MercoPress. South Atlantic News Agency

Antarctic beauty masks damage to ozone layer

The rare nacreous cloud, top, is seen high in the stratosphere some 20 kilometres above Australia's Mawson station in Antartica.

Some of the coldest temperatures on Earth have fostered a rare cloud formation over Australia's Mawson station in Antarctica, scientists said on Tuesday.

The clouds only occur at high polar latitudes in winter, requiring temperatures less than approximately minus 80 Celsius. A weather balloon measured temperatures down to minus 87 C on the day the photos were taken.

Reflecting like an airborne mother-of-pearl shell, the cloud colours are produced when fading light at sunset passes through water-ice crystals blown along a strong jet of stratospheric air more than 10 kilometres above the ground.

But the stunning sight was a reminder of environmental damage being inflicted on the ozone layer by decades of chlorofluorocarbon emissions.

Andrew Klekociuk, an atmospheric physicist with the Australian Antarctic Division, said nacreous clouds "are catalysts that convert chlorofluorocarbons, changing them into forms that can destroy ozone in the presence of sunlight".

As a result, they always attract the attention of Antarctic scientists. Dr Klekociuk said nacreous clouds ? "the name means mother-of-pearl-like" ? form about 20 kilometres up and only when the mercury falls below minus 80 degrees. Weather balloons sent up to investigate the clouds on July 25 recorded winds of almost 230 km/h and temperatures of minus 87 degrees. "Antarctic air doesn't get much colder," Dr Klekociuk said.

Ms Baker, a Bureau of Meteorology officer who transferred from Longreach to Antarctica in November, said the clouds covered "almost a quarter of the horizon, their colours ranging from a very vibrant pearl to white".

Ms Baker, who has taken more than 5000 photographs in Antarctica, said yesterday was another beautiful, if short, Mawson day. "We got to just below minus 30 this morning, but we are warming up. At 9.30 it was minus 23.1 degrees."