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This page gives information about ozone at Halley, Rothera and Vernadsky/Faraday stations. It was either updated or new data was added on 2016 April 25.   The next full update is likely to be in early May.

Background / Ozone Bulletins / Ozone data

Antarctic Situation at 2016 April 25

Antarctic ozone today:  The 2015 ozone hole is over.  The ozone distribution is that of autumn with ozone amounts fairly uniform over the continent, and near their normal autumn minimum.   Values currently range from around 240 DU to around 340 DU.  There are significant differences between the various satellite measurements.   Temperatures in the ozone layer are cooling from their summer peak and are generally close to, or little below the normal.   Temperatures in the ozone layer are well above the threshold for Polar Stratospheric Cloud (PSC) formation. 

The 2015 ozone hole:  Meteorological conditions were favourable for the creation of a significant ozone hole, with a stable polar vortex and a cold stratosphere.  Ozone hole levels were briefly reached over the Antarctic Peninsula on August 5 and over Halley the next day in a dynamic event.  Significant ozone depletion over the continent began in mid August as the sun returned.  Depletion became more widespread by September, exceeding the mean for the last decade and greater than in the last couple of years.  Ozone declined by about 1% per day near the centre of the ozone hole.   The ozone hole peaked at some 26 million square kilometres in the first half of October.  It was the largest ozone hole ever for the time of year in the second half of October.   It became more elliptical in early November, affecting the Falkland Islands and South Georgia over November 4 and 5, and again around November 20 to 23.   It remained amongst the largest of the decade into mid December.  The polar vortex was the largest over the past decade in the upper part of the ozone layer from July to October and the area with PSCs was also larger than average during this period.  At lower levels the vortex was largest ever, by a considerable amount, from October and into December.  Some volcanic aerosol from the eruption of Calbuco in southern Chile in late April 2015 reached Antarctica and this may have lead to additional ozone depletion.

PSCs were visible from the UK on February 1 and 2 and again at the end of the month.  The dense form known as nacreous or mother-of-pearl clouds was most noticed in the earlier displays (eg this shot by Alan Tough from Alloa), however diffuse clouds with the appearance of high stratocumulus were more widespread.


See the final situation report for last year for information on the 2014 - 2015 season.

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.  All 197 Member States have now ratified the protocol up to and including the Beijing amendments.  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).  On occasion atmospheric vertical motions create small areas with ozone substantially below the long term average.  Different satellites give different views of the exact ozone distribution.  The continent covers 14 million sq. km.  A summary of the WMO/UN 2014 Ozone Assessment, the  Assessment for Decision-Makers was released on 2014 September 10.

zminoct nocurve.JPG (129164 bytes)zmin lin fit.JPG (115942 bytes)Observations from Halley since 1994 (the year when ozone depleting gasses were at their peak according to one estimate) show a slow increase of about 1 DU per year in the minimum ozone amount recorded each October, however the inter-annual variation is such that this trend is not yet significant (at the 99% level), ie the data is also consistent with no change in the minimum amount.  Although the amount of ozone destroying substances in the atmosphere is going down, the inter-annual variation in the size and depth of the ozone hole is largely controlled by the meteorological conditions in the stratosphere.  It is still too soon to say that we have had the worst ever ozone hole, particularly as there has been no major volcanic eruption in the Southern Hemisphere since 1992.  There has also been little cooling of the lower stratosphere since the mid 1990s.  The provisional Halley 2015 minimum value was lower than that of 2014, 2013 and 2012.  The low value in 2015 was mostly due to the prevailing meteorological conditions, but may also have been influenced by the eruption from Calbuco in southern Chile.

Click on a thumbnail to get the latest graph or high resolution images, which are updated more frequently than the thumbnails.  

Halley - Total ozone:  The Dobson ozone observing season at Halley begins at the end of August and ends in mid April.  Note: very early and late season observations are made with the Sun at low elevation, and are less accurate than those made during the main observing period of September 6 to April 6.  In addition the Dobson at Halley was changed in 2012 February and required maintenance in 2013 August, so the zenith sky tables of the current instrument are not yet fully determined.  The preliminary Dobson values given here should therefore be treated with some caution and will be revised.  During the winter, Dobson observations using the Moon as a light source are possible and measurements in late June and early July showed values dropping from around 330 DU to 230 DU as the polar vortex rotated.   Further observations at the next lunation showed values dropping from around 300 DU  in late July to 250 DU in early August.   When moon and solar observations became possible in the last ten days of August ozone values were around 255 DU and they dropped to around 125 DU by mid October (60% depletion), a decline of about 1% (3 DU) per day.  Values slowly rose, with occasional pauses, reaching around 280 DU (15% depletion) in early January.  Values since then slowly declined to around 240 DU (20% depletion) by mid April, when routine observations ceased.  Mean Dobson ozone values were below the ozone hole threshold from August 31 until December 1.  The lowest daily value this season was 116 DU on October 13, the lowest ozone value here since 2011 The mean for November was the second lowest for the month on record.  The highest daily value was 302 DU on January 5.
Halley also has a SAOZ spectrometer, and measurements with this began in early August.   Surprisingly, these early measurements suggested that ozone amounts rose from around 200 DU in early August to around 270 DU by mid month.  The low value around August 6 and this broad increase is confirmed by OMI data, suggesting a dynamic event that generated substantial ozone loss.  Ozone values fell to reach around 110 DU in mid October and then rose slowly to mid November and then more quickly to around 260 DU at the end of the year.  They have been within 15 DU of 255 DU during 2016 until the equinox and have now fallen to around 240 DU.  The lowest SAOZ daily value this season was 104 DU on October 14.  Daily SAOZ values dropped below the ozone hole threshold on August 25 and remained there until December 10.  In general mean Dobson observations look to the north, whilst mean SAOZ observations look towards the south. 

Rothera - Total ozone:    Real-time graphs showing current ozone and NO2 levels.  Mean ozone values slowly fell from around 300 DU at the beginning of 2015 to around 270 DU by early May.   Values then rose to a peak of around 330 DU in early July, then dropped rapidly to reach ozone hole levels by early September.  They fell more slowly and variably,  reaching around 165 DU in mid November, with minima around 170 DU in mid September and around 160 DU in mid October.  From mid November to the end of the month they rose rapidly to reach around 280 DU, peaking at 290 DU in early December.  They have been within 20 DU of 290 DU during 2016 to date.  Daily values were briefly below 220 DU on August 5 and again from August 22 to 25.   Mean values were below the ozone hole threshold from September 5 to 29 and from October 4 to November 23.  The lowest SAOZ daily value  this season was 126 DU on November 3.  The highest spring time ozone was 344 DU on December 8, though 361 DU was reached in June.  Superimposed on the general trends described here 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.    The observing season at Vernadsky began in late July, when ozone values were around 300 DU.  Mean values declined slowly from around 290 DU at the beginning of August (close to the normal) to around 210 DU (45% depletion) in mid November.  Within this slow decline there were significant variations, with a minimum of around 200 DU in mid September (40% depletion), a maximum of  around 300 DU (10% depletion) at the beginning of October and a minimum of 210 DU (40% depletion) in mid October.  Values rose rapidly from mid November to reach a peak of around 340 DU (10% depletion) at the end of the month.  Values declined to around 295 DU (15% depletion) by the end of the year.   They have been within 20 DU of 295 DU during 2016 to date and are now close to the normal.   The lowest daily value this season was 160 DU on November 3.  The highest values were 378 DU on September 30 and 377 DU on December 8.  Superimposed on the general trends described here 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, which is usually near the edge region of the polar vortex.   Very early and late season observations are made with the Sun at low elevation, and are less accurate than those made during the main observing period of August 6 to May 6. 

nacreous_20070712a.JPG (233412 bytes)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.

Both Halley and Rothera see displays of nacreous clouds.  Those at Halley are of the form described during the IGY as "ultra-cirrus".  This season, Rothera have  seen the clouds on July 1, 7, 21, August 3, 12, 13, 24, 25.

Halley - 100 hPa temperature:   The stratosphere cooled over the winter, with the 100 hPa temperature falling below -80C.    At the beginning of August it was around -85C, a little cooler than the normal, and it rose, initially slowly, then more quickly to a peak of around -41C in early January, a little cooler than the normal.  It is now cooling and has reached -64C.  It was a little cooler than the normal from January to mid March. The mean for June was a little below normal, whilst July was less variable than usual and the second coldest on record. Overall the August temperature was near to the normal, but more variable than usual.  The monthly means for October and November were the coldest on record and it was still well below the normal in December.


Peninsula - 100 hPa temperature:     The 100 hPa temperature was around -76C during August, a little cooler than the normal.  It fell to around -80C, significantly colder than usual, in mid September but then rose to around -71C (near the normal) by the beginning of October.  It fell to reach -77C after mid month, but slowly rose to -70C by mid November, which is some 22 colder than the normal.  Later in the month it rose rapidly to -51C, and then more slowly to reach -50C in early December, but fell to -58C in mid month, which is some 15 colder than the normal.   It finally rose to the summer peak at the end of the year, reaching -43C, very close to the normal.  It is now cooling, generally remaining a little below the normal and has dropped to around -56C.  There is often large day to day variation because the area is in the edge region of the circumpolar vortex.   The temperature is usually lowest in late August.  The mean for June was near normal, whilst that for July was colder than average.

Satellite: Satellite imagery gives a global perspective on the ozone hole, though there are notable differences between the different satellites, demonstrating the need for verification by ground based stations.  Our 2015/2016 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.  The KNMI model is generally better at analysis and forecasting in the Antarctic.   In general the NCEP analysis in the Southern Hemisphere tends to over-emphasize ozone depletion and the forecast further increases the amount of depletion, but on occasion (for example in early August 2011)  also ignores real ozone depletion.  The SMOBA and TOAST analyses both use SBUV and TOVS data, but the TOAST algorithm may at times over-estimate ozone depletion.  US NWS CPC plots from NOAA show the current area of the ozone hole, though note that this is often a preliminary plot.  The Sciamachy uv index from the ESA  Tropospheric Emission Monitoring Internet Service shows the exposure risk at any location.

Arctic Ozone values across the Arctic and temperate parts of the Northern Hemisphere are generally high, though declining and range from around 320 DU  to around 440 DU.  A spring warming took place in early March and temperatures are now well above the PSC formation threshold.  Ozone values over the UK are around 390 DU.  During January the Arctic stratosphere was near its coldest for the winter and its temperature was generally much colder than average for this time of year, with minimum values close to or below the long term minimum, leading to the development of PSCs.   A short lived spring warming event took place in early February, but temperatures remained colder than the normal for the time of year.  Significant ozone depletion took place as the sun returned, though values did not drop below the 220 threshold for an ozone hole.  It would be worth setting a different limit for the Arctic as a proportionally greater depletion is required here to meet the threshold which was set for the Antarctic.  A second warming event took place in early March, this time pushing stratospheric temperatures above the PSC formation threshold.

The north polar vortex is usually smaller and more disturbed than the corresponding one that forms during the Antarctic winter.  In 2010/11 a generally more stable than usual Arctic vortex allowed stratospheric temperatures to drop below the PSC formation threshold for a substantial period over the northern winter.   Warmings occurred in early January and early February, however parts of the Arctic ozone layer within the vortex remained cold enough for stratospheric clouds to form until early April, with temperatures substantially colder than the normal.  With large amounts of clouds sunlit, ozone depletion reached its greatest towards the end of March.  Ozone values at Lerwick dropped to 249 DU on 2011 March 29, when the major depletion event passed near the UK, but values across the UK returned to near normal by mid April.  The major spring warming of the stratosphere occurred in early April and temperatures from then on were then too warm for PSCs to exist.  By contrast the 2012/13 vortex was very unstable with stratospheric warmings occurring in early and late December 2012.  Temperatures had warmed above the PSC formation threshold in late December and were at or near record levels in 2013 January.  In 2015/16 the vortex was again very cold and stable and in early February the vortex elongated south across the UK.  Spectacular displays of PSCs and nacreous clouds were seen across the UK on February 1 and 2; good views were had from Cambridge.  Ozone depletion occurred, with unusually low values recorded on January 31/February 1, for example 224 DU at Reading on February 1. The vortex elongated again towards the end of the month, and further clouds were seen from parts of the UK, with 240 DU recorded at Lerwick on February 29. 

There are sometimes significant differences (over 100 DU) between modeled, satellite and ground-based measurements, particularly when there is large variation in total column ozone.  Ozone values over the Arctic during 2015/16 are shown in our Northern Hemisphere TOMS movie.   For more UK information see the DEFRA UK Stratospheric Ozone Measurements page.    

Equator: Ozone levels are normally lowest over the topics and OMI data shows nothing unusual.

Measurements reported here refer to ozone in the "ozone layer", where most of the ozone in the atmosphere is found.  This "layer" stretches from roughly 10 to 40km above the Earth's surface, with a peak at around 20km.  Bringing all the ozone in the "layer" down to ground level would give a thickness of around 3mm of pure ozone, which reduces to around 1mm at the height of the ozone hole.  A little ozone also exists closer to the Earth's surface and recent research shows that natural halogens in Antarctica can produce depletion in this near surface layer.  The theoretical basis for the formation of the Antarctic ozone hole and its link with the halogen chemistry of man-made substances is well established and the mechanism is described at sites such as the Ozone Hole Tour at the Cambridge University Centre for Atmospheric Science.  

Background and related material

  • UNEP video describing the ozone layer 2015 July 19
  • A summary of the WMO/UN 2014 Ozone Assessment, the  Assessment for Decision-Makers was released on 2014 September 10.
  • Nature PastCast on the Ozone Hole 2013 May 17
  • NERC Planet Earth Podcast on the Ozone Hole 2011 November 22
  • A Paper by Murry Salby et al suggests that the ozone hole is recovering.
  • Main presentation and secondary presentation given at the WMO ozone workshop held in 2011 February at Hradec Kralove.
  • An opinion piece by Jonathan Shanklin to mark the 25th anniversary of the ozone hole appeared in Nature on 2010 May 6.  
  • A revised edition of the BAS ozone pamphlet was published in 2010.
  • Timor Leste ratified the Montreal Protocol on 2009 September 16, making it the first environmental treaty to be ratified by all UN Member States
  • Upper stratospheric ozone recovering ? [SPIE news 2009 July 27]
  • Ozone and Cosmic Rays
  • BAS Scientific Report No 90: Measurements of atmospheric ozone at the Argentine Islands and Halley Bay, 1957-72
  • The paper on the discovery of ozone depletion in Antarctica is available as an abstract from Nature online.
  • Forty Years ' Research on Atmospheric Ozone at Oxford: a History. G M B Dobson 1968 (scanned by NOAA ESRL GMD)
  • Listen again to the BBC Radio 4 programme "The Reunion" broadcast on 2007 April 29, which brings together the discoverers of the ozone hole
  • Slides from talk given to the Royal Meteorological Society on 2006 October 18
  • Theory of the Dobson from the NOAA ESRL GMD (formerly CMDL)
  • Institute of Physics i-seminar on the ozone hole and climate change given on 2005 October 31
  • The NASA ozone hole watch page
  • Some links to other sources of ozone information (updated 2004 November 19).
  • BAS Press Release on 2005 September 14 on 20th Anniversary of ozone hole discovery: International Ozone Day
  • Royal Astronomical Society ozone fact sheet
  • The 2001 July edition of Weather included an article on the ozone hole entitled 'Back to basics:- The ozone hole'. This version is slightly revised and updated.
  • WMO Press Release on 2003 September 16 (Antarctic ozone hole unusually large)
  • BAS Press Release on 2003 September 12 (BA Festival of Science - The ozone hole)
  • Slides of talk 'The split Antarctic vortex - has it ever happened before ?' given at the RMS/ACSG meeting on 2003 August 29
  • Twenty Questions and Answers about the Ozone Layer - WMO/UNEP Scientific Assessment of Ozone Depletion 2002
  • Why does the ozone hole form over Antarctica?
  • BAS was involved in the QUOBI project in 2003 to contrast the ozone layer over the Arctic with that of the Antarctic.  Trial ozonesonde flights took place at Rothera in March and regular flights began at the end of June.  Animation of the ozonesonde flight results.
  • Institute of Physics awards BAS Scientists the Charles Chree Medal and Prize
  • SCI Press Release BAS Scientists Awarded Environment Medal. This is what the medal looks like.
  • Severe Arctic ozone depletion in 2000
  • BAS was involved in a big international collaboration to measure the ozone hole in 1999 September and October. Details of ape-gaia are on the project web page.
  • Statement on stratospheric Ozone and the Ozone Hole
  • The BAS press release of 1997 October 2 'Ozone hole starts to form in midwinter at sunlit edge of Antarctica'. A postscript image shows the calculated ozone depletion on 1994 July 23.
  • An ozone hole did not exist in 1956 (despite suggestions to the contrary) [updated 2002 October 14].
  • UK ozone information from the Met Office.
  • The ozone FAQ
  • Yahoo ozone discussion group
  • Canadian Met Service ozone information
  • Somewhat related is the subject of nacreous clouds , which were widely seen over the UK on 1996 February 18 and over Scotland on 1999 November 30. Very low ozone values were recorded over the North Sea on the later occasion, more details are available from NASA-TOMS . This event was probably caused by a combination of stratospheric and tropospheric dynamics (the stratosphere was very cold), with ozone depletion playing a minor role. On 2000 January 29 nacreous clouds were again seen over large parts of the UK. Stratospheric analyses show temperatures over the UK below -75 deg C on that day and the day before. Martin Brown has compiled a page of further information and pictures of the display. Significant ozone depletions of up to 30% were seen in some areas of the Arctic during early March.

  • Ozone bulletins

    The BAS ozone bulletins contained the actual ozone values reported together with an analysis of the situation. These were distributed by email on request, but are now superceded by this web site.  The last email ozone bulletin was issued on 2002 May 28.  The final situation report of each season is archived for historical reference.

    Ozone data

    Please read this metadata description before asking any questions about the data. [updated 2013 December 2].
    Two documents describe our standard operating procedures: The BAS Dobson Manual and the BAS ozone station instructions. A paper describing the stations, observing programs and reduction procedures is in preparation. Most of our data is available on line, however please note that this is provisional and likely to change without warning.  You must request permission to reproduce the data and I may be able to supply more suitable or more up to date material.  If data from Halley is used you must give the station name as Halley;  Halley Bay was a geographical feature that no longer exists.

    Provisional daily mean ozone values for 2015/2016 for Halley  [Updated 2016 April 25] and Vernadsky.  [Updated 2016 April 25].  Note : The Dobson at Halley was changed in 2012 February and required maintenance in 2013 August.  The calibration of the current instrument is not yet fully determined.  The zenith sky tables or other calibration values were last revised on 2016 February 26, but the daily means may still have errors up to 10%, particularly when ozone values or the solar elevation are low.  These preliminary Halley values should therefore be treated with some caution.  The instrument constants for Dobson 123 at Vernadsky were revised on 2016 April 4.
    Provisional daily mean ozone values for Faraday/Vernadsky and Halley between 1972 and 2013 April. [Updated 2013 June 24]
    Provisional daily mean ozone values for Vernadsky in 2013/14 , 2014/15 , 2015/16.
    Provisional daily mean ozone values for Halley in 2013/14 , 2014/15 , 2015/16.
    Provisional monthly mean ozone values for Faraday/Vernadsky and Halley between 1956 and 2015 December.
    Provisional monthly minimum ozone values for Faraday/Vernadsky between 1972 and 2015 April and Halley between 1956 and 2015 April.
    Mean daily ozone values for the period 1957 - 1972 for Faraday and Halley. [NB: not corrected to Bass-Paur]
    Daily ozone values for the period 1957 - 1973
    for Faraday and Halley. [Revised to Bass-Paur]
    Provisional Halley SAOZ total column nitrogen dioxide and ozone: 2013 , 2014 , 2015 , 2016 [updated  2016 April 25, processing revised 2013 November 22] and as real-time graphs showing current ozone and NO2 levels [Not yet available].

    Temperature and Ozone graphs for Halley and Vernadsky/Faraday. [Updated 2015 October 23].  The historic period shown in the inline graphs is for 1957 - 1972.

    Rothera - Ozonesondes:  During 2003 we carried out ozone sonde flights at Rothera as part of the QUOBI project.  Data from these flights is available in NASA-AMES format.  Animation of the ozonesonde flight results [note that although the ozone scale on these graphs reads nanobars, it should read mPa].

    Rothera - Ozone & nitrogen dioxide:  
    SAOZ total column nitrogen dioxide and ozone: 1996 , 1997 , 1998 , 1999 , 2000 , 2001 , 2002 , 2003 , 2004 , 2005 , 2006 , 2007 and 2008 [to 2008 January 22].  
    "New" SAOZ total column nitrogen dioxide and ozone: 2006 , 2007 , 2008 , 2009 , 2010 , 2011 , 2012 , 2013 , 2014 , 2015 , 2016 [updated 2016 April 25] and as real-time graphs showing current ozone and NO2 levels.  Data is missing between 2013 December 23 and 2014 January 6.
    Bentham ozone. Provisional values for 1997 / 1998 / 1999 / 2000 / 2001 / 2003 / 2004 [updated 2004 November 5 ].  The Bentham instrument ran until 2012, but data from it has not been used to produce further ozone values.

    Some background information on Halley, Rothera and Faraday stations is available from BAS. Information about Vernadsky station is also available from the Ukrainian Antarctic Centre. Information about Vladimir Ivanovich Vernadsky

    Some surface and upper air synoptic data is also available on line from our public data page.

    Southern Hemisphere ozone hole movies for 1997/1998 , 1998/1999 , 1999/2000 , 2000/2001 , 2001/2002 , 2002/2003 , 2003/2004 , 2004/2005 , 2005 [TOMS], 2005/2006 , 2006/2007 , 2007/2008 , 2008/2009 , 2009/2010 , 2010/2011 , 2011/2012 , 2012/2013 , 2013/2014 , 2014/2015 , 2015/2016 [OMI, updated 2016 April 25].  A short sequence of the 2001 ozone hole.
    Northern Hemisphere movies for 2000/2001 , 2001/2002 , 2002/2003 , 2003/2004 , 2004/2005 , 2005 [TOMS], 2005/2006 , 2006/2007 , 2007/2008 , 2008/2009 , 2009/2010 , 2010/2011 , 2011/2012 , 2012/2013 , 2013/2014 , 2014/2015 , 2015/2016 [OMI, updated 2016 April 25]  A short sequence of ozone depletion during the 2002/03 northern winter showing the difference from the normal.
    The annual movies are about 7Mb and were compiled from daily TOMS images until the end of 2005; from 2005/06 they have been compiled from OMI images. The movies begin and end in June.
    Today's OMI global image
    The current area of the hole and other latest details are available from the NOAA Climate Prediction Center.
    Environment Canada have an excellent set of daily maps showing both northern and southern ozone levels from a variety of sources.
    The Sciamachy uv index from the ESA  Tropospheric Emission Monitoring Internet Service.  Note that west longitude is negative when entering co-ordinates.


    Requests for permission to use this data or for further information should be sent to Jon Shanklin who maintains these pages.

    NERC / BAS / MET


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