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| Titel |
Development of a chemistry module for GCMs: first results of a multiannual integration |
| VerfasserIn |
B. Steil, M. Dameris, C. Brühl, P. J. Crutzen  , V. Grewe, M. Ponater, R. Sausen |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 16, no. 2 ; Nr. 16, no. 2, S.205-228 |
| Datensatznummer |
250013158
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| Publikation (Nr.) |
 copernicus.org/angeo-16-205-1998.pdf |
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| Zusammenfassung |
The comprehensive chemistry module CHEM has
been developed for application in general circulation models (GCMs) describing
tropospheric and stratospheric chemistry, including photochemical reactions and
heterogeneous reactions on sulphate aerosols and polar stratospheric clouds. It
has been coupled to the spectral atmospheric GCM ECHAM3. The model configuration
used in the current study has been run in an "off-line" mode, i.e. the
calculated chemical species do not affect the radiative forcing of the dynamic
fields. First results of a 15-year model integration indicate that the model
ECHAM3/CHEM runs are numerically efficient and stable, i.e. that no model drift
can be detected in dynamic and chemical parameters. The model reproduces the
main features regarding ozone, in particular intra- and interannual variability.
The ozone columns are somewhat higher than observed (approximately 10%), while
the amplitude of the annual cycle is in agreement with observations. A
comparison with HALOE data reveals, however, a serious model deficiency
regarding lower-stratosphere dynamics at high latitudes. Contrary to what is
concluded by observations, the lower stratosphere is characterized by slight
upward motions in the polar regions, so that some of the mentioned good
agreements must be considered as fortuitous. Nevertheless, ECHAM3/CHEM well
describes the chemical processes leading to ozone reduction. It has been shown
that the mean fraction of the northern hemisphere, which is covered by polar
stratospheric clouds (PSCs) as well as the temporal appearance of PSCs in the
model, is in fair agreement with observations. The model results show an
activation of chlorine inside the polar vortex which is stronger in the southern
than in the northern winter hemisphere, yielding an ozone hole over the
Antarctic; this hole, however, is also caused to a substantial degree by the
dynamics. Interhemispheric differences concerning reformation of chlorine
reservoir species HCl and ClONO2 in spring have also been well
reproduced by the model.
Key words. Atmospheric composition and structure ·
Middle atmosphere · Meteorology and atmospheric dynamics · Climatology ·
General circulation |
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