Longman Dictionary of Contemporary English
Wiktionary
n. A region of the stratosphere, between 15 and 30 kilometres in altitude, containing a relatively high concentration of ozone; it absorbs most solar ultraviolet radiation
WordNet
n. a layer in the stratosphere (at approximately 20 miles) that contains a concentration of ozone sufficient to block most ultraviolet radiation from the sun [syn: ozonosphere]
Wikipedia
The ozone layer or ozone shield is a region of Earth's stratosphere that absorbs most of the Sun's ultraviolet (UV) radiation. It contains high concentrations of ozone (O) in relation to other parts of the atmosphere, although still small in relation to other gases in the stratosphere. The ozone layer contains less than 10 parts per million of ozone, while the average ozone concentration in Earth's atmosphere as a whole is about 0.3 parts per million. The ozone layer is mainly found in the lower portion of the stratosphere, from approximately above Earth, although the thickness varies seasonally and geographically.
The ozone layer was discovered in 1913 by the French physicists Charles Fabry and Henri Buisson. Measurements of the sun showed that the radiation sent out from its surface and reaching the ground on Earth is usually consistent with the spectrum of a black body with a temperature in the range of 5,500–6,000 K (Kelvin) (5,227 to 5,727°C), except that there was no radiation below a wavelength of about 310 nm at the ultraviolet end of the spectrum. It was deduced that the missing radiation was being absorbed by something in the atmosphere. Eventually the spectrum of the missing radiation was matched to only one known chemical, ozone. Its properties were explored in detail by the British meteorologist G. M. B. Dobson, who developed a simple spectrophotometer (the Dobsonmeter) that could be used to measure stratospheric ozone from the ground. Between 1928 and 1958, Dobson established a worldwide network of ozone monitoring stations, which continue to operate to this day. The " Dobson unit", a convenient measure of the amount of ozone overhead, is named in his honor.
The ozone layer absorbs 97 to 99 percent of the Sun's medium-frequency ultraviolet light (from about 200 nm to 315 nm wavelength), which otherwise would potentially damage exposed life forms near the surface.
The United Nations General Assembly has designated September 16 as the International Day for the Preservation of the Ozone Layer.
Venus also has a thin ozone layer at an altitude of 100 kilometers from the planet's surface.
Usage examples of "ozone layer".
These bits of rock had been hurled far above the weather, far above aircraft and balloons, above even the ozone layer, fragments of Rabaul mingling with the meteorites, burning brightly and briefly.
Li Chengdu was an ascetically lean, sallow-faced man who had been born in Singapore of a Chinese merchant family, educated in Shanghai and Geneva, and was rumored to be in line for a Nobel Prize for his research in atmospheric physics: he had found a way to reverse the depletion of the ozone layer and close the long-dreaded ozone hole in the upper atmosphere.
What they point out, essentially, is that the whole notion of the ozone layer as something fixed and finite, to be eroded away at a faster or slower rate like shoe leather, is all wrong to begin with—.
Not only are they greenhouse gases, but they are also devastatingly effective in destroying the protective ozone layer.
The dominant organisms, whoever they are-who have gone to so much trouble to rework the surface-are simultaneously destroying their ozone layer and their forests, eroding their topsoil, and performing massive, uncontrolled experiments on their planet's climate.
They didn't see Nature for what She was, and as a result they lived lives that were aimed only at hurting or even destroying Her, driving cars that injected hydrocarbons into the atmosphere, using chemicals that found their way into the water, pesticides that killed birds or kept them from reproducing, aiming spray cans at their hair whose propellants destroyed the ozone layer.