Aeronomy

Antarcrtic AeronomyAtmospheric 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).

"Wonder Chemicals"
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.

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 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.

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.

total ozone graphThanks 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.

How is the Ozone Hole Monitored?
  • 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.

Did You Know?
antarctic cloudsThe 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.