These are best observed during winters in more northerly latitudes. Although polar stratospheric clouds can form in the Arctic, they rarely last long enough for extensive decreases in ozone. The nitric acid in polar stratospheric clouds reacts with chlorofluorocarbons to form chlorine, which catalyzes the photochemical destruction of ozone [3, 34]. 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. The particles grow from the con-densation of water and nitric acid (HNO3). These beautiful images of polar stratospheric clouds were taken over Tromso City in Norway. Polar stratospheric clouds create the conditions for drastic ozone destruction, providing … 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 (PSCs) are the exception. PSCs form during winters in the Arctic and Antarctic stratospheres. Figure Q10-2. Lower average winter temperatures in the upper atmosphere might explain why nacreous clouds seem to be appearing with increased frequency and distribution. Below: Dangerous beauty. 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. Then, there is the formation of Polar Stratospheric Clouds (PSCs). 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. The polar vortex and polar stratospheric clouds exist only over Antarctica, which is why the ozone "hole" exists only there. Polar stratospheric clouds (PSCs) are common in … Polar stratospheric clouds. While the clouds look amazing, they can be potentially quite dangerous to our planet. Polar mesospheric clouds (PMCs) are a diffuse scattering layer of water ice crystals near the summer polar mesopause. The clouds But the bigger the hole gets, the thinner the ozone layer will become over the rest of the earth. "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." A polar winter vortex also forms in the Northern Hemisphere. However, in general, it is neither as strong nor as cold as the one that forms in the Antarctic. Arctic ozone decreases of as much as 40 percent have been measured. This means more dangerous UV radiation will reach the Earth's surface. 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