Record Depletion of Arctic Ozone – 2011
2011 has seen the largest ever depletion of Arctic stratospheric ozone. Studies carried out by the Alfred Wegener
Institute for Polar and Marine Research in the Helmholtz Association (AWI) have just confirmed that
anthropogenic destruction of Arctic ozone has never been so evident.
See the press release from the Alfred Wegener Institute at:
[http://www.awi.de/en/news/press_releases/detail/item/record_depletion_of_arctic_ozone_layer_caused_incre
ased_uv_radiation_in_scandinavia/?cHash=d1e47412e17142c25c7a361a4229653b].
The World Meteorological Organization (WMO) also issued a press release in parallel to this work, it can be
viewed at:
[http://www.wmo.int/pages/mediacentre/press_releases/pr_912_en.html]
Ozone is a gas that is found throughout the atmosphere but has its strongest concentrations in a region called the
stratosphere. The majority of this ozone over Ireland is found in between the heights 15km – 30km and is
frequently referred to as the ‘ozone layer’. This ozone layer acts as a shield that helps block most of the harmful
ultraviolet radiation from the sun reaching the ground. Exposure to ultraviolet radiation can lead to a higher risk
of skin cancer, eye cataracts and crop failure.
For ozone destruction to occur, three conditions are required; very cold stratospheric temperatures, sunlight and
the presence of ozone depleting substances such as industrial chlorofluorocarbons (CFCs) or related compounds.
Ozone destruction was particular large this year due to unusually low temperatures in the atmosphere above the
Arctic.
The Montreal Protocol (and its amendments) has dramatically reduced the industrial release of further CFCs into
the atmosphere. Despite the record low levels of Arctic ozone this year it is still expected that the depletion of
ozone due to CFCs will not be a significant concern towards the end of the century. But as the existing CFC
‘burden’ already in the atmosphere will take many years before they it is naturally removed, seasonal ozone
destruction will continue into the near future. Monitoring the ozone layer remains of critical importance.
Monitoring Stratospheric Ozone in Ireland
Met Éireann monitors stratospheric ozone above Ireland from its Meteorological and Geophysical Observatory at
Valentia, Caherciveen, Co. Kerry. Two monitoring techniques are utilised to measure ozone high above Ireland.
One is a ground based instrument called a Brewer Spectrophotometer, the other is a device called an Ozonesonde
which is launched into the atmosphere attached to a weather balloon.
Total Column Ozone (Brewer Spectrophotometer)
The MK IV Brewer Ozone Spectrophotometer #088 was installed at Valentia Observatory in February 1993. It has
been in constant operation ever since. The Brewer is an automated instrument which is continuously taking
measurements during daylight hours. Much information is contained in the light coming from the sun. By
analysing the light reaching the ground, information on the Earth’s atmosphere, which the light has just passed
through, can be extracted. The Brewer instrument uses this technique to make very accurate total column ozone
measurements when the sun is directly visible (a Direct Sun [DS] measurement) and can also make a good
approximation of total column ozone in cloudy conditions (a Zenith Sky [ZS] measurement).
Met Éireann Valentia Observatory - April 2011
Fig.1 MkIV Brewer #088 located at Met Éireann’s
Valentia Observatory, Co. Kerry
Fig.2 The ozone time series for Valentia in 2010. Direct sun data (DS;
red), zenith sky data (ZS; blue) and smoothed DS data (green) are
shown. The dashed blues lines show the typical climatological
variation of ozone expected at Valentia. (Graphic generated by the
WOUDC)
Vertical Profile Ozone (Ozonesondes)
Since January 1994 Valentia Observatory has run an Ozonesonde programme, monitoring vertical ozone profiles
in air masses moving into Ireland / Europe from the Atlantic. Valentia uses ECC6A ozonesondes (ECC 5A 1994 1997) which are flown on meteorological weather balloons. An ozonesonde is based on a mechanical pump which
sucks air in from its surroundings and passes it through a chemical sensing cell. From this the ozone concentration
in the sampled air can be determined.
Fig.3 A typical example of a vertical ozonesonde profile from
Valentia Observatory showing the height and concentration
of the ozone layer above Ireland.
Fig.4 Looking at a year’s worth of weekly ozonesonde ascents side
by side one can see the varying nature of stratospheric ozone
above Ireland. (Graphic generated by the WOUDC)
Met Éireann Valentia Observatory - April 2011
Combining total column ozone and vertical profiles
Both the total column ozone measurements from the Brewer and the vertical profile measurements from the
ozonesondes have their advantages. The Brewer can provide routine automated ozone measurements
throughout the day. The ozonesondes provide important information on the vertical structure of the ozone layer.
Combining the two programmes greatly complement each other as well as providing a useful quality control tool.
Fig.5 This graph compares the total column ozone as measured by the Brewer at Valentia (blue), the value obtained by the NASA Ozone
Monitoring Instrument onboard the AURA satellite (green) and the integrated ozone value as derived from ozonesondes at Valentia (red).
Excellent agreement can be seen between the three ozone monitoring techniques.
By combining ground, balloon and satellite ozone observations from all over the world, the annual cycle of ozone
and it hopeful future recovery can be monitored and measured.
For further information contact: Met Éireann, Valentia Observatory, Caherciveen, Co. Kerry, Ireland
Tel: +353 (0)66 9473460 Email: [email protected]
Other Links of interest:
The European Space Agency - Record loss of ozone over Arctic
http://www.esa.int/esaCP/SEMIF24SZLG_index_0.html
World Ozone and Ultraviolet Data Centre (WOUDC) – Ozone maps
http://woudc.ec.gc.ca/e/ozone/Curr_allmap_g.htm
NASA – Ozone facts
http://ozonewatch.gsfc.nasa.gov/facts/ozone.html
Met Éireann Valentia Observatory - April 2011