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Atmospheric
science is an expensive and active field of Antarctic research.
Global warming and ozone destruction
have made the study of atmospheric gases a major discipline, and
the Antarctic has an important role to play in this research.
In the
stratosphere, the region of the atmosphere between about 10 and
50 kilometers (6-30 miles) above the Earth's surface, ozone (O3)
plays a vital role by absorbing harmful ultraviolet radiation from
the sun.
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"Wonder
Chemicals"
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Once widely used as propellants
in spray cans, refrigerants, electronics cleaning agents,
and in foam and insulating products, CFCs had been hailed
as the "wonder chemicals." But the very properties that make
them useful - chemical inertness, non-toxicity, insolubility
in water - also make them resistant to removal in the lower
atmosphere.
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Stratospheric
ozone is threatened by some of the human-made gases that have been
released into the atmosphere, including those known as chlorofluorocarbons
(CFCs). CFCs are
mixed worldwide by the large-scale motions of the atmosphere and survive
until, after 1-2 years, they reach the stratosphere and are broken
down by ultraviolet radiation.
The word "aeronomy" was introduced
by S. Chapman in 1932. It indicates the study of the chemical
and physical phenomena in the atmosphere of the Earth at a height
above 30 km. |
The
chlorine atoms within them are released and
directly
attack ozone. In
the process of destroying ozone, the chlorine atoms are regenerated
and begin to attack other ozone molecules... and
so on, for thousands of cycles before the chlorine atoms are removed
from the stratosphere by other processes.
Thanks to Antarctic research, we now have
a much clearer picture of the whole complex cycle. During
the winter polar night, sunlight does not reach the south pole. A
strong circumpolar wind develops in the middle to lower stratosphere.
These strong winds are known as the 'polar vortex'. This has the effect
of isolating the air over the polar region. 
Since there is no sunlight,
the air within the polar vortex can get very cold. So cold that
special clouds can form once the air temperature gets to below about
-80C.These clouds are called Polar Stratospheric Clouds (or PSCs).
PSCs are composed of ice particles with nitric acid dissolved in
them. These PSCs are crucial for ozone loss to occur because they
alter the chemical balance between the chlorine derived from the
breakdown of the CFCs and other gases in the stratosphere, thus
acting as a catalyst for destructive chemical reactions.
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How is
the Ozone Hole Monitored?
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- Satellites stare down
on the continent, reporting the concentrations of ozone
as seen from above.
- Looking up from the
ground, many countries use Dobson or Brewer spectrophotometers
to monitor stratospheric ozone.
- Upward-pointing laser
systems can also detect the formation of the stratospheric
clouds in which ozone destruction occurs.
- There are even direct
measurements of ozone obtained by launching hydrogen or
helium-filled balloons with detectors aboard.
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