These clouds enable the release of chlorine for ozone-depleting reactions. Observations of Antarctic Polar Stratospheric Clouds by GLAS Stephen P. Palm Michael Fromm Jim Spinhirne Polar Stratospheric Clouds (PSCs) frequently occur in the polar regions during winter and are important because they play a role in the destruction of stratospheric ozone. They are classified into Types I (clouds with more diffuse and less bright colors) and II (nacreous or mother-of-pearl clouds), according to … Nacreous clouds are polar stratospheric clouds that occur high in the stratosphere moments after sunset in regions close to or in the Arctic Circle. Our Lady of the Snows Shrine, a.k.a. Noctilucent clouds are also called Polar Mesospheric Clouds, PMCs. NLCs are comprised of extremely small ice crystals some 0.1 micron (1/10,000 mm) diameter. As temperatures in the lower stratosphere cools below -80'C, Polar Stratospheric Clouds (PSC's) start to form. In the extreme cold of the polar winter, however, stratospheric clouds of different types may form, which are classified according to theirphysical state and chemical composition. Noctilucent clouds are also called Polar Mesospheric Clouds, PMCs. 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. Polar stratospheric clouds occur only in high-latitude regions during the winter, or near winter, when temperatures in the lower and middle stratosphere fall below about −78 °C for nitric acid trihydrate, −81 °C for supercooled ternary solution polar stratospheric clouds and −85 °C for ice polar stratospheric clouds. These high altitude clouds form only at very low temperatures help destroy ozone in two ways. In addition, the stratosphere remained cold, leading to the formation of polar stratospheric clouds, which allowed chemical reactions to release reactive forms of chlorine and cause ozone depletion. The stratospheric clouds form only in regions of very low temperature and so the warming produced by the clouds is concentrated in polar winter regions. The following list highlights the characteristics and facts of the stratosphere in more detail. The clouds can also be associated with very high surface winds, which may indicate the presence of, or induce, winds and waves in the stratosphere. 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. In fact, such a cloud would be known as fog, ice fog, or mist. the stratosphere by solid polar stratospheric cloud (PSC) par-ticles. 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. Pure nacreous clouds, a type of polar stratospheric cloud, are composed of ice crystals. Nacreous clouds (Type II PSCs) glow brightly with vivid iridescent colours. Ozone holes are caused by chemical reactions that take place primarily on the surface of polar stratospheric clouds, ice particles, or liquid droplets, which form at high altitudes in the extreme cold of the polar regions. Dark blue colors correspond to the thinnest ozone, while light blue, green, and yellow pixels indicate progressively thicker ozone. #Nacreous Clouds or Polar Stratospheric Clouds. This study statistically examines the simultaneous appearance of polar stratospheric clouds (PSCs) and upper tropospheric clouds (UCs) using satellite lidar observations for five austral winters of 2007-2011. These reactions lead to the production of free radicals of chlorine in the stratosphere which directly destroy ozone molecules. 1. More than a decade ago it was suggested that a cooling of stratospheric temperatures by 1 K or an increase of 1 ppmv of stratospheric water vapour could promote denitrification, the permanent removal of nitrogen species from the stratosphere by solid polar stratospheric cloud (PSC) particles. From satellites, PMCs are most frequently observed above 70°–75° in latitude and have a season of 60 to 80 days duration centered about a peak which occurs about 20 days after the … In the Northern hemisphere, the generation of lee waves by mountains may locally cool the lower stratosphere and lead to the formation of lenticular PSCs. Hence, at this time the polar stratospheric clouds tend to form. It starts a photochemical reaction of chlorine release and thus destroying the ozone in the process. 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