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| Titel |
An improved cirrus detection algorithm MeCiDA2 for SEVIRI and its evaluation with MODIS |
| VerfasserIn |
F. Ewald, L. Bugliaro, H. Mannstein, B. Mayer |
| 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 ; 6, no. 2 ; Nr. 6, no. 2 (2013-02-11), S.309-322 |
| Datensatznummer |
250017391
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| Publikation (Nr.) |
 copernicus.org/amt-6-309-2013.pdf |
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| Zusammenfassung |
| In this study, a substantially improved version of the Meteosat cirrus
detection algorithm (MeCiDA2) will be presented, which now allows application
to the full earth disc visible by the Meteosat satellite. As cirrus clouds
have an influence on the radiation budget of the earth, their optical
properties and their global coverage has to be monitored at the global scale
using instruments aboard geostationary satellites. Since MeCiDA was optimised
for the area of Europe only, various changes were necessary to handle the
variable conditions found over the full Meteosat disc. Required changes
include the consideration of the viewing angle dependency and of the
sensitivity of the 9.7 μm channel to the ozone column. To this
end, a correction is implemented that minimises the influence of the
variability of the stratospheric ozone. The evaluation of the proposed
improvements is carried out by using MeCiDA applied to MODIS (moderate resolution imaging spectrometer) data to address
viewing angle-dependent cirrus detection, and by additionally comparing it to
the cloud optical properties MOD06 cirrus product. The new MeCiDA version
detects less cirrus than the original one for latitudes larger than
40°, but almost the same amount elsewhere. MeCiDA's version for MODIS
is more sensitive than that for SEVIRI (spinning enhanced visible and infrared imager) with cirrus occurrences higher by
10%, and the new MeCiDA provides almost the same cirrus coverage
(±0.1) as given by the cloud phase optical properties from MODIS for
latitudes smaller than 50°. Finally, the influence of sub-pixel
clouds on the SEVIRI cirrus detection has been examined: more than 60%
of the undetected SEVIRI cirrus pixels have a cirrus coverage smaller than
0.5. |
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