Rare Colorful Polar Stratospheric Clouds

[Carmen Elsa Irarragorri Wyland]

 

Published on Dec 26, 2015

Rare Colorful Polar Stratospheric Clouds Spotted Over Norway In a town where the sun doesn't rise for month s, there are still spectacular sights to see in in the sky. These dazzling photos from Truls Tiller of Tromsø, Norway show colorful, glowing phenomena known as polar stratospheric clouds. "Here the sun is gone for now, but this beautiful view makes the winter and the dark months nice to be in as well," Tiller wrote on Spaceweather.com. "Virtually all the clouds we see occur in the troposphere, the lowest layer of the atmosphere extending up to about 12 miles above the ground," weather.com senior meteorologist Jonathan Erdman said. "Polar stratospheric clouds form at a height of at least 70,000 feet, over double the altitude commercial airlines fly." These clouds are visible only in higher latitudes in the northern and southern hemispheres. The lack of sunlight in the polar regions mixed with extraordinarily cold temperatures in the stratosphere changes water vapor in the atmosphere to a super cooled liquid or ice crystals. They're rare, yes, but also dangerous. "They play an indirect role in the destruction of stratospheric ozone," Erdman said. As it turns out, these clouds are the breeding grounds for chemical reactions that involve chemical compounds derived from chlorofluorocarbons (CFCs), releasing chlorine gas that kills the ozone in the atmosphere. http://www.weather.com/news/weather/n... You can keep up with Tiller and his breathtaking photos from Norway on his Facebook page. https://www.facebook.com/tillerfoto/

Very Cold Polar Stratospheric Clouds Appear over UK on Feb 2, 2016. These type 2 clouds are associated with temperatures of -85C and are 80% of the time sighted over Antarctica. This insistence of cloud sightings was incredibly far south.

The stratosphere above the Arctic Circle is getting cold … very cold. That’s one way – the only way for space weather scientists – to explain these colorful clouds – polar stratospheric clouds (PSCs) – which require temperatures around -85ºC to form and appeared over Norway and Sweden on Dec. 20th:

This absolutely stunning display of stratospheric clouds appeared high above the ordinary gray rainclouds. It’s very seldom to see PSCs with such vivid colors as today.

Polar stratospheric clouds over Norway on December 20, 2017. By Fredrik Broms / www.northernlightsphotography.no

As their name implies, these surreal clouds form in the extremely dry stratosphere, high above Earth’s surface. In this second layer of Earth’s atmosphere – starting between 33,000–43,000 ft; 6.2–8.1 mi) and ending at 50 km (160,000 ft; 31 mi) almost no clouds of any type can form.

Polar stratospheric clouds over Norway on December 20, 2017. By Fredrik Broms / www.northernlightsphotography.no

Polar stratospheric clouds over Norway on December 20, 2017. By Fredrik Broms / www.northernlightsphotography.no

However, when the the air up there becomes extremely cold, rare water molecules coalesce and form ice crystals. High-altitude sunlight refracting on the ice creates these mind-blowing iridescent colors.

Nacreous clouds over Sweden on December 20, 2017. By Oliver Wright

Nacreous clouds over Sweden on December 20, 2017. By Oliver Wright

Keep your eyes to the sky, the 2017-18 winter season for polar stratospheric clouds is just starting.

[William J. Coblentz]

Well, that altitude range fits with the clouds being cirrus. One gathers that the frequency of occurrence is increasing, since there are so many pictures posted of more recent dates. Is there a correspondence with the ozone layer's recent travails? Curious...

[William J. Coblentz]

Oops, re-visited the title caption, so somewhat silly question...