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| Titel |
Assessment of the calibration performance of satellite visible channels using cloud targets: application to Meteosat-8/9 and MTSAT-1R |
| VerfasserIn |
S.-H. Ham, B. J. Sohn |
| 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 ; 10, no. 22 ; Nr. 10, no. 22 (2010-11-25), S.11131-11149 |
| Datensatznummer |
250008913
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| Publikation (Nr.) |
 copernicus.org/acp-10-11131-2010.pdf |
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| Zusammenfassung |
To examine the calibration performance of the Meteosat-8/9 Spinning Enhanced
Visible Infra-Red Imager (SEVIRI) 0.640-μm and the Multi-functional
Transport Satellite (MTSAT)-1R 0.724-μm channels, three calibration
methods are employed. Total eight months during the 2004–2007 period are
used for SEVIRI, and total seven months during the 2007–2008 period are
used for MTSAT-1R. First, a ray-matching technique is used to compare
Meteosat-8/9 and MTSAT-1R visible channel reflectances with the
well-calibrated Moderate Resolution Imaging Spectroradiometer (MODIS)
0.646-μm channel reflectances. Spectral differences of the response
function between the two channels of interest are taken into account for the
comparison. Second, collocated MODIS cloud products are used as inputs to a
radiative transfer model (RTM) to calculate Meteosat-8/9 and MTSAT-1R
visible channel reflectances. In the simulation, cloud three-dimensional
(3-D) radiative effect associated with subgrid variations is taken into
account using the lognormal-independent column approximation (LN-ICA) to
minimize the simulation bias caused by the plane-parallel homogeneous
assumption. Third, an independent method uses the typical optical properties
of deep convective clouds (DCCs) to simulate reflectances of selected DCC
targets.
Although all three methods are not in perfect agreement, the results suggest
that calibration coefficients of Meteosat-8/9 0.640-μm channels are
underestimated by 6–7%. On the other hand, the calibration accuracy of
MTSAT-1R visible channel appears to be variable with the target reflectance
itself because of an underestimate of calibration coefficient (up to 20%)
and a non-zero space offset. The results further suggest that the solar
channel calibration scheme combining the three methods in this paper can be
used as a tool to monitor the calibration performance of visible sensors
that are particularly not equipped with an onboard calibration system. |
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