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| Titel |
An unusual stratospheric ozone decrease in the Southern Hemisphere subtropics linked to isentropic air-mass transport as observed over Irene (25.5° S, 28.1° E) in mid-May 2002 |
| VerfasserIn |
N. Semane, H. Bencherif, B. Morel, A. Hauchecorne, R. D. Diab |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 6, no. 7 ; Nr. 6, no. 7 (2006-06-02), S.1927-1936 |
| Datensatznummer |
250003898
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| Publikation (Nr.) |
 copernicus.org/acp-6-1927-2006.pdf |
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| Zusammenfassung |
| A prominent ozone minimum of less than 240 Dobson Units (DU) was observed
over Irene (25.5° S, 28.1° E), a subtropical site in the Southern
Hemisphere, by the Total Ozone Mapping Spectrometer (TOMS) during May 2002
with an extremely low ozone value of less than 219 DU recorded on 12 May,
as compared to the climatological mean value of 249 DU for May between
1999 and 2005. In this study, the vertical structure of this ozone minimum
is examined using ozonesonde measurements performed over Irene on 15 May 2002,
when the total ozone (as given by TOMS) was about 226 DU. It is shown
that this ozone minimum is of Antarctic polar origin with a low-ozone layer
in the middle stratosphere above 625 K (where the climatological ozone
gradient points equatorward), and is of tropical origin with a low-ozone
layer in the lower stratosphere between the 400-K and 450-K isentropic
levels (where the climatological ozone gradient is reversed). The upper and
lower depleted parts of the ozonesonde profile for 15 May are then
respectively attributed to equatorward and poleward transport of low-ozone
air toward the subtropics in the Southern Hemisphere. The tropical air
moving over Irene and the polar one passing over the same area associated
with enhanced planetary-wave activity are successfully simulated using the
high-resolution advection contour model of Ertel's potential vorticity
MIMOSA. The unusual distribution of ozone over Irene during May 2002 in the
middle stratosphere is connected to the anomalously pre-conditioned
structure of the polar vortex at that time of the year. The winter
stratospheric wave driving leading to the ozone minimum is investigated by
means of the Eliassen-Palm flux computed from the European Center for
Medium-range Weather Forecasts (ECMWF) ERA40 re-analyses. |
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