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Satellite spots prelude to ozone hole.

Since the late 1970s, when it first appeared, the annual Antarctic ozone hole has become a rite of spring in the southern hemisphere. Each September, sunlight beaming into the Antarctic sky energizes chlorine pollution, which efficiently destroys much of the protective ozone in the stratosphere over the southernmost continent. But data from NASA's Upper Atmosphere Research Satellite (UARS), launched last year, now reveal that many of the ingredients necessary for ozone destruction appear in the atmosphere by June, months before ozone levels start to decline.

Chlorine in the stratosphere normally resides in the form of inactive compounds, such as chlorine nitrate, that do not destroy ozone. But the UARS information shows that by June and July, much of the chlorine has switched from inactive forms into the more dangerous chlorine monoxide molecule, which can destroy ozone. This critical transformation, believed to occur on the surface of ice particles, takes place far earlier than scientists had expected, according to UARS researchers.

The satellite measurements suggest that all the ingredients for ozone destruction appear to be in place when the sunlight returns to the region in August, but the measurements do not show any ozone loss until September. UARS scientists say ozone-rich air from the tropics may penetrate into the polar region, masking any early ozone destruction.
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Title Annotation:ozone destruction appears in Antarctic atmosphere months before levels start declining
Author:Monastersky, Richard
Publication:Science News
Article Type:Brief Article
Date:Dec 19, 1992
Words:215
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