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| Titel |
What controlls CO and H2O in the UTLS? |
| VerfasserIn |
Peter Hoor, Heini Wernli |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250039143
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| Zusammenfassung |
| The upper troposphere/lower stratosphere (UTLS) of the extratropics is affected by frequent
mixing events across the extratropical tropopause, in the region of the subtropical
jet as well as air originating from the ’tropical controlled’ transition layer above
Î=380K. The distributions of CO and H2O have been extensively used to investigate
transport and mixing across the extratropical tropopause and define the structure of the
lowermost stratosphere – particularly the extratropical transition region (ExTL).
Here, we investigate the distributions of CO and H2O in the extratropical UTLS and
their relation to transport time and Lagrangian cold point temperature, respectively,
using a statistical data set of 90-day backward trajectories driven by ERA interim
windfields.
We show that the upper boundary of H2O in the lowermost stratosphere is under
non-local controll and driven by the annual temperature cycle at the (sub-)tropical
tropopause. Using H2O ozone scatter plots from observations we show that the location of
the ExTL upper boundary deduced from water vapour is controlled by the Brewer
Dobson circulation, rather than transport across the tropopause in the extratropics. In
contrast, CO isopleths tend to follow the local tropopause mirroring the transit time of
airparcels having crossed the tropopause in the extratropics and subtropics. Thus, CO
and H2O mirror complementary properties of transport and we discuss possible
consequences for the definitions of transport regimes deduced from CO and H2O in the
UTLS. |
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