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Frigid Arctic Circle Flights Key To Ozone Processes

As people use more fossil fuels, ozone plumes form in polluted cities and drift around the world, and background levels continue to rise in the lower atmosphere.

Scientists are concerned that an overburdened atmosphere may lose its ability to adequately cleanse itself. The peculiar chemistry of the Arctic spring is key to understanding ozone and pollution processes across the northern latitudes.

So every other Sunday, a former military transport plane packed with scientists and specialized instruments flies out of Colorado toward the brutal cold of the Arctic Circle to scrutinize an annual springtime rise in lower-atmosphere ozone levels.

The researchers are measuring for the first time an array of chemicals that could shed light on ozone production, atmospheric cleansing and pollution transport in the northern latitudes. The National Center for Atmospheric Research (NCAR) leads the February-May mission. NCAR's primary sponsor, the National Science Foundation, is funding the experiment.

"Ozone is produced and destroyed all of the time, but if the balance gets too skewed, we may end up with more pollution than we can tolerate," says NCAR's Elliot Atlas, chief scientist for the experiment.

The NSF-owned C-130 aircraft flies 1,400 land miles to Churchill, Manitoba, on the Hudson Bay. Many more flight miles are added as the plane rises and falls to measure chemical compounds at various altitudes along the way.

Churchill is a tourist spot for viewing white whales in the summer and polar bears in the fall. But to scientists working there in the frigid spring, what's most striking are the cold, the blizzards, the severe beauty -- and the lack of an airplane hangar.

Churchill's aircraft facilities are a runway and fuel. Through nighttime lows of -30 degree Celsius (-22 degree Fahrenheit), the plane sits outside, full of sensitive instruments that are ruined if they freeze.

Inside the cabin, heaters running on jet fuel fight the cold; outside, electric block heaters warm the engines. Staff take turns staying up all night to tend heaters and instruments.

From Churchill, the team sometimes flies another 1,400 miles to Thule, Greenland, and then on to Alert. "Sometimes I wonder how we got into this. A week seems like a month up there," says Atlas, who helped design the experiment. "But the scientific questions are so important that it's worth the hardship."

Ozone levels in the Arctic troposphere (lower eight kilometers, or five miles, of the atmosphere) increase from 30-40 parts per billion (ppb) in winter to 50-60 ppb in the spring -- about half the concentration above Los Angeles on a bad day.

Meanwhile, in the stratosphere above, the returning springtime sun triggers chemical reactions that deplete ozone, creating a smaller, northern version of the Antarctic ozone hole.

Why these springtime highs and lows? Scientists suspect that some ozone sinks from the stratosphere into the troposphere. But how much?

As springtime weather changes circulation patterns, ozone and ozone-producing compounds travel into the far north from the polluted regions of northern and central Europe. To what extent does this influx speed up the chemical processes that accompany the return of sunlight?

Scientists believe measurements of 20 or so chemical species throughout the troposphere will provide answers. Already they have found surprises in the levels of some important compounds.

To complicate matters further, at ground level scientists have found ozone-empty bands about 30 miles across. To explore these areas, the C-130 coasts 100 feet above Hudson and Baffin Bays and the Arctic Ocean, sampling chemistry occurring over the ice and open leads.

The NCAR researchers and their colleagues hope to find the crucial data to explain why ozone builds up in the lower atmosphere even as it vanishes entirely from some surface areas.

Back at NCAR, the measurements are helping scientists to fine-tune their atmospheric chemistry models to better understand the chemistry and dynamics of the Arctic's lower atmosphere as winter gives way to spring.

Other participants in the experiment, called Tropospheric Ozone Production about the Spring Equinox (TOPSE), include NASA's Goddard and Langley Research Centers; Dalhousie, Georgia Tech, Harvard, Rutgers, and York Universities; and the Universities of California (Berkeley and Irvine), Colorado, Maryland, New Hampshire, Rhode Island, and Virginia.

Also collaborating are colleagues at Environment Canada and Purdue University, who are conducting ground-based research in the high Arctic.

NCAR is managed by the University Corporation for Atmospheric Research, a consortium of more than 60 universities offering Ph.D.s in atmospheric and related sciences.

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