High-frequency ocean radar support for Tsunami Early Warning Systems

Abstract

Abstract A high-frequency (HF) ocean radar system is a shore-based remote sensing system to simultaneously monitor ocean surface currents, waves and wind far beyond the horizon. The system operation is based on electromagnetic wave propagation coupling to salty water. Depending on operational frequencies, which are usually chosen between 5 and 30 MHz, a radar coverage of ocean surface may be extended up to 300 km offshore. The primary output of these radar systems is well used for various applications such as ocean current and wave mapping, vessel traffic service, search and rescue, monitoring of pollutants drift, and ocean sciences. Observations of the 2011 Japan tsunami event and recent meteotsunami events by HF radar technology confirmed that ocean radar systems are capable to measure tsunami-induced surface current velocity in real time. If the shelf edge width extension occupies tens of kilometers then the first appearance of specific tsunami currents can be monitored by an HF radar system in advance, already starting at the shelf edge. Hence, the radar measurements may be utilized to raise a tsunami alert. Moreover, the ocean radar can be a valuable tool to support Tsunami Early Warning Systems. The National Multi-Hazard Early Warning System in Oman launched in 2015 already includes a network of phased-array WERA® ocean radar systems to provide real-time tsunami monitoring. The radar measurements are considered to confirm a tsunami pre-warning from seismic, tide gauge and buoy components of the system.