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16 October 2013

 

Area of Antarctic ozone depletion reaches annual peak

The area of the annually recurring Antarctic ozone hole reached its peak at 24.0 million square kilometers on 16 September according to data from NASA. This is more than in 2012 and 2010, but less than in 2011.

The World Meteorological Organization’s newest Antarctic Ozone Bulletin said the ozone hole area averaged over the ten last days of September was 20.9 million km2  (data from the Royal Netherlands Meteorological Institute, KMNI). The ozone mass deficit averaged over the same period was 19.59 megatonnes. This is more than in 2010 and 2012 but less than in 2011.

As the temperatures rise after the southern hemisphere winter, the ozone depletion rate will slow down. It is still too early to give a definitive statement about the degree of ozone loss that will occur in 2013. Existing data indicates that this year’s ozone hole is larger than in 2012 and possibly also 2010, but smaller than the one of 2011.

The ozone bulletin is based on observations from the ground, weather balloons and satellites from WMO’s Global Atmosphere Watch Program and its network of scientific stations in some of the world’s most inhospitable terrain. Most stations reported clear signs of ozone depletion.

For example, on 17 September, the ozone hole extended all the way to the southern tip of the South American continent and affected inhabited places such as Ushuaia and Río Gallegos, where Argentinian scientists carry out observations of the stratospheric ozone layer. Such episodes typically occur a handful of times each September-November. Especially in November, when the sun is high in the sky, they can lead to a significant increase in the intensity of solar ultraviolet radiation that hits the earth's surface.

The meteorological conditions in the Antarctic stratosphere found during the austral winter (June-August) set the stage for the annually recurring ozone hole. The last ten days of September is typically the time period when the ozone hole reaches its maximum extent.

By most criteria, the largest ozone hole was observed in 2006. An international agreement banning the worst ozone depleting substances has stemmed the destruction of the ozone layer. However, severe Antarctic ozone holes are expected to continue during the next couple of decades.

More information on the Antarctic ozone hole and ozone loss

 

Ozone hole on 17 Sept extended to southern tip of South American continent. The dot on the map is the GAW station at Ushuaia operated by the national meteorological service of Argentina. Blue colours indicate ozone depleted air masses. The map is calculated by a so-called data assimilation model run at the Belgian Institute for Space Aeronomy. It uses meteorological data from ECMWF and satellite data from the MLS instrument on board the NASA-operated AURA satellite in combination with our best knowledge of the chemical reactions that cause ozone depletion.

 

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