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| Titel |
Synergetic cloud fraction determination for SCIAMACHY using MERIS |
| VerfasserIn |
C. Schlundt, A. A. Kokhanovsky, W. Hoyningen-Huene, T. Dinter, L. Istomina, J. P. Burrows |
| 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 ; 4, no. 2 ; Nr. 4, no. 2 (2011-02-22), S.319-337 |
| Datensatznummer |
250001677
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| Publikation (Nr.) |
 copernicus.org/amt-4-319-2011.pdf |
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| Zusammenfassung |
Since clouds play an essential role in the Earth's climate system,
it is important to understand the cloud characteristics as well as
their distribution on a global scale using satellite observations.
The main scientific objective of SCIAMACHY
(SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY)
onboard the ENVISAT satellite is the retrieval of vertical columns of
trace gases.
On the one hand, SCIAMACHY has to be sensitive to low variations in
trace gas concentrations which means the ground pixel size has to be large enough.
On the other hand, such a large pixel size leads to the problem that
SCIAMACHY spectra are often contaminated by clouds. SCIAMACHY spectral
measurements are not well suitable to derive a reliable sub-pixel cloud fraction
that can be used as input parameter for subsequent retrievals of cloud
properties or vertical trace gas columns.
Therefore, we use MERIS/ENVISAT spectral measurements
with its high spatial resolution
as sub-pixel information for the determination of
MerIs Cloud fRation fOr Sciamachy (MICROS).
Since MERIS covers an even broader swath width than SCIAMACHY,
no problems in spatial and temporal collocation of measurements occur.
This enables the derivation of a SCIAMACHY cloud fraction with an accuracy
much higher as compared with other current cloud fractions that are based
on SCIAMACHY's PMD (Polarization Measurement Device) data.
We present our new developed MICROS algorithm, based on the threshold approach,
as well as a qualitative validation of our results
with MERIS satellite images for different locations, especially
with respect to bright surfaces such as snow/ice and sands.
In addition, the SCIAMACHY cloud fractions derived from MICROS are intercompared
with other current SCIAMACHY cloud fractions based on different approaches
demonstrating a considerable improvement regarding
geometric cloud fraction determination using the MICROS algorithm. |
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