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The Atmospheric Ozone Layer
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| Term Paper Title | The Atmospheric Ozone Layer |
| # of Words | 2223 |
| # of Pages (250 words per page double spaced) | 8.89 |
The Atmospheric Ozone Layer
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 spring of 1979.
This discovery placed the British scientists into the limelight of world
publicity, for it revived a somewhat sagging public interest in the potential
destruction of the stratospheric ozone layer by anthropogenic trace gases,
particularly nitrogen species and chlorofluorocarbons.
Ozone concentrations peak around an altitude of 30km in the tropics and around
15-20km over the polar regions. The ozone formed over the tropics is distributed
poleward through the stratospheric circulat
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