Although polar stratospheric clouds can form in the Arctic, they rarely last long enough for extensive decreases in ozone. Polar stratospheric clouds (PSCs) are the exception. Polar stratospheric clouds (PSCs) are common in … Though nacreous clouds are officially known as "polar stratospheric clouds", they are now common over Scotland, and have been observed as far south as the Midlands. Description. These beautiful images of polar stratospheric clouds were taken over Tromso City in Norway. Arctic ozone decreases of as much as 40 percent have been measured. However, in general, it is neither as strong nor as cold as the one that forms in the Antarctic. While the clouds look amazing, they can be potentially quite dangerous to our planet. The nitric acid in polar stratospheric clouds reacts with chlorofluorocarbons to form chlorine, which catalyzes the photochemical destruction of ozone [3, 34]. Then, there is the formation of Polar Stratospheric Clouds (PSCs). This photo-graph of an Arctic polar stratospheric cloud (PSC) was taken from the ground at Kiruna, Sweden (67°N), on 27 January 2000. Polar stratospheric clouds. These are best observed during winters in more northerly latitudes. Polar mesospheric clouds (PMCs) are a diffuse scattering layer of water ice crystals near the summer polar mesopause. A polar winter vortex also forms in the Northern Hemisphere. Lower average winter temperatures in the upper atmosphere might explain why nacreous clouds seem to be appearing with increased frequency and distribution. This means more dangerous UV radiation will reach the Earth's surface. Below: Dangerous beauty. Also known as nacreous clouds, these are the clouds that form in the winter polar stratosphere. Polar stratospheric clouds create the conditions for drastic ozone destruction, providing … PSCs appear in the lower stratosphere near the poles in winter. During the continuously dark polar winter, the air inside the polar vortices becomes extremely cold, a necessary condition for polar stratospheric cloud formation. Polar stratospheric clouds can form at temperatures below about 195 K. Chemical reactions on the surfaces of the particles that form these clouds convert chlorine compounds from inert forms into highly reactive species. PSCs form during winters in the Arctic and Antarctic stratospheres. The clouds "A 'warm' polar stratosphere is typically in the temperature range -73 o to -63 o C. Of course, as soon as the wave has dissipated, the polar region begins to cool down again." Meanwhile, chlorine concentrations build up during the polar winter, and consequent ozone destruction is greatest when the sunlight returns in polar winter . Polar stratospheric clouds (PSCs) are clouds in the winter polar stratosphere at altitudes of 15,000–25,000 m (49,000–82,000 ft). Figure Q10-2. 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