Infrared Device Measures Wave Temperatures, Dude

Kathleen G. Tatterson

SAN DIEGO -- If surfers here want a sure-fire way to find the "hottest" waves, they might do well to adopt a technique from the University of Washington's Applied Physics Laboratory in Seattle. Scientists are using an infrared imager to measure the temperature difference in the ocean as waves break through the surface and create a wake.
Scientists studying waves have traditionally relied on radar to track ocean conditions for shipping, transportation and environmental studies. With the infrared technique, researchers can see the area of the wake following each breaking wave and can measure the energy dissipated by individual breaking waves -- something they previously have been unable to do.
The team used an AGEMA Model 880LW infrared imager operating at 8- to 12-µm aboard a Navy research platform to scan the waters off the San Diego coast. "The program started in 1991 when focal plane technology was not commercially widespread," explained Andrew Jessup, senior oceanographer at the laboratory. The team will upgrade its camera with an additional grant from the Office of Naval Research, which funded the original research along with NASA.
The device measures temperature changes that occur during the disruption and recovery of the ocean's top millimeter, or "skin layer." Normally, the top layer is a few tenths of a degree cooler than the water below. When breaking waves disturb the skin, the imager can detect the warmer water brought to the surface, which reveals the amount of turbulent mixing happening at once and helps to quantify how much wind energy gets transferred into the water.
The next step for the team is to use infrared imaging to study the effects of "microscale breaking," or the breaking of smaller-scale waves from 10 cm to 1 m. Although there are no plans to commercialize the technology, the Navy is interested in applying the infrared technique to model background clutter encountered in the tracking of cruise missiles. Or maybe surfers could use the technology to cruise for the big kahuna.