WERA Ocean Radar Capability of Real-Time Tsunami Detection

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1 WERA Ocean Radar Capability of Real-Time Tsunami Detection Dr. Anna Dzvonkovskaya Helzel Messtechnik GmbH Kaltenkirchen, GERMANY member of and

2 Worldwide WERA HF Ocean Radar Installations Permanent WERA Installation Temporary WERA Installation Planned WERA Installation

3 Sultanate of Oman: National Multi-Hazard Early Warning System (NMHEWS), March 2015

4 Ocean Networks Canada, British Columbia, March 2016

5 University of Concepcion, Chile, April 2016

6 HF Ocean Radar Remote-Sensing Basics: Resonant Backscatter from Ocean Waves WERA (Wellen Radar) is a shore-based radar remote sensing system operating at 5 50 MHz and using the over-the-horizon radar technology to monitor ocean surface currents, waves and wind direction. A vertically polarised electromagnetic wave is coupled to the conductive salty ocean water and follows the curvature of the earth. The rough ocean surface interacts with the radio wave and due to the Bragg Effect back-scattered signals can be detected at ranges of more than 200 km

7 HF Ocean Radar Remote-Sensing Basics: Radar Spectrum The back-scattered radar signal will be Doppler shifted with a specific frequency offset given by the velocity of the gravity wave that is responsible for the resonant Bragg scattering. fcurrent fcurrent An ocean surface current simultaneously shifts the Bragg peaks in frequency. Doppler Shift at no Radial Current g πλ0 The Doppler shifted signals are symmetrical around the centre frequency as long as the ocean surface does not exist. g πλ0 A Doppler frequency shift is converted to radial surface velocity.

8 HF Ocean Radar Remote-Sensing Basics: Radial Surface Current Velocity on a Grid

9 Multi-Purpose Remote Sensing by HF Radar WERA Radar System Information update every 33 sec Online Data Signal Processing Oceanography TSUNAMI Operating continuously 24/7 without human operators Simultaneous multi-purpose spectrum analysis Coastal Surveillance

10 WERA Permanent Acquisition Processing Software 128 samples 512 samples The WERA software reads a series of coherent files with 128 samples each and combines them to form sub-spectra. There is a special routine that controls this process. Once the coherent series of files is interrupted, the process to combine files is restarted repeatedly. For Ship Tracking and Tsunami Detection a defined sample number of 512 samples is needed. For current measurements, the sub-spectra (yellow) are averaged until the user defined sample number is covered (e. g samples) to form the gridded spectra file (green) for currents. These files are written at time increments samples samples For wave measurements, the sub-spectra (yellow) are averaged until the user defined sample number is covered (e. g samples) to form the gridded spectra file (red) for waves. These files are written at time increments.

11 WERA Permanent Acquisition Processing Software 128 samples NTSU_STEP.TSU.SPEC.TSU.SPEC Tsunami Detection Currents.TSU.SPEC.TSU.SPEC Waves.TSU.SPEC.TSU.SPEC.TSU.SPEC

12 Features of the Unique System Concept The unique, parallel and phase conserving signal processing of the WERA system allows software beamforming to provide data from entire range within short integration time: 20 min for wave data on a grid 5 min for surface current mapping 2 min in 30-sec steps for ship tracking / disaster warning

13 WERA Parallel Implementation of Ship Tracking and Oceanography + WERA Positions AIS Positions

14 HF Radar System Concept for Tsunami Monitoring: Necessary Criteria to Support Tsunami Detection and Information to TEWS Known bottom topography to plan an effective ocean radar installation. Ocean shelf extension to allow time for issuing and transmitting a tsunami alert Good spatial resolution of radar mapping to resolve the tsunami current signatures at different directions a phased-array radar system with beamforming in real-time High temporal resolution of radar data to detect the rapidly changing surface velocity with periods of several minutes a phased-array radar system with beamforming in real-time (direction-finding compact ocean radar systems lacks of fast measurement mode) Uninterrupted power supply unit a radar system should be equipped with an additional UPS unit (possible power outage) Transmission link the transmission link between a radar site and a central server of TEWS should be stable and independent of local communication networks (possible network failure) HELZEL Messtechnik GmbH

15 Tsunami Detection: a Time-Sensitive Application! Short integration time and fast update data rate The software beamforming for directivity in real-time Coherent intergration time 133 sec Radial velocity resolution 0.14 m/s Coherent intergration time 532 sec Radial velocity resolution 0.04 m/s

16 Linear Wave Theory Tsunami phase velocity: Horizontal orbital velocity:

17 Robust Detection of Small Tsunami Surface Currents Tsunami Detection Thresholds based on Linear Wave Theory

18 Proposed Tsunami Detection and Alerting by WERA Ocean Radar Ocean surface current velocity on a gridded map Remove natural tidal currents Tsunami current velocity map Tsunami probability map Tsunami ALERT decision Alert Message to Tsunami Warning Center

19 Underwater Earthquake near Japan, March 2011 Region: NEAR THE EAST COAST OF HONSHU, JAPAN Magnitude: 9.0 Time: March 11, 2011 at 05:46:23 UTC (02:46:23 PM at epicenter) Location: N, E Depth: 32 km Distances: 130 km E of Sendai, Honshu, Japan 178 km ENE of Fukushima, Honshu, Japan 373 km NE of TOKYO, Japan

20 The Japan Tsunami Propagation Time

21 WERA HF Radar at Rumena, Chile Transmit power 30 W Range up to 50 km Operating frequency 22 MHz Bandwidth 500 khz Range cell 0.3 km Linear FMCW waveform 8 receive antenna elements

22 Ocean Surface Current Estimation fcurrent fcurrent Radial surface current velocity: 0 2 v radcurr fcurrent First-Order Peaks Doppler frequency shift at no radial current 4 D tanh 0 0 g g 0 4 D tanh 0

23 HF Radar Spectrum Changes During Tsunami Runups Japan Tsunami

24 Radial Surface Current Velocity Measured in Chile m/s Data from

25 Residuals of Radial Surface Current Velocity Measured by WERA in Chile m/s Data from

26 Tsunami Wave Period Estimation

27 Comparison Between NOAA Modeled Heights and Water Level Measured by the Tide Gauge in Lebu By courtesy of Christopher Moore, NOAA, USA, and Dante Figueroa, University of Concepcion, Chile

28 Comparison Between NOAA Modeled Velocities and Tsunami Velocities Measured by WERA Ocean Radar cm/s m/s By courtesy of Christopher Moore, NOAA, USA, and Dante Figueroa, University of Concepcion, Chile

29 Bathymetry at Radar Coverage

30 Bathymetry at Radar Coverage

31 Real-Time Visualization of Tsunami Probability Provided by WERA System

32 Tsunami Alert Decision Provided by WERA System Tsunami ALERT Tsunami is possible No Tsunami 04:27

33 Ocean Networks Canada, British Columbia since March 2016

34 Ocean Networks Canada, British Columbia, March 2016 Transmit 13.5 MHz, 30 W, LFMCW Linear Receive Array with 12 elements

35 Ocean Networks Canada, British Columbia since March 2016

36 Typhoon Songda in the Northwest Pacific Ocean in October 2016 Oct 16, 2016 Oct 14, 2016 Oct 3, 2016

37 Real-Time Meteotsunami Observation on 14 October 2016 by WERA System in Canada Tide Gauge Data Meteo Buoy WERA Data

38 Real-Time Meteotsunami Observation on 14 October 2016 by WERA System in Canada WERA-Tofino DataViewer

39 Real-Time Meteotsunami Observation on 14 October 2016 by WERA System in Canada

40 Real-Time Meteotsunami Observation on 14 October 2016 by WERA System in Canada

41 Meteotsunami Observation on 29 May 2017 by Tide Gauges at the North Sea Tide Gauges WERA (Netherlands) WERA (Germany)

42 Meteotsunami Observation on 29 May 2017 by WERA Systems at the Dutsch Coast

43 Conclusions HF ocean radar systems have a unique capability to monitor the ocean surface over the horizon. The unique event detected on October 14, 2016, by the WERA ocean radar system showed that the system was capable to measure and track unusual patterns of surface current velocity starting 60 km offshore and in real-time. In locations where the shelf edge is extended tens of kilometers off the coast the first appearance of tsunami waves can be monitored early enough to issue an automatic alert. The analysis of the available data records from nearby tide gauges and a meteorological buoy located in the radar coverage showed that this unusual event was caused by a sharp pressure drop during the cold atmospheric frontal passage. The event can be potentially identified as a type of meteotsunami. The outstanding temporal resolution makes WERA system a perfect component for parallel time-critical applications like tsunami warning and vessel tracking.