Ocean Kinetic Energy Backscatter Parametrization on Unstructured Grids: Impact on Global Eddy‐Permitting Simulations
Abstract 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...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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American Geophysical Union (AGU)
2020-01-01
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| Series: | Journal of Advances in Modeling Earth Systems |
| Subjects: | |
| Online Access: | https://doi.org/10.1029/2019MS001855 |
| _version_ | 1818441979735834624 |
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| author | Stephan Juricke Sergey Danilov Nikolay Koldunov Marcel Oliver Dmitry Sidorenko |
| author_facet | Stephan Juricke Sergey Danilov Nikolay Koldunov Marcel Oliver Dmitry Sidorenko |
| author_sort | Stephan Juricke |
| collection | DOAJ |
| description | Abstract 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. |
| first_indexed | 2024-12-14T18:36:51Z |
| format | Article |
| id | doaj.art-3b05bcc09609423cbe1498e6b9fc5d55 |
| institution | Directory Open Access Journal |
| issn | 1942-2466 |
| language | English |
| last_indexed | 2024-12-14T18:36:51Z |
| publishDate | 2020-01-01 |
| publisher | American Geophysical Union (AGU) |
| record_format | Article |
| series | Journal of Advances in Modeling Earth Systems |
| spelling | doaj.art-3b05bcc09609423cbe1498e6b9fc5d552022-12-21T22:51:35ZengAmerican Geophysical Union (AGU)Journal of Advances in Modeling Earth Systems1942-24662020-01-01121n/an/a10.1029/2019MS001855Ocean Kinetic Energy Backscatter Parametrization on Unstructured Grids: Impact on Global Eddy‐Permitting SimulationsStephan Juricke0Sergey Danilov1Nikolay Koldunov2Marcel Oliver3Dmitry Sidorenko4Mathematics Jacobs University Bremen GermanyMathematics Jacobs University Bremen GermanyAlfred Wegener Institute for Polar and Marine Research Bremerhaven GermanyMathematics Jacobs University Bremen GermanyAlfred Wegener Institute for Polar and Marine Research Bremerhaven GermanyAbstract 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.https://doi.org/10.1029/2019MS001855ocean kinetic energy backscattersubgrid eddy parametrizationinverse energy cascadeviscosity closureeddy‐permitting resolution |
| spellingShingle | Stephan Juricke Sergey Danilov Nikolay Koldunov Marcel Oliver Dmitry Sidorenko Ocean Kinetic Energy Backscatter Parametrization on Unstructured Grids: Impact on Global Eddy‐Permitting Simulations Journal of Advances in Modeling Earth Systems ocean kinetic energy backscatter subgrid eddy parametrization inverse energy cascade viscosity closure eddy‐permitting resolution |
| title | 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_short | 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 |
| topic | ocean kinetic energy backscatter subgrid eddy parametrization inverse energy cascade viscosity closure eddy‐permitting resolution |
| url | https://doi.org/10.1029/2019MS001855 |
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