Real-time capability of meteotsunami detection by WERA ocean radar system

High-frequency (HF) ocean radar systems have demonstrated their capability to capture the signal from tsunami currents after the 2011 Tohoku earthquake and tsunami. However, these systems were configured for mapping surface currents in the coastal zones and not for detecting specific patterns of tsunami waves in real-time. The WERA^® ocean radar system was optimized for tsunami alerting and installed for real-time tsunami monitoring at the coast of Tofino, British Columbia, Canada. If the shelf extends tens of kilometers off the coast then the first appearance of tsunami waves can be monitored early enough to issue an alert message. On 14 October 2016, the WERA system detected strong changes in measured radial currents at distances up to 60 km off the coast and triggered an alert immediately. The system tracked the unusual current pattern in real-time following the wave propagation coincided with an atmospheric cold frontal passage. No earthquake occurred at that time but strong storm currents caused most likely by remnants of typhoon Songda were the most likely reason for the detection. This localized event seems to be the combination of the strong currents caused by the typhoon, the storm surge, and a large wave that could be classified as a meteorological tsunami (meteotsunami). This detection showed the capability of the radar to measure unusual surface current velocities induced by tsunami waves. The real-time detection and alerting on this tsunami-like current have shown a good applicability of HF phased-array radar technology for offshore tsunami monitoring and navigation safety.

1. Introduction

High-frequency (HF) ocean radars give a unique capability to deliver simultaneous wide area measurements of ocean surface current fields and sea state parameters far beyond the horizon. The WERA® ocean radar system is a shore-based remote sensing system to monitor ocean surface in real-time and under all-weather conditions. The system operation is based on electromagnetic wave propagation along ocean water. The radar frequency is usually chosen between 3 and 30 MHz to provide a large coverage of ocean surface that is capable of extension to more than 300 kilometers offshore. The primary output of these radar systems is used for various applications such as ocean currents and wave mapping, wave energy management, search and rescue, and vessel traffic service. The ocean radar systems are well-known as an operational tool for coastal monitoring. Multiple examples are described in [1]–[3].