[BAS Science]   [BAS home]   [ Met home]	Meteorology and Ozone Monitoring Unit

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 2011 June 24.

Situation at 2011 June 24

Ozone values across the continent are generally within 70 DU of 290 DU,  with a rather patchy distribution as the polar vortex builds.  Generally ozone values are higher surrounding the continent and lower over the continental interior.  The lower stratospheric temperature is declining, with some areas now below the polar stratospheric cloud formation temperature, and is near the normal for this time of year.

There was substantial Arctic ozone depletion over the northern winter.  The summer circulation pattern is now established.

Ozone values over parts of the Antarctic Peninsula fell rapidly rapidly to around 240 DU in the first half of July, but then recovered.  By early August the ozone hole had begun to form, though it was a slow start to the season and significant depletion did not commence until towards the end of the month.  Ozone values at Rothera fell below the ozone hole threshold for the first time on August 17, but then recovered.   The ozone hole was at its largest in late September at around 20 million square kilometres, which was well below the average size of the last decade.  This slow start and relatively shallow ozone hole was linked to warmer than usual stratospheric temperatures reducing the volume of stratospheric clouds early in the season.  After its peak the ozone hole slowly declined in area but was a record size for the time of year during December.  Ozone values finally rose above the "ozone hole" threshold of 220 DU around December 21.  In the belt surrounding Antarctica outside the polar vortex ozone, values  peaked at a little above 400 DU.   At its largest during August and September, the polar vortex was slightly above the average area of the last decade and at 70hPa persisted well into December.   The temperature of the ozone layer within it was at the winter minimum in August and had risen above the PSC formation threshold by early November. The fringes of the ozone hole extended over the tip of South America and South Georgia over September 6 - 9,  16 - 21, October 10 - 12 and18 - 23.   A relict area of low ozone crossed southern South America and the Falkland Islands over January 1 to 5 and an area was over Tasmania on January 13.  

See the final situation report for last year for information on the 2009 - 2010 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 observing season at Halley began in late August, with preliminary values around 220 DU (25% depletion).  Mean values reached around 160 DU (50% depletion) at the end of September and broadly remained at this level until the second half of October when a significant rise to around 225 DU (30% depletion) occurred.  Values remained near this level, with daily values varying between 180 and 290 DU until early December (increasing to 40% depletion, as this was the time when ozone values used to be rising), when the final warming began.   Mean values peaked at around 310 DU (13% depletion) just after mid December.  Values then slowly and irregularly declined, and reaching around 250 DU (15% depletion) by mid April.  The observing season has now ended.  The lowest daily value recorded this season was 140 DU on October 15.  Excluding 2002, when the ozone hole split, this is the highest minimum October value since 1988.  This does not yet indicate a recovery of the ozone hole as stratospheric temperatures were unusually warm during the winter, reducing the formation of stratospheric clouds.  The highest value recorded this season was 331 DU on December 19.  Note that the instrument constants were slightly revised on November 12, resulting in a small increase in previously published values.

Rothera - Total ozone:    Real-time graphs showing current ozone and NO2 levels.   Mean values rose steadily from the autumn minimum at 260 DU in late February and reached around 320 DU in late June.   Values then dropped as ozone depletion set in, reaching around 195 DU in mid October.  A major warming occurred at the end of the month, with daily values rising above 350 DU though they subsequently declined, with brief excursions back to ozone hole levels.  Mean values remained around 260 DU from mid November until the end of the year, before rising to around 300 DU early in the new year.  They have slowly declined from around 300 DU in February to around 285 DU in mid June, though with an excursion to around 270 DU in the first half of March.  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.  The lowest daily value recorded this season was 155 DU on September 7, although the lowest running mean was around 170 DU in mid October.

Vernadsky - Total ozone:   Vernadsky station is run by the National Antarctic Scientific Centre of Ukraine.    The observing season at Vernadsky began in late July, with values towards the end of the month of around 290 DU.  From the beginning of August mean values slowly dropped until around the time of the equinox, reaching around 210 DU, some 35% below pre-ozone hole values.   Values then rose to around 290 DU (15% depletion) at the end of September as the vortex swung away from the station, but returned to around 220 DU (40% depletion).   Values rose to near the normal of 360 DU at the end of October, but then declined reaching around 280 DU (15% depletion) by the end of the year.  Values slowly rose to reach around 310 DU at the end of February, but dropped to reach 260 DU in the first half of March.  They rose to around 285 DU in the second half of the month and remained at this level to the end of April.  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.  The lowest daily value recorded this season was 168 DU on October 19 and the highest 378 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.   Note: "the normal" is used to refer to the long term mean for the time of year.

Rothera have seen several displays of nacreous clouds this year.  There was a very bright display on July 15 (Mike) , July 15 (Rebecca), and a fainter one on July 12.  This display was noted as being seen through altostratus, but it is possible that this was layer type PSC.  PSCs were also seen on August 5.  PSC were also seen from Halley on five occasions during July and again on September 9.

Halley - 100 hPa temperature:  The 100 hPa temperature reached its winter minimum at around -85°C in mid August .  An unusually low value of -88.3°C was recorded on August 18.  The temperature rose slowly and irregularly to around -48°C just after mid December,  some 7° below the normal, and then declined.  A second peak to -43°C occurred in early January, still around 3° below the normal and then declined.  Finally the temperature rose to near the normal late in the month.    By February the temperature was slowly declining and had reached -62°C by the end of April.  It has generally been a little below the normal since the summer.  Such a low peak temperature in December is unusual, and December 2010 was the third coldest on record at 100 hPa, with 2008 and 1990 being colder.

 Peninsula - 100 hPa temperature:   The mean 100 hPa temperature in the Antarctic Peninsula  rose from around -79°C at the beginning of August to around -71°C in mid October, around 9° below the normal for this time of year.  A more rapid rise then took place, with the temperature reaching -57°C by the end of the month.  Temperatures fell again in November reaching around -62°C by mid month before rising to reach around -52°C in mid December, still substantially below the normal of -44°C but then fell to around -57°C.   The temperature finally rose to near the normal value in early January.  Temperatures began declining in February.  Values had fallen to around -57°C by the end of April, close to the normal.  December 2010 was the third coldest on record at 100 hPa, though the pattern of variation was different to that of December 1990 and 1996, when a much more stable vortex persisted into January.  The temperature is normally at its lowest at the end of August at around -76°C.  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 2010/2011 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.