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| Titel |
Equatorial total column of nitrous oxide as measured by IASI on MetOp-A: implications for transport processes |
| VerfasserIn |
P. Ricaud, J.-L. Attié, H. Teyssèdre, L. Amraoui, V.-H. Peuch, M. Matricardi, P. Schluessel |
| 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 ; 9, no. 12 ; Nr. 9, no. 12 (2009-06-17), S.3947-3956 |
| Datensatznummer |
250007428
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| Publikation (Nr.) |
 copernicus.org/acp-9-3947-2009.pdf |
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| Zusammenfassung |
| In this paper we use the total columns of nitrous oxide (N2O) as
retrieved from the radiance spectra as measured by the Infrared Atmospheric
Sounding Interferometer (IASI) instrument aboard the MetOp-A platform and
distributed by the European Organisation for the Exploitation of
Meteorological Satellites (EUMETSAT) during the March–May (MAM) 2008 period.
Since the total column of N2O reflects concentrations in the middle
troposphere, cloud-free columnar N2O measurements are used to assess
transport processes in the equatorial band (10° S–10° N). We compare
the measured data set with the outputs produced by the 3-D chemical-transport
model MOCAGE during the period MAM 2002–2004. To reflect MAM 2008
concentrations, MOCAGE results have been scaled by a factor 1.0125 in order
to represent the change in concentration of N2O since 2004. IASI
N2O equatorial measurements show a maximum over Africa (4.96×10−3 kg m−2)
and a minimum over South America (4.86×10−3 kg m−2)
in reasonable agreement with the outputs from MOCAGE despite the fact that
emissions of N2O are more intense over America than over Africa. The
amplitude of the longitudinal variation of total column N2O along the
equatorial band is twice as intense in the measurements (~1.6%)
than as in the model calculations (~0.8%), and much greater than
the IASI mean random error (0.16–0.33%). A difference between the two
data sets is observed above the Western Pacific (110° E–150° E) with a
marked minimum in IASI compared to MOCAGE. Recent theoretical studies
(Ricaud et al., 2007 and 2009) have shown the potentially important effect
of the Walker and the Hadley cells on the tropospheric distribution of
N2O in producing a local maximum in N2O above Africa. Based on
equatorial total columns of N2O retrieved from IASI, our results are
consistent with the fact that Africa is a zone of convergence of airmasses
coming from different convective regions whilst Western Pacific behaves more
like a divergence zone. |
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