By Dr. Hugh Roarty
Research Project Manager
Coastal Ocean Observation Laboratory
Rutgers University
Co-authors: Ms. Lisa Hazard, Dr. Lucy Wyatt, Dr. Jack Harlan and Mr. Enrique Alvarez Fanjul
The Global High Frequency Radar Network is a vision for a global operational system measuring ocean surface currents to support monitoring of marine and coastal ecosystems. The measurement of ocean currents is fundamental to ocean forecasting. High frequency (HF) radar has proven to be an efficient tool for the measurement of surface currents along the coast out to 200 kilometers.
Figure 1: Ocean surface currents as measured by High Frequency radar. This image was captured at July 4, 2014, 14:00 GMT as Hurricane Arthur had just passed over North Carolina into the Atlantic Ocean. Image Credit: Hugh Roarty, Rutgers University
The 2012-2015 work plan for the Group on Earth Observations (GEO) describes an HF radar component for two GEO tasks:åÊ Earth Observing Systems (IN-01) and Oceans and Society: Blue Planet (SB-01). Each of these components calls for the ÛÏrapid development of a global high-frequency-radar network to measure coastal surface currentsÛ. The Global HF Radar Network was established at the GEO-VIII Plenary in Istanbul, Turkey. This paper aims to provide an update on the status of this work and outline future plans for the global HF radar network.
High Frequency Radar Theory
High Frequency radar transmits radio signals in the 3-30 megahertz band, which scatter off ocean surface waves. The scattered signals are Doppler shifted by the ocean wave velocity as well as an underlying ocean current velocity. Once the velocity due to the surface gravity wave is removed, then the radial current toward or away from the radar can be measured. Combining the radial measurements of currents from several stations provides a map of the 2-D structure of the surface current (Figure 1). HF radar has gained wide acceptance as a remote sensing tool within the oceanography community. The reader is referred to [1, 2] for a present review of the technology and its applications.
The Global Effort
The Global High Frequency Radar Network was inaugurated with a kickoff meeting at Oceanology International in London, England, on March 14, 2012. The goals of the network were set forth as:
- Increase the number of coastal radars operating around the world
- Ensure that HF radar data are available in a single standardized format in real-time
- Establish worldwide quality standards
- Distribute a set of easy-to-use standard products
- Assimilate the data into ocean and ecosystem models.
Figure 2: Map of the world showing the location of high frequency radars the authors have been able to locate. These radars are deployed in a sustained manner for long-term obserations. Image Credit: Hugh Roarty, Rutgers University
In order to gauge the increase of radars operating, we first had to take inventory of the current status of radars operating around the world. As of this publication, there are approximately 380 radars operating in 34 countries making measurements of ocean currents åÊ(Figure 2 and Figure 3). This inventory also was utilized to populate the global site information database being developed by the International Telecommunications Union (ITU), which will serve as an informational source for HF oceanographic radar users throughout the globe. Three working groups were established at the meeting. The focus areas for the working groups were data management, application success stories and capacity building. The topic of radio frequency management also was discussed in light of the passage of Resolution 612 at the 2012 World Radiocommunication Conference. This resolution by the International Telecommunication Union officially recognized oceanographic High Frequency radars with primary, provisional primary and secondary bands.
A second meeting was held at Oceans’13 in Bergen, Norway, on June 11, 2013. Leading up to this meeting, a series of webinars were given on High Frequency radar data management and applications. Presentations at the meeting were given on success stories and applications of High Frequency radar data, data management and network construction. A key message at this meeting was that a data management plan is the first priority for a country’s national network. Once this plan is in place, it allows for the growth of the network. Fifteen countries submitted a total of 60 stories on the application of High Frequency radar data. The stories were grouped by application type to form 11 distinct application types and are summarized in Figure 4. The most popular applications so far have been for ocean circulation studies, oil spill response, and search and rescue.
Figure 3: Bar chart showing the distribution of radar systems among the 34 countries identified as operating high frequency radar systems.
Figure 4: Frequency of the different type of application stories for High Frequency radar.
The most recent meeting for the Global Network coincided with the Ocean Radar Conference for Asia (ORCA) on April 3, 2014. Speakers from the United States, Australia, Taiwan and Thailand gave presentations on lessons learned from the construction of their national networks. The topics of data and metadata formatting standards, information sharing and capacity building were discussed.
Conclusion
We are halfway through our effort to create a Global High Frequency Radar Network as outlined in the GEO work plan. We have taken inventory of the number and location of HF radar stations operating around the globe. We have assembled 60 application and success stories related to the use of the data. We view this as an exciting period for the development and application of High Frequency radar as a remote sensing tool for marine monitoring. Please join us as we grow the community and share in our success.
Acknowledgement
The authors would like to thank and recognize Ms. Zdenka Willis, director of the United States Integrated Ocean Observing System, for her leadership and vision in establishing the Global High Frequency Radar Network.
Author Bios
Dr. Hugh Roarty is a research project manager with the Rutgers University Center for Ocean Observing Leadership (RUCOOL). He has worked with High Frequency radar for the past 12 years and was part of the team that made HF radar operational with the U.S. Coast Guard for search and rescue. He can be reached at hroarty@marine.rutgers.edu.
Ms. Lisa Hazard is the operation manager with the Scripps Institute of Oceanography Coastal Ocean Observing Research and Development Center. She has been instrumental in the establishment and operations of the United States National High Frequency Radar Network.
Dr. Lucy Wyatt was director of the Australian Coastal Ocean Radar Network from 2011 to 2014. She is returning to the U.K. and Sheffield University at the end of 2014 where she will continue her work on wave and wind measurement with HF radar. She can be reached at l.wyatt@sheffield.ac.uk.
Dr. Jack Harlan is national project manager for the Integrated Ocean Observing System (IOOS) United States National HF Radar Network and has worked in the field of HF radar for more than 25 years.
Mr. Enrique Alvarez Fanjul is head of the Physical Oceanography Division at Puertos del Estado of Spain, responsible foråÊnational numerical forecast systems of waves, storm surges and currents (MyOcean), and a network of 25 oceanographic buoys and 39 tide gauges. He is responsible of the first operational HF radar at Spanish waters and coordinator of the Puertos del Estado HF radar network (eight sites) and the Iberian network on HF radars association (IberoRedHF).
REFERENCES
[1]J. D. Paduan and L. Washburn, “High-Frequency Radar Observations of Ocean Surface Currents,” Annual Review of Marine Science, Vol 5, vol. 5, pp. 115-136, 2013. [2]S. Fujii, M. Heron, K. Kim, J.-W. Lai, S.-H. Lee, X. Wu, X. Wu, L. Wyatt, and W.-C. Yang, “An overview of developments and applications of oceanographic radar networks in Asia and Oceania countries,” Ocean Science Journal, vol. 48, pp. 69-97, 2013/03/01 2013.