 |
| Titel |
Quantification of broken and inhomogeneous cloud impact on satellite cloud-phase retrievals |
| VerfasserIn |
E. L. A. Wolters, H. M. Deneke, B. J. J. M. van den Hurk, J. F. Meirink, R. A. Roebeling |
| Konferenz |
EGU General Assembly 2009
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250027783
|
|
|
|
|
|
| Zusammenfassung |
| One of the basic variables necessary for the development of accurate climate model cloud
parameterizations is the global distribution of cloud thermodynamic phase, i.e.,
whether clouds are composed of either ice or water particles or a combination of both.
Within EUMETSAT’s Climate Monitoring Satellite Application Facility (CM-SAF),
a technique was developed to discriminate water from ice clouds, using visible
(0.6 μm), near-infrared (1.6 μm), and thermal infrared (10.8 μm) spectral channel
radiances.
This presentation addresses the question to what extent broken cloudiness and cloud
horizonal inhomogeneity influence satellite cloud-phase retrievals at different spatial
resolutions and for two climate regions (subtropical ocean and mid-latitude land)
when using the operational cloud-phase retrieval technique of the CM-SAF. This
technique is applied to measured radiances from the Moderate-Resolution Imaging
Spectroradiometer (MODIS) onboard NASA’s Earth Observing System (EOS)
Terra and Aqua satellites. The cloud-phase retrievals are made for 1x1 km and 3x3
km2 nominal resolution, the latter simulating those for the Spinning Enhanced
Visible and Infrared Radiometer Instrument (SEVIRI) onboard the Meteosat-8 and -9
satellites.
The research is broken up into two components. First, the impact of broken
cloudiness and cloud inhomogeneity on the cloud-phase retrieval is scrutinized using
synthetic datasets. Second, for May and August of 2007 1x1- and 3x3-km2 retrievals
from Terra and Aqua radiances are compared with these synthetic retrievals and
the effect on cloud-phase determination is quantified for the two aforementioned
areas.
The MODIS observations reveal that for broken clouds over Central Europe the retrieved
water cloud occurrence frequency is up to 21% higher at low resolution than at high
resolution. Over the Atlantic Ocean, the difference is up to 12%. For overcast inhomogeneous
clouds, over both areas gradually less water clouds are retrieved at low resolution
and increasing cloud inhomogeneity, although the changes are generally within
5%. |
|
|
|
|
|
|