Underwater microphones can be used to detect hurricanes

Washington, April 11 : MIT researchers have found a cost effective way in detecting hurricanes, by placing microphones deep under water to measure wind power as a function of the intensity of the sound of an approaching hurricane.

The roiling action of the wind, churning up waves and turning the water into a bubble-filled froth, causes a rushing sound whose volume is a direct indicator of the storm's destructive power, measured by the hydrophones.

Nicholas Makris, associate professor of mechanical and ocean engineering and director of MIT's Laboratory, developed this method for undersea remote sensing.

Along with his former graduate student Joshua Wilson, Makris showed that Hurricane Gert, in 1999, happened to pass nearly over a hydrophone anchored at 800 meters depth above the mid-Atlantic Ridge at about the latitude of Puerto Rico.

"The case produced exactly the results that had been predicted, providing the first experimental validation of the method," said Makris. "There was almost a perfect relationship between the power of the wind and the power of the wind-generated noise," he added.

According to Makris, the current warning systems are estimated to save 2.5 billion dollars a year in the United States, and improved systems could save even more.

Since many parts of the world that are subject to devastating cyclones cannot afford the cost of hurricane-monitoring aircraft, the potential for saving lives and preventing devastating damage is even greater elsewhere.

To that end, Makris has been collaborating with the Mexican Navy's Directorate of Oceanography, Hydrography and Meteorology, using a meteorological station on the island of Socorro, off Mexico's west coast.

The island lies in one of the world's most hurricane-prone areas - an average of three cyclones pass over or near the island every year.

The team installed a hydrophone in waters close to the island and are waiting for a storm to come by and provide further validation of the technique.

According to Makris and Wilson, when there's a hurricane on its way toward shore, a line of acoustic sensors could be dropped from a small plane into the ocean ahead of the storm's path, while conditions are still safe, and could then provide detailed information on the storm's strength to aid in planning and decision-making about possible evacuations.

The total cost for such a deployment would be a small fraction of the cost of even a single flight into the storm, they said.

Permanent lines of such sensors could also be deployed offshore in storm-prone areas, such as the Sea of Bengal off India and Bangladesh.

ANI