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| Titel |
Representation of spatial and temporal variability of daily wind speed and of intense wind events over the Mediterranean Sea using dynamical downscaling: impact of the regional climate model configuration |
| VerfasserIn |
M. Herrmann, S. Somot, S. Calmanti, C. Dubois, F. Sevault |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1561-8633
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| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 11, no. 7 ; Nr. 11, no. 7 (2011-07-19), S.1983-2001 |
| Datensatznummer |
250009567
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| Publikation (Nr.) |
 copernicus.org/nhess-11-1983-2011.pdf |
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| Zusammenfassung |
Atmospheric datasets coming from long term reanalyzes of low spatial
resolution
are used for different purposes. Wind over the sea is, for example, a major
ingredient of oceanic simulations. However, the shortcomings of those datasets
prevent them from being used without an adequate corrective preliminary
treatment. Using a regional climate model (RCM) to perform a dynamical
downscaling of those large scale reanalyzes is one of the methods used in order
to produce fields that realistically reproduce atmospheric chronology and where
those shortcomings are corrected. Here we assess the influence of the configuration
of the RCM used in this framework on the representation of wind speed spatial and
temporal variability and intense wind events on a daily timescale. Our RCM is
ALADIN-Climate, the reanalysis is ERA-40, and the studied area is the Mediterranean Sea.
First, the dynamical downscaling significantly reduces the underestimation of
daily wind speed, in average by 9 % over the whole Mediterranean. This
underestimation has been corrected both globally and locally, and for the whole
wind speed spectrum. The
correction is the strongest for periods and regions of strong winds. The representation
of spatial variability has also been significantly improved. On the other hand, the
temporal correlation between the downscaled field and the observations
decreases all the more that one moves eastwards, i.e. further from the atmospheric flux entry. Nonetheless, it remains ~0.7,
the downscaled dataset reproduces therefore satisfactorily the real chronology.
Second, the influence of the choice of the RCM configuration has an influence
one order of magnitude smaller than the improvement induced by the initial
downscaling. The use of spectral nudging or of a smaller domain helps to
improve the realism of the temporal chronology. Increasing the resolution
very locally (both spatially and temporally) improves the representation of
spatial variability, in particular in regions strongly influenced by the
complex surrounding orography. The impact of the interactive air-sea coupling
is negligible for the temporal scales examined here. Using two different
forcing datasets induces differences on the downscaled fields that are
directly related to the differences between those datasets. Our results also
show that improving the physics of our RCM is still necessary to increase the
realism of our simulations. Finally, the choice of the optimal configuration
depends on the scientific objectives of the study for which those wind
datasets are used. |
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