Assessment of global wave models on regular and unstructured grids using the Unresolved Obstacles Source Term
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Assessment of global wave models on regular and unstructured grids using the Unresolved Obstacles Source Term Lorenzo Mentaschi 1 & Michalis Vousdoukas 1 & Tomas Fernandez Montblanc 2,3 & Georgia Kakoulaki 1 & Evangelos Voukouvalas 4 & Giovanni Besio 5 & Peter Salamon 1 Received: 1 May 2020 / Accepted: 9 September 2020 / Published online: 24 September 2020 # The Author(s) 2020
Abstract The Unresolved Obstacles Source Term (UOST) is a general methodology for parameterizing the dissipative effects of subscale islands, cliffs, and other unresolved features in ocean wave models. Since it separates the dissipation from the energy advection scheme, it can be applied to any numerical scheme or any type of mesh. UOST is now part of the official release of WAVEWATCH III, and the freely available package alphaBetaLab automates the estimation of the parameters needed for the obstructed cells. In this contribution, an assessment of global regular and unstructured (triangular) wave models employing UOST is presented. The results in regular meshes show an improvement in model skill, both in terms of spectrum and of integrated parameters, thanks to the UOST modulation of the dissipation with wave direction, and to considering the cell geometry. The improvement is clear in wide areas characterized by the presence of islands, like the whole central-western Pacific Basin. In unstructured meshes, the use of UOST removes the need of high resolution in proximity of all small features, leading to (a) a simplification in the development process of large scale and global meshes, and (b) a significant decrease of the computational demand of accurate large-scale models. Keywords Wave modeling . Global wave modeling . Subscale modeling . Unresolved obstacles . Unresolved Obstacles Source Term . UOST . WAVEWATCH III . WW3 . Global unstructured mesh . Global triangular mesh
1 Introduction This article is part of the Topical Collection on the 16th International Workshop on Wave Hindcasting and Forecasting in Melbourne, AU, November 10-15, 2019 Responsible Editor: Jenny M Brown Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10236-020-01410-3) contains supplementary material, which is available to authorized users. * Lorenzo Mentaschi [email protected] 1
Joint Research Centre (JRC), European Commission, Ispra, Italy
2
Department of Physics and Earth Sciences, Universitá degli Studi di Ferrara, Via Saragat, 1, 44122 Ferrara, Italy
3
Department of Earth Sciences, University of Cádiz, Avda. República Saharaui s/n, Puerto Real 11510 Cádiz, Spain
4
Unisystems Luxembourg Sàrl, Luxembourg, Luxembourg
5
Dipartimento di Ingegneria Chimica, Civile ed Ambientale (DICCA), Università di Genova, Genova, Italy
The dissipative effect of unresolved islands and small obstacles is a major source of error in wave models if neglected, both locally and on large scale. This is more evident in basins characterized by the presence of large number of islands, such as the Pacific Ocean or the Baltic Sea
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