 |
| Titel |
The determination of cloud fraction in SCIAMACHY pixels using MERIS measurements |
| VerfasserIn |
Cornelia Martinecz, Alexander A. Kokhanovsky, Wolfgang von Hoyningen-Huene, Tilman Dinter, Marco Vountas, John P. Burrows |
| Konferenz |
EGU General Assembly 2010
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250032773
|
|
|
|
|
|
| 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. One of the main scientific objectives of SCIAMACHY (SCanning Imaging
Absorption spectroMeter for Atmospheric CHartographY) on ENVISAT is the
retrieval of cloud parameters which are also relevant for the study of tropospheric
constituents.
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 not well suitable to
derive a reliable 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 with spatial and temporal
matches 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 imageries 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 “true” cloud fraction determination using the MICROS
algorithm. |
|
|
|
|
|
|