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Titel |
Comparison of CO2 retrievals from IASI-A, IASI-B and GOSAT in the thermal infrared for nearly coincident measurements over the Arctic ocean in summer |
VerfasserIn |
Claude Camy-Peyret, Jérôme Bureau, Sebastien Payan |
Konferenz |
EGU General Assembly 2015
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 17 (2015) |
Datensatznummer |
250113403
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Publikation (Nr.) |
EGU/EGU2015-13599.pdf |
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Zusammenfassung |
The capabilities to retrieve reliable information on the concentration of greenhouse gases in
the lower atmosphere from thermal infrared (TIR) spectra collected by nadir sounders is
still to be assessed. We have selected the two months period of July-August in
the high latitude polar region where it is possible to observe almost coincident or
superimposed footprints (IFOV) of the three infrared sounders considered in this
study, namely IASI-A, IASI-B (on the MetOp platforms) and TANSO-FTS (on
GOSAT). Retrievals of the column averaged mixing ratio of carbon dioxide XCO2
(and of the surface temperature) have been performed for three years i.e. 2010,
2013 and 2014 over Arctic waters. The summer period was chosen because ice free
IFOVs (in the latitude band 68N to 82N) can be selected for which retrievals are less
sensitive to surface inhomogeneity (as compared to IFOVs located over land). The
emissivity of sea water is also better constrained. The inversion configuration (using the
atmospheric window covering the so-called CO2 laser band in the interval 940-980 cm-1)
will be described. The sensitivity of the retrieved XCO2 to the different layers of
the lower atmosphere as a function of thermal contrast, temperature and humidity
profiles will be presented. The precision/accuracy of the retrieved XCO2 will be
discussed and compared between sounders. The CO2 trends is clearly captured over the
years analysed in this work. The retrieved values will be compared to similar XCO2
products available from other sources (Leicester Univ., NIES, SRON/KIT). Some
remaining spectroscopic issues in the vicinity of 948 cm-1 have been identified and
circumvented. The retrieved sea surface temperature Tsurf used as a control variable is also
providing an additional check of the performances of the retrievals and is compared
to the Eumetsat IASI Tsurf product. These results are interesting starting points
for preparing future missions like IASI-NG on MetOp-SG as well as GOSAT-2. |
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