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Thundering typhoons wreak havoc

tech reviews Updated: Nov 16, 2007 01:40 IST
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What is a cyclone?
Tropical cyclones are severe spinning storms with wind speed greater than 119kmh and occur over the ocean near the tropics. Cyclone, meaning turning wind with one eye, is derived from “Cyclops” the one-eyed creature in Greek mythology.

Why do they occur?
A cyclone is an area of low atmospheric pressure characterised by inward spiraling winds that rotate. The direction of spin depends on the hemisphere. In the Southern hemisphere they spin in a clockwise motion and Northern hemisphere, anti-clockwise. Their life cycle is about seven days, but can extend to over three weeks.

Are they different from hurricanes and typhoons?
Not much, just in intensity. In the Atlantic and eastern Pacific, including the Hawaiian islands, they are called hurricanes, in the western Pacific they are called typhoons and in Australia and the Indian Ocean they are called cyclones.

What is a super cyclone?
It is a more intense version of a cyclone with faster wind speed. For example, the 1999 super cyclone in Orissa had wind speeds of nearly 300km.

How are they named?
These names are taken from lists which vary from region to region and are drafted a few years ahead of time. The lists are decided upon either by committees of the World Meteorological Organization or by national weather offices involved in the forecasting of the storms.

Which is the worst cyclone till date?
The 1970 Bhola cyclone, which killed over 300,000 people. But the 2005 Hurricane Katrina is considered the costliest worldwide causing damages worth $40.6 billion in insured losses, and an estimated $81 billion in total losses.

Can they be prevented?
No, but their effect can be minimised. While scientists are experimenting with seeding severe cyclones with microscopic dust, the US has conducted experiments to weaken hurricanes by dropping silver iodide into them. India is using Cyclone Surveillance Radars, satellite picture receiving equipment, radiometers for reliable cyclone forecast.

Sources: AOML, NIDM, IMD