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Die Natur als Erfindung des Menschen
Umwelt     Natur-Nature


deutsch Wirbelwinde

Storm isn´t just whirlwind.When violent hurricans rage, they are nothing else than usual low-pressure-areas. They come into being by temperature contrasts between the relative warm sea and an arctic coldfront which built up into a cyclone.

The tropic whirlwinds, which rage in the Carribean Sea and at the Gulf of Mexico are called hurricane, precisely said: in the Western Pacific they are called Taifun (which means ,,great wind" in Chinese, at India they are called ,,Willy-Willy". They are built up over the Grear Seas when warm water heats up the air . Often the storms are several 100 kilometres wide and in the inside they reach up to 400 km/h.

Another kind of whirlwinds are tornados, which come to the Northern America every year. In the average 900 whirlwinds are counted in one year. The bad ones demand about 100 or more casualties.

At the ,,record day", the 3rd April of 1974, 18 tornados raged within 18 hours, left 315 dead and 5000 injured persons.

Tornados tell apart from the tropic whirlwinds:they are built up over the mainland , are just 50 kilometres wide but whirl with a speed of 500 km/h around their own axles.

As by the formation of hurricans or tayfuns, there are also special conditions for the formation of a tornado. The giantic vortexes are built up when two big air-masses hit each other.

In Northern America raises, when the air begins to heat up, from March on sultry air over the Gulf of Mexico and moves into the direction of the mainland. At the same time cold and dry winds from the Rocky Mountains over the bleak areas of the Llano Estacado into the direction of the Gulf. The two layers of air are pushed above each other, the cold air from the mountains above the warm air which comes from the Gulf.

Warm air spreads and loses weight, that´s why it raises up like a balloon and builts up drops of water, which comes down to earthas a cloud in an enormous thundercloud.

Two conditions are necessary for a tornado coming into existence: sidewind in a big height, which catches the balloonof warm, rising air, puts it into a turning movement and forces the warm air, which comes from downside, to circulation.

This whirl becomes more and more narrow, more and more fast until a hose is built up. This hose licks warm air from downside and gets more and more temperature and energy. Then the hose breaks through the underside of the thundercloud and grows - because it wants to lick more warm air – vertical or slanting into the depth.

At the beginning the proboscis is snowwhite, because it exists just of fine water.drops. But as soon as the proboscis gets in touch with the earth, it becomes black because it licks up leaves, dust, branches and things and whirls them through the air with an enormous force. Now hell has broken loose for minutes at the track, which the tornado takes with it.

obenAutoren: Klasse 11-3 (97/98), teacher Christine Hartmann, Web: Mathias Schönmann  Datum: Juli 98. Last update am 28. April 2000
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