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Ozone loss in the Arctic from 1988-89 to present.
| Reference details: |
Sixth European Symp. on Stratospheric Ozone, Göteborg, Sweden 2-6 September 2002. Abstracts of presentations and posters. p.20. http://www.ozone-sec.ch.cam.ac.uk/EORCU/Workshops/Sixthabstracts2.pdf |
| Type: |
Parts of books/reports - KAP |
| Year: |
2002 |
| Authors: |
Braathen, G.O., Sinnhuber, B.M. and Müller, M. |
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Synopsis:
Presenter: G. Braathen
geir@nilu.no
Several of the winters during the 1990s were characterised by substantial ozone loss in the north
polar vortex. The Arctic sonde network built during the last decade makes it possible to quantify
this loss throughout the winter. The ozone mixing ratio based on ozonesonde data from a number
of stations is studied as function of time at several isentropic levels from 400 to 550K. Data from
16 stations between 60 and 83ºN have been used in the study. The ozone data are corrected for
the diabatic descent that takes place during the winter. Diabatic descent has been calculated with
the Cambridge SLIMCAT model. The model calculated descent has been checked against highprecision
tracer measurements. This comparison shows good agreement between modelled and
measured descent around 475K. A tracer-tracer correlation (N2O vs CFC-11) also shows that the
amount of mixing across the vortex edge at 475K was negligible during mid-winter (late Jan. to
early March) of 2000. This means that the observed ozone loss, after the effect of diabatic
descent has been accounted for, represents the chemical ozone loss. Results for the 475K level
show that the degree of chemically-induced ozone loss varies a lot from year to year. It is clear
from the comparison between the ozone loss and the PSC area that the winters with the biggest
ozone loss are the winters that have been cold most of the time from early January and into
March. A cold spell, where T drops below TNAT at the end of the winter will of course cause
substantial ozone loss, but it will not be enough to cause the same accumulated loss as the most
severe winters. The three winters with the most severe loss are 1994-95, 1995-96 and 1999-00.
All these winters had PSC temperatures from early December and through most of the winter.
Two winters with late cold spells were 1993-94 and 1996-97, but these winters had much less
PSCs during the early winter. Whereas the accumulated loss for the three severe winters was
around 70% at 475 K, the 1993-94 and 1996-97 winters experienced a loss of 38 and 47%,
respectively.
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