Designing variable ocean model resolution based on the observed ocean variability

Sein, Dmitry V.; Danilov, Sergey; Biastoch, Arne; Durgadoo, Jonathan V.; Sidorenko, Dmitry; Harig, Sven; Wang, Qiang

doi:10.1002/2016ms000650

Cited by 57 publications

(72 citation statements)

References 18 publications

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“…The investigation of solution-adaptive multi-scale representations, in which grid resolution is adapted to spatial variability in model state (Sein et al, 2016), is also an obvious direction for future investigation.…”

Section: Discussionmentioning

confidence: 99%

JIGSAW-GEO (1.0): locally orthogonal staggered unstructured grid generation for general circulation modelling on the sphere

Engwirda

2017

Geosci. Model Dev.

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Abstract. An algorithm for the generation of non-uniform, locally orthogonal staggered unstructured spheroidal grids is described. This technique is designed to generate very high-quality staggered Voronoi-Delaunay meshes appropriate for general circulation modelling on the sphere, including applications to atmospheric simulation, ocean-modelling and numerical weather prediction. Using a recently developed Frontal-Delaunay refinement technique, a method for the construction of high-quality unstructured spheroidal Delaunay triangulations is introduced. A locally orthogonal polygonal grid, derived from the associated Voronoi diagram, is computed as the staggered dual. It is shown that use of the Frontal-Delaunay refinement technique allows for the generation of very high-quality unstructured triangulations, satisfying a priori bounds on element size and shape. Grid quality is further improved through the application of hill-climbing-type optimisation techniques. Overall, the algorithm is shown to produce grids with very high element quality and smooth grading characteristics, while imposing relatively low computational expense. A selection of uniform and non-uniform spheroidal grids appropriate for highresolution, multi-scale general circulation modelling are presented. These grids are shown to satisfy the geometric constraints associated with contemporary unstructured C-gridtype finite-volume models, including the Model for Prediction Across Scales (MPAS-O). The use of user-defined meshspacing functions to generate smoothly graded, non-uniform grids for multi-resolution-type studies is discussed in detail.

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Section: Discussionmentioning

confidence: 99%

JIGSAW-GEO (1.0): locally orthogonal staggered unstructured grid generation for general circulation modelling on the sphere

Engwirda

2017

Geosci. Model Dev.

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“…If the criteria was extended to include additional aspects, e.g. ocean variability (Sein et al, 2016), then this factor will reduce, and the benefits of the multiscale approach become less apparent. If, however, fine-resolution process representation is desirable, then the scaling clearly favours multiscale modelling, and if we are sufficiently confident in the refinement criteria to use a coarser base resolution than would be otherwise be chosen (i.e.…”

Section: Discussionmentioning

confidence: 99%

Prospects for improving the representation of coastal and shelf seas in global ocean models

et al. 2017

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Abstract. Accurately representing coastal and shelf seas in global ocean models represents one of the grand challenges of Earth system science. They are regions of immense societal importance through the goods and services they provide, hazards they pose and their role in global-scale processes and cycles, e.g. carbon fluxes and dense water formation. However, they are poorly represented in the current generation of global ocean models. In this contribution, we aim to briefly characterise the problem, and then to identify the important physical processes, and their scales, needed to address this issue in the context of the options available to resolve these scales globally and the evolving computational landscape.We find barotropic and topographic scales are well resolved by the current state-of-the-art model resolutions, e.g. nominal 1/12 • , and still reasonably well resolved at 1/4 • ; here, the focus is on process representation. We identify tides, vertical coordinates, river inflows and mixing schemes as four areas where modelling approaches can readily be transferred from regional to global modelling with substantial benefit. In terms of finer-scale processes, we find that a 1/12 • global model resolves the first baroclinic Rossby radius for only ∼ 8 % of regions < 500 m deep, but this increases to ∼ 70 % for a 1/72 • model, so resolving scales globally requires substantially finer resolution than the current state of the art.We quantify the benefit of improved resolution and process representation using 1/12 • global-and basin-scale northern North Atlantic nucleus for a European model of the ocean (NEMO) simulations; the latter includes tides and a k-ε vertical mixing scheme. These are compared with global stratification observations and 19 models from CMIP5. In terms of correlation and basin-wide rms error, the high-resolution models outperform all these CMIP5 models. The model with tides shows improved seasonal cycles compared to the highresolution model without tides. The benefits of resolution are particularly apparent in eastern boundary upwelling zones.To explore the balance between the size of a globally refined model and that of multiscale modelling options (e.g. finite element, finite volume or a two-way nesting approach), we consider a simple scale analysis and a conceptual grid refining approach. We put this analysis in the context of evolving computer systems, discussing model turnaround time, scalability and resource costs. Using a simple cost model compared to a reference configuration (taken to be a 1/4 • global model in 2011) and the increasing performance of the UK Research Councils' computer facility, we estimate an unstructured mesh multiscale approach, resolving process scales down to 1.5 km, would use a comparable share of the computer resource by 2021, the two-way nested multiscale approach by 2022, and a 1/72 • global model by 2026. However, we also note that a 1/12 • global model would not have a comparable computational cost to a 1 • global model in 2017 until 2027. Hence, we conc...

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“…In global ocean climate simulations, the value of unstructured meshes can be more outstanding. One can design meshes with resolution varying continuously in space 10 according to the strength of ocean variability, for example, by considering observed sea surface height variability (Sein et al, 2016) and/or Rossby radius, to permit or resolve mesoscale eddies in mid to low latitudes. It would be interesting to use this kind of global meshes together with specific mesh refinement in the Arctic Ocean for the purpose of Arctic Ocean studies, as the lower latitude ocean will be better resolved with acceptable increase of computational cost and provide more faithful oceanic linkage with the Arctic Ocean.…”

Section: Unstructured-mesh Modelingmentioning

confidence: 99%

A 4.5 km resolution Arctic Ocean simulation with the global multi-resolution model FESOM1.4

Wang¹,

Wekerle²,

Danilov³

et al. 2017

Preprint

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Abstract. In the framework of developing a global modeling system which can facilitate modeling studies on Arctic Ocean and high-mid latitude linkage, we evaluate the Arctic Ocean simulated by the multi-resolution ocean sea-ice model FESOM.To explore the value of using high horizontal resolution for Arctic Ocean modeling, we use two global meshes differing in Atlantic Water (AW) mean state and variability. The deepening and thickening bias of the AW layer, a common issue found in coarse resolution simulations, is significantly alleviated by using higher resolution. The topographic steering of the AW is stronger and the seasonal and interannual temperature variability along the ocean bottom topography is enhanced in the high resolution simulation. The high resolution also improves the ocean surface circulation, mainly through a better representation of the narrow straits in the Canadian Arctic Archipelago (CAA). The representation of CAA throughflow not only influences 10 the release of water masses through the other gateways, but also the circulation pathways inside the Arctic Ocean. However, the mean state and variability of Arctic freshwater content and the variability of freshwater transport through the Arctic gateways appear not to be very sensitive to the increase in resolution employed here. We also discuss model issues that are not directly linked to resolution, highlighting the need for further model development including improving parameterizations.

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Designing variable ocean model resolution based on the observed ocean variability

Cited by 57 publications

References 18 publications

JIGSAW-GEO (1.0): locally orthogonal staggered unstructured grid generation for general circulation modelling on the sphere

JIGSAW-GEO (1.0): locally orthogonal staggered unstructured grid generation for general circulation modelling on the sphere

Prospects for improving the representation of coastal and shelf seas in global ocean models

A 4.5 km resolution Arctic Ocean simulation with the global multi-resolution model FESOM1.4

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