Next-Generation Weather Observations – Achieving Requirements with the Horus Phased Array Radar

The Horus radar¹ was designed by the University of Oklahoma’s Advanced Radar Research Center (ARRC) with support from the NOAA National Severe Storms Laboratory. It consists of a mobile, fully digital, polarimetric, S-band phased array radar (PAR) developed from its inception to achieve demanding mission-critical observational requirements for next-generation weather surveillance. This state-of-the-art proof-of-concept system has been operational since 2022. Data collection experiments are more frequently conducted as the system matures.

Dual-polarization technology is a non-negotiable requirement for future meteorological observations. High-quality polarimetric measurements are critical to forecasters and automatic algorithms for accurate severe-weather detection and quantitative precipitation estimation. It is well known that phased array antennas can induce biases in polarimetric weather measurements, imposing a significant challenge in achieving high-quality polarimetric measurements. Nevertheless, it has been reported that the Horus antenna has extremely high levels of copolar H/V beam matching and ultra-low cross-polarization levels (<-50 dB in the principal planes)². Furthermore, advanced algorithms such as mutual coupling self-calibration and cross-polar cancellers, only feasible with fully digital PAR technology, are used to mitigate biases induced by the antenna system.

In this presentation, we report on quantitative data comparisons between data collected in a coordinated experiment with the Horus and the Rapid-scanning X-band Polarimetric (RaXPol) radars. Given that these systems have different specifications (such as operating frequency, antenna beamwidth, and transmit power), a custom signal processing software is developed to minimize differences in spatial resolution, sensitivity, and data quality of these radars. Results are meant to inform the potential of the Horus radar for achieving high temporal resolution observations (< 1 min) over full volume scans, while exceeding the quality of estimates from the operational WSR-88D network.

1. D. Palmer et al., "Horus—A Fully Digital Polarimetric Phased Array Radar for Next-Generation Weather Observations," in IEEE Transactions on Radar Systems, vol. 1, pp. 96-117, 2023, doi: 10.1109/TRS.2023.3280033
2. Zrnić, D. Schvartzman, R. D. Palmer and A. V. Ryzhkov, "Effects of Horus Antenna Patterns on the Copolar Correlation of Weather Returns," in IEEE Transactions on Radar Systems, vol. 1, pp. 282-294, 2023, doi: 10.1109/TRS.2023.3283560.