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| Titel |
Non-uniform adaptive vertical grids for 3D numerical ocean models |
| VerfasserIn |
Richard Hofmeister, Hans Burchard, Jean-Marie Beckers |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250032170
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| Zusammenfassung |
| A new, adaptive strategy for the vertical gridding in terrain-following 3D ocean models is
presented here, which is designed for reducing discretisation errors in ocean models. The
vertical grid adaptivity is partially given by a vertical diffusion equation for the vertical
layer positions, with diffusivities being proportional to shear, stratification and
distance from the boundaries. In the horizontal, the grid can be smoothed with
respect to z-levels, grid layer slope and density. Lagrangian tendency of the grid
movement is supported. The adaptive terrain-following grid can be set to be an
Eulerian-Lagrangian grid, a hybrid Ï-Ï or Ï-z grid and combinations of these with great
flexibility. With this, internal flow structures such as pycnoclines can be well resolved and
followed by the grid. The grid adaption strategy is easy to implement in various
types of terrain-following ocean models. A set of idealised examples is presented,
which show that the introduced adaptive grid strategy reduces pressure gradient
errors and numerical mixing significantly. The idealised examples give evidence that
the adaptive grids can improve realistic, long-term simulations of stratified seas
while keeping the advantages of terrain-following coordinates. Additionally to the
idealised examples, a first assessment of the performance of the adaptive vertical
coordinates in a realistic application, the Baltic Sea, is provided. The numerical mixing is
compared directly to the physically induced mixing for fixed and adaptive vertical grids
in the experiments. This shows, that due to the reduced numerical mixing and an
optimised resolution of the vertical gradients, the performance of the turbulent
mixing calculation in the model can be enhanced when using adaptive vertical grids. |
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