Brian Dunbar NASA Headquarters, Washington, D.C. Embargoed Until (Phone: 202/453-1547) March 16, 1990 Bill Brennan Joan Vandiver Frisch NOAA, Boulder, Colo. Nat. Ctr. for Atmospheric Res. (Phone: 303/497-6286) Boulder, Colo. (303/497-8720) Jean Drummond Clough Randee Exler Langley Res. Ctr., Hampton, Va. Goddard SF Ctr., Greenbelt, Md. (Phone: 804/864-6122) (Phone: 301/286-7277 RELEASE: 90-41 STUDY DETECTS POSSIBLE OZONE LOSS OVER ARCTIC Chemical processes that lead to ozone depletion in the Antarctic are present in the far Northern Hemisphere, and some regions of the Arctic stratosphere may have suffered ozone losses up to 17 percent during the winter of 1988-89, results of the 1989 Airborne Arctic Stratospheric Expedition (AASE) indicate. At the conclusion of the mission in February, AASE scientists released a statement that "no unequivocal signature of photochemical loss of Arctic ozone was identified before the end of this mission. However, by the end of this mission a considerable portion of the vortex air was primed for destruction." After almost a year of analysis has refined that conclusion, with several investigators, using different analytical methods, reported the Arctic ozone losses. For example, a team led by Dr. Edward Browell of NASA's Langley Research Center, Hampton, Va., used a laser-based technique similar to radar to measure ozone distribution and observed depletions of up to 17 percent at some altitudes. A group led by Dr. Mark Schoeberl of Goddard Space Flight Center, Greenbelt, Md., inferred average photochemical ozone losses of 0.44 percent per day over the mission at altitudes above approximately 12 miles. - more - - 2 - Chemical analyses showed increased levels of active chlorine and lower-than-expected levels of nitrogen oxides in the atmosphere. In their prologue, Richard Turco of UCLA, Alan Plumb of MIT and Estelle Condon of NASA's Ames Research Center, Mountain View, Calif., wrote that these measurements indicate that chemically "the Arctic stratosphere is primed for an ozone hole." Meteorological conditions, however, were found to be unsuitable for the development of an Arctic ozone hole similar to the one observed over the Antarctic. An "ozone hole" similar to the one that appears annually over the South Pole is unlikely to occur in the north because of substantially different weather patterns there. In the Antarctic, the photochemical breakdown of ozone is aided by a strong vortex of stratospheric winds that circle a continent-sized area and effectively isolate air over the pole. Within the vortex, cold temperatures enhance the formation of polar stratospheric clouds (PSCs), which serve as catalysts in the transformation of non-reactive chlorine compounds into reactive chlorine. Whereas the Antarctic vortex often remains intact for most of the austral spring, the Arctic vortex usually breaks up before the spring sunrise can begin the chlorine-ozone reactions. More than a third of the AASE papers focus on PSCs, key components of the chemistry of ozone depletion. In situ and satellite measurements defined the microscopic structures of PSCs, with the results indicating that nitric acid vapor is a key element in PSCs' formation and therefore, that denitrification of the stratosphere is an indicator that the potential for ozone depletion exists. Turco, Plumb and Condon, however, cautioned that the exact process of PSC formation is not fully understood. The papers resulting from the AASE address a wide range of ozone-related issues, from meteorology and polar stratospheric clouds to trace chemistry and ozone depletion. The January 1989 expedition, based in Stavanger, Norway, flew a variety of instruments to measure meteorological conditions and atmospheric physics and chemistry on 28 flights of NASA's ER-2 and DC-8 research aircraft. The findings of the expedition, coordinated by NASA and co-sponsored by the National Oceanic and Atmospheric Administration, the National Science Foundation and the Chemical Manufacturers Association, will be published in the April issue of Geophysical Research Letters, a publication of the American Geophysical Union. Scientists from the National Center for Atmospheric Research, Harvard University, University of Denver, NASA and NOAA took part, with international participation from Norway, United Kingdom, the Federal Republic of Germany, Denmark and Sweden. - end - TO: MDS/PRA Group 1615 L Street, N.W. - Suite 100 Washington, D.C. 20036 DATE & TIME: March 15, 1990 2:00pm ORDERED BY: Edward Campion NASA Headquarters/LMD 400 Maryland Avenue, SW Washington, DC 20546 PHONE: 202/453-8400 PROJECT TITLE: Release No: 90-41 PRINT ORDER: 2228 PRINTING: Camera Ready, lst pg on NASA logo, other pages plain ENCLOSE & MAIL: Release of 2 pages MAIL DATE: March 16, 1990 EXTRA COPIES: Deliver specified quanities to locations below: 50 copies 275 copies 75 copies -------------------- ------------------- ----------------- National Press Club NASA Mailroom NASA Newsroom 13th floor newsrack NASA Headquarters NASA Headquarters National Press Building 600 Independ. 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