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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 2015 June 22.

Antarctic Situation at 2015 June 22

Antarctic ozone today:  The 2014 ozone hole ended in early December.  The ozone distribution is now that of early winter with lower ozone amounts across the continent and higher (and increasing) values around the Southern Ocean.   Values currently range from around 270 DU over the continent to around 370 DU over part of the Southern Ocean.  There are significant differences between the various satellite measurements.  Temperatures in the ozone layer are below the threshold for Polar Stratospheric Cloud (PSC) formation over parts of Antarctica, particularly in the upper part of the ozone layer.  Through most of the ozone layer temperatures are close to or a little below the long term average.  

The 2014 Ozone Hole:  The ozone hole began to form in early August and grew rapidly from mid month, covering some 23 million square kilometres at its peak in mid September.  During August and September it was generally similar in size to the ozone hole of 2013, and mostly smaller than the decadal mean.  During October and November it was around the decadal mean and larger than the holes of 2012 or 2013.  By late November the size had declined to around 6 million square kilometres, remaining close to the average for the decade, but it was over by early December.  Temperatures in the ozone layer became cold enough for PSCs to form by May and were generally a little below the long term mean for most of the winter.  They became too warm for PSCs to exist by early November.  The polar vortex was generally close to the decadal mean in size, beginning to form in early May, reaching a maximum of around 32 million square kilometres in mid August, and lasting into December.  A possible infolding of tropical stratospheric air with associated colder than usual temperatures briefly pushed ozone values below the ozone hole threshold over the Antarctic Peninsula around the time of the autumn equinox.

The edge of the ozone hole covered the southern tip of South America from September 13 to 18, the southern tip of South America, the Falkland Islands and South Georgia from October 7 to 15 and South Georgia on August 25 to 27, September 28, 29, October 3, 4, 24 and November 1 to 2.   The fringes of the hole covered the region from November 12 to 21.  The final fragment of the ozone hole was spat out over the southern tip of South America between December 12 and 13.The centre of the ozone hole is often offset from the pole towards the Atlantic.  Stations near the edge of the ozone hole (often those nearest Australia or in the northern Antarctic Peninsula) move from within the ozone hole to outside it as the polar vortex rotates. 

It will be interesting to see if the eruption from Calbuco in southern Chile has any effect on ozone values when spring 2016 comes along.  To date most of the volcanic aerosol has remained north of Antarctica.

See the final situation report for last year for information on the 2013 - 2014 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.

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 2014 minimum value was lower than that of both 2013 and 2012.  It will be interesting to see if the eruption from Calbuco in southern Chile has any effect on ozone values when spring 2015 comes along.  To date most of the volcanic aerosol has remained north of Antarctica.

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.  In 2014 the station was unable to make any observations from late July to late August due to power problems.  Limited scientific observations began again in late August. During the winter, Dobson observations using the Moon as a light source were possible, and measurements in early July give ozone values around 290 DU.  The initial zenith ozone observations in late August gave values around 200 DU and they had dropped to around 140 DU by early October (55% depletion).   Values rose, initially slowly then more quickly, to peak at around 310 DU (15% depletion) in mid December.  They had fallen to around 250 DU (15% depletion) by mid April when observations ceased.  The lowest daily Dobson mean this season was 123 DU on October 4.   The highest this season was 323 DU on December 19.  The main observing season for Halley ended in mid April, however some further lunar observations were made in early June indicating values around 270 DU.  Halley also has a SAOZ spectrometer, and measurements with this began in late August, indicating ozone values around 210 DU and they had dropped to a minimum around 115 DU at the end of September.  Values began to rise and reached 170 DU by late November.  A more rapid rise ensued and values peaked in mid December at around 290 DU, falling to 245 DU by late March.  Values then rose and were around 275 DU when observations ceased in early May.   The lowest daily SAOZ mean this season was 111 DU on October 1 and the highest was 301 DU on December 18.   In general mean Dobson observations look to the north, whilst mean SAOZ observations look towards the south.  Halley was within the ozone hole from when measurements began at the end of August until December 1.  

Rothera - Total ozone:    Real-time graphs showing current ozone and NO2 levels.  Mean ozone values declined slightly from around 290 DU at the beginning of 2014 to around 280 DU by early May then increased to around 310 DU by late June.  They then started to fall quite quickly, reaching 190 DU by late August.  At the end of the month they rose rapidly, reaching around 260 DU in early September.  Values from mid September to early October were at a broad minimum around 170 DU.  Values rose rapidly to a peak of around 270 DU in mid October then fell to 190 DU by mid November.  They rose to a peak of around 340 DU in early December and slowly fell to around 270 DU by early May.  By the June solstice values had risen to around 320 DU.  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 values this season were 131 DU on August 23 and 139 DU on October 1.  The highest this season was 356 DU on December 1.  Daily values at Rothera dropped below the ozone hole threshold of 220 DU for the first time on July 17 and did so again on August 6 and 7.  The station was within the ozone hole from August 18 to 26, from September 6 to October 14 and from November 6 to 23.  Values were below the ozone hole threshold on March 22 during an unusual dynamic event, which may have involved infolding of air from the tropical stratosphere. 

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 amounts were around 260 DU.  Ozone levels fell to about 220 DU by the third week of August, but then rose to 280 DU by early September.  They fell to 190 DU by mid month (45% depletion), then rose, initially slowly to 220 DU by early October (40% depletion), and then very rapidly, to reach 325 DU in mid October (10% depletion).   Values then irregularly dropped to around 220 DU (45% depletion) in mid November, but rose to a peak of around 350 DU (10% depletion) in early December.  Mean values had declined to around 285 DU (5% depletion) by the equinox, but are now slowly rising and reached 315 DU (close to normal) by the end of April.  They were around 285 DU in May.  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.   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.  The lowest daily value this season was 170 DU on October 10 and the highest was 381 DU on November 29.  Ozone values at Vernadsky first dropped below the ozone hole threshold of 220 DU on August 18 and it was within the ozone hole from September 11 to October 2.  Values were below the ozone hole threshold on March 22 during an unusual dynamic event, which may have involved infolding of air from the tropical stratosphere.  The instrument constants were revised on 2014 December 19, which produced an increase of around 10 - 15 DU in previously quoted values.

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 year, Rothera saw the clouds on June 17 and 22 and on 11 days in July.

Halley - 100 hPa temperature:   In June the 100 hPa temperature was a little warmer than average at -74.9°C and was more variable than average.  In July it was a little cooler than average at -81.0°C.  The lower ozone layer had cooled to around -82°C by late July.  The station was unable to conduct any balloon flights between late July and early October due to power problems.  When flights resumed the 100 hPa temperature was around -77°C, a little colder than the normal for the time of year.  The temperature remained near this value for most of October, but rose to reach a peak of -41°C in mid December.  It is cooling and is now approaching -80°C.   It has been colder than the normal for the time of year, and mostly substantially so, apart from in early December and since late March.  The mean May temperature was a little colder and more variable than average.

Peninsula - 100 hPa temperature:   The mean 100 hPa temperature in the Antarctic Peninsula showed an underlying cooling from -77°C in early August to around -82°C in mid September and this was roughly 6°C cooler than the normal during this period.  A short-lived warming (lasting 20 days) took place in late August (to -71°C, 4°C above the normal) and and a major warming began in late September, reaching -65°C by mid October. The temperature remained around this value until mid November, but then rose rapidly to a peak of around -42°C in early December.  It then dropped but remained around -46°C for much of the summer.  It has now cooled to around -70°C.  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.  In June the 100 hPa temperature was cooler than average at -69.1° and a little more variable than average.  In July it was also cooler than average at -74.2°C and more variable than average.  August was also cooler than average at -78.1°C.  Apart from a short period in late August and in October it was substantially below the normal from August until the end of November.  It was again significantly below the normal in late December and early January.

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 2014/2015 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.