The seasonal ozone declines continue.It's that time of year again, when the ozone over Antarctica grows almost as sparse as the hair on a balding man's head and provides little more protection against the sun's cancer-causing rays. So far, however, this year's ozone measurements are producing a confused picture. Data taken from a U.S. spectrometer flown aboard a Russian satellite suggest that the protective layer has thinned almost as much as it did last October, researchers told SCIENCE NEWS. But data from instruments on balloons sent into the stratosphere hint that things aren't that bad. The ozone layer ozone layer or ozonosphere, region of the stratosphere containing relatively high concentrations of ozone, located at altitudes of 12–30 mi (19–48 km) above the earth's surface. helps guard Earth from the sun's damaging ultraviolet radiation. In the spring, when sunlight finally reaches Antarctica, the protective blanket of gas thins as light activates chlorine and bromine bromine (brō`mēn, –mĭn) [Gr.,=stench], volatile, liquid chemical element; symbol Br; at. no. 35; at. wt. 79.904; m.p. –7.2°C;; b.p. 58.78°C;; sp. gr. of liquid 3.12 at 20°C;; density of vapor 7. particles, which help break apart ozone molecules. By November, as the polar stratosphere warms, the hole begins to mend. Concentrations of ozone should bottom out around Oct. 10, says Samuel J. Oltmans of the National Oceanic and Atmospheric Administration Noun 1. National Oceanic and Atmospheric Administration - an agency in the Department of Commerce that maps the oceans and conserves their living resources; predicts changes to the earth's environment; provides weather reports and forecasts floods and hurricanes and in Boulder, Colo. Last October's record-breaking 70 percent drop in ozone probably resulted in part from the dose of sulfur dioxide sulfur dioxide, chemical compound, SO2, a colorless gas with a pungent, suffocating odor. It is readily soluble in cold water, sparingly soluble in hot water, and soluble in alcohol, acetic acid, and sulfuric acid. that Mt. Pinatubo shot into the stratosphere when it erupted in 1991 (SN: 10/16/93, p.247). In the last 2 weeks, the low recorded by researchers using the balloon instruments was 103 Dobson units of ozone -- about 10 percent more than last year at the same time, Oltmans says. This slight increase doesn't suggest a permanent comeback for ozone, he warns. The data have a margin of error of plus or minus 4 Dobson units. [CHART OMITTED] Satellite records suggest that the rate of ozone decline has almost matched last year's, says Arlin J. Krueger of NASA's Goddard Space Flight Center The Goddard Space Flight Center (GSFC) is a major NASA space research laboratory established on May 1, 1959 as NASA's first space flight center. GSFC employs approximately 10,000 civil servants and contractors, and is located approximately 6.5 miles northeast of Washington, D.C. in Greenbelt, Md. He and his colleagues recorded a low of 100 Dobson units of ozone on Sept. 30 and expect it will drop to last year's low of 90, he says. The margin of error is 10 Dobson units. The ozone hole ozone hole n. An area of the ozone layer, such as the large area over Antarctica or the smaller area over the North Pole, that periodically becomes depleted of ozone. has become more extensive in the past few years. It now covers about 23 million square kilometers, roughly the size of North America North America, third largest continent (1990 est. pop. 365,000,000), c.9,400,000 sq mi (24,346,000 sq km), the northern of the two continents of the Western Hemisphere. . |
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