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| Titel |
Assimilation of IASI partial tropospheric columns with an Ensemble Kalman Filter over Europe |
| VerfasserIn |
A. Coman, G. Foret, M. Beekmann, M. Eremenko, G. Dufour, B. Gaubert, A. Ung, C. Schmechtig, J.-M. Flaud, G. Bergametti |
| 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 ; 12, no. 5 ; Nr. 12, no. 5 (2012-03-07), S.2513-2532 |
| Datensatznummer |
250010859
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| Publikation (Nr.) |
 copernicus.org/acp-12-2513-2012.pdf |
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| Zusammenfassung |
Partial lower tropospheric ozone columns provided by the IASI (Infrared
Atmospheric Sounding Interferometer) instrument have been assimilated into a
chemistry-transport model at continental scale (CHIMERE) using an Ensemble
Square Root Kalman Filter (EnSRF). Analyses are made for the month of July
2007 over the European domain. Launched in 2006, aboard the MetOp-A
satellite, IASI shows high sensitivity for ozone in the free troposphere and
low sensitivity at the ground; therefore it is important to evaluate if
assimilation of these observations can improve free tropospheric ozone, and
possibly surface ozone. The analyses are validated against independent ozone
observations from sondes, MOZAIC1 aircraft and ground based stations
(AIRBASE – the European Air quality dataBase) and compared with respect to
the free run of CHIMERE. These comparisons show a decrease in error of
6 parts-per-billion (ppb) in the free troposphere over the Frankfurt area,
and also a reduction of the root mean square error (respectively bias) at
the surface of 19% (33%) for more than 90% of existing ground
stations. This provides evidence of the potential of data assimilation of
tropospheric IASI columns to better describe the tropospheric ozone
distribution, including surface ozone, despite the lower sensitivity.
The changes in concentration resulting from the observational constraints
were quantified and several geophysical explanations for the findings of
this study were drawn. The corrections were most pronounced over Italy and
the Mediterranean region, we noted an average reduction of 8–9 ppb in the
free troposphere with respect to the free run, and still a reduction of 5.5
ppb at ground, likely due to a longer residence time of air masses in this
part associated to the general circulation pattern (i.e. dominant western
circulation) and to persistent anticyclonic conditions over the
Mediterranean basin. This is an important geophysical result, since the
ozone burden is large over this area, with impact on the radiative balance
and air quality.
1 Measurements of OZone, water
vapour, carbon monoxide and nitrogen oxides by in-service AIrbus airCraft
(http://mozaic.aero.obs-mip.fr/web/). |
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