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| Titel |
Seasonal and inter-annual variations in troposphere-to-stratosphere transport from the tropical tropopause layer |
| VerfasserIn |
J. G. Levine, P. Braesicke, N. R. P. Harris, J. A. Pyle |
| 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 ; 8, no. 13 ; Nr. 8, no. 13 (2008-07-10), S.3689-3703 |
| Datensatznummer |
250006278
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| Publikation (Nr.) |
 copernicus.org/acp-8-3689-2008.pdf |
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| Zusammenfassung |
| In an earlier study of troposphere-to-stratosphere transport (TST) via the
tropical tropopause layer (TTL), we found that the vast majority of air
parcels undergoing TST from the base of the TTL enter the extratropical
lowermost stratosphere quasi-horizontally and show little or no regional
preference with regards to origin in the TTL or entry into the stratosphere.
We have since repeated the trajectory calculations – originally limited to a
single Northern Hemisphere winter period – in a variety of months and years
to assess how robust our earlier findings are to change of timing. To first
order, we find that the main conclusions hold, irrespective of the season,
year and phase of the El Niño Southern Oscillation (ENSO). We also
explore: the distribution of TST between the Northern and Southern Hemispheres; the sensitivity of modelled TST to the definition of the
tropopause; and the routes by which air parcels undergo transport
exclusively to the stratospheric overworld. Subject to a dynamical
definition of the tropopause, we identify a strong bias towards TST in the
Southern Hemisphere, particularly during the Northern Hemisphere summer. The
thermal tropopause, defined according to the World Meteorological
Organization, lies above the dynamical tropopause throughout the
extratropics. Inevitably, on switching to the thermal definition, we
calculate much less transport across the tropopause, particularly in the
subtropics, which could be important with regards to interpretation of
processes affecting ozone chemistry in the extratropical lowermost
stratosphere (ELS). In contrast to the rather homogeneous nature of TST into
the ELS, we find that transport to the overworld takes place from relatively
well-defined regions of the TTL, predominantly above the West Pacific and
Indonesia, except for an El Niño period in which most transport takes
place from regions above the East Pacific and South America. |
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