Two-way embedding algorithms: a review

Debreu, Laurent; Blayo, Éric

doi:10.1007/s10236-008-0150-9

Cited by 99 publications

(54 citation statements)

References 35 publications

(43 reference statements)

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“…The GCM builds on a global configuration [Tropical Atlantic Nest at 1 /108 (TRATL01)] of the Nucleus for European Modeling of the Ocean (NEMO) code (Madec 2008) in which the grid resolution of 0.58 is refined to 0.18 in the Atlantic Ocean between 308N and 308S via two-way nesting (Debreu and Blayo 2008). It includes 46 vertical levels, with increasing thickness from 6 m at the surface to 250 m at depth.…”

Section: Model Simulationsmentioning

confidence: 99%

Annual and Semiannual Cycle of Equatorial Atlantic Circulation Associated with Basin-Mode Resonance

Brandt

Claus

Greatbatch

et al. 2016

Journal of Physical Oceanography

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Seasonal variability of the tropical Atlantic circulation is dominated by the annual cycle, but semiannual variability is also pronounced, despite weak forcing at that period. This study uses multiyear, full-depth velocity measurements from the central equatorial Atlantic to analyze the vertical structure of annual and semiannual variations of zonal velocity. A baroclinic modal decomposition finds that the annual cycle is dominated by the fourth mode and the semiannual cycle is dominated by the second mode. Similar local behavior is found in a high-resolution general circulation model. This simulation reveals that the annual and semiannual cycles of the respective dominant baroclinic modes are associated with characteristic basinwide structures. Using an idealized, linear, reduced-gravity model to simulate the dynamics of individual baroclinic modes, it is shown that the observed circulation variability can be explained by resonant equatorial basin modes. Corollary simulations of the reduced-gravity model with varying basin geometry (i.e., square basin vs realistic coastlines) or forcing (i.e., spatially uniform vs spatially variable wind) show a structural robustness of the simulated basin modes. A main focus of this study is the seasonal variability of the Equatorial Undercurrent (EUC) as identified in recent observational studies. Main characteristics of the observed EUC including seasonal variability of transport, core depth, and maximum core velocity can be explained by the linear superposition of the dominant equatorial basin modes as obtained from the reduced-gravity model.

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Section: Model Simulationsmentioning

confidence: 99%

Annual and Semiannual Cycle of Equatorial Atlantic Circulation Associated with Basin-Mode Resonance

Brandt

Claus

Greatbatch

et al. 2016

Journal of Physical Oceanography

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“…In theory, this is extendable to the global scale, with multiple nests placed to locally resolve coastal ocean processes. Several approaches exist to couple the two grids, reviewed by Debreu and Blayo (2008). Because this occurs "in memory", these can be substantially more sophisticated than offline nesting by file exchange, and essentially aim to link solution approaches in the two grids, coupling at the time steps of the respective grid.…”

Section: Options For Multiscale Modellingmentioning

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 our case, even though we employ a one-way nesting scheme for the downscaling of the operational MFS, two-way nesting could have been used. For a review on nesting schemes, we refer to Debreu and Blayo (2008). Recent nesting schemes relevant to our application are obtained in Haley and Lermusiaux (2010) and Mason et al (2010).…”

Section: Irenom-interactive Relocatable Nested Ocean Modelmentioning

confidence: 99%

A relocatable ocean model in support of environmental emergencies

et al. 2014

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During the Costa Concordia emergency case, regional, subregional, and relocatable ocean models have been used together with the oil spill model, MEDSLIK-II, to provide ocean currents forecasts, possible oil spill scenarios, and drifters trajectories simulations. The models results together with the evaluation of their performances are presented in this paper. In particular, we focused this work on the implementation of the Interactive RElo- Concordia emergency and on its validation using drifters released in the area of the accident. It is shown that thanks to the capability of improving easily and quickly its configuration, the IRENOM results are of greater accuracy than the results achieved using regional or subregional model products. The model topography, the initialization procedures, and the horizontal resolution are the key model settings to be configured. Furthermore, the IRENOM currents and the MEDSLIK-II simulated trajectories showed to be sensitive to the spatial resolution of the meteorological fields used, providing higher prediction skills with higher resolution wind forcing.

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Two-way embedding algorithms: a review

Cited by 99 publications

References 35 publications

Annual and Semiannual Cycle of Equatorial Atlantic Circulation Associated with Basin-Mode Resonance

Annual and Semiannual Cycle of Equatorial Atlantic Circulation Associated with Basin-Mode Resonance

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

A relocatable ocean model in support of environmental emergencies

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