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| Titel |
Assessment of valley cold pools and clouds in a very high-resolution numerical weather prediction model |
| VerfasserIn |
J. K. Hughes, A. N. Ross, S. B. Vosper, A. P. Lock, B. C. Jemmett-Smith |
| 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 ; 8, no. 10 ; Nr. 8, no. 10 (2015-10-06), S.3105-3117 |
| Datensatznummer |
250116596
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| Publikation (Nr.) |
 copernicus.org/gmd-8-3105-2015.pdf |
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| Zusammenfassung |
| The formation of cold air pools in valleys under stable conditions represents
an important challenge for numerical weather prediction (NWP). The challenge
is increased when the valleys that dominate cold pool formation are on
scales unresolved by NWP models, which can lead to substantial local errors
in temperature forecasts. In this study a 2-month simulation is presented
using a nested model configuration with a finest horizontal grid spacing of
100 m. The simulation is compared with observations from the recent COLd air Pooling Experiment (COLPEX)
project and the model's ability to represent cold pool formation, and the
surface energy balance is assessed. The results reveal a bias in the model
long-wave radiation that results from the assumptions made about the
sub-grid variability in humidity in the cloud parametrization scheme. The
cloud scheme assumes relative humidity thresholds below 100 % to diagnose
partial cloudiness, an approach common to schemes used in many other models.
The biases in radiation, and resulting biases in screen temperature and cold
pool properties are shown to be sensitive to the choice of critical relative
humidity, suggesting that this is a key area that should be improved for
very high-resolution modeling. |
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