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| Titel |
Generation and transfer of internal variability in a regional climate model |
| VerfasserIn |
Thorsten Simon, Dinan Wang, Andreas Hense, Clemens Simmer, Christian Ohlwein |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250090801
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| Publikation (Nr.) |
 EGU/EGU2014-5059.pdf |
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| Zusammenfassung |
| There is a strong need for tools allowing the comparison between the performance of a
regional climate model (RCM) and the corresponding model providing lateral boundary
conditions (LBC) for the RCM, which is a global general circulation model (GCM) in most
cases. A method is presented to investigate the temporal scales on which a RCM is able to
generate internal variability on its own and on which variability is copied from the driving
model. This is implemented by a cross-spectral analysis between the RCM output and a
bi-linearly interpolated version of the driving model, leading to an estimate of the coherence
spectrum.
Applying the aforementioned technique to surface temperature and temperature and
specific humidity at 850hPa from the RCM COSMO-CLM East Asia with a horizontal
resolution of 50km and its driving model ECHAM5, it was found that features in the
spatial distribution of coherence are related to atmospheric dynamics in East Asia,
e.g.monsoons and inter-tropical convergence zone (ITCZ). A further application to a
double-nesting approach, where COSMO-CLM East Asia is the driving model for two
domains – namely the Haihe catchment and the Poyang catchment – each with a
horizontal resolution of 7km, shows that the frequencies on which internal variability
is generated by the driven model are much higher compared to the first nesting
step.
Concluding RCMs can produce a considerable variability on the respective
temporal-scales. This implies that a dynamical downscaling with a re-analysis as
LBC is conceptually different to a regional re-analysis, i.e. data assimilation on the
regional-scale.
References
T. Simon, D. Wang, A. Hense, C. Simmer and C. Ohlwein, 2013: Generation
and transfer of internal variability in a regional climate model. Tellus A. 65.
http://dx.doi.org/10.3402/tellusa.v65i0.22485 |
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