WMO’s new Antarctic Ozone Bulletin provides the latest update on the state of the annually recurring ozone hole. It says that the Antarctic polar vortex (a large low-pressure system where high velocity winds circle the Antarctic continent) was still depleted early December, although no new depletion was occurring.
During the first half of August, the ozone hole area increased more slowly than at the same time in most of the recent years. From the end of August the ozone hole area started to increase but remained lower than for any other year since 2003 until around 20 September. From late September until early November the ozone hole area was similar to that observed in 2007 and on many days larger than in 2009. From early November until early December the ozone hole was larger than both in 2007 and 2009. From 4-6 December, the ozone hole has been larger than any year during the 2003-2009 time period.
Antarctic ozone holes are expected to reoccur annually as long as the stratosphere still contains an excess of ozone depleting substances due to the long atmospheric lifetimes of these compounds. Thanks to the Montreal Protocol, ozone depleting gases will slowly disappear from the atmosphere over the next decades.
The latest issue of the Ozone Bulletin reports observations from nineteen stations, with special emphasis on ground-based and balloon measurements. WMO and the scientific community will keep a close eye on the development during the coming weeks. The fifth and final ozone bulletin of the season will be issued in February 2011.