Ocean Kinetic Energy Backscatter Parametrization on Unstructured Grids: Impact on Global Eddy-Permitting Simulations
In this study we demonstrate the potential of a kinetic energy backscatter scheme for use in global ocean simulations. Ocean models commonly employ (bi)harmonic eddy viscosities causing excessive dissipation of kinetic energy in eddy-permitting simulations. Overdissipation not only affects the small...
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ftdatacite:10.23689/fidgeo-4728 2023-05-15T13:44:15+02:00 Ocean Kinetic Energy Backscatter Parametrization on Unstructured Grids: Impact on Global Eddy-Permitting Simulations Juricke, Stephan Danilov, Sergey Koldunov, Nikolay Oliver, Marcel Sidorenko, Dmitry 2020 https://dx.doi.org/10.23689/fidgeo-4728 https://e-docs.geo-leo.de/handle/11858/9074 en eng FID GEO Text Article article-journal ScholarlyArticle 2020 ftdatacite https://doi.org/10.23689/fidgeo-4728 2021-11-05T12:55:41Z In this study we demonstrate the potential of a kinetic energy backscatter scheme for use in global ocean simulations. Ocean models commonly employ (bi)harmonic eddy viscosities causing excessive dissipation of kinetic energy in eddy-permitting simulations. Overdissipation not only affects the smallest resolved scales but also the generation of eddies through baroclinic instabilities, impacting the entire wave number spectrum. The backscatter scheme returns part of this overdissipated energy back into the resolved flow. We employ backscatter in the FESOM2 multiresolution ocean model with a quasi-uniform 1/4° mesh. In multidecadal ocean simulations, backscatter increases eddy activity by a factor 2 or more, moving the simulation closer to observational estimates of sea surface height variability. Moreover, mean sea surface height, temperature, and salinity biases are reduced. This amounts to a globally averaged bias reduction of around 10% for each field, which is even larger in the Antarctic Circumpolar Current. However, in some regions such as the coastal Kuroshio, backscatter leads to a slight overenergizing of the flow and, in the Antarctic, to an unrealistic reduction of sea ice. Some of the bias increases can be reduced by a retuning of the model, and we suggest related adjustments to the backscatter scheme. The backscatter simulation is about 2.5 times as expensive as a simulation without backscatter. Most of the increased cost is due to a halving of the time step to accommodate higher simulated velocities. Text Antarc* Antarctic Sea ice DataCite Metadata Store (German National Library of Science and Technology) Antarctic The Antarctic |
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English |
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In this study we demonstrate the potential of a kinetic energy backscatter scheme for use in global ocean simulations. Ocean models commonly employ (bi)harmonic eddy viscosities causing excessive dissipation of kinetic energy in eddy-permitting simulations. Overdissipation not only affects the smallest resolved scales but also the generation of eddies through baroclinic instabilities, impacting the entire wave number spectrum. The backscatter scheme returns part of this overdissipated energy back into the resolved flow. We employ backscatter in the FESOM2 multiresolution ocean model with a quasi-uniform 1/4° mesh. In multidecadal ocean simulations, backscatter increases eddy activity by a factor 2 or more, moving the simulation closer to observational estimates of sea surface height variability. Moreover, mean sea surface height, temperature, and salinity biases are reduced. This amounts to a globally averaged bias reduction of around 10% for each field, which is even larger in the Antarctic Circumpolar Current. However, in some regions such as the coastal Kuroshio, backscatter leads to a slight overenergizing of the flow and, in the Antarctic, to an unrealistic reduction of sea ice. Some of the bias increases can be reduced by a retuning of the model, and we suggest related adjustments to the backscatter scheme. The backscatter simulation is about 2.5 times as expensive as a simulation without backscatter. Most of the increased cost is due to a halving of the time step to accommodate higher simulated velocities. |
format |
Text |
author |
Juricke, Stephan Danilov, Sergey Koldunov, Nikolay Oliver, Marcel Sidorenko, Dmitry |
spellingShingle |
Juricke, Stephan Danilov, Sergey Koldunov, Nikolay Oliver, Marcel Sidorenko, Dmitry Ocean Kinetic Energy Backscatter Parametrization on Unstructured Grids: Impact on Global Eddy-Permitting Simulations |
author_facet |
Juricke, Stephan Danilov, Sergey Koldunov, Nikolay Oliver, Marcel Sidorenko, Dmitry |
author_sort |
Juricke, Stephan |
title |
Ocean Kinetic Energy Backscatter Parametrization on Unstructured Grids: Impact on Global Eddy-Permitting Simulations |
title_short |
Ocean Kinetic Energy Backscatter Parametrization on Unstructured Grids: Impact on Global Eddy-Permitting Simulations |
title_full |
Ocean Kinetic Energy Backscatter Parametrization on Unstructured Grids: Impact on Global Eddy-Permitting Simulations |
title_fullStr |
Ocean Kinetic Energy Backscatter Parametrization on Unstructured Grids: Impact on Global Eddy-Permitting Simulations |
title_full_unstemmed |
Ocean Kinetic Energy Backscatter Parametrization on Unstructured Grids: Impact on Global Eddy-Permitting Simulations |
title_sort |
ocean kinetic energy backscatter parametrization on unstructured grids: impact on global eddy-permitting simulations |
publisher |
FID GEO |
publishDate |
2020 |
url |
https://dx.doi.org/10.23689/fidgeo-4728 https://e-docs.geo-leo.de/handle/11858/9074 |
geographic |
Antarctic The Antarctic |
geographic_facet |
Antarctic The Antarctic |
genre |
Antarc* Antarctic Sea ice |
genre_facet |
Antarc* Antarctic Sea ice |
op_doi |
https://doi.org/10.23689/fidgeo-4728 |
_version_ |
1766199448757600256 |