by Medindia Content Team on  October 4, 2007 at 6:02 PM Environmental Health
Ozone Hole Over Antartica Has Shrunk Compared to Last Year
The ozone hole over Antarctica has shrunk 30 percent as compared to last year's record size, measurements made by the European Space Agency's Envisat satellite has revealed.

Envisat measurements showed that this year's ozone loss peaked at 27.7 million tonnes, compared to the 2006 record ozone loss of 40 million tonnes.

Ozone loss is derived by measuring the area and the depth of the ozone hole.

The area of this year's ozone hole - where the ozone measures less than 220 Dobson Units - was found to be 24.7 million sq km, roughly the size of North America.

The minimum value of the ozone layer is around 120 Dobson Units.

A Dobson Unit is a unit of measurement that describes the thickness of the ozone layer in a column directly above the location being measured.

Scientists say this year's smaller hole - a thinning in the ozone layer over the South Pole - is due to natural variations in temperature and atmospheric dynamics, and is not indicative of a long-term trend.

"Although the hole is somewhat smaller than usual, we cannot conclude from this that the ozone layer is recovering already," said Ronald van der A, a senior project scientist at Royal Dutch Meteorological Institute (KNMI).

"This year's ozone hole was less centred on the South Pole as in other years, which allowed it to mix with warmer air, reducing the growth of the hole because ozone is depleted at temperatures less than -78 degrees Celsius," the agency quoted him as saying.

Source: ANI

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