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The Atmospheric Ozone Layer
The stratospheric ozone layer exists at altitudes between about 10 and 40km depending on latitude, just above the tropopause. Its existence is crucial for life on earth as we know it, because the ozone layer controls the absorption of a portion of the deadly ultraviolet (UV) rays from the sun. UV-A rays, including wavelengths between 320 and 400nm, are not affected by ozone. UV-C rays between 200 and 280nm, are absorbed by the other atmospheric constituents besides ozone. It is the UV-B rays, between 280 and 320nm, absorbed only by ozone, that are of the greatest concern. Any loss or destruction of the stratospheric ozone layer could mean greater amount of UV-B radiation would reach the earth, creating among other problems, an increase in skin cancer (melanoma) in humans. As UV-B rays increase, the possibility of interferences with the normal life cycles of animals and plants would become more of a reality, with the eventual possibility of death. Stratospheric ozone has been used for several decades as a tracer for stratospheric circulation. Initial measurements were made by ozonesondes attached to high altitude balloons, by chemical-sondes or optical devices, which measured ozone concentrations through the depletion of UV light. However, the need to measure ozone concentrations from the surface at regular intervals, led to the development of the Dobson spectrophotometer in the 1960s. The British Antarctic Survey has the responsibility to routinely monitor stratospheric ozone levels over the Antarctic stations at Halley Bay (76°S 27°W) and at Argentine Islands (65°S 64°W). Analysis of ozone measurements in 1984 by a team led by John Farnam, made the startling discovery that spring values of total ozone during the 1980-1984 period had fallen dramatically compared to the earlier period between 1957-73. This decrease had only occurred for about six weeks in the Southern Hemisphere spring and had begun in the s... Please login to view comments from other users.
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