How many ozone holes are there

Ozone depletion is directly related to the temperature in the stratosphere, which is the layer of the atmosphere between around 10 km and round 50 km altitude.

These polar stratospheric clouds contain ice crystals that can turn non-reactive compounds into reactive ones, which can then rapidly destroy ozone as soon as light from the sun becomes available to start the chemical reactions. Stratospheric ozone concentrations have been observed to have reduced to near-zero values over Antarctica around 20 to 25 km of altitude hPa , with the ozone layer depth coming just below Dobson Units, about a third of its typical value outside of ozone hole events.

During the Southern Hemisphere spring season August - October the ozone hole over the Antarctic increases in size, reaching a maximum between mid-September and mid-October. When temperatures high up in the atmosphere stratosphere start to rise in late Southern Hemisphere spring, ozone depletion slows, the polar vortex weakens and finally breaks down, and by the end of December ozone levels have returned to normal.

Skip to main content. Tags: Ozone. Published 6 October Human-made chemicals migrate into the stratosphere and accumulate inside the polar vortex. It begins to shrink in size as warmer temperatures dominate. The Antarctic hole was unprecedented as the polar vortex kept the temperature of the ozone layer cold, preventing the mixing of ozone depleted air above Antarctica with ozone rich air from higher latitudes. Since the ban on halocarbons, the ozone layer has slowly been recovering, according to WMO.

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Tags: Ozone. Published 6 January Strong Polar Vortex Ozone depletion is directly related to the temperature in the stratosphere, which is the layer of the atmosphere between around 10 km and round 50 km altitude. Montreal Protocol The Montreal Protocol on Substances that Deplete the Ozone Layer is the landmark multilateral environmental agreement that regulates the production and consumption of nearly chemicals referred to as ozone depleting substances ODS.

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Disaster risk reduction. Elsewhere on the WMO website Observations.