Fri, Jun 03, 2005
NASA Spacecraft Measures Unusual Arctic Ozone Conditions
Despite near-record levels of chemical ozone destruction in the
Arctic this winter,
observations from NASA's Aura spacecraft showed that other
atmospheric processes
restored ozone amounts to near average and stopped high levels of
harmful ultraviolet
radiation from reaching Earth's surface.
Analyses from Aura's Microwave Limb Sounder indicated Arctic
chemical ozone destruction
this past winter peaked at near 50 percent in some regions of the
stratosphere, a region of Earth's atmosphere that begins about 8 to
12 kilometers (5 to 7 miles) above Earth's poles.
This was the second highest level ever recorded, behind the 60
percent level estimated for the 1999-2000 winter. Data from another
instrument on Aura, the Ozone Monitoring
Instrument, found the total amount of ozone over the Arctic this
past March was similar to
other recent years when much less chemical ozone destruction
occurred. So what
tempered the ozone loss? The answer appears to lie in this year's
unusual Arctic
atmospheric conditions.
"This was one of the most unusual Arctic winters ever," said
scientist Dr. Gloria Manney of
NASA's Jet Propulsion Laboratory, Pasadena, CA, who led the
Microwave Limb Sounder
analyses. "Arctic lower stratospheric temperatures were the lowest
on record. But other
conditions like wind patterns and air motions were less conducive
to ozone loss this year."
While the Arctic polar ozone was being chemically destroyed
toward the end of winter,
stratospheric winds shifted and transported ozone-rich air from
Earth's middle latitudes into the Arctic polar region, resulting in
little net change in the total amount of ozone. As a
result, harmful ultraviolet radiation reaching Earth's surface
remained at near-normal levels.
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