Polar stratospheric clouds over northern Norway

Polar stratospheric clouds over northern NorwayShow more

Polar stratospheric clouds (PSCs) are clouds in the winter polar stratosphere at altitudes of 15,000–25,000 m (49,000–82,000 ft). They are best observed during civil twilight, when the Sun is between 1 and 6 degrees below the horizon, as well as in winter and in more northerly latitudes. One main type of PSC is made up mostly of supercooled droplets of water and nitric acid and is implicated in the formation of ozone holes. The other main type consists only of ice crystals which are not harmful. This type of PSC is also referred to as nacreous (/ˈneɪkriəs/, from nacre, or mother of pearl, due to its iridescence.

Polar Stratospheric Clouds

Scientists recently discovered that polar stratospheric clouds, long known to play an important role in Antarctic ozone destruction, are occurring with increasing frequency in the Arctic. These high altitude clouds form only at very low temperatures help destroy ozone in two ways:

https://www.nasa.gov/image-article/polar-stratospheric-clouds/