Hypercane

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Image:Redspot.jpg A hypercane is a hypothetical class of hurricane that would be formed by extreme circumstances, such as an asteroid impact. It would be a phenomenal storm: spiralling beyond the usual mechanisms which control hurricanes, to reach 20 miles high, with winds approaching 500 miles an hour.

1 Description
2 Examples
3 See also
4 External links

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Description

According to Kerry Emanuel, an atmospheric scientist at MIT:

"We were trying to predict the maximum intensity that ordinary hurricanes could reach, and we noticed that if we made the ocean too warm and the atmosphere too cold, the equation didn't yield any sensible solution -- it kind of blew up.' Unable to solve the problem with pencil and paper, Emanuel and his colleagues ran a computer simulation of a hurricane over a pool of hot ocean. The computer spat out a phenomenal storm--20 miles high, with winds approaching 500 miles an hour.

"The water that created this hypercane was so hot--120 degrees at the center of the pool--that the team knew such a storm couldn't occur in the present climate "or in any climates that Earth had experienced, except maybe near its origin. But we thought that under extraordinary circumstances one might have observed such a storm." A large asteroid or comet slamming into the ocean floor, for instance, would release a lot of heat. If an area of ocean at least 30 miles across were heated to around 120 degrees, Emanuel and his colleagues have found, the result would be a hypercane. An ordinary hurricane forms over a much larger region of the ocean, and one that has been baked to a much lower temperature by the sun. The warm water heats the air above it, and as that warm air begins to rise, it creates a low-pressure zone that draws in air from all sides. The wind causes more water to evaporate, which transfers more heat to the air, which accelerates the nascent storm--and since Earth is spinning, the storm spins, too.

In an ordinary hurricane, friction exerted by the sea on the swirling winds limits their speed to 200 miles an hour or less. But in a hypercane, that control is overwhelmed by the tremendous heat, which keeps pumping energy into the storm. "The heat engine of the hurricane just runs away," Emanuel says. "Friction can't keep up with it." The winds accelerate to 500 miles an hour. Because the angular momentum of the storm must stay the same, it shrinks to a tight knot just 10 miles across--around a sixth of the diameter of an ordinary hurricane. Meanwhile it is growing to twice the height, 20 miles high or so, because the air in its center is so hot; that air must rise until it has cooled to the temperature of the air around it. The result is a storm tall enough and strong enough to catapult a huge amount of material -- water vapor, sea salt, and maybe dust, if the crater happened to nick a coastline -- well into the stratosphere.

The "120 degrees" is presumably Fahrenheit, equal to 49 degrees Celsius.

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