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

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 colours as today.

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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.

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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.

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polar stratospheric cloud norway december 2017, polar stratospheric cloud, polar stratospheric cloud season 2017/2018, polar stratospheric cloud december 2017 pictures
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.

 

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