the half-power beamwidth [2]) and with no degradation in other performance parameters, such as the sensitivity or the standard deviation (SD) of radar-variable estimates.