BOULDER -- This winter a team of scientists from the National Center forAtmospheric Research (NCAR) is part of the largest international projectever mounted to measure levels of ozone and learn more about itslifecycle in the upper atmosphere of the Arctic. Prompted byobservations of very low levels of ozone in the Arctic stratosphere inrecent winters, scientists from the United States, Europe, Russia, andJapan are hoping to explain the ozone loss by making detailedmeasurements of the chemistry and dynamics of this under-studied region.
The SAGE III Ozone Loss and Validation Experiment, sponsored by theNational Aeronautics and Space Administration, is being conductedjointly with the European Commission-sponsored Third EuropeanStratospheric Experiment on Ozone. With some 350 scientistsparticipating, SOLVE/THESEO-2000 is the largest stratospheric fieldmission ever conducted, according to project manager Michael Craig ofNASA's Ames Research Center. NCAR's primary sponsor is the NationalScience Foundation.
Begun in the Arctic darkness of November and continuing through March asthe sun climbs higher above the horizon, the mission is timed to capturechemical changes in the stratosphere brought about by interaction withincreasing solar radiation. As temperatures fall during Arctic winter,polar stratospheric clouds (PSCs) can form. A complex series of chemicalreactions on the surface of PSC cloud particles frees up active chlorineand bromine, which react with sunlight to catalyze ozone destructionwhen the sun returns in early spring. The sources of chlorine andbromine are human-produced chlorofluorocarbons (CFCs) and halocarbons.The colder the Arctic spring, the longer the clouds linger and the moreozone loss. Scientists need to understand the complex interactions amongsolar radiation, temperature, water, CFCs, aerosol particles, and polarstratospheric clouds before predictions of ozone loss in the NorthernHemisphere can become more reliable.
An array of research instruments aboard NASA's DC-8 and ER-2 aircraft istaking measurements in flight and bringing back air samples for testingin the lab. NCAR researchers William Mankin and Michael Coffey developedtechniques for using a spectrometer aboard the DC-8 to measure amountsof chlorine, nitrogen-containing gases, CFCs, ozone, and otherstratospheric gases important to polar ozone chemistry. They expect theinstrument to also detect the infrared signature of polar stratosphericclouds, allowing them to determine cloud structure and composition. Alsoaboard the DC-8, Richard Shetter's spectroradiometers are gathering dataon photolysis (sunlight-produced chemical changes) of 15 differentmolecules important to the production and destruction of ozone. Histeam's measurements of actinic flux, which serves as a tracer ofphotolysis, are the first to be made in the Arctic stratosphere.
The ER-2 is carrying an instrument developed by Darrel Baumgardner,Bruce Gandrud, and colleagues to determine the size and concentration ofPSC cloud particles from 0.3 to 20 micrometers (thousandths of amillimeter) in diameter. A whole air sampler is collecting and storingup to 32 air samples per ER-2 flight. The samples are shipped the sameweek to NCAR, where Elliot Atlas is analyzing them using severaldifferent gas chromatographs to look for halocarbons, hydrocarbons, andorganic nitrates.
Several European aircraft are also participating, and additionalmeasurements will be taken by instruments carried up to 100,000 feetaloft by research balloons. Instruments on the ground in Sweden andNorway will round out the profile of the Arctic stratosphere. SOLVEscientists are based above the Arctic Circle at the airport in Kiruna,Sweden, where winter temperatures can reach -50_ Fahrenheit or lower.
The stratosphere ranges from about 30,000 to 180,000 feet in altitude.Ozone in the stratosphere acts as a protective layer, keeping most ofthe sun's ultraviolet radiation from reaching the earth, where it causesdamage to people and other living things. Most of the ozone in thestratosphere is concentrated between 50,000 and 100,000 feet--withinrange of SOLVE's aircraft and balloons.
The Antarctic ozone hole and its causes made news in the 1980s.International efforts to reduce manufacture of ozone-destroying CFCsculminated in a production ban for industrialized countries in 1996. TheArctic ozone layer seemed unaffected; ozone concentrations werenaturally higher there, and relatively warmer Arctic temperatures stayedabove the levels necessary for CFCs to interfere with ozone chemistry.In the late 1990s, however, scientists detected dramatically lowerlevels of ozone over the Arctic, raising concerns about the possibilityof a second ozone hole above the North Pole.
NCAR is managed by the University Corporation for Atmospheric Research,a consortium of more than 60 universities offering Ph.D.s in atmosphericand related sciences.
Note to Editors: Journalists are invited to the main field stagingarea in Kiruna, Sweden, during media week, January 21-28. Members ofmost of the science teams, including NCAR's, will be on hand. A newsroomwill operate in the Scandic Hotel Ferrum near the airport. Duringescorted tours into the research area, journalists may meet withscientists. Contact for media week is Chris Rink--before January 22:NASA Langley Research Center, Hampton, Virginia, phone: 757-864-6786,fax: 757-864-6333, e-mail: [email protected];January 21-28: NASA newsroom, Kiruna, Sweden, phone: 011 46-980-398-787,fax: 011 46-980-398-788, e-mail: [email protected]
Writer: Zhenya Gallon
The above story is based on materials provided by National Center For Atmospheric Research (NCAR). Note: Materials may be edited for content and length.
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