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| Titel |
Retrieval of tropospheric CO column from hyperspectral infrared sounders – application to four years of Aqua/AIRS and MetOp-A/IASI |
| VerfasserIn |
T. Thonat, C. Crevoisier, N. A. Scott, A. Chédin, T. Schuck, R. Armante, L. Crépeau |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1867-1381
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Measurement Techniques ; 5, no. 10 ; Nr. 5, no. 10 (2012-10-17), S.2413-2429 |
| Datensatznummer |
250003123
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| Publikation (Nr.) |
 copernicus.org/amt-5-2413-2012.pdf |
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| Zusammenfassung |
| Four years of tropospheric integrated content of
CO were retrieved from infrared hyperspectral observations of AIRS onboard
Aqua and IASI onboard MetOp-A, for the period July 2007–June 2011. The
retrieval method is based on a double differential approach that relies on
the difference between brightness temperatures observed by the sounder and
BT simulated by the Automatised Atmospheric Absorption Atlas (4A) radiative
transfer model on colocated ECMWF reanalyses, for several couples of
channels located in the 4.67 μm CO band. AIRS and IASI give access to
similar integrated contents of CO with a maximum sensitivity near 450 hPa
and a half-height width of the weighting function between 200 and 750 hPa
depending on the thermal contrast (i.e., the difference between the surface
temperature and the temperature of the first pressure level). However,
differences in their spectral and radiometric characteristics yield
differences in the retrieval characteristics with AIRS selected couples of
channels being more sensitive to surface characteristics. Moreover, IASI
covers the whole CO absorption band, with a 3 times better spectral
resolution, giving access to channels presenting a 3 times higher signal to
noise ratio. This results in a better precision and lower standard deviation
of the IASI retrievals. Conservatively, comparisons with CARIBIC aircraft
measurements yield an averaged relative difference of 3.4% for IASI and
4.9% for AIRS. On average, AIRS and IASI retrievals are in very good
agreement, showing the same seasonality, seasonal amplitudes, interannual
variability and spatial distribution. The analysis of the monthly evolution
of CO particularly highlights the expected strong influence of biomass
burning on the evolution of CO in several tropical regions. In particular, a
sharp increase in CO in 2010 in the southern tropics, especially over South
America and South Africa, is observed, and is shown to be related to El
Niño and to the Atlantic Multidecadal Oscillation. |
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