BOULDER--This winter a team of scientists from the National Center for Atmospheric Research (NCAR) is part of the largest international project ever mounted to measure levels of ozone and learn more about its lifecycle in the upper atmosphere of the Arctic. Prompted by observations of very low levels of ozone in the Arctic stratosphere in recent winters, scientists from the United States, Europe, Russia, and Japan are hoping to explain the ozone loss by making detailed measurements of the chemistry and dynamics of this under-studied region.
The SAGE III Ozone Loss and Validation Experiment, sponsored by the National Aeronautics and Space Administration, is being conducted jointly with the European Commission-sponsored Third European Stratospheric Experiment on Ozone. With some 350 scientists participating, SOLVE/THESEO-2000 is the largest stratospheric field mission ever conducted, according to project manager Michael Craig of NASA's Ames Research Center. NCAR's primary sponsor is the National Science Foundation.
Begun in the Arctic darkness of November and continuing through March as the sun climbs higher above the horizon, the mission is timed to capture chemical changes in the stratosphere brought about by interaction with increasing solar radiation. As temperatures fall during Arctic winter, polar stratospheric clouds (PSCs) can form. A complex series of chemical reactions on the surface of PSC cloud particles frees up active chlorine and bromine, which react with sunlight to catalyze ozone destruction when the sun returns in early spring. The sources of chlorine and bromine are human-produced chlorofluorocarbons (CFCs) and halocarbons. The colder the Arctic spring, the longer the clouds linger and the more ozone loss. Scientists need to understand the complex interactions among solar radiation, temperature, water, CFCs, aerosol particles, and polar stratospheric clouds before predictions of ozone loss in the Northern Hemisphere can become more reliable.
An array of research instruments aboard NASA's DC-8 and ER-2 aircraft is taking measurements in flight and bringing back air samples for testing in the lab. NCAR researchers William Mankin and Michael Coffey developed techniques for using a spectrometer aboard the DC-8 to measure amounts of chlorine, nitrogen-containing gases, CFCs, ozone, and other stratospheric gases important to polar ozone chemistry. They expect the instrument to also detect the infrared signature of polar stratospheric clouds, allowing them to determine cloud structure and composition. Also aboard the DC-8, Richard Shetter's spectroradiometers are gathering data on photolysis (sunlight-produced chemical changes) of 15 different molecules important to the production and destruction of ozone. His team's measurements of actinic flux, which serves as a tracer of photolysis, 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 of PSC cloud particles from 0.3 to 20 micrometers (thousandths of a millimeter) in diameter. A whole air sampler is collecting and storing up to 32 air samples per ER-2 flight. The samples are shipped the same week to NCAR, where Elliot Atlas is analyzing them using several different gas chromatographs to look for halocarbons, hydrocarbons, and organic nitrates.
Several European aircraft are also participating, and additional measurements will be taken by instruments carried up to 100,000 feet aloft by research balloons. Instruments on the ground in Sweden and Norway will round out the profile of the Arctic stratosphere. SOLVE scientists 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 of the sun's ultraviolet radiation from reaching the earth, where it causes damage to people and other living things. Most of the ozone in the stratosphere is concentrated between 50,000 and 100,000 feet--within range 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 CFCs culminated in a production ban for industrialized countries in 1996. The Arctic ozone layer seemed unaffected; ozone concentrations were naturally higher there, and relatively warmer Arctic temperatures stayed above the levels necessary for CFCs to interfere with ozone chemistry. In the late 1990s, however, scientists detected dramatically lower levels of ozone over the Arctic, raising concerns about the possibility of 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 atmospheric and related sciences.
Note to Editors: Journalists are invited to the main field staging
area in Kiruna, Sweden, during media week, January 21-28. Members of
most of the science teams, including NCAR's, will be on hand. A newsroom
will operate in the Scandic Hotel Ferrum near the airport. During
escorted tours into the research area, journalists may meet with
scientists. 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: c.p.rink@express.larc.nasa.gov;
January 21-28: NASA newsroom, Kiruna, Sweden, phone: 011-46-980-398-787,
fax: 011-46-980-398-788, e-mail: c.p.rink@express.larc.nasa.gov
Writer: Zhenya Gallon