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Titel |
Observationally derived transport diagnostics for the lowermost stratosphere and their application to the GMI chemistry and transport model |
VerfasserIn |
S. E. Strahan, B. N. Duncan, P. Hoor |
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 ; 7, no. 9 ; Nr. 7, no. 9 (2007-05-11), S.2435-2445 |
Datensatznummer |
250004958
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Publikation (Nr.) |
copernicus.org/acp-7-2435-2007.pdf |
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Zusammenfassung |
Transport from the surface to the lowermost stratosphere (LMS) can
occur on timescales of a few months or less, making it possible for
short-lived tropospheric pollutants to influence stratospheric composition
and chemistry. Models used to study this influence must demonstrate the
credibility of their chemistry and transport in the upper troposphere and
lower stratosphere (UT/LS). Data sets from satellite and aircraft
instruments measuring CO, O3, N2O, and CO2 in the UT/LS are
used to create a suite of diagnostics for the seasonally-varying transport
into and within the lowermost stratosphere, and of the coupling between the
troposphere and stratosphere in the extratropics. The diagnostics are used
to evaluate a version of the Global Modeling Initiative (GMI) Chemistry and
Transport Model (CTM) that uses a combined tropospheric and stratospheric
chemical mechanism and meteorological fields from the GEOS-4 general
circulation model. The diagnostics derived from N2O and O3 show
that the model lowermost stratosphere has realistic input from the overlying
high latitude stratosphere in all seasons. Diagnostics for the LMS show two
distinct layers. The upper layer begins ~30 K potential temperature
above the tropopause and has a strong annual cycle in its composition. The
lower layer is a mixed region ~30 K thick near the tropopause that
shows no clear seasonal variation in the degree of tropospheric coupling.
Diagnostics applied to the GMI CTM show credible seasonally-varying
transport in the LMS and a tropopause layer that is realistically coupled to
the UT in all seasons. The vertical resolution of the GMI CTM in the UT/LS,
~1 km, is sufficient to realistically represent the extratropical
tropopause layer. This study demonstrates that the GMI CTM has the transport
credibility required to study the impact of tropospheric emissions on the
stratosphere. |
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