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Hurricanes 'too powerful'
23/09/2005 08:10 - (SA)
Denver - It sounds like a great idea: Let's just blast hurricanes like Rita and Katrina out of the sky before they hurt more people. Or, at least weaken the storms and steer them away from cities.
Atmospheric scientists say it's wishful thinking that we could destroy or even influence something as huge and powerful as a hurricane. They abandoned such a quest years ago after more than two decades of inconclusive government-sponsored research.
Private companies have conducted tests on a much smaller scale, but have made little progress despite initially claiming to erase storm clouds from the atmosphere.
"It would be like trying to move a car with a pea shooter," said hydrometeorologist Matthew Kelsch of the National Centre for Atmospheric Research in Boulder. "The amount of energy involved in a hurricane is far greater than anything we're going to impart to it."
The federal government's hurricane modification programme was called Project Stormfury. The idea was raised during the Eisenhower administration after several major storms hit the East Coast in the mid-1950s, killing 749 people and causing billions in damages.
But it wasn't until 1961 that initial tests were conducted on Hurricane Esther with a Navy plane releasing silver iodide crystals. Some reports indicate winds were reduced by 10% to 30%.
During Stormfury, scientists also seeded hurricanes in 1963, 1969 and 1971 over the open Atlantic Ocean far from land.
Researchers dropped silver iodide, a substance that serves as an effective ice nuclei, into clouds just outside of the hurricane's eyewall.
Sometimes experiments appeared to work
The idea was that a new ring of clouds would form around the artificial ice nuclei. The new clouds were supposed to change rain patterns and form a new eyewall that would collapse the old one. The reformed hurricane would spin more slowly and be less dangerous.
Sometimes, the experiments appeared to work. Hurricane Debbie in 1969 was seeded twice over four days by several aircraft. Researchers noted that its intensity waxed and waned by up to 30%.
For cloud seeding to be successful, clouds must contain sufficient supercooled water that is still liquid even though it is below 0 Celsius. Raindrops form when the artificial nuclei and the supercooled water combine.
But scientists also learned that hurricanes contain less supercooled water than other storm clouds, so seeding was unreliable. And, hurricanes grow and dissipate all on their own, even forming new walls of clouds.
This made it impossible to determine whether storm reductions were the result of human intervention. Project Stormfury was abandoned in the 1980s after spending hundreds of millions of dollars.
Other storm modification methods that have been suggested include cooling the tropical ocean with icebergs and spreading particles or films over the ocean surface to inhibit storms from evaporating heat from the sea.
- AP
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