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British
Antarctic Survey
Ozone Bulletins
Situation at 2007 December 28
The ozone hole of 2007 is over. The temperature of the ozone layer is now
highest over Antarctica and cools northwards. It is too warm for polar
stratospheric clouds (PSCs) to exist. Generally across Antarctica, ozone values
are around 300 DU. Values are now slowly dropping towards the normal autumn
normal minimum.
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.
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 is 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.
Final ozone layer situation reports
The BAS ozone web page is updated regularly, with the situation report from
the final update of the season being archived.
BAS issues regular ozone bulletins. Issues available are:
- 1
(02/11/01), 2
(2001/02 summary) (28/05/02).
- 1
(02/10/00), 2
(07/11/00), 3
(30/01/01). 4
(2000/01 summary) (11/05/01).
- 1
(06/09/99), 2
(20/09/99), 3
(04/10/99), 4
(20/10/99), 5
(1/11/99), 6
(11/11/99), 7
(30/11/99), 8
(17/12/99), 9
(10/01/00), 10
(14/02/00), 11
(12/04/00), 12
(1999/2000 summary) (02/06/00).
- 1
(24/08/98), 2
(22/09/98), 3
(02/10/98), 4
(15/10/98). 5
(30/10/98), 6
(13/11/98), 7
(1998/99 summary) (13/05/99).
- 1
(15/08/97), 2
(29/08/97), 3
(05/09/97), 4
(12/09/97), 5
(19/09/97), 6
(26/09/97), 7
(03/10/97), 8
(10/10/97), 9
(17/10/97), 10
(24/10/97), 11
(31/10/97), 12
(07/11/97), 13
(14/11/97), 14
(21/11/97), 15
(08/12/97), 16
(09/01/98), 17
(06/02/98), 18
(1997/98 summary) (25/05/98).
- Summary
(15/08/97), 1
(30/08/96), 2
(10/09/96), 3
(15/09/96), 4
(20/09/96), 5
(27/09/96), 6
(7/10/96), 7
(14/10/96), 8
(18/10/96), 9
(28/10/96), 10
(1/11/96), 11
(10/1/97), 12
(20/1/97)
- Summary
- 5
(22/09/95), 6
(02/10/95), 7
(06/10/95), 8
(13/10/95), 9
(23/10/95), 10
(30/10/95), 11
(03/11/95), 12
(10/11/95), 13
(17/11/95), 14
(03/12/95), 15
(10/12/95), 16
(19/12/95), 17
(11/06/96).
- Summary
- Summary
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