High Frequency (HF) Radar

A receive antenna for the most common type of HR radar system

 A receiving antenna for a common type of HF radar system

Latest CODAR SeaSonde single pole co-located transmit/receive antenna

Latest CODAR SeaSonde single pole co-located transmit/receive antenna, deployed at many IOOS HF radar sites

High frequency (HF) radar systems measure the speed and direction of ocean surface currents in near real time. Currents in the ocean are equivalent to winds in the atmosphere because they move things from one location to another. These currents carry nutrients as well as pollutants, so it is important to know the currents for ecological and economic reasons. The currents carry any floating object, which is why U.S. Coast Guard search and rescue operators use HF radar data to make critical decisions when rescuing disabled vessels and people stranded in the water. 

These radars can measure currents over a large region of the coastal ocean, from a few kilometers offshore up to 200 km, and can operate under any weather conditions. They are located near the water’s edge, and need not be situated atop a high point of land.  Traditionally, crews placed current measuring devices directly into the water to retrieve current speeds.  While these direct measurement systems are still widely used as a standard reference, HF radars are the only sensors that can measure large areas at once with the detail required for the important applications described here.  Not even satellites have this capability.


Applications and Success Stories

Applications of High Frequency Radar Data

Nearly every application of ocean monitoring requires, to some extent, measurements of surface current velocities.

Measuring Surface Currents

Ocean currents determine the movement of surface waters, providing critical information to support pollutant tracking, search and rescue, harmful algal bloom monitoring, navigation, and a number of other applications discussed in this report. Existing oceanographic monitoring systems are insufficient to provide the level of detail required by scientists and forecasters to measure surface current speed and direction.

Coast Guard Search and Rescue

U.S. Coast Guard operations off Alaska. (USCG)

U.S. Coast Guard operations off Alaska. (USCG)

The U.S. Coast Guard uses HF radar in its Search and Rescue operations within the mid-Atlantic region.

Tests showed that by ingesting these data into the Search and Rescue system, the search area decreased by 66% over 96 hours.  By reducing the search area, crews can focus their efforts and save more lives.

The U.S. Coast Guard integrated HF radar data into its Search and Rescue system in the mid-Atlantic region in 2009.  HF radar data are available in the Coast Guard’s Environmental Data Server (EDS) that is accessible by all USCG SAR teams.  IOOS-funded Short-term Prediction System (STPS) predicted flows based on the HF radar data are also available in the EDS.
Click here for - real-time predictions for the northeastern coastal areas.

Hazardous Materials Spills Response

Water Quality - NEED CAPTION

Oil spills threaten marine life

NOAA is responsible for providing scientific support to the Federal On-Scene Coordinator for oil and hazardous material spills. To support this mandate, NOAA’s Office of Response and Restoration Emergency Response Division provides 24-hour, 7 day a week response to spill events.  High frequency radar data is often used to help forecast where the oil or other material will flow.

A large cargo ship, the Cosco Busan, collided with the Bay Bridge in San Francisco Bay in November 2007 causing a breach in the hull, which spilled fuel from its tanks.  As NOAA’s Emergency Response Division tracked the spill, they used HF radar data to determine that the spill would not reach the Farallon Islands marine sanctuary off the coast of San Francisco. This allowed spill responders to focus their equipment and manpower on more threatened areas.

Water Quality Monitoring

Water Quality - trash in the water

Water Quality monitoring aids decision making.

In 2008, the City and County of San Francisco’s wastewater system managers used HF radar data. They used daily forecasts based on these data to decide whether to close nearby beaches after finding a defect in the wastewater system would cause a point-source discharge of partially-treated wastewater.

The City of San Diego, Department of Environmental Health uses the Tijuana River Plume Trajectory, which relies on HF radar data, to help guide decisions about water sampling and beach closures. 

In November 2006, the City of Los Angeles used HF radar data to make decisions about beach closures during a major maintenance operation on a 50-year-old outflow pipe. City officials estimate that they could have avoided $750 million in unneeded repairs in previous years, had HF radar data been available then.


Monitoring Harmful Algal Blooms

Surface current mapping has proven to be an essential tool for managers and scientists to assess and respond to harmful algal blooms (HABs) and will be instrumental in developing the ability to forecast these events.  When HABs are detected through the California Harmful Algal Bloom Monitoring and Alert Program, HF radar-derived surface currents are used as part of a suite of sampling and data products to help determine their extent and severity.  Surface current data from HF radars operating in the Northwest Association of Networked Ocean Observing Systems is among the chemical and biological information included in the Pacific Northwest Harmful Algal Bloom Bulletin, which provides comprehensive early warning information for Washington coast razor clam toxicity and amnesic shellfish poisoning events.

Fisheries Management

Data from High Frequency Radar used for Modeling

Data from High Frequency Radar used for Modeling

Ocean conditions change from year to year and the ongoing measurements of surface currents made by HF radar are a crucial backbone for ocean observations along the coast. Unlike buoys and ships, which collect information at single points and times, HF radar provides full, archived mapping, day and night, of our coastal waters up to 200 km offshore. Long-term monitoring of surface currents is used to track impacts on marine populations. Off Bodega Bay, California, researchers are using HF radar derived surface current data to obtain seasonal to annual information on ocean conditions that likely influence the survival rate of young salmon when they first enter the ocean.

Coastal surface currents can also provide important input to establishing and evaluating marine protected areas (MPAs); it provides the only multiyear data with enough spatial coverage to assess how larvae of marine populations are dispersed from the location where they originate to where they settle and grow to maturity. HF radar data from a regional network in California have demonstrated the connectivity between central California marine protected areas (MPAs) by back-projecting trajectories from 10 MPAs over more than a 40-day period. Clarifying this connectivity is an important step toward understanding the movement of invertebrate and fish larvae.

Marine Navigation

High frequency radar data are a core component of a simple but very effective near real time, customized, interactive Website displaying environmental conditions at the entrance to the Ports of Los Angeles and Long Beach. http://www.sccoos.org/data/harbors/lalb. The National Ocean Service Center for Operational Oceanographic Products and Services (CO-OPS) provides tidal predictions using HF radar data for Chesapeake Bay and San Francisco Bay.

Ocean Energy Production

US IOOS regional partner, Rutgers University, has been funded by the New Jersey Board of Public Utilities to develop a 3-D wind resource map to support the offshore wind energy community. The work will use available forecast models and a new deployment of a radar sub-network (four sites) along the southern New Jersey coast. This network creates a higher resolution HF radar coverage area within the Mid-Atlantic Bight.

The University of North Carolina is operating a long-range CODAR SeaSonde HF radar for studying the Gulf Stream near Cape Hatteras, NC.  The State of North Carolina is investigating the area for potential marine hydrokinetic energy production from the strong currents inherent in the Gulf Stream.


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Locations and Spatial Coverage of High Frequency Radars within the U.S.

Dozens of institutions own and operate HF radars within the United States.  As those institutions move, add or remove radars, efforts will be made to provide updated maps on this IOOS website.

HFR coverage maps

HFR Coverage maps, clockwise from top left: East and Gulf Coasts, West Coast, Hawaii, and Puerto Rico.


Proposed HF Radar Sites and Their Spatial Coverage

Google Earth format of proposed HF radar sites
and their nominal spatial coverage.
(kml, 110kb)



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Programmatic Topics

Gap Analyses

The gap analyses documents from the Regional Coastal Ocean Observing Systems (RCOOS’s) that provided input to the proposed HF radar site distribution are available at: http://www.usnfra.org/governance/committees.html

Additional Capabilities in Viewing the Near-Real-Time Data Maps

For more capabilities in viewing the near-real-time data maps, please visit IOOS HF radar websites:

* To view all KML files it is necessary to have Google Earth installed.  To download Google Earth click here.

The Integrated Ocean Observing System High-Frequency Radar Network: Status and Local, Regional, and National Applications

Marine Technology Society Journal, November/December 2010 Volume 44 Number 6
Download Article (pdf, 568Kb)


Ocean Current Radar Calibration with Ships of Opportunity and the Automatic Identification System

  • Small Business Innovative Research Phase 2 Project Report
    Download (pdf, 1.4MB)

  • Small Business Innovative Research Phase 1 Project Report
    Download (pdf, 549Kb)


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Radiowave Operators Working Group, ROWG

IOOS National HF Radar Technical Steering Team

July 24-25, 2014 -
National HF Radar Technical Steering Team Annual Meeting,
Boulder, CO

April 16-17, 2013 -
National HF Radar Technical Steering Team Annual Meeting,
Boulder, CO

July 17-18, 2012 -
National HF Radar Technical Steering Team Annual Meeting,
Boulder, CO

July 19-20, 2011 -
National HF Radar Technical Steering Team Annual Meeting,
Boulder CO

July 28, 2010 -
National IOOS HF Radar Steering Team Inaugural Meeting,
Washington, DC


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Access Actual HFR Data

HFRnet at Scripps Institution of Oceanography

SCRIPPS hosts the National Data Assembly Center for High Frequency Radar data.  They provide national system monitoring tools and convenient APIs for accessing HFR visualizations and data.  Additionally they provide access to the gridded processed surface current fields via their THREDDS Data Server for access to data via OPeNDAP.


National HF Radar Data Assembly Center at NDBC

The National Data Buoy Center provides an operational mirror of the surface current data (also served via THREDDS) as well as a mapping interface to visualize HFR data.


Global HF Radar Network

Learn about the Group on Earth Observation, GEO Global High Frequency (HF) Radar Network Component


Overview Poster of IOOS
HF Radar Network - March 2014

Taiwan 2014 GEO Global HF Radar Workshop (pdf)


International Telecommunications Union (ITU) Radio Frequency Usage

Final ITU Document HF Ocean Radar 2014 (pdf)

Summary of WRC-12 HF Radar Frequency Outcomes (pdf)

National Plans

A Plan to Meet the Nation’s Needs for Surface Current Mapping (updated May 2015)

This plan presents the uses of high frequency radar, the requirements that drive the measurement of ocean surface currents, and the implementation design for a five-year, national build-out effort.
Download PDF

U.S. IOOS National Surface Current Mapping Plan


Organizations and Partners Involved

Presently, 10 of the 11 U.S. IOOS regions operated high frequency radar systems.  Ocean surface current data from these radars are shared on national servers, which deliver the data to anyone who needs it.


HF Radar in Action


Resources and References

The Integrated Ocean Observing System High-Frequency Radar Network: Status and Local, Regional, and National Applications

Marine Technology Society Journal, MTS, November/December 2010 Volume 44 Number 6
Download Article (pdf)


Technical HF Radar Documents