Global tide simulations with ICON-O: testing the model performance on highly irregular meshes
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Global tide simulations with ICON-O: testing the model performance on highly irregular meshes Kai Logemann 1
&
Leonidas Linardakis 2 & Peter Korn 2
&
Corinna Schrum 1,3
Received: 17 July 2020 / Accepted: 29 November 2020 # The Author(s) 2020
Abstract The global tide is simulated with the global ocean general circulation model ICON-O using a newly developed tidal module, which computes the full tidal potential. The simulated coastal M2 amplitudes, derived by a discrete Fourier transformation of the output sea level time series, are compared with the according values derived from satellite altimetry (TPXO-8 atlas). The experiments are repeated with four uniform and sixteen irregular triangular grids. The results show that the quality of the coastal tide simulation depends primarily on the coastal resolution and that the ocean interior can be resolved up to twenty times lower without causing considerable reductions in quality. The mesh transition zones between areas of different resolutions are formed by cell bisection and subsequent local spring optimisation tolerating a triangular cell’s maximum angle up to 84°. Numerical problems with these high-grade non-equiangular cells were not encountered. The results emphasise the numerical feasibility and potential efficiency of highly irregular computational meshes used by ICON-O. Keywords Ocean modelling . Tides . Unstructured grids . Mesh refinement . ICON-O
1 Introduction Numerical modelling of global ocean dynamics using a regular (structured) grid generally leads to two problems: first, the meridional convergence, i.e. the impossibility to uniformly resolve the sphere. Though rotated spherical coordinates are shifting the North Pole onto a land mass (e.g. Marsland et al. 2003) to avoid the most severe computational problems, the Responsible Editor: Eric Deleersnijder * Kai Logemann [email protected] Leonidas Linardakis [email protected] Peter Korn [email protected] Corinna Schrum [email protected] 1
Institute of Coastal Research, Helmholtz Centre Geesthacht, Max-Planck-Str. 1, 21502 Geesthacht, Germany
2
Max-Planck-Institute for Meteorology, Bundesstr. 53, 20146 Hamburg, Germany
3
Institute of Oceanography, Centre for Earth System Sustainability, University of Hamburg, Bundesstr. 53, 20146 Hamburg, Germany
fact remains that the resolution varies in a way, which is not exclusively oriented along oceanographic criteria. This also points to the second problem: oceanic fluxes exist on a broad band of scales. Thereby, fluxes caused by smaller scale processes like the flow through a strait or a western boundary current can have crucial consequences up to the basin-scale. However, simulations with sufficiently high-resolution structured grids, that would resolve these small scales, are too costly to be performed effectively. Hence, unstructured grid ocean modelling became an attractive alternative, because it offers the possibility to circumvent the pole problem and at the same time to freely vary the resolution within the model domai
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