March 4, 2009

Ozone Layer In Sweden Thickest In Decades

Sweden's ozone layer was thicker in February that it has been in decades, according to a report released Tuesday from the Swedish Meteorological Institute (SMHI).

The measurements show a dramatic reversal from last year, when the ozone layer was the second-thinnest on record.

The institute obtained measurements in February at its station in Norrkoeping, near Stockholm, which showed the ozone layer was 426 Dobson units (DU), the thickest since recordings began there in 1988.  And a record high reading of 437 DU was measured at the Vindeln station in the northern part of the country, where records began being kept in 1991.

To find levels that high, "We have to go as far back to the measurements taken in Uppsala between 1951 and 1966" the SMHI said in a statement.

The highest level for February was measured in 1957, when a value of 439 DU was recorded.

The Arctic circumpolar whirl, a polar high-pressure system consisting of a column of cold air that develops during the long Arctic night, disappeared rapidly in mid-January, warming the stratosphere over the course of just few days, SMHI explained.

Because of this, "the low temperatures that usually cause rapid depletion of the ozone layer did not take place," the institute said.

Sweden's ozone layer typically reaches its peak thickness during the spring, before thinning during the summer months and reaching a minimum during the winter, the SMHI said.

Ozone provides a protective filter against the sun's damaging ultra-violet rays, which can cause sunburn, skin cancer, cataracts along with damaging vegetation.

Ozone depletion is a result of extreme cold temperatures at high altitude and an accumulation in the atmosphere of a certain type of pollution from chemicals used in refrigeration, aerosol sprays and some plastic foams.

Although many of these chemicals, called chlorofluorocarbons (CFCs), are being phased out under the 1987 Montreal Protocol, they can remain in the atmosphere for years.


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