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The animation shows the development of stratospheric temperatures and the Antarctic ozone hole at the South Pole. The measurements were made with balloon-borne ozone instruments launched at regular intervals at the Amundsen-Scott South Pole Station.
The historical ozone hole animations from previous years' data clearly show ozone depletion in the September to October period, following sunrise, when ozone in the 12 - 24 kilometer (40,000 to 79,000 feet) altitude region is destroyed by chemical reactions involving chlorine and bromine from human-produced chlorofluorocarbons (CFCs). The total ozone "thermometer" gives a measure of the total column of ozone, which is related to the area of the colored portion of the ozone profile, nearly two-thirds of which is lost.
The 14 - 21 kilometer region, where ozone is almost totally destroyed, is centered within the altitude region where clouds form in the extremely cold (-90°C or 130 Fahrenheit degrees below zero) stratosphere during the long 6 month darkness of Antarctic winter (March through August). These clouds contain ice particles which provide a surface upon which unusual chemistry occurs, chemistry which allows the reactive chlorine and bromine atoms brought to the stratosphere by CFCs to do their destructive work. CFCs have been banned through regulations developed as a result of the Montreal Protocol on substances which deplete the ozone layer, and are currently declining in concentration in the lower atmosphere.