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| Titel |
A modelling study of tropospheric distributions of the trace gases CFCl3 and CH3CCl3 in the 1980s |
| VerfasserIn |
K.-Y. Wang, D. E. Shallcross |
| 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 ; 18, no. 8 ; Nr. 18, no. 8, S.972-986 |
| Datensatznummer |
250014047
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| Publikation (Nr.) |
 copernicus.org/angeo-18-972-2000.pdf |
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| Zusammenfassung |
Interhemispheric transport is a key process
affecting the accuracy of source quantification for species such as methane by
inverse modelling, and is a source of difference among global three-dimensional
chemistry transport models (CTMs). Here we use long-term observations of the
atmospheric concentration of long-lived species such as CH3CCl3
and CFCl3 for testing three-dimensional chemistry transport models (CTMs);
notably their ability to model the interhemispheric transport, distribution,
trend, and variability of trace gases in the troposphere. The very striking
contrast between the inhomogeneous source distribution and the nearly
homogeneous trend, observed in the global ALE/GAGE experiments for both CH3CCl3
and CFCl3 illustrates an efficient interhemispheric transport of
atmospherically long-lived chemical species. Analysis of the modelling data at
two tropical stations, Barbados (13° N, 59° W) and Samoa
(14° S, 124° W), show the close relationship between
inter-hemispheric transport and cross-equator Hadley circulations. We found that
cross-equator Hadley circulations play a key role in producing the globally
homogeneous observed trends. Chemically, the most rapid interaction between CH3CCl3
and OH occurs in the northern summer troposphere; while the most rapid
photolysis of CH3CCl3 and CFCl3, and the
chemical reactions between CFCl3 and O(1D), take place in
the southern summer stratosphere. Therefore, the cross-equator Hadley
circulation plays a key role which regulates the southward flux of chemical
species. The regulation by the Hadley circulations hence determines the amount
of air to be processed by OH, O(1D), and ultraviolet photolysis, in
both hemispheres. In summary, the dynamic regulation of the Hadley circulations,
and the chemical processing (which crucially depends on the concentration of OH,
O(1D), and on the intensity of solar insolation) of the air
contribute to the seasonal variability and homogeneous growth rate of observed
CH3CCl3 and CFCl3.
Key words: Atmospheric composition and structure
(middle atmosphere - composition and chemistry; pollution - urban and regional)
- Meteorology and atmospheric dynamics (convective processes) |
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