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ANTARCTIC OZONE

This page gives information about ozone at Halley, Rothera and Vernadsky/Faraday stations. It was either updated or new data was added on 2010 June 25.

Situation at 2010 June 25

Ozone values over the continent are between around 230 DU and 380 DU with some areas now being affected by ozone depletion.  The polar vortex is building around the continent.  The temperature of the ozone layer over Antarctica is continuing to cool from its summer maximum and some areas are colder than the threshold at which polar stratospheric clouds (PSCs) begin to form.  

During the early winter, the polar vortex was often rather more elliptical than it was in 2008, and this lead to some early depletion in circumpolar regions as stratospheric clouds became exposed to sunlight.   It reverted to a more circular circulation as winter progressed and this led to another relatively slow start to the growth of the ozone hole (as measured by NASA/SBUV2), with the "hole" not beginning until mid August.  The vortex became more elliptical again in late August, with South Georgia being affected by the fringes of the ozone hole between September 2 and 6.  The hole grew to reach an area of around 24 million square kilometres by mid September, and then lasted until the end of November, although the final remnants of the polar vortex lingered until towards the end of the month.  The 2009 ozone hole season finished in late November, when the continent experienced the final stratospheric spring warming.   From mid August to mid November the ozone hole remained around the average area seen over the past decade.  The tip of South America and South Georgia were affected by the fringes of the ozone hole from September 24 to September 30, from October 3 to October 7 and from November 8 to 25.  South Georgia was affected on November 6.

See the final situation report for last year for information on the 2008 - 2009 season.

An opinion piece by Jonathan Shanklin to mark the 25th anniversary of the ozone hole appeared in Nature on May 6.  The main BAS web page carries additional links. A meeting to mark the 25th anniversary of the discovery of the ozone hole was held at Cambridge University on Friday, May 7.  It was web-cast by Varsity, the Cambridge student newspaper.

Notes:  The Antarctic ozone hole is usually largest in early September and deepest in late September to early October.  September 16 is world ozone day, and in 2009 the final UN Member State to ratify the Montreal Protocol signed up.  2007 was the International Year of the Ozone Layer.  Prior to the formation of ozone holes, Antarctic ozone values were normally at their lowest in the autumn (ie March).  

Click on a thumbnail to get the latest graph or high resolution image.

Halley - Total ozone:    The measurements before mid September are of low accuracy due to the low solar elevation.  The earliest ozone measurements gave a total ozone column of around 200 DU in late August, a depletion of around 35%.  Ozone values dropped, to reach a minimum of around 125 DU (60% depletion) in late September.  The lowest daily value measured was 107 DU on October 1.  This minimum value is similar to those recorded each October since the early 1990s.  Values rose quickly to around 200 DU in mid October, but then stood still until early November, when they started rising again.   They peaked at around 300 DU (15% depletion) in mid December, and had declined to around 250 DU by mid April.  There was a weak autumn minimum in March.  The highest daily mean value is 327 DU on December 12.  The observing season at Halley finished on April 13.

Rothera - Total ozone:    Real-time graphs showing current ozone and NO2 levels.  Mean values remained around 280 DU until the end of May, but rose to around 310 DU by early July.  Significant ozone depletion began late in the month and the daily value dropped below the nominal "ozone hole threshold" of 220 DU for the first time on July 29, with 209 DU recorded.  Mean values had dropped to around 200 DU by late August, but  then rotation of the polar vortex gave a rise to 230 DU in early September.  Values dropped again as the edge of the vortex moved away from the station and reached a minimum of around 125 DU in late September.  The lowest daily value measured was 109 DU on September 26.  A spring warming then took place as the polar vortex moved away from the station and mean values rose to around 300 DU, with a peak daily value of 360 DU on October 14.  By mid November values had fallen back to 160 DU as the vortex became re-established near the station.  Mean values then rose for the final time to peak at 300 DU in the first half of  December and reached the autumn minimum at 260 DU in late February.  They rose steadily and reached around 320 DU in early June.   Values are now falling and had reached 290 DU by the winter solstice.  Superimposed on the general trends are fluctuations with periods of days to around a month and values can change by over 50% in a few days in the spring when the polar vortex rotates across the station.  

Vernadsky - Total ozone:   Vernadsky station is run by the National Antarctic Scientific Centre of Ukraine.   Observations recommenced in late July, with initial results (of low accuracy due to the low solar elevation) suggesting that ozone values were around 300 DU, but dropped rapidly, reaching 220 DU towards the end of the month.  They then rose again to around 270 DU in early August, but had dropped to 210 DU by the end of the month, a depletion of around 35%.   They rose to around 260 DU by mid September (20% depletion), but fell to a minimum of around 170 DU (50% depletion) at the end of the month.   Values rose around 330 DU (10% depletion) in mid October, but then fell to around 180 DU (55% depletion) in mid November.  They rose, to peak at around 320 DU (10% depletion) in mid December and are then slowly declined.   The lowest daily mean value recorded this year was 133 DU on September 25 and the highest 379 DU on October 28.

Temperature and PSCs:   The 100 hPa pressure level is near the base of the ozone layer, but is reached by most radiosonde flights.    The temperature at this height is sufficiently cold from July to October that polar stratospheric clouds (PSCs) can form.   Temperatures were at their minimum in late August and early September, with the spring warming beginning in early October.  Temperatures had risen above the PSC threshold by November, and peaked in late December.  They are now cooling and have passed the PSC threshold in some areas.

Rothera saw this spectacular display of nacreous clouds on 2007 July 12, and in 2008 saw them on June 3 (time lapse sequence taken by Rob Webster) and 30.   In 2009 the clouds have been seen at Rothera on July 9, 10, 13, 19, August 20.  Occasionally they are seen from Halley, and in 2008 were seen on September 2.

Halley - 100 hPa temperature:  The 100 hPa temperature reached its winter minimum at around -84°C in late August.  It rose slowly until late October, but then fell a little, before continuing to rise.  It peaked at around -42°C in late December,  a few degrees below the normal.   It fell back to around -45°C in early January, significantly below the normal of -40°C, but then recovered a little in mid January.  It is declining towards the late winter minimum.  It remains a few degrees below the normal and has been near or below the normal all season.  The July mean of -78.6 equalled the third warmest on record for the month.

 Peninsula - 100 hPa temperature:   The mean 100 hPa temperature in the Antarctic Peninsula  fell to the winter minimum at around -82°C in late August, which is significantly below the normal.  It rose to around -73°C, close to the normal, in mid September, but then fell to -80°C later in the month.  More sustained warming took place in October, with the temperature rising to around -57°C towards the end of the month, a little above the normal.  It then fell, reaching -72°C in mid November, about 20° below the normal, before rising to -44°C by mid December, still a little below the normal.  It is declining towards the late winter minimum.  There is often large day to day variation because the area is in the edge region of the circumpolar vortex.  

Satellite: Satellite imagery gives a global perspective on the ozone hole.  Our 2009/2010 Antarctic ozone hole movie is produced from OMI images, which are generally well calibrated with respect to ground based measurements.   The NCEP and KNMI analyses are shown on the Canadian Met Service daily ozone maps pages.  In general the NCEP analysis in the Southern Hemisphere tends to over-emphasise ozone depletion and the forecast further increases the amount of depletion.  The KNMI model is generally better at analysis and forecasting in the Antarctic.  The SMOBA and TOAST analyses both use SBUV and TOVS data, but the TOAST algorithm frequently over-estimates ozone depletion.  US NWS CPC plots from NOAA show the current area of the ozone hole.  The Sciamachy uv index from the ESA  Tropospheric Emission Monitoring Internet Service shows the exposure risk at any location.