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| Titel |
On the hiatus in the acceleration of tropical upwelling since the beginning of the 21st century |
| VerfasserIn |
J. Aschmann, J. P. Burrows, C. Gebhardt, A. Rozanov, R. Hommel, M. Weber, A. M. Thompson |
| 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 ; 14, no. 23 ; Nr. 14, no. 23 (2014-12-05), S.12803-12814 |
| Datensatznummer |
250119209
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| Publikation (Nr.) |
 copernicus.org/acp-14-12803-2014.pdf |
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| Zusammenfassung |
| Chemistry–climate models predict an acceleration of the upwelling branch of
the Brewer–Dobson circulation as a consequence of increasing global surface
temperatures, resulting from elevated levels of atmospheric greenhouse gases.
The observed decrease of ozone in the tropical lower stratosphere during the
last decades of the 20th century is consistent with the anticipated
acceleration of upwelling. However, more recent satellite observations of
ozone reveal that this decrease has unexpectedly stopped in the first decade
of the 21st century, challenging the implicit assumption of a continuous
acceleration of tropical upwelling. In this study we use three decades of
chemistry-transport-model simulations (1980–2013) to investigate this
phenomenon and resolve this apparent contradiction. Aside from a high-bias
between 1985–1990, our model is able to reproduce the observed tropical
lower stratosphere ozone record. A regression analysis identifies a
significant decrease in the early period followed by a statistically robust
trend-change after 2002, in qualitative agreement with the observations. We
demonstrate that this trend-change is correlated with structural changes in
the vertical transport, represented in the model by diabatic heating rates
taken from the reanalysis product Era-Interim. These changes lead to a hiatus
in the acceleration of tropical upwelling between 70–30 hPa and a southward
shift of the tropical pipe at 30 and 100 hPa during the past decade, which
appear to be the primary causes for the observed trend-change in ozone. |
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