BOULDER -- Every other Sunday a former military transport plane, packedwith scientists and specialized instruments, flies out of Coloradotoward the brutal cold of the Arctic Circle to scrutinize an annualspringtime rise in lower-atmosphere ozone levels. The researchers aremeasuring for the first time an array of chemicals that could shedlight on ozone production, atmospheric cleansing, and pollutiontransport in the northern latitudes. The National Center forAtmospheric Research (NCAR) leads the February-May mission. NCAR'sprimary sponsor, the National Science Foundation, is funding theexperiment.
As people use more fossil fuels, ozone plumes form in polluted citiesand drift around the world, and background levels continue to rise inthe lower atmosphere. Scientists are worried that an overburdenedatmosphere may lose its ability to adequately cleanse itself. Thepeculiar chemistry of the Arctic spring is key to understanding ozoneand pollution processes across the northern latitudes.
"Ozone is produced and destroyed all of the time, but if the balancegets too skewed, we may end up with more pollution than we cantolerate," says NCAR's Elliot Atlas, chief scientist for theexperiment.
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 theplane rises and falls to measure chemical compounds at variousaltitudes along the way.
Churchill is a tourist spot for viewing white whales in the summerand polar bears in the fall. But to scientists working there in thefrigid spring, what's most striking are the cold, the blizzards, thesevere beauty--and the lack of an airplane hangar. Churchill'saircraft 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. Insidethe cabin, heaters running on jet fuel fight the cold; outside,electric block heaters warm the engines. Staff take turns staying upall night to tend heaters and instruments.
From Churchill the team sometimes flies another 1,400 miles to Thule,Greenland, and then on to Alert, the last settlement on the northerntip of the last piece of North America--Ellesmere Island. At leastThule has a hangar.
"Sometimes I wonder how we got into this. A week seems like a monthup there," says Atlas, who helped design the experiment. "But thescientific questions are so important that it's worth the hardship."
Ozone levels in the Arctic troposphere (lower eight kilometers, orfive miles, of the atmosphere) increase from 30-40 parts per billion(ppb) in winter to 50-60 ppb in the spring--about half theconcentration above Los Angeles on a bad day. Meanwhile, in thestratosphere above, the returning springtime sun triggers chemicalreactions that deplete ozone, creating a smaller, northern version ofthe Antarctic ozone hole.
Why these springtime highs and lows? Scientists suspect that someozone 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 pollutedregions of northern and central Europe. To what extent does thisinflux speed up the chemical processes that accompany the return ofsunlight? Scientists believe measurements of 20 or so chemicalspecies throughout the troposphere will provide answers. Already theyhave found surprises in the levels of important compounds.
To complicate matters more, at ground level scientists have foundozone-empty bands about 30 miles across. To explore these areas, theC-130 coasts 100 feet above Hudson and Baffin Bays and the ArcticOcean, sampling chemistry occurring over the ice and open leads. TheNCAR researchers and their colleagues hope to find the crucial datato explain why ozone builds up in the lower atmosphere even as itvanishes entirely from some surface areas.
Back at NCAR the measurements are helping scientists to fine tunetheir atmospheric chemistry models to better understand the chemistryand dynamics of the Arctic's lower atmosphere as winter gives way tospring.
Other participants in the experiment, called Tropospheric OzoneProduction about the Spring Equinox (TOPSE), include NASA's Goddardand Langley Research Centers; Dalhousie, Georgia Tech, Harvard,Rutgers, and York Universities; and the Universities of California(Berkeley and Irvine), Colorado, Maryland, New Hampshire, RhodeIsland, and Virginia. Also collaborating are colleagues atEnvironment Canada and Purdue University, who are conducting ground-based research in the high Arctic.
NCAR is managed by the University Corporation for AtmosphericResearch, a consortium of more than 60 universities offering Ph.D.sin atmospheric and related sciences.
Note to Editors: Reporters are invited to view the airplane andinterview the chief scientists when they are in Colorado. Pleasecontact Anatta (303-497-8604) to arrange a visit.
Materials provided by National Center For Atmospheric Research (NCAR). Note: Content may be edited for style and length.
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