Tsunami was observed by Radar

Tsunami was observed by Radar

For the first time a tsunami has been observed by radar, raising the possibility of new early warning systems. As it swept toward their coasts the tsunami that devastated Japan on March 11 was picked up by high-frequency radar in California and Japan according to U.S. and Japanese scientists.

Largier and his colleagues have been using a high-frequency radar array at the Bodega Marine Lab to study ocean currents for the last 10 years, according to a University of California, Davis press release. Largier, together with collaborators from Hokkaido and Kyoto universities in Japan and San Francisco State University, used data from radar sites at Bodega Bay, Trinidad, California, and two sites in Hokkaido, Japan, to look for the tsunami offshore.

The scientists found that the radar picks up not the actual tsunami wave which is small in height while out at sea but changes in currents as the wave passes.

The researchers found they could see the tsunami once it entered shallower coastal waters over the continental shelf. As the waves enter shallower water, they slow down, increase in height and decrease in wavelength until finally hitting the coast. The continental shelf off the California coast is quite narrow, and approaches to the coast are already well-monitored by pressure gauges, Largier noted.