鈥淢OUNTAIN waves鈥� in the atmosphere above Antarctica create rare clouds that are helping destroy the ozone layer.
Over the last two decades, chlorofluorocarbons (CFCs) released by human activity have opened a hole in the ozone layer over Antarctica. Key chemical reactions that lead to ozone depletion happen on the surface of rare polar stratospheric clouds (PSCs), which form high up in the atmosphere. Here, sunlight breaks down the CFCs into products that react to produce chlorine, which in turn decomposes ozone. 鈥淭he question was: how are these clouds generated?鈥� says Lars Hoffmann of the J眉lich Research Centre in Germany.
Steve Eckermann of the US Naval Research Laboratory in Washington DC, along with Hoffmann and colleagues, used satellite infrared data to study atmospheric temperatures above the Antarctic Peninsula. They found pockets of high and low temperature air in the stratosphere, and these only occurred above mountains. The colder pockets fell below -78 掳C, which is cold enough for PSCs to form.
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This implicates so-called mountain waves, which are created when an airstream flows over high relief. The waves churn up the air high in the atmosphere and appear to create the temperature variations (Geophysical Research Letters, ).
