A shining theory of ozone depletion.A shining theory of ozone depletion Ozone depletion describes two distinct, but related observations: a slow, steady decline of about 4 percent per decade in the total amount of ozone in Earth's stratosphere since around 1980; and a much larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions The cause of the steadily worsening polar "ozone holes" (SN:3/1/86,p.133) and the drop in global ozone levels (SN:6/28/86,p.404) in the last few years is still a mystery. But one theory that is getting a lot of attention is an idea developed by Linwood B. Callis at NASA NASA: see National Aeronautics and Space Administration. NASA in full National Aeronautics and Space Administration Independent U.S. Langley Research Center Langley Research Center (LaRC) Oldest of NASA's field centers, LaRC is located in Hampton, Virginia and directly borders Poquoson, Virginia and Langley Air Force Base. LaRC focuses primarily on aeronautical research, though the Lunar Lander was flight-tested at this facility and a and Murali Natarajan at SASC SASC Senate Armed Services Committee SASC Small Arms School Corps (UK) SASC South African Society of Cinematographers SASC South Asian Subcontinent (airlines) SASC San Angeles Saluki Club, Inc. Technologies, Inc., both in Hampton, Va. The key to their idea, published in the Sept. 20 JOURNAL OF GEOPHYSICAL RESEARCH Journal of Geophysical Research is a publication of the American Geophysical Union. JGR was formerly titled Terrestrial Magnetism from its founding by the AGU's president Louis A. , is "odd nitrogen" compounds (named for their electronic structure). These compounds catalytically destroy ozone. They are produced in the thermosphere ther·mo·sphere n. The outermost shell of the atmosphere, between the mesosphere and outer space, where temperatures increase steadily with altitude. ther , the topmost atmospheric layer, with the help of the sun. Callis and Natarajan think the unusually high solar activity levels in late 1979 and early 1980, during the second largest solar maximum in 250 years, led to increased production of odd nitrogen. Using satellite and ground-based data, they have found that from 1979 to 1984, stratospheric strat·o·spher·ic adj. 1. Of, relating to, or characteristic of the stratosphere. 2. Extremely or unreasonably high: "money borrowed at today's stratospheric rates of interest" odd nitrogen levels increased by as much as 60 percent in the Southern Hemisphere and 30 percent globally. Callis and Natarajan propose that during the polar winter, odd nitrogen molecules are caught in a vortex of winds at the poles and sink down into the stratosphere, where they attack ozone once the sunshine returns in the spring. The hole disappears every polar summer because the vortex dissipates then. Once in the stratospere, odd nitrogen can exist for three to four years - which is one reason why the researchers think the ozone hole has persisted beyond the solar maximum. If their theory is correct, says Callis, the presently developing Antarctic ozone hole should be no more severe than last year's and should begin to disappear next year. While he says continued industrial emissions of ozone-attacking chlorine compounds should somewhat counterbalance the effects of decreasing stratospheric odd nitrogen, he expects the declining trend in global ozone to slow, and possibly reverse, in the next few years. |
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