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| Titel |
Change in ozone depletion rates beginning in the mid 1990s: trend analyses of the TOMS/ SBUV merged total ozone data, 1978-2003 |
| VerfasserIn |
J. W. Krzyścin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 24, no. 2 ; Nr. 24, no. 2 (2006-03-23), S.493-502 |
| Datensatznummer |
250015489
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| Publikation (Nr.) |
 copernicus.org/angeo-24-493-2006.pdf |
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| Zusammenfassung |
| Statistical analyses have been applied to the gridded
monthly means of total ozone from combined TOMS and SBUV measurements
(version 8 of the data) for the period 1978-2003. We focus on the detection of a
change in the trend pattern by searching for a turnaround in the previous
downward trend. The ozone time series have been examined separately for each
grid point and season, taking into account the various descriptions of the trend
term: double-linear, proportional to the index of the overall chlorine content in
the stratosphere, and a smooth curve without an a priori defined shape (the
output of the regression model). Standard explanatory variables representing
physical and chemical processes known to influence the ozone distribution
have been considered: Mg II index, QBO wind at 10 and 30 hPa, zonal wind
anomalies at 50 hPa along the 60° north or 60° south circle, the index of
the stratospheric aerosols loading in the NH or SH, and the tropopause pressure. The
multivariate adaptive regression splines methodology is used to find an
optimal set of the explanatory variables and shape of the trend curve. The
statistical errors of the models' estimates have been calculated using block
bootstrapping of the models' residuals. The results appear to be consistent
among models using different formulations of the trend pattern. The 2003
level of total ozone after the removal of the variations due to the
parameterized dynamical/chemical forcing on the ozone is still below the
long-term (1978-2003) mean level over the extratropical regions. The deficit
is ~2-5% in the NH and much larger in the SH and exhibits clear seasonal
variability, ~15% in autumn, ~10% in winter, and
~-5% in spring and summer. The present total ozone level is higher beyond
the tropics than that in the mid 1990s but it is too early to announce a
beginning of the ozone recovery there because of the trend uncertainties, due
to errors of the regression estimates for individual grid points and
longitudinal variability of the trend pattern. A rigorous statistical test
has shown the statistically significant turnaround for some grid points over
the extratropical region and a deepening of the ozone negative trend has not
been found for any grid point. |
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