polar-stratospheric-clouds

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Rare Nacreous Clouds

Also called polar stratospheric clouds or mother of pearl clouds, nacreous clouds are mostly visible within two hours after sunset or before dawn. They blaze unbelievably bright with vivid, iridescent colors. These clouds are rare and occur in the polar stratosphere at altitudes of 15,000–25,000 meters. They are so bright because at those heights, they are still sunlit.

Although incredibly beautiful, they have a negative impact on our atmosphere. They create ozone holes by supporting chemical reactions that produce active chlorine which catalyzes ozone destruction.

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Have you ever seen such an iridescent sky? These spectacular cloudscapes aren’t the work of photoshop. This is a natural phenomenon known as Polar stratospheric clouds or Nacreous clouds. While clouds like these are incredibly beautiful to behold, they’re also an indicator of a damaged ozone layer:

They get their brilliant, rainbow colors from sunlight that’s reflected from below the horizon. The clouds are so high — up to 82,000 feet above the Earth — that they continue to glow in these incredible hues long after the sun has gone down.

Unfortunately these clouds also contain nitric acid, which reacts with chlorine that’s released by industrial processes — and that little combination of chemicals tends to rip ozone to shreds. So this cloud may be beautiful, but it’s also destroying the atmosphere.

These sunning photos were recently taken by photographer Deven Stross who is currently working down (way, way down) in Antarctica at McMurdo Station. The round silhouette in the top photo is NASA’s radome, which protects their MG-1 Antenna.

Deven Stross is a portrait and commercial photographer who divides his time between Portland, OR and Antarctica. Visit Deven Stross’ website to view more of his amazing photography.

[via io9]

Polar stratospheric clouds (PSCs) form in the stratosphere at altitudes of 50,000–80,000 ft. They are classified into Types I (clouds with more diffuse and less bright colors) and II (nacreous or mother-of-pearl clouds), according to their formation temperature and particle size. Unfortunately, Polar stratospheric clouds play a key role in the massive ozone depletion over the Arctic and Antarctic. NASA explains that PSCs “form only at very low temperatures. They help destroy ozone in two ways: they provide a surface which converts benign forms of chlorine into reactive, ozone-destroying forms, and they remove nitrogen compounds that moderate the destructive impact of chlorine. In recent years, the atmosphere above the Arctic has been colder than usual, and polar stratospheric clouds have lasted into the spring. As a result, ozone levels have been decreasing.”

Photo:  NAT GEO

During winter months near the South Pole, the low temperatures cause the pressure to drop to a point where significant condensation occurs (PV= nRT).  This low pressure combined with the wind from Earth’s rotation creates a vortex of spinning air mass with speeds that can exceed 300 km/hr. Polar stratospheric clouds are formed by the condensation of gases in the vortex. Decreases in result in the formation of crystals that contain water sulfuric and nitric acids within these clouds. It is on the surfaces of these clouds that many ozone depleting reactions take place, primarily the formation of chlorine radicals. This is why we have temporary holes in the ozone layer over Antarctica during certain periods of the year.

Polar stratospheric clouds

Formed at icy temperatures (-85 C) high up in the stratosphere (some 25km above the ground), an outbreak of these beautiful iridescences may be starting in the boreal regions of the world, exemplified by this shot taken in Norway a couple of days ago. They are also called nacreous or mother of pearl clouds, and display a wonderful spread of shifting colours as the sunlight gets diffracted by the tiny ice crystals forming the nebulosity. They are best seen in twilight, when the angle of the solar rays produces the best effect.

Chemically they are very complex, and play a role in the destruction of stratospheric ozone caused by chlorine and bromine products such as CFC’s, that we have released into the air over the past decades. The ice particles provide a physical support to a series of complicated chemical interactions and remove nitric acid from the air, changing the cycles of these elements in such a manner as to promote ozone destruction, resulting in the inevitable increase in cancer causing UVB rays reaching the surface. There are several types, depending on their composition, measured using LIDAR (laser radar, put simply). Type 1 contain water and nitric/sulphuric acid and are the main contributors to ozone destruction, while type 2 are made mainly of plain water.

Loz

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http://www.antarctica.gov.au/about-antarctica/environment/atmosphere/polar-stratospheric-clouds
http://www.seas.harvard.edu/climate/eli/research/equable/psc.html
http://www.theozonehole.com/psc.htm

This is called “Perlemorskyer” in Norway or we would call it Polar Stratospheric Clouds or nacreous clouds. This photo was taken by Elin Fumuholt in Norway. They’re rare because the stratosphere doesn’t hold much moisture and they need to be lit from sunlight below meaning this happens around dawn or dusk. WILD!

A detailed explanation of these clouds is found here: http://en.wikipedia.org/wiki/Polar_stratospheric_cloud

Polar Stratospheric Clouds

Polar stratospheric clouds (PSCs) form in the stratosphere at altitudes of 50,000–80,000 ft. They are classified into Types I (clouds with more diffuse and less bright colors) and II (nacreous or mother-of-pearl clouds), according to their formation temperature and particle size. Unfortunately, Polar stratospheric clouds play a key role in the massive ozone depletion over the Arctic and Antarctic. NASA explains that PSCs “form only at very low temperatures. They help destroy ozone in two ways: they provide a surface which converts benign forms of chlorine into reactive, ozone-destroying forms, and they remove nitrogen compounds that moderate the destructive impact of chlorine. In recent years, the atmosphere above the Arctic has been colder than usual, and polar stratospheric clouds have lasted into the spring. As a result, ozone levels have been decreasing.”

Read more: http://www.toptenz.net/top-10-unusual-but-fascinating-cloud-formations.php#ixzz1aliA7jE5