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| Titel |
Diagnostics of the Tropical Tropopause Layer from in-situ observations and CCM data |
| VerfasserIn |
E. Palazzi, F. Fierli, F. Cairo, C. Cagnazzo, G. Donfrancesco, E. Manzini, F. Ravegnani, C. Schiller, F. D'Amato, C. M. Volk |
| 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 ; 9, no. 24 ; Nr. 9, no. 24 (2009-12-15), S.9349-9367 |
| Datensatznummer |
250007796
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| Publikation (Nr.) |
 copernicus.org/acp-9-9349-2009.pdf |
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| Zusammenfassung |
A suite of diagnostics is applied to in-situ aircraft measurements and one
Chemistry-Climate Model (CCM) data to characterize the vertical structure of
the Tropical Tropopause Layer (TTL). The diagnostics are based on
vertical tracer profiles and relative vertical tracer gradients,
using tropopause-referenced coordinates, and
tracer-tracer relationships in the tropical Upper Troposphere/Lower
Stratosphere (UT/LS).
Observations were obtained during four tropical campaigns performed from 1999 to
2006 with the research aircraft Geophysica and have been compared to
the output of the ECHAM5/MESSy CCM. The model vertical resolution in the TTL
(~500 m) allows for appropriate comparison with high-resolution aircraft observations
and the diagnostics used highlight common TTL features between the model and
the observational data.
The analysis of the vertical profiles of water vapour, ozone, and nitrous
oxide, in both the observations and the model, shows that concentration
mixing ratios exhibit a strong gradient change across the tropical
tropopause, due to the role of this latter as a transport barrier and that
transition between the tropospheric and stratospheric regimes occurs within a
finite layer. The use of relative vertical ozone and carbon monoxide gradients, in addition to
the vertical profiles, helps to highlight the region where this transition
occurs and allows to give an estimate of its thickness. The analysis of the
CO-O3 and H2O-O3 scatter plots and of the Probability Distribution
Function (PDF) of the H2O-O3 pair completes this picture as it allows
to better distinguish tropospheric and stratospheric regimes that can be
identified by their different chemical composition.
The joint analysis and comparison of observed and modelled data allows to
state that the model can represent the background TTL structure and its
seasonal variability rather accurately. The model estimate of the thickness of the
interface region between tropospheric and stratospheric regimes agrees well
with average values inferred from observations. On the other hand, the measurements
can be influenced by regional scale variability, local transport processes as
well as deep convection, that can not be captured by the model. |
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