» Serial entrepreneur Waqar Azmi has launched Smart Business Box to help startups and SMEs fight the Covid-19 pandemic » Bradman in making in this Kerala backyard Special reactions that occur on PSCs, combined with the isolation of polar stratospheric air in the polar vortex, allow chlorine and bromine reactions to produce the ozone hole in Antarctic springtime. 1. Dramatic springtime depletions of ozone in polar regions require that polar stratospheric air has a high degree of dynamical isolation and extremely cold temperatures necessary for the formation of polar stratospheric clouds. Polar Stratospheric Clouds and Ozone Depletion Clouds rarely form in the dry, Antarctic stratosphere, but when they do, they chemically conspire with chlorofluorocarbons to create the "ozone hole" that opens up every spring by Owen B. Toon and Richard P. Turco More than two dozen scientists boarded a … These ozone-depleting chemicals adhere to cloud particles that form in cold stratospheric layers, providing a surface where runaway reactions that destroy ozone molecules occur. Ozone depletion occurs in such polar stratospheric clouds. The … During the cold dark Antarctic winter, stratospheric ice clouds (PSCs, polar stratospheric clouds) form when temperatures drop below -78C. The constant cold, development of stratospheric clouds, and the development in ozone-destroying chlorine monoxide eventually supported the depletion of the ozone in … Polar stratospheric clouds create the conditions for drastic ozone destruction, providing … above Antarctica. Dynamite in a fluffy package: The shocking Antarctic ozone losses had many scientists intrigued, including atmospheric chemist Susan Solomon. After some of the first observations of PSCs by McCormick et al. Ozone depletion is highly dependent on the formation of polar stratospheric clouds, which accumulate chlorine and bromine compounds in the cold polar night and then release these ozone-eaters when the sunlight of spring returns. These clouds are called “polar stratospheric clouds” (PSCs). The colder the temperatures, the greater the likelyhood of Polar Stratospheric Clouds to form and the greater amount of photochemical distruction of ozone by activated chlorine molecules. (1) the unique CIRCUMPOLAR CIRCULATION PATTERN over Antarctica Chlorine concentrations build up during the polar winter, and the consequent ozone destruction is greatest when the sunlight returns in spring. Their surfaces act as a catalyst which converts chlorine molecules into free radicals and therefore speeds up ozone depletion. . The thinning or reduction of Ozone depletion is most prominent in the Polar Regions, especially over Antarctica. Stratospheric temperatures fall below –88°C. 3) Discuss the formation of Polar Stratospheric Clouds and their role in the depletion of the ozone layer. Factors responsible for the depletion of ozone: Depletion of ozone is due to many factors, the most dominant of which is the release of chlorine from CFCs (Chlorofluorocarbons) which destroys the ozone. Their findings indicate that chlorine may hibernate in condensed, non-reactive phase during the frigid Antarctic winter, residing in polar stratospheric clouds or in some molecular state not yet identified. research is to study stratospheric ozone depletion in polar regions. Temperatures in the lower stratosphere are closely coupled to ozone through dynamics and photochemistry. Based on her expertise in modeling atmospheric chemistry and air movements, Solomon suspected that some unknown chemical processes involving CFCs or CFC products were causing these losses. that protects humans and other living things from harmful ultraviolet (UV) radiation from This e"ect is particularly strong in the southern hemisphere, where the polar vortex is colder and more stable than northern counterpart. The North Pole, however, is an ocean surrounded by land, and that land is irregular in shape and altitude. 3. The dynamics of the stratospheric polar vortex and its relation to springtime ozone depletions. The ice crystals that make up these PSCs are where heterogeneous photo-chemical destruction of ozone take place. This is the reason ozone depletion in the Arctic primarily takes place inside the polar vortex. Without the presence of stratospheric clouds, reactions leading to the destruction of the ozone layer are negligible. The pattern of climate trends during the past few decades is marked by rapid cooling and ozone depletion in the polar lower stratosphere of both hemispheres, coupled with an increasing strength of the wintertime westerly polar vortex and a poleward larger, but seasonal, decrease in stratospheric ozone over Earth's polar regions during the same period. ARCTIC OZONE DEPLETION LINKED TO LONGEVITY OF POLAR STRATOSPHERIC CLOUDS. The ozone hole is formed each year in the Southern Hemisphere spring (September-November) when there is a sharp decline (currently up to 60%) in the total ozone over most of Antarctica. However, because it gets very cold above the S. Pole in the winter, polar stratospheric clouds do sometimes form (they are made from water and other materials). 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. ANSWER: (a) 71. Prather, M.J., 1992: More rapid polar ozone depletion through the reaction of HOCl with HCI on polar stratospheric clouds. These very high altitude clouds are composed of ice crystals, sometimes greatly enriched in nitrogen oxide specis ("NO x ") that can enhance the ozone degredation reactions discussed above. Extremely low stratospheric temperatures (lower than -78 C) over the Antarctic region are believed to contribute to depletion of ozone, in that low temperatures lead to the presence of polar stratospheric clouds (PSCs). Readings: Turco: p. 422-432, 440-443; Brimblecombe: 195-202. in increased condensation of nitric acid in polar stratospheric clouds. The largest amount of ozone molecules (O 3) is found in the stratosphere with about 90 % of it at altitudes between 15 and 30 km. Also in 1986, Michael B. McElroy and colleagues described a role for bromine in ozone-depleting reactions. Among the key papers explaining the atmospheric chemistry of CFCs and ozone depletion was one by Susan Solomon and several colleagues. In addition to this well-known stratospheric ozone depletion, there are also tropospheric ozone depletion events, which occur near the surface in polar regions during spring. Most of the available chlorine (HCl and ClONO2) was converted by reactions on polar stratospheric clouds to reactive ClO and Cl2O2 throughout the Arctic polar vortex before midwinter. But during the months when ozone depletion is greatest, giant clouds of ice particles–so-called polar stratospheric clouds–block the ultraviolet rays. Also, if the polar vortex is stronger, the winter is also longer in the South Pole and stronger polar stratospheric clouds are formed. Figure Q9-1. Ozone destruction is greatest at the South pole where very low stratospheric temperatures in winter create polar stratospheric clouds. Reduced ozone levels as a result of ozone depletion ozone depletionA chemical destruction of the stratospheric ozone layer beyond natural reactions. from total ozone changes Averages Uncertainty ranges. This layer is where the active chemical depletion of ozone occurs on ice crystals in polar stratospheric clouds. Schoeberl MR, Hartmann DL. magnitude for that eruption) and thereby increase polar ozone loss [e.g., Deshler et al., 1994; Portmann et al., 1996; Bregman et al., 1997], whether smaller volcanic enhancements in stratospheric sulfate aerosol abundances could have had some influence on polar ozone depletion received less attention. from combined ozone, cloud, and aerosol changes. Volcanic stratospheric aerosols. Topic: Conservation, environmental pollution and degradation, environmental impact assessment. magnitude for that eruption) and thereby increase polar ozone loss [e.g., Deshler et al., 1994; Portmann et al., 1996; Bregman et al., 1997], whether smaller volcanic enhancements in stratospheric sulfate aerosol abundances could have had some influence on polar ozone depletion received less attention.
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