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| Titel |
On the structural changes in the Brewer-Dobson circulation after 2000 |
| VerfasserIn |
H. Bönisch, A. Engel, Th. Birner, P. Hoor, D. W. Tarasick, E. A. Ray |
| 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 ; 11, no. 8 ; Nr. 11, no. 8 (2011-04-28), S.3937-3948 |
| Datensatznummer |
250009659
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| Publikation (Nr.) |
 copernicus.org/acp-11-3937-2011.pdf |
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| Zusammenfassung |
| In this paper we present evidence that the observed increase in tropical
upwelling after the year 2000 may be attributed to a change in the
Brewer-Dobson circulation pattern. For this purpose, we use the concept of
transit times derived from residual circulation trajectories and different
in-situ measurements of ozone and nitrous dioxide. Observations from the
Canadian midlatitude ozone profile record, probability density functions of
in-situ N2O observations and a shift of the N2O-O3
correlation slopes, taken together, indicate that the increased upwelling in
the tropics after the year 2000 appears to have triggered an intensification
of tracer transport from the tropics into the extratropics in the lower
stratosphere below about 500 K. This finding is corroborated by the fact
that transit times along the shallow branch of the residual circulation into
the LMS have decreased for the same time period (1993–2003). On a longer
time scale (1979–2009), the transit time of the shallow residual circulation
branch show a steady decrease of about −1 month/decade over the last 30 yr, while the transit times of the deep branch remain unchanged. This
highlights that changes in the upwelling across the tropical tropopause are
not sufficient as an indicator for changes in the entire Brewer-Dobson
circulation. |
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