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Par ECOLA Dernière modification 01/05/2016 13:12

Joint Kick-off meeting COASTVAR (ANR) and COMODO-WAVES (LEFE/MANU): 28-29 May 2015, Toulouse. Sessions and abstracts HERE.

Tridimensional modeling of nearshore dynamics

LEGOS team: Patrick Marchesiello, Rachid Benshila et Rafael Almar

In the past ten years, robust formalisms have emerged to model the three-dimensional effect of waves on the ocean circulation, especially in the nearshore region. The first objective of COMODO-WAVES is to assemble developers of 3D coastal ocean circulation models with the scientific community traditionally working on nearshore oceanography. It provide a framework to test their respective approaches and models: 2D or 3D equations, structured or unstructured grids, wave-resolving or wave-averaged models. Our objectives are also part of a longstanding international collaboration with UCLA.

The project relies on both ideal and realistic test cases (Biscarosse beach off the Aquitanian coast) to evaluate the performance of different approaches to modeling. The first task involves the comparison of 2D and 3D models and those with structured and unstructured meshes (accuracy and computational cost) in order to better assess the respective quality and defects. The second task concerns the quantification of intrinsic and forced components of the Very Low Frequency (VLF) variability of coastal current systems (rip currents for that matter) and how that can be related to modeling methods. The answer to such questions will determine the future of coastal models (e.g., promoting phase-resolving or -averaged models). A last objective is the optimization of the use of coastal video imaging for modeling the coastal flow and morphodynamics, including methods of data assimilation.

Expected Results

Our project represents a first attempt to coordinate the work of 3D coastal circulation modeling in France and bring together the offshore and nearshore communities. As for the COMODO project, model inter-comparisons alone will provide important outcome that can help decide how to move forward in nearshore and shelf oceanographic disciplines.

The expected methodological contribution of this project lies in consolidating wave-current interaction formalisms; refining parametrizations of vertical structure functions (wave breaking, turbulence, bottom streaming ...);  optimizing the use of video imagery, which eventually could make in situ measurements less crucial for monitoring; and benchmarking the models in use today. Toward the end of the project, we will be able to set priorities for the development of shelf and nearshore modeling.

The expected scientific contribution of the project is a better assessment of scale interaction (particularly shelf-surf interaction) and nearshore dynamical processes, based on a realistic (but sufficiently simple) three-dimensional application.

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