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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 2008 July 4.

Situation at 2008 June 3

The ozone hole of 2007 ended at around the time of the summer solstice.   The temperature of the ozone layer is now coolest over Antarctica and warmest in the circum-polar region.  It is cold enough for polar stratospheric clouds (PSCs) to exist and they have already been seen from Rothera.  Temperatures are dropping further as winter progresses.  Ozone values are above 350 DU in parts of the circum-polar regions as the circum-polar vortex builds, dropping to around 250 DU towards the pole and equator.  Ozone values are quite low in the Atlantic sector and it seems likely that some ozone depletion is already taking place.

In general the circum-polar stratospheric vortex was more disturbed this year than it was last year, however there were also periods of stability.  Some areas of Antarctica saw ozone values down to ozone hole levels (less than 220 DU) in mid June, suggesting the possibility of early chemical depletion, combined with some dynamic processes.  In mid July the minimum temperature of the Antarctic stratosphere at 70 & 50 hPa was close to the normal, although that at 30 hPa was below the normal, and I suggested the likelihood of another strong ozone hole year.  Early August saw the largest ozone hole recorded for this time of year, although at the same time very high ozone levels existed over the northern Antarctic Peninsula.  The vortex was more circular in mid September but returned to an elliptical shape and initially warmed slowly.  In mid September the ozone hole area reached a maximum of just over 24 million square kilometres, but it then slowly shrank as the vortex warmed further.  A spring warming took place over the Pacific coast of Antarctica and the Antarctic Peninsula in late October, however this subsided as the ozone hole became more symmetric again.  A second major warming took place towards the end of November, but subsided in early December.   Around December 8 the ozone hole was briefly the largest on record for the date.   The tip of South America and the Falkland Islands saw ozone levels below 250 DU on August 24, with South Georgia experiencing similar levels on September 4.  The fringes of the ozone hole were over South Georgia on September 11.  The area was intermittently affected from September 22 to October 22, with South Georgia particularly affected on September 25, when values dropped below 175 DU. The Falklands and South Georgia were affected for a final time between November 23 and 25.

See the final situation report for last year for information on the 2006 - 2007 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.  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).  

The September 27th edition of Nature has a news item that calls into question existing theories that explain the formation of the ozone hole.  The note details research which shows that the rate of photolysis of the chlorine monoxide dimer may be an order of magnitude lower than previously thought.  Whilst this needs further investigation and verification by other groups, it does not invalidate previous work which shows an unequivocal link between the abundance of chlorine monoxide and ozone depletion.  The news note does not mention bromine monoxide, which also plays a significant part in ozone depletion.

Click on a thumbnail to get the latest graph.

Halley - Total ozone:    Some lunar observations made in late July suggest that ozone levels were near normal.  The first zenith observations, of low accuracy,  made in late August show that mean ozone values were around 190 DU (35% depletion), and they had dropped to around 130 DU (55% depletion) by the end of September.  Mean values had risen to around 140 DU (55% depletion) by mid October and then rose more quickly to reach 250 DU (25% depletion) by early November.  By mid month values had dropped back to 180 DU (50% depletion), but had climbed to 260 DU (30% depletion) in early December.   Values again fell, with the daily value below 220 DU (40% depletion) on December 7, however mean values then rose to a maximum of around 310 DU (10% depletion) in mid month.  Values slowly fell to the autumn minimum and had reached 260 DU (15% depletion) by mid April.  Day to day variation rose when the station was closer to the edge of the polar vortex.  The lowest value recorded was 118 DU on October 3.  A daily mean of 323 DU was recorded on November 4 and 333 DU on December 25.  The ozone observation season has now ended.

Rothera - Total ozone:    At the beginning of 2007 ozone values had commenced the decline to the autumn minimum and reached around 250 DU in mid March.  Daily values rose above 300 DU at the beginning of April, but were generally around 270 DU until early June, with variation due to planetary wave activity.  Very low values were recorded in the second half of June, falling below 220 DU at times.  Values then rose as the mid latitude high ozone belt extended further south, reaching over 360 DU in late July, before falling to ozone hole levels by mid August.   The station is often near the edge region of the ozone hole and values can change dramatically from one day to the next.  Mean values dropped to around 120 DU in late September, but then slowly rose, followed by a rapid rise to around 350 DU in late October.  By mid November they had dropped back to below 200 DU but thereafter rose to reach summer values around 320 DU by the end of the month.  Total ozone levels then fell towards the autumn minimum, and had dropped to around 280 DU at the end of 2007.  The lowest value recorded  was 102 DU on September 23.  The new SAOZ became the operational instrument from January 1 and produces real-time graphs showing current ozone and NO2 levels.  Values dropped a little, with a broad autumnal minimum of around 270 DU between mid January and mid March.  Values rose a little to reach around 290 DU in early April.  They are now around 270 DU.

Vernadsky - Total ozone:   Vernadsky station is run by the National Antarctic Scientific Centre of Ukraine.   Early observations showed that ozone levels rose at the end of July to reach over 350 DU.  By the beginning of August they had returned to near the normal of 320 DU and were declining rapidly; they reached 200 DU (40% depletion) by the end of the month.  During the first week of September values rose to 240 DU (25% depletion), with near normal values on some days, but dropped during the rest of the month.  Late in the month mean values bottomed out at around 160 DU (50% depletion).  In early November they had risen to around 370 DU, close to the normal for this time of year, however they dropped back to 240 DU (40% depletion) in the second half of the month, before rising to summer values around 330 DU (10% depletion) at the end of the month.   By late March they were near the autumn minimum, at around 280 DU (10% depletion), and remained around this level into May.  The lowest daily value was 134 DU on September 29.  The station is often near the edge region of the ozone hole and values can change dramatically from one day to the next.

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.    Rothera saw this spectacular display of these clouds on 2007 July 12, and also so them on August 12, 14, 15 and 17.  The Antarctic stratosphere temperature is now cooling and  PSCs have already formed, as is shown in this time lapse sequence taken by Rob Webster at Rothera on June 3. 

  
Halley - 100 hPa temperature:  The 100 hPa temperature at Halley reached the late winter minimum at around -85°C in late August and then rose slowly to reach -80°C in mid October.  More rapid warming then took place, and the temperature had reached -66°C by early November, but then fell back to -70° by mid month.  After that, the temperature generally rose to a peak of -44°C in mid December, but then dropped and was significantly below the normal into the new year.  Maximum temperatures of around -42°C were reached in mid January, and since then slow cooling has taken place, reaching -61°C by the end of April.  In general the temperature has remained a little below the normal.

    
Peninsula - 100 hPa temperature:   The 100 hPa temperature in the Antarctic Peninsula area reached minimum values below -80°C during August, September and early October.  The temperature rose rapidly in late October to well above the normal in a relatively early spring warming event.  As the vortex relaxed to a more circular form temperatures fell and in mid November were significantly below the seasonal normal of  -52°C, but recovered by the end of the month to near normal values around -45°C, where they remained into the New Year.  The temperature is now slowly falling, and was around -56°C at the end of April.  In general the temperature has been a little below the normal over the past three months.