The Ozone Layer Essay

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The 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
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Since the level of peak ozone is considerably higher in altitude in the tropics, ozone descends as it moves toward the poles, where because of very low photochemical destruction, it accumulates, particularly in the winter hemisphere (see fig.1).
Some ozone eventually enters the troposphere over the poles.

Seasonal variations are much stronger in the polar regions reaching 50% of the annual mean in the Arctic. In spring, Northern Hemisphere transport of ozone toward the poles builds to a maximum (40-80°N), associated with the maximum altitude difference in the major ozone regions of the tropics and the poles. The polar flux of ozone ceases as the westerly circulation dominant in winter is replaced by easterlies over the tropics. In the Southern Hemisphere the spring maximum occurs near 60°S, one to two months after the maximum in the subtropics.
Throughout the summer, photochemical reactions reach a maximum in the lower tropical stratosphere and ozone concentrations fall. Autumn circulations are the weakest, with the latitudinal gradient between the poles and the equator virtually disappearing. Ozone concentrations throughout most of the stratosphere reach a minimum. As the circumpolar vortex expands for winter, the strength of circulation increases rapidly, ozone transport from the tropics also increases strongly, and meridional circulation and variability

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