The Northern Lights are a stunning, kaleidoscopic meteorological phenomenon accessible to those willing to brave the frigid temperatures of winters in the far North. But the Aurora Borealis is just one of several atmospheric sensations that can sometimes be seen during Polar winters.
Polar stratospheric clouds, also called rainbow clouds or nacreous clouds are a rare and stunning natural display that sometimes manifests specifically during the coldest days of the year. This past December, residents of the United Kingdoms, Finland, Norway, Sweden, and Alaska were treated to an iridescent display of nacreous clouds, Live Science reports.
What are Nacreous clouds?
According to Live Science, the term “nacreous clouds” comes from the word “nacre” which is the “mother of pearl” shiny material found in mollusk shells. Polar stratospheric clouds get their nickname from the iridescent and colorful patterns that appear in the rainbow clouds.
These clouds, according to Space.com , occur significantly higher up in the atmosphere than other clouds and weather systems do. They form about 15 miles off the ground, in the stratosphere, whereas the average cloud forms eight miles up.
They happen only in the frigid winter in or near the Polar regions, when the stratosphere reaches temperatures below negative 108 degrees Fahrenheit. The cold air causes ice crystals to form that are smaller than the ones that form lower in the atmosphere.
The curvature of the Earth and the sunlight being refracted and diffracted through those tiny ice particles produce rainbow colors that light up the clouds.
The outlook in Oslo
Between December 18 and December 22, rainbow clouds were visible in Northern Europe around sunset, as far south as parts of Scotland. According to LiveScience, it’s typically rare for these displays to persist for several days, however a storm system that brought cold winds and long-lasting low temperatures, was in this case responsible for the prolonged display.
Ramunė Šapailaitė, a Norwegian photographer, who captured the clouds on camera told Live Science “The colors are spectacular. The clouds were visible in the sky all day, but the colors really exploded just before sunset.”
Alister Doyle, another Oslo resident who photographed the clouds agreed. He tells Space.com that “The clouds brighten up the winter, lingering in the sky an hour after the sun set just after 3 pm I'm always spellbound — they're an ethereal dose of winter magic, trapping the colors of the rainbow frozen across the sky. Photographer Gaurav Madan described the phenomenon as “the reflecting rainbow colors from the ice clouds that turned to pink and red as it got dark.”
Climate change and rainbow clouds
According to Live Science, these shiny, bright and colorful clouds sometimes come with a dark side. There are two types of nacreous clouds. The second type, those that were visible in Northern Europe in late December, are formed from just ice crystals. They are more beautiful and iridescent than the first type of rainbow clouds, which are formed from both ice crystals and nitric acid.
This nitric acid, NASA shares, can have a destructive impact on the ozone layer in two ways. First of all, chlorine on the surface of these clouds can transform into a more reactive form that eats away at the ozone layer. Secondly, these clouds pull nitrogen compounds from the atmosphere, where it would otherwise play a role in moderating the presence of the destructive chlorine compounds.
These clouds that grace the Northern skies show nature’s radiant dance of color. However, witnessing these mesmerizing visuals should also be a warning sign of the potential environmental impacts of these clouds and of human actions on the global climate. There are actions that everyone can take to preserve the pristine beauty of the sky and land and all of nature’s magical displays, including these stratospheric rainbow clouds.
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