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.

FMI: www.nasa.gov/vision/earth/lookingatearth/ozone-aura.html