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[JAKARTA] A tsunami has been observed with radar for the first time, promising a cheap and more accurate early warning method, according to a study.

Researchers have found that the devastating tsunami that hit Japan on 11 March could had been spotted up to 45 minutes before it reached tide gauges, using high-frequency radars installed along the shorelines in California and Japan.

The warning time depended on how shallow the water was — the shallower the water, further away the method can detect a tsunami.

So the method would work best in regions with wide and shallow continental shelves such as South-East Asia and the west coast of India, where it could give the most warning time, according to John Largier, an oceanographer at the Bodega Marine Laboratory, University of California, Davis, and a co-author of the study published in Remote Sensing last month (3 August).

"The benefit of using the shore-based radar systems to provide warning of tsunamis is that one obtains data at many locations, improving the detection in terms of both timing and intensity of the tsunami at the coast, which can vary significantly," Largier told SciDev.Net.

Such a system would also measure waves that sometimes follow within a day of the initial tsunami, which the current systems do not detect well, he said.

Radar is already commonly used in ports around the world for monitoring surface current flow, and used for oil spill response, search and rescue, fisheries, and ecosystem management, so transforming it for tsunami detection would be cost-effective, but would need dedicated funds, said Largier.

"No funds exist for the modest development effort to convert the existing hardware into a tsunami system," he said, but added that compared with some other initiatives, such as tracking tsunamis from space, "development of an operational radar-based system is 'low hanging fruit' that can be plucked with relatively little additional funding".

"This system should be combined with existing offshore buoys and predictive computer models. One does not remove the value of the other. But, in regions where offshore buoys are absent, this radar approach may be more cost effective — specifically given the multiple benefits."

But the need to process radar data into reliable information for the public could slow down the development of the new system, warned Indonesian scientists.

"Radar gives data much quicker than the tide gauge, [but] at the end of the day, it is the ensuing data processing that matters," said Baba Barus, a senior geology lecturer at the Bogor Agricultural University, Indonesia.

Didit Okta Pribadi, a radar expert at the Indonesian Institute of Sciences, said there was no doubt that radar would outperform the current tsunami early warning system because "radar can see through the depth of the ocean".

But the shortage of radar operators and experts in South-East Asian countries means it may take some time before such a method could be deployed there.

"In Indonesia, those who know the nitty-gritty of radar can still be counted on fingers," Didit said. "I think other South-East Asian nations have the same situation."

Link to full paper in Remote Sensing

References

Remote Sensing doi:10.3390/rs3081663 (2011)

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