Observed from the ground, this phenomenon is known as noctilucent clouds. NASA image: Night-shining clouds. Such low temperatures are rarer in the Arctic. These Polar Stratospheric Clouds (PSC's) are composed of ice crystals that provide the surface for a multitude of reactions, many of which speed the degredation of ozone molecules. Together with the fog, they reflect weather patterns and interact with the ground, sun and atmosphere thus playing an important role in what the weather does. For all aerosol only aerosols layers are considered, while clouds and polar stratospheric clouds are removed. 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. … 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. Nacreous Clouds (Type II Polar Stratospheric Clouds) Nacreous Clouds over Antarctica Imaged by Cherie Ude at McMurdo Base in 2004. They are wave clouds and their undulating sheet-like forms reveal the winds and waves of the stratosphere. Dark blue colors correspond to the thinnest ozone, while light blue, green, and yellow pixels indicate progressively thicker ozone. The severe depletion of stratospheric ozone in late winter and early spring in the PSCs form at very low temperatures, below −78 °C (−108 °F). Polar Stratospheric Clouds or nacreous clouds contain water, nitric acid and/or sulfuric acid. Cold temperature enables the stratospheric clouds to form. Polar stratospheric cloud (PSC) observations, The polar stratospheric cloud (PSC) season at the Australian Antarctic continental stations (Mawson, Davis and Casey) typically…, Environmental Impact Assessment approvals, Australia and the Antarctic Treaty System, Convention for the Conservation of Antarctic Marine Living Resources, What happens before departure & on arrival at station, Message for family and friends of expeditioners, Classification of scientific publications, Antarctic Strategy and Action Plan: Prime Minister’s Foreword, First harbingers of ozone depletion detected, Information on meteorological conditions in the polar stratosphere. The timing and duration of PSC events, their geographic extent and vertical distributions, and their annual variability are not well understood. Though nacreous clouds are officially known as "polar stratospheric clouds", they are now common over Scotland, and have been observed as far south … They are formed mainly during the event of polar vertex in winter; more intense at south pole. They are 80-85 km high (50-53 mile) a few km below the mesopause, the coldest part of the atmosphere. The Australian Antarctic Division encourages people travelling to Antarctica to keep a lookout for these clouds, and to report any sightings. Their formation requires temperatures below –78 °C, which limits their appearance to the winter months. Nacreous clouds (Type II PSCs) glow brightly with vivid iridescent colours. 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. 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