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| Titel |
Improved Climate Simulations through a Stochastic Parameterization of Ocean Eddies |
| VerfasserIn |
Paul Williams, Nicola Howe, Jonathan Gregory, Robin Smith, Manoj Joshi |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250140295
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| Publikation (Nr.) |
 EGU/EGU2017-3663.pdf |
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| Zusammenfassung |
| In climate simulations, the impacts of the subgrid scales on the resolved scales are
conventionally represented using deterministic closure schemes, which assume that the
impacts are uniquely determined by the resolved scales. Stochastic parameterization relaxes
this assumption, by sampling the subgrid variability in a computationally inexpensive
manner.
This study shows that the simulated climatological state of the ocean is improved in many
respects by implementing a simple stochastic parameterization of ocean eddies into a coupled
atmosphere–ocean general circulation model. Simulations from a high-resolution,
eddy-permitting ocean model are used to calculate the eddy statistics needed to inject realistic
stochastic noise into a low-resolution, non-eddy-permitting version of the same model. A
suite of four stochastic experiments is then run to test the sensitivity of the simulated climate
to the noise definition by varying the noise amplitude and decorrelation time within
reasonable limits.
The addition of zero-mean noise to the ocean temperature tendency is found to have a
nonzero effect on the mean climate. Specifically, in terms of the ocean temperature and
salinity fields both at the surface and at depth, the noise reduces many of the biases in the
low-resolution model and causes it to more closely resemble the high-resolution model. The
variability of the strength of the global ocean thermohaline circulation is also improved. It is
concluded that stochastic ocean perturbations can yield reductions in climate model error that
are comparable to those obtained by refining the resolution, but without the increased
computational cost. Therefore, stochastic parameterizations of ocean eddies have the
potential to significantly improve climate simulations.
Reference
Williams PD, Howe NJ, Gregory JM, Smith RS, and Joshi MM (2016) Improved Climate
Simulations through a Stochastic Parameterization of Ocean Eddies. Journal of Climate, 29,
8763–8781. http://dx.doi.org/10.1175/JCLI-D-15-0746.1 |
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