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Why has an ozone hole appeared over Antarctica when ozone-depleting substances are present throughout the Stratosphere ?. Requirements : low T (1) + isolation (2) + sunlight (3) T < -78°C: PSCs form ClONO 2 + HCl -> Cl2 + HNO3 Cl is an ozone depleting catalyst
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Whyhas an ozone hole appearedoverAntarcticawhenozone-depletingsubstancesarepresentthroughouttheStratosphere? Requirements: low T (1) + isolation (2) + sunlight (3) • T < -78°C: PSCs form • ClONO2 + HCl -> Cl2 + HNO3 • Cl is an ozonedepletingcatalyst • Even moreeffectivewhendenitrificationoccurs • Polar vortexisolatesthe polar airmass • Increasesas T decrease in winter (high T gradients) • ODS cannotescape • Catalyticcyclesbecomeactivewithsunlight
... andwhatabouttheArctic? Nolong-lasting ozone-holes as such! • Temperaturesare on averagehigherandmore variable, so PSCs don‘ttendtoexistforlong • Polar vortexis not that strong