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| Titel |
Stability constraints for oceanic numerical models: implications for the formulation of space-time discretizations |
| VerfasserIn |
Florian Lemarié, Laurent Debreu, Gurvan Madec |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250105046
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| Publikation (Nr.) |
 EGU/EGU2015-4490.pdf |
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| Zusammenfassung |
| Except for vertical diffusion (and possibly the external mode and bottom drag), oceanic
models usually rely on explicit time-stepping algorithms subject to Courant-Friedrichs-Lewy
(CFL) stability criteria. Implicit methods could be unconditionally stable, but an algebraic
system must be solved at each time step and other considerations such as accuracy and
efficiency are less straightforward to achieve. Depending on the target application, the
process limiting the maximum allowed time-step is generally different. In this study, we
introduce offline diagnostics to predict stability limits associated with internal gravity waves,
advection, diffusion, and rotation. This suite of diagnostics is applied to a set of
global, regional and coastal numerical simulations with several horizontal/vertical
resolutions and different numerical models. We show that, for resolutions finer that 1/2°,
models with an eulerian vertical coordinate are generally constrained by vertical
advection in a few hot spots and that numerics must be extremely robust to changes in
Courant number. Based on those results, we review the stability and accuracy of
existing numerical kernels in vogue in primitive equations oceanic models with a
focus on advective processes and the dynamics of internal waves. We emphasize the
additional value of studying the numerical kernel of oceanic models in the light of
coupled space-time approaches instead of studying the time schemes independently
from spatial discretizations. From this study, we suggest some guidelines for the
development of temporal schemes in future generation multi-purpose oceanic models. |
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