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| Titel |
Combined assimilation of IASI and MLS observations to constrain tropospheric and stratospheric ozone in a global chemical transport model |
| VerfasserIn |
E. Emili, B. Barret, S. Massart, E. Le Flochmoen, A. Piacentini, L. El Amraoui, O. Pannekoucke, D. Cariolle |
| 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 ; 14, no. 1 ; Nr. 14, no. 1 (2014-01-08), S.177-198 |
| Datensatznummer |
250118251
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| Publikation (Nr.) |
 copernicus.org/acp-14-177-2014.pdf |
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| Zusammenfassung |
| Accurate and temporally resolved fields of free-troposphere ozone are of
major importance to quantify the intercontinental transport of pollution and
the ozone radiative forcing. We consider a global chemical transport model
(MOdèle de Chimie Atmosphérique à Grande Échelle, MOCAGE) in
combination with a linear ozone chemistry scheme to examine the impact of
assimilating observations from the Microwave Limb Sounder (MLS) and the
Infrared Atmospheric Sounding Interferometer (IASI). The assimilation of the
two instruments is performed by means of a variational algorithm (4D-VAR) and
allows to constrain stratospheric and tropospheric ozone simultaneously. The
analysis is first computed for the months of August and November 2008 and
validated against ozonesonde measurements to verify the presence of
observations and model biases. Furthermore, a longer analysis of 6 months
(July–December 2008) showed that the combined assimilation of MLS and IASI is
able to globally reduce the uncertainty (root mean square error, RMSE) of the
modeled ozone columns from 30 to 15% in the
upper troposphere/lower stratosphere (UTLS, 70–225 hPa). The assimilation of
IASI tropospheric ozone observations (1000–225 hPa columns, TOC – tropospheric O3 column)
decreases the RMSE of the model from 40 to 20% in the tropics
(30° S–30° N), whereas it is not effective at higher latitudes.
Results are confirmed by a comparison with additional ozone data sets like the
Measurements of OZone and wAter vapour by aIrbus in-service airCraft (MOZAIC)
data, the Ozone Monitoring Instrument (OMI) total ozone columns and several
high-altitude surface measurements. Finally, the analysis is found to be
insensitive to the assimilation parameters. We conclude that the combination
of a simplified ozone chemistry scheme with frequent satellite observations
is a valuable tool for the long-term analysis of stratospheric and
free-tropospheric ozone. |
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