Ultima Thule

In ancient times the northernmost region of the habitable world - hence, any distant, unknown or mysterious land.

Wednesday, August 02, 2006

Scientists worried by rare cloud formation over Antarctica

By Aussiegirl

It's either too hot or too cold. Typically, meteorologists are not that different from the rest of us when it comes to our reaction to the weather. It's a marvelous world, isn't it? Look at the beauty of that cloud! I'm sure that the ozone layer has come and gone through the millenia, and we are all still here. Meanwhile, let's just sit back and enjoy the show.

globeandmail.com : Scientists worried by rare cloud formation over Antarctica

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

Meteorological officer Renae Baker captured spectacular images of the nacreous clouds, also known as polar stratospheric clouds, on July 25.

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

“Amazingly, the winds at this height were blowing at nearly 230 kilometres per hour,” Ms. Baker said on the Australian government's Antarctic Division's website.

A rare and spectacular nacreous cloud (top) appears high in the stratosphere about 20 kilometres above Australia's Mawson station in Antartica. (Renae Baker/AFP/Getty Images)

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.

Australian Antarctic Division atmospheric scientist Andrew Klekociuk said the clouds were seldom seen but could have long-ranging effects.

“These clouds are more than just a curiosity,” he said. “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,” Ms. Klekociuk said.


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