Extreme conditions cause rare Antarctic clouds
Extreme conditions cause rare Antarctic clouds
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Wednesday, 02, Aug 2006 02:41
Clouds forming above Antarctica at the end of the polar night have been described as "rare and spectacular" by the Australian Antarctic Division (AAD).
The clouds showed delicate colours "produced when the fading light at sunset passed through tiny water-ice crystals blown along on a strong jet of stratospheric air".
It is thought that they provide a vital clue to climate change as they occur only when there are extreme conditions in the atmosphere.
Temperatures of less than -80C are required for them to form, and the photographer who captured the clouds for the Australian Bureau of Meteorology, Renae Baker, said that the recorded temperature of -87C was "about as cold as the lowest temperatures ever recorded on the surface of the Earth".
Atmospheric scientist Dr Andrew Klekociuk of the AAD said: "These clouds are more than just a curiosity. They reveal extreme conditions in the atmosphere, and promote chemical changes that lead to destruction of vital stratospheric ozone.
"We are using instruments on the ground, on balloons and on satellites in an international program to find out what this type of phenomenon tells us about the current and future state of climate," he added.
Showing similar colours to a Mother of Pearl shell, the clouds are seldom seen not only because of the low temperature required but because observers have to be in the right part of Antarctica in winter with the sun just below the horizon to see them.
The study of the clouds will continue through the forthcoming international polar year, which will focus on the Earth's polar regions from 2007 to 2009.