Polar Stratospheric Cloud Background These clouds exist at very high altitude (~70,000 ft) within Earth's stratosphere.Clouds do not normally form in the stratosphere due to its extreme dryness. Pure nacreous clouds, a type of polar stratospheric cloud, are composed of ice crystals. For comparison, some of the highest clouds in the troposphere have a ceiling height of about 40,000 feet. a cloud that forms at altitudes of about 21,000 m during the Arctic and Antarctic winter or early spring, when air temperatures drop below -80C. Most of the anarctic stratospheric chlorine ends up in resevoir compounds such as ClONO2 or HCl. Nacreous clouds develop at very high altitudes, within the lower stratosphere at 70,000 feet or above. The second problem with modeled denitrification shown in Figure 10 is that the HNO 3 at 63°S is about 1–3 ppbv smaller than the observed abundance from mid‐July until the end of the season. Polar Stratospheric Clouds Tropical Cyclones One explanation for the decrease in the equator to pole temperature difference (EPTD) during equable climates examines the influence of polar stratospheric clouds (PSCs) on longwave radiation leaving the Earth in the high-latitudes and, as a result, on temperatures near the poles. 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. Polar stratospheric clouds or PSCs, also known as nacreous clouds (/ ˈ n eɪ k r iː. During winter at high latitudes, however, stratospheric temperature sometimes becomes low enough to promote formation of clouds. The chlorine activation and subsequent ozone loss of the northern winter lower stratosphere have been modelled using different schemes for type I polar stratospheric clouds (PSCs) and sulphate aerosols. Clouds generally do not form in the stratosphere because there is not enough moisture. The Type 1 PSCs form when the stratospheric temperature drops below -108 F. They are primarily composed of nitric acid, water, and sulfuric acid. Bottom line: Polar stratospheric clouds – also called nacreous clouds or mother-of-pearl clouds – have been putting on a show for those at latitudes near the Arctic Circle. polar stratospheric clouds. CALIPSO = Cloud‐Aerosol Lidar and Infrared Pathfinder Satellite Observations; PSC = polar stratospheric cloud. As temperatures in the lower stratosphere cools below -80'C, Polar Stratospheric Clouds (PSC's) start to form. In spite of nearly three decades of research, significant gaps in our understanding of processes in Polar Stratospheric Clouds (PSC) still exist. greenhouse gases. ə s /, from nacre, or mother of pearl, due to its iridescence), are clouds in the winter polar stratosphere at altitudes of 15,000–25,000 meters (49,000–82,000 ft). 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