Contact:  Barbara McGehan         IMMEDIATE RELEASE
                                  1/31/96

MILITARY RADARS USED TO MAP OCEAN CURRENTS

Military "over-the-horizon" radars, designed to scan the horizon for enemy bombers and ships, can be put to valuable peacetime use such as mapping ocean currents, according to Commerce Department scientists in Boulder, Colo.

Researchers Thomas M. Georges and Jack A. Harlan at the National Oceanic and Atmospheric Administration's Environmental Technology Laboratory have, for the first time, used two U.S. Navy high-frequency radar systems to map open-ocean currents off the coast of Florida. In a paper to be published in the Feb. 1 issue of Nature, Georges and Harlan describe the experiment where they used the over-the-horizon (OTH) radars located in Texas and Virginia to measure ocean currents 900 miles from the radars.

The success of this experiment indicates the potential for using OTH radars for mapping the circulation of the entire Caribbean Sea and Gulf of Mexico. Little is known about the ocean circulation in these areas, or how the currents that become the Gulf Stream merge and travel up the East Coast of the United States. "We know practically nothing about ocean currents and how they change with time," Georges said. "Yet, it's of great importance for fisheries management, search and rescue efforts, and studies of climate change."

Only two percent of the radar systems' potential coverage was used to perform this test, indicating the possibilities of using these and other OTH radars to map huge areas of the ocean. Previous studies have employed one radar to look at ocean currents but by using overlapping radar fields, a more complete picture of ocean currents was achieved.

The radars employ huge transmitting and receiving antenna arrays that were originally designed by the military to track aircraft and ships. These OTH radars work by bouncing high- frequency radio beams off the ionosphere, an electrically charged layer in the upper atmosphere. In the early days of radio, it was discovered that by bouncing radio signals off the ionosphere, shortwave signals could be received thousands of miles away.

According to Georges, several OTH radars around the world that now lie idle could be mapping other features of ocean circulation, such as boundary currents and mesoscale eddy systems, which could give us a new, more detailed picture of ocean circulation.

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