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| Titel |
Past changes in the vertical distribution of ozone – Part 3: Analysis and interpretation of trends |
| VerfasserIn |
N. R. P. Harris, B. Hassler, F. Tummon, G. E. Bodeker, D. Hubert, I. Petropavlovskikh, W. Steinbrecht, J. Anderson, P. K. Bhartia, C. D. Boone, A. Bourassa, S. M. Davis, D. Degenstein, A. Delcloo, S. M. Frith, L. Froidevaux, S. Godin-Beekmann, N. Jones, M. J. Kurylo, E. Kyrölä, M. Laine, S. T. Leblanc, J.-C. Lambert, B. Liley, E. Mahieu, A. Maycock, M. De Mazière, A. Parrish, R. Querel, K. H. Rosenlof, C. Roth, C. Sioris, J. Staehelin, R. S. Stolarski, R. Stübi, J. Tamminen, C. Vigouroux, K. A. Walker, H. J. Wang, J. Wild, J. M. Zawodny |
| 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 ; 15, no. 17 ; Nr. 15, no. 17 (2015-09-07), S.9965-9982 |
| Datensatznummer |
250120017
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| Publikation (Nr.) |
 copernicus.org/acp-15-9965-2015.pdf |
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| Zusammenfassung |
Trends in the vertical distribution of ozone are reported and compared for a
number of new and recently revised data sets. The amount of ozone-depleting
compounds in the stratosphere (as measured by equivalent effective
stratospheric chlorine – EESC) was maximised in the second half of the 1990s. We
examine the periods before and after the peak to see if any change in trend
is discernible in the ozone record that might be attributable to a change in
the EESC trend, though no attribution is attempted. Prior to 1998, trends in the
upper stratosphere (~ 45 km, 4 hPa) are found to be −5 to −10 % per decade at mid-latitudes and closer to −5 % per decade in the
tropics. No trends are found in the mid-stratosphere (28 km, 30 hPa).
Negative trends are seen in the lower stratosphere at mid-latitudes in both
hemispheres and in the deep tropics. However, it is hard to be categorical
about the trends in the lower stratosphere for three reasons: (i) there are
fewer measurements, (ii) the data quality is poorer, and (iii) the
measurements in the 1990s are perturbed by aerosols from the Mt Pinatubo
eruption in 1991. These findings are similar to those reported previously
even though the measurements for the main satellite and ground-based records
have been revised.
There is no sign of a continued negative trend in the upper stratosphere
since 1998: instead there is a hint of an average positive trend of
~ 2 % per decade in mid-latitudes and ~ 3 %
per decade in the tropics. The significance of these upward trends is
investigated using different assumptions of the independence of the trend
estimates found from different data sets. The averaged upward trends are
significant if the trends derived from various data sets are assumed to be
independent (as in Pawson et al., 2014) but are generally not significant if the
trends are not independent. This occurs because many of the underlying
measurement records are used in more than one merged data set. At this point
it is not possible to say which assumption is best. Including an estimate of
the drift of the overall ozone observing system decreases the significance
of the trends. The significance will become clearer as (i) more years are
added to the observational record, (ii) further improvements are made to the
historic ozone record (e.g. through algorithm development), and (iii) the
data merging techniques are refined, particularly through a more rigorous
treatment of uncertainties. |
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