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| Titel |
Evaluation of ice and snow content in the global numerical weather prediction model GME with CloudSat |
| VerfasserIn |
S. Reitter, K. Fröhlich, A. Seifert, S. Crewell, M. Mech |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 4, no. 3 ; Nr. 4, no. 3 (2011-07-06), S.579-589 |
| Datensatznummer |
250001776
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| Publikation (Nr.) |
 copernicus.org/gmd-4-579-2011.pdf |
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| Zusammenfassung |
The present study evaluates the global numerical weather prediction model GME
with respect to the grid-scale parameterization of frozen particles, both ice
and snow, focusing on the performance of a diagnostic versus a prognostic
precipitation scheme. As a reference, CloudSat Cloud Profiling Radar
observations are utilized – the so far only near-globally available data set
which vertically resolves clouds. Both the observation-to-model and the
model-to-observation approach are applied and compared to each other. For the
latter, the radar simulator QuickBeam is utilized. Criteria are applied to
further improve the comparability between model and observations. The two
model versions are statistically evaluated for a four-month period.
The comparison reveals that the prognostic scheme reproduces the shape of the
CloudSat frequency distributions for both ice water content (IWC) and
reflectivity factor well, while the diagnostic scheme produces no large IWCs
or reflectivity factors because snow falls out instantaneously. However, the
prognostic scheme overestimates the occurrence of high ice water paths (IWP),
especially in the mid-latitudes. Sensitivity tests show that an increased
fall speed of snow successfully reduces IWP. Both evaluation approaches
capture the general features, but for details, the two together deliver the
largest informational content. In case of limited resources, the
model-to-observation approach is recommended. Finally, the results indicate
that the lack of IWC in most global circulation models might be attributed to
the use of diagnostic precipitation schemes, i.e., the lack of snow aloft.
Based on its good performance the prognostic scheme went into operational
mode in February 2010. The adjusted snow fall speed went operational in
December 2010. However, continual improvements of the ice microphysics are
necessary, which can be assessed by the proposed evaluation technique. |
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