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| Titel |
On the uses of a new linear scheme for stratospheric methane in global models: water source, transport tracer and radiative forcing |
| VerfasserIn |
B. M. Monge-Sanz, M. P. Chipperfield, A. Untch, J.-J. Morcrette, A. Rap, A. J. Simmons |
| 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 ; 13, no. 18 ; Nr. 13, no. 18 (2013-09-30), S.9641-9660 |
| Datensatznummer |
250085723
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| Publikation (Nr.) |
 copernicus.org/acp-13-9641-2013.pdf |
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| Zusammenfassung |
| This study evaluates effects and applications of a new linear
parameterisation for stratospheric methane and water vapour. The new scheme
(CoMeCAT) is derived from a 3-D full-chemistry-transport model (CTM). It is
suitable for any global model, and is shown here to produce realistic profiles
in the TOMCAT/SLIMCAT 3-D CTM and the ECMWF (European Centre for Medium-Range
Weather Forecasts) general circulation model (GCM). Results from the new
scheme are in good agreement with the full-chemistry CTM CH4 field and
with observations from the Halogen Occultation Experiment (HALOE). The scheme
is also used to derive stratospheric water increments, which in the CTM
produce vertical and latitudinal H2O variations in fair agreement with
satellite observations. Stratospheric H2O distributions in the ECMWF GCM
show realistic overall features, although concentrations are smaller than in
the CTM run (up to 0.5 ppmv smaller above 10 hPa). The potential of the new
CoMeCAT tracer for evaluating stratospheric transport is exploited to assess
the impacts of nudging the free-running GCM to ERA-40 and ERA-Interim
reanalyses. The nudged GCM shows similar transport patterns to the offline
CTM forced by the corresponding reanalysis data. The new scheme also impacts
radiation and temperature in the model. Compared to the default CH4
climatology and H2O used by the ECMWF radiation scheme, the main effect on
ECMWF temperatures when considering both CH4 and H2O from CoMeCAT is a
decrease of up to 1.0 K over the tropical mid/low stratosphere. The effect
of using the CoMeCAT scheme for radiative forcing (RF) calculations is
investigated using the offline Edwards–Slingo radiative transfer model.
Compared to the default model option of a tropospheric global 3-D CH4
value, the CoMeCAT distribution produces an overall change in the annual mean
net RF of up to −30 mW m−2. |
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