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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 2009 June 18.

Situation at 2009 June 18

The 2008 ozone hole season is over and the scene is being set for the 2009 season.  Contrasts are increasing as the polar vortex builds with some circumpolar areas now above 370 DU and parts of the continent below 220 DU.  Ozone levels generally remain below normal across the continent, though there are areas above normal in the circumpolar belt.  The temperature of the ozone layer over Antarctica is cooling from the summer maximum, and an increasing area is now cold enough for polar stratospheric clouds (PSCs) to form. The ozone layer temperature remains generally a little below the normal.  

The polar vortex was very stable throughout the season, and this governed the evolution of the 2008 ozone hole.  During its initial stages, the ozone hole was much smaller than has been usual for August, but it grew rapidly as stratospheric clouds were exposed to sunlight.  It covered over 25 million square kilometres in mid September, about the same as last year and remained at around 24 million square kilometres until early October.  It shrank quite slowly, and persisted until the end of December, making it one of the longest lasting ozone holes on record.  The vortex briefly showed a more elliptical circulation pattern at the end of October, and the ozone hole extended over the tip of South America, the Falkland Islands and South Georgia between October 28th and 30th.   PSCs were seen from Rothera on several occasions and also at Halley.

See the final situation report for last year for information on the 2007 - 2008 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).  

Click on a thumbnail to get the latest graph or high resolution image.

Halley - Total ozone:    The ozone observation season started towards the end of August, and observations show that total ozone amounts fell at around 2 DU per day, from around 200 DU at the end of August (30% depletion) to around 125 DU (60% depletion) in late September.  Values rose to reach 180 DU (45% depletion) in late October, but remained there until late November.   From then they rose to reach  300 DU (10% depletion) in early January and had dropped to around 220 DU (25% depletion) by the end of the observing season in mid April.  Superimposed on the general trends are small fluctuations with periods of days to around a month.  The lowest daily value recorded was 118 DU on October 11.  The December mean was the lowest on record for the month.

Rothera - Total ozone:    Real-time graphs showing current ozone and NO2 levels.  Values were around 300 DU at the start of the year, then dropped a little, remaining at around 280 DU between mid January and mid May.  Ozone amounts rose from mid May until early July, reaching 320 DU.  From July values fell and reached 140 DU in early October.   Daily values initially rose rapidly in early October but then remained around 210 DU until late November.  Values rose to 320 DU in early December, but fell to 260 DU before rising rapidly at the end of the year.  They remained around 280 DU until early June, but have now 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 as the polar vortex rotates across the station.  The lowest value  recorded was 118 DU on October 5.  Note: The SAOZ instrument constants were revised in July, and ozone values have been increased by about 2% compared to previously published values.

Vernadsky - Total ozone:   Vernadsky station is run by the National Antarctic Scientific Centre of Ukraine.   Observations recommenced in late July and the preliminary results suggest that ozone levels dropped rapidly, and  reached ozone hole levels in early August.  They  recovered to around 270 DU in mid August, but  then dropped, reaching around 180 DU in early October (50% depletion).  Values generally rose until mid November, and reached around 290 DU (25% depletion).  Values then fell as the vortex extended over the station and reached 230 DU (40% depletion) towards the end of the month, before rising to 310 DU (15% depletion) in early December.  Values fell to 260 DU (25% depletion) in late December before rising to 290 DU (15% depletion) in early January, and they remained near 280 DU (10% depletion) until the end of the observing season.  Superimposed on the general trends are large fluctuations with periods of days to around a month, with daily values varying between 140 and 320 DU in the space of a few days.  The lowest daily value reached was 134 DU on October 5.  

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.    The Antarctic stratosphere temperature is cooling, and in some areas is already cold enough for stratospheric clouds to form.   Rothera saw this spectacular display of these clouds on 2007 July 12, and in 2008 saw them on June 3 (time lapse sequence taken by Rob Webster) and 30.   Occasionally they are seen from Halley, and this year were seen on September 2.

  
Halley - 100 hPa temperature:  The mean 100 hPa temperature at Halley remained at winter temperatures of around -83°C until early October.  It rose, somewhat unsteadily, and peaked at -40°C in mid January, close to the normal.    The stratosphere is cooling and the 100 hPa temperature has now dropped to -75°C, which is close to the normal.  The mean has remained below the normal since late August, and the December mean was the coldest on record for the month.

    
Peninsula - 100 hPa temperature:   The mean 100 hPa temperature in the Antarctic Peninsula remained at around -77°C until early October, significantly below the normal for this time of year (-74°C).  Values then slowly rose, with the final rapid spring warming occurring at the end of November.  The mean rose to -48°C in early December, a little below the normal of -44°C, and then cooled to -51°C in late December.  It peaked at -43°C in mid January, close to the normal for this time of year, but has now fallen to around -67°C, which is close to the normal for mid June.  During the spring there is often large day to day variation because the area is in the edge region of the circumpolar vortex.