Spectral processing and ground clutter mitigation for dual polarization staggered PRT signals in Doppler weather radars

Ambiguities in range (out-of-trip echoes) and velocity (aliasing) arise in Doppler weather radars due to the large spatial extent and significant velocities associated with some weather conditions. Sirmans (1976) suggested that the staggered pulse repetition time (PRT) waveform could be used as a viable means to reduce range and velocity ambiguities. In the staggered PRT technique, two interlaced sampling rates are used to decrease (or eliminate) velocity aliasing while maintaining adequate range coverage at the expense of reducing the effectiveness of ground clutter filtering. For a while, the operational implementation of the staggered PRT algorithm had been prevented due to the inability to provide adequate ground clutter filter suppression. Sachidananda and Zrnic (2000) proposed a solution to this issue by introducing the Spectral Algorithm for Clutter Harmonics Identification (SACHI) which exploits spectral processing of samples from interlaced PRTs with a 2/3 ratio. More recently, Warde and Torres (2011) showed that the CLutter Environment Analysis using Adaptive Processing (CLEAN-AP) filter, described by the same authors in 2009, could be used not only to filter but to detect ground clutter contamination in staggered PRT waveforms with any PRT ratio. As Doppler weather radars are modernized to incorporate dual-polarization, future operational implementation of staggered PRT will require the computation of polarimetric variables. In this work, we present a dual-polarization staggered-PRT algorithm based on the framework provided in the CLEAN-AP filter which is valid for any staggered PRT ratio. The performance of the proposed algorithm is shown using simulations and archived WSR-88D data; these results confirm the suitability of this technique for future upgrades of the NEXRAD network.