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Diving Deeper: High Frequency Radar

Episode 36 (Feb. 16, 2012)

HOST: Welcome to Diving Deeper where we interview National Ocean Service scientists on the ocean topics and information that are important to you! I'm your host Kate Nielsen.

Today's question is...What is high frequency radar?

High frequency radar systems are installed on shore or islands. These systems bounce signals off the water to measure surface current speed and direction in near real time. By knowing what surface currents are doing, scientists can better predict how things in the water will move.

To help us dive a little deeper into this question, we will talk by phone with Jack Harlan on high frequency radar. Jack is the High Frequency Radar Project Manager with NOAA's Integrated Ocean Observing System Program. Hi Jack, welcome to our show.

JACK HARLAN: Hi, thanks for having me here.


HOST: So Jack, can you tell us a little more about what exactly high frequency radar is?

JACK HARLAN: Sure, high frequency radar, which we often just call HF radar, is a small radar system that sends out radio waves across the ocean surface which then bounce back to the radar and the signal that is received at the radar is then interpreted and analyzed and it enables us to determine what the ocean surface currents are over the entire area where those radio waves bounced off which with an HF radar is quite a large area, covering hundreds of square kilometers.

HOST: And how does this work exactly? How do we get the data and information from high frequency radar?

JACK HARLAN: Well, the technology is really the same thing as the Doppler weather radars that people see on their local weather forecasts. Same type of principle works here where we determine the speed of the ocean surface by the Doppler shift that comes back to the radar system. So we can determine surface currents and knowing where the surface currents are going, helps us know where anything that's floating on the ocean surface is going.

HOST: Jack, where are the sites physically positioned?

JACK HARLAN: Well typically, they're located at the shoreline or very close to the shoreline. Ideally we want that location to be fairly close to the water's edge, just for maximizing the connection of the radar signal with the water surface.

HOST: OK, so you're saying then that they can be located close to the water's edge. I'm guessing that means that they're probably also found a lot on beaches. Is this harmful to beachgoers - the high frequency radar?

JACK HARLAN: No, it's not, although that's certainly a question that has come up and it's a valid question. But the power levels that are used for these small radars are so low that it's really less than the power emanated from just a typical incandescent light bulb, so no there's absolutely no reason for anyone to have concerns about health issues related to these radars.

HOST: Jack, what does one of the systems look like? Is it something that I would recognize if I passed by it on a beach?

JACK HARLAN: You might, but it's a good chance you wouldn't because most of them are quite small and they would just look like a small antenna that you might see for a CB radio and other small-antenna systems. So, some of them are even disguised quite ingeniously so that it doesn't obstruct the view and really isn't noticeable to the average beachgoer.

The typical antennas are only about 10-15 feet tall so they can be disguised fairly easily at times and in fact one of them is inside of a flag pole at a Florida location on a very heavily used beach, so no one is even aware of that one being there. Another one is at a very heavily used beach in Waikiki in Hawaii that I'm sure most people would never realize that there are antennas on top of the structure right there at the beachside.

HOST: So Jack, we talked a little bit about where physically these systems are located, close to the water's edge. Where are they found in the U.S. or around the world, where are they established to collect some of this data?

JACK HARLAN: In the U.S., nearly every single coastal state has HF radars at this point, including also Puerto Rico. And overseas, there are dozens of countries using HF radars, really too many to name, but nearly every developed country in the world has HF radars and even among some of the developing countries, they are starting to deploy them for their own ocean monitoring systems.

HOST: Since sites are located in almost all the coastal states of the U.S., are they durable enough to withstand the many different kinds of weather conditions that we see all across the country? By this, I mean are your sites still functional after let's say a hurricane moves through an area?

JACK HARLAN: Yes, the sites are very durable. Many of them have been out for as much as 10-15 years now. There's even a case last August, when the Hurricane Irene went up the eastern seaboard, our partners at University of North Carolina kept their radars going right through the brunt of that hurricane which passed right over them. Really did an amazing effort. Kept those radars going even though there was no power, it was by using generators. And all the way up the coast to the mid-Atlantic, nearly every radar was up and running during that hurricane, so collected some really amazing data sets that will be of interest to researchers and analysts for several years to come.

HOST: So they can operate under any weather conditions?

JACK HARLAN: Pretty much, there's not too many conditions that really would adversely affect them.


HOST: So Jack, I think the question that most of us have and we've touched on this a little bit through our questions today, what do we use high frequency radar data for?

JACK HARLAN: Well there are really a multitude of applications. One of the really high profile uses is the use by the U.S. Coast Guard for search and rescue. So, by getting the HF radar data into their forecasting system, they've actually shown that they can reduce their search area by 66 percent over 96 hours period so basically that allows them to get to people faster and ultimately helps them save lives.

The second real high-profile use is tracking and forecasting where oil spills and other pollutants will go. NOAA uses the HF radar data routinely to help them in their forecasts of where an oil spill may float to so that's certainly one of our most high profile applications as well. There was actually kind of an interesting case where a dentist threw hazardous materials into the ocean and when they washed up on shore, they were able to determine, using the HF radar data, where those hazardous waste items were thrown into the water. So it actually ended up helping to convict that particular individual.

That's kind of an unusual application, but some of the more commonly used applications include water quality monitoring which is a big issue in many parts of the U.S. particularly in southern California, they've made a great deal of use of HF radar for monitoring coastal beach water quality. Another really widespread use is harmful algal bloom monitoring which occur in several areas throughout the U.S. so the data is really used for a multitude of applications by people all over the U.S. coastal areas.

HOST: Who uses high frequency radar data?

JACK HARLAN: Well, we have our federal partners that I've mentioned, the Coast Guard of course, and NOAA organizations such as the spill response groups, so within NOAA we have quite a lot of use and in some federal partners such as the Coast Guard, but in addition we have state spill responders that use the data, we have even county and city officials that rely on the data for monitoring their water quality, we even have lifeguards in Southern California for example that use the data. So, it's really something where it's a broad spectrum of people and agencies that use the data on a regular basis.

HOST: Jack, what do you think is the greatest benefit of high frequency radar data?

JACK HARLAN: I think the greatest benefit is probably the Coast Guard search and rescue use of the data. The data's used to help them save lives and rescue people and property. It's hard to imagine something more important than that.

HOST: How does high frequency radar compare with other technologies that collect surface current data? What makes this technology better or unique in some way?

JACK HARLAN: Well, traditionally to get current measurements in the ocean, one uses an in situ, that is some device that's put in the water directly, and those are still used today all over the world including the U.S., but those devices just measure a single point in the ocean whereas the radars can measure hundreds of square kilometers of surface current velocities simultaneously. So it would be equivalent to having hundreds and hundreds of current meters in the water. Not even satellite data can obtain the current measurements that an HF radar can. They just don't have the ability to do it with the time resolution that we do, where we can do this, hour after hour, day after day in the same spot over and over.

HOST: What is the role of your office, the Integrated Ocean Observing System Program, also known as IOOS, with high frequency radar?

JACK HARLAN: Well IOOS really, brings together the data from nearly 130 of these HF radars throughout the country and makes it accessible to the people who really need it via a one-stop shop if you will and we make that data available 24 by 7 in a standardized format that can be read and used by anyone who needs it throughout the coastal areas of the United States.

HOST: So Jack, my final question for you, do you have any closing words for our listeners today?

JACK HARLAN: Yeah one thing that I think is pretty interesting is that the HF radars were actually invented in the NOAA Boulder labs in Boulder, Colorado back in the 1970s and sometimes people forget that or didn't realize that so it's kind of interesting that all these decades later that the radars are now being used on a daily basis.

HOST: Thanks Jack for joining us on Diving Deeper and talking more about high frequency radar. To learn more, please visit

That's all for today's show. Please join us for our next episode in two weeks.