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ANTARCTIC OZONE

This page gives information about ozone at Halley, Rothera and Vernadsky/Faraday stations. It was updated for the final time on 2019 June 24.  

Antarctic Situation at 2019 June 24

Antarctic ozone today:  The 2018 ozone hole filled by the end of 2018 November and the 2018 southern polar vortex had dissipated by mid December.  The 2019 vortex is beginning to form and is growing.  The temperature throughout the ozone layer is falling overall.  The growing polar vortex is unusually offset towards the Indian Ocean and is centred over East Antarctica.  Lowest ozone values, around 240 DU, are near Princess Elizabeth Land.  Ozone amounts are building over the southern ocean  and here amounts are higher, up to 390 DU in places.  The offset means that both the Antarctic Peninsula and southern Australia are experiencing high ozone values.  There are marked differences between the various satellite ozone measurements and analyses.  The KNMI analysis and TEMIS forecasts are close to the observed values, whereas the Canadian analysis seems largely based on SMOBA data and is clearly at variance with ground based observations.   Temperatures in the ozone layer are over half way to the winter minimum and have reached the  -78°C Polar Stratospheric Clouds (PSC) formation threshold through much of the ozone layer.  They are highest over mid latitudes and decline towards the equator and the pole.  In the lower stratosphere they are not far from the normal, though are below the normal in the upper part of the ozone layer. 

The 2018 ozone hole:  The polar vortex began to form in early May and reached its maximum area in late September at around 34 million square kilometres.  It was a little larger than the decadal mean in size, and was generally of average or above average stability.  PSCs began to form in mid May and the maximum area with potential PSCs was larger than the decadal mean and close to the maximum of the last decade at around 27 million square kilometres.  Ozone hole values below 220 DU were reached in late August, later than in the past couple of years; this was largely due to the stability in the stratosphere this year.  The ozone hole grew rapidly and by its maximum in late September was above the average size for the decade at 24.8 million square kilometres.  The stratosphere became less stable at the end of September, but then returned to stable conditions.  The ozone hole shrank when it was unstable, but stopped shrinking with the return to stability.  It became much less stable in November, with the vortex oscillating between a very elongated form and a more circular form.  This lack of stability in early November lead to a rapid filling of the ozone hole.  The area with ozone hole values had declined to zero by the end of November, later than in the last two years, but sooner than the decadal average.  The vortex itself lasted until mid December.  When the vortex became less stable the ozone hole became more elongated and South Georgia was at the edge of the ozone hole at times during October and November.  NASA observations show that a minimum ozone amount of 102 DU was reached on October 11 and 12.  Although this is a low value it is not as low as around 1990 to 2000.  Ozone depletion would have been much worse this year without the protection of the Montreal Protocol.

Note that the US Government shutdown earlier this year means that some NOAA/NASA data about the stratosphere is not currently available.

See the final situation report for last year for information on the 2017 - 2018 season.

Notes:  An ozone hole is defined as an area with values below 220 Dobson Units (DU).  On average a column of air will hold 300 DU of ozone, equivalent to 3mm of ozone at sea-level pressure.  Most of the ozone is between 10 and 40 km with a peak at around 20 km.   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.  2017 was the 30th Anniversary of the Montreal Protocol.

News:  Observations reported in Nature in May 2018 showed that the rate of decline of CFC-11, an ozone depleting substances in the atmosphere, which is also a greenhouse gas, had become slower than predicted.  This suggested that either something unusual was taking place in the atmosphere or that there were additional man-made emissions.  The paper suggested that the most likely reason was illegal manufacture and release from somewhere in eastern Asia.  Investigation by the EIA has found that production of polyurethene foam in China can explain the observed changes.  They encourage the Chinese government to take immediate action.  This became news again in May 2019 when another paper was published in Nature.

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.  The provisional Halley 2015 October minimum value was lower than that of 2014, 2013 and 2012 and this was due to the prevailing meteorological conditions.  It was also influenced by the eruption from Calbuco in southern Chile.  The recovery in springtime (ie September and October) minimum ozone values at Halley is now statistically significant.  A simple extrapolation of the trend in minimum values gives the final year with ozone hole levels as 2073, though the error bars on this estimate are very large.  Models suggest that recovery may be more rapid after 2010.  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. 

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 normally 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.  Ozone observations at the station ceased on 2017 February 15 when the station was shut down for the winter due to the risk of calving of the ice shelf on which it is located.  Manual observations resumed on 2017 December 7, but ceased for the winter on 2018 February 26.  Jonathan Shanklin was on station over the summer and made many calibration observations.  An automated Dobson ran for a short while during 2018 January and February.  An automated SAOZ did not run over the winter, but some data from 2018 March may be recovered.  The preliminary Dobson values given here should be treated with some caution and will be revised. 

Manual observations resumed on 2018 December 10 and suggested that ozone values were around 315 DU (15% depletion).  They slowly declined to around 280 DU (10% depletion) when the station was closed for the winter.  Manual observations ceased on 2019 February 16, though the automated instrument continued running until the Sun became too low for observation in mid April.  Data from this suggests that ozone amounts remained steady at around 280 DU (5% depletion) until mid April.  The graph is a composite, using auto data after February 16.  All being well automated observations will resume in late August.

Rothera - Total ozone:    Real-time graphs showing current ozone and NO2 levels.  There are occasional periods when the computed values appear erroneous and this is likely due to internal clock errors.  During the first two months of 2018 ozone values slowly declined to around 280 DU but rose during March to around 330 DU.  They fell to 275 DU in early April, but irregularly rose to 310 DU by late July.  Mean values fell to reach a minimum of around 145 DU in late September.  They remained around 165 DU until early November, when they began to rise rapidly and to around 330 DU around November 18.  They then remained around 300 DU for the rest of the year.  They were around 280 DU in the first half of January.  The instrument then stopped working for a lengthy period, but following a return to measurements, values have been around 290 DU, with wave activity giving some longer period fluctuation of around +/- 20 DU.  Values began to rise in the second week of June and are now around 330 DU.  This is unusually high for the time of year and is associated with the offset of the polar vortex towards the Indian Ocean.  Mean ozone hole values were reached on 2018 August 30 and the station was within the ozone hole until November 9.  The lowest value seen during 2018 was 119 DU on September 25 and the highest was 348 DU on November 20.  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.   No data is available for November 12 to 19 when ozone values were rising rapidly, and for December 14 to 16.  Continuing computer problems mean that no useable data was collected between January 18 and March 4 and again between March 27 and April 8.

Vernadsky - Total ozone:   Vernadsky station is run by the National Antarctic Scientific Centre of Ukraine.  It is some 250 km north of Rothera.  The observing season at Vernadsky began in late July with provisional ozone values of around 290 DU; they fell to a minimum of around 165 DU (50% depletion) in late September.  They rose slowly and irregularly during October to reach 200 DU (45% depletion) by the end of the month.   Values rose very rapidly in November and were around 330 DU (15% depletion) by November 22.  They slowly fell to around 260 DU (15% depletion) in early March.  Ozone amounts then rose to around 290 DU (5% depletion) in late March and had declined to around 270 DU (10% depletion) by the end of April.  They were around 290 DU in May.  Observations ceased for the winter after May 23.  Wave activity, with a period of about three weeks was quite strong this year.  The lowest value seen in 2018 was 137 DU on September 25 and the highest was 376 DU on November 23.  The October mean of 187 DU was provisionally the lowest on record.  This is a result of the unusually stable conditions in the stratosphere this year.  The overall mean from August to April was 258 DU, the lowest since 2011,  (256 DU), which itself was the lowest on record.  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.  The instrument constants were revised in 2016 November, which resulted in some previously listed values for 2016 and earlier being updated.  A further revision may be required.  See the data section for current provisional values for 1972 - date.

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".   Rothera observed the clouds on 2018 June 12, July 7, 19, 27 29, August 2, 16, 20 and September 1.  The 2019 season started early with a sighting on May 22.

Halley - 100 hPa temperature:   With the closure of the station over the 2017 and 2018 winters there were no radio-sonde launches from 2017 February 14 to 2017 December 6, from 2018 February 26 to 2018 December 10 and since 2019 February 16.  When launches resumed in 2018 December the 100 hPa temperature was around  -50°C, some 8° below the normal.  It rose to a peak of around  -41°C, close to, though below the normal, in early January.   There was a dip back to  -44°C by late January, followed by a rise before the temperature started falling again.  It was a little below the normal at around -44°C when flights ceased for the winter on February 16.