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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 2013 June 24.

Antarctic Situation at 2013 June 24

The 2012 ozone hole is long over and the 2012 winter polar vortex over Antarctica has dissipated.  The ozone layer is cooling with the 2013 winter polar vortex forming, and it is cold enough for PSC formation.  Ozone distribution is beginning to organise, with highest values at around 360 DU surrounding Antarctica at about 50 - 60°S and lowest values at around 260 DU over the continental margins.  The 2013 ozone hole is beginning to be created.  Different satellites give different views of the exact ozone distribution.

Ozone values outside the vortex reached a peak of 470 DU around October 11 and then declined.  Inside the vortex ozone depletion rapidly took place as the sun returned with values declining to a minimum of around 125 DU in early October, after which values began to rise.   NOAA measurements indicate a much smaller ozone hole than normal during August and early September, but it then grew rapidly to around 19 million square kilometres in the second half of September.  This is smaller than the mean for the last decade, but comparable to that of 2010.   The hole shrank quickly during October, and had just about disappeared by mid November.  It was close to the smallest it has been over the last decade during the second half of October and into November.  In general the zonal minimum ozone layer temperature (between 70 and 30 hPa) was a little cooler than the normal during the early winter, however a warming event took place in late August.  The vortex split in early November, only the second time this has been seen.   The temperature throughout the main part of ozone layer is now near its maximum and is well above the Polar Stratospheric Cloud (PSC) formation temperature.  The warming event in August meant that the amount of PSC available for ozone depletion was smaller than usual, leading to the smaller, shallower ozone hole.  The fringes of the ozone hole passed over the tip of South America, the Falkland Islands and South Georgia over August 24 to 28, September 21 to 24 and October 10 to 12, whilst a spun-off fragment passed over the area between September 4 and 7.  South Georgia was under the edge of the hole between October 17 and 18.

See the final situation report for last year for information on the 2011 - 2012 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.  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).  

Observations from Halley since 1993 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, 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.

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

Halley - Total ozone:  The observing season at Halley began at the end of August, with initial observations suggesting a rapid decline from 230 DU (25% depletion) in late August to around 150 DU (50% depletion) just after the September equinox.   Values rose sharply to around 175 DU (40% depletion) in early October, before falling back to around 160 DU (45% depletion).   Mean values then rose to 310 DU (10% depletion) in early November before falling to 275 DU (25% depletion) by mid month.  Values rose to around 330 DU (10% depletion) in early December but slowly and irregularly fell to reach 270 DU (10% depletion) in mid February, where it remained until early March.  A rise to 290 DU took place in mid March, with values falling later in the month.  They were around 245 DU (20% depletion) in mid April.  The routine observing season has now finished.  The lowest daily value recorded this season was 137 DU on September 21 and 23; the highest value was 355 DU on November 9.  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 February, and the zenith sky tables of the current instrument are not yet fully determined.  The preliminary values given here should therefore be treated with some caution and may be revised by up to 10%.

Rothera - Total ozone:    Real-time graphs showing current ozone and NO2 levels.  2012 began with mean values at around 295 DU and they slowly declined to 270 DU by early May, with fluctuations on a timescale of around 20 days.  They had risen to around 315 DU by the winter solstice, but dropped to around 180 DU by mid September.  Mean values rose to around 250 DU in late September, but then fell to 155 DU in early October, with a major rise to around 340 DU in early November.  Mean values then fell back to around 255 DU in mid month, but rose to 335 DU in early December.  They began to fall later in December, and remained not far from 280 DU until late May 2013.  They have now risen to around 330 DU, the highest at this time of year for a decade.  The lowest daily value recorded this season was 132 DU on October 7; the highest value was 407 DU on November 2.  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.    The observing season at Vernadsky began in late July, when mean values were around 260 DU (15% depletion).   Early August values were around 270 DU (15% depletion) and they declined, rather erratically, to around 195 DU (40% depletion) by mid September.  Mean values then rose to around 270 DU (20% depletion) in late September before declining to 200 DU (40% depletion) in early October.  In mid month daily values rose above 300 DU, with the mean reaching 335 DU (10% depletion) in early November.  Values then fell to reach 285 DU (25% depletion).   Late in the month values rose and reached 335 DU (5% depletion) in early December.  Values began to fall later in December, albeit rather irregularly, and by the equinox were around 275 DU (10% depletion).  They remained near this value to the end of the season in the second half of May.  The routine ozone observing season has now finished, though lunar observations are possible.  The lowest daily value recorded this season was 150 DU on September 21; the highest daily value was 387 DU on November 2.  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.

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".  The 2012/13 season began early at Rothera, with sightings on May 30, 31, June 13, 26, July 9, August 1, 5, 17, 24.

Halley - 100 hPa temperature:  The mean 100 hPa temperature was generally a little below the normal during the winter and remained at around -84°C until mid September.  It had risen to around -55°C by early November, in a slightly earlier than usual spring warming.  The temperature fell back to -59°C by mid month, but then rose to a peak of -42°C in early December, where it remained until early February.  The lower ozone layer is now cooling and the 100 hPa temperature has reached -77°C.  The temperature has generally been below to close to the normal all season, apart from the short period of the spring warming in early November.

Peninsula - 100 hPa temperature:   The mean 100 hPa temperature in the Antarctic Peninsula  has been below the normal during the early winter.  The temperature is usually at its lowest at the end of August at around -76°C, but this year declined from near normal at around -75°C in early August to -80°C by late September, some 8° below the normal for the time of year.   It rose, and reached -50°C in early November, a relatively early spring warming.  It dropped to -57°C in mid month, but then rose to a peak of  -42°C in early December.  It was around -45°C until mid February, but it has slowly cooled to around -68°C.  It was above the normal from mid October to early November, in early December and from early to late April.  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, though there are notable differences between the different satellites, demonstrating the need for verification by ground based stations.  Our 2012/2013 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-emphasise 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.  The Sciamachy uv index from the ESA  Tropospheric Emission Monitoring Internet Service shows the exposure risk at any location.