{"id":801,"date":"2008-09-06T02:39:07","date_gmt":"2008-09-06T06:39:07","guid":{"rendered":"http:\/\/mseas.net16.net\/?p=801"},"modified":"2021-08-16T20:41:25","modified_gmt":"2021-08-17T00:41:25","slug":"multi-scale-modelling-nested-grid-and-unstructured-mesh-approaches-editorial","status":"publish","type":"post","link":"https:\/\/mseas.mit.edu\/?p=801","title":{"rendered":"Multi-Scale Modelling: Nested Grid and Unstructured Mesh Approaches, Editorial"},"content":{"rendered":"In 1969, the Journal of Computational Physics published a\r\nseminal article by K. Bryan presenting the first ocean\r\ngeneral circulation model. Since then, many numerical\r\nstudies of the World Ocean, as well as regional or coastal\r\nflows, used models directly or indirectly inspired by the\r\nwork of Bryan and his colleagues. A number of these\r\nmodels have evolved into highly modular and versatile\r\ncomputational systems, including multiple physical modules\r\nand options as well as varied biogeochemical,\r\necosystem and acoustics modeling capabilities. Several\r\nmodeling systems are now well-documented tools, which\r\nare widely used in research institutions and various\r\norganizations around the world. The list of such modeling\r\nsystems is large and too long to be summarized in this\r\neditorial.\r\nOver the last three decades, significant progress has been\r\nmade in the parameterization of subgrid-scale processes, in\r\ndata assimilation methodologies and in boundary condition\r\nschemes, as well as in the efficient implementation of\r\nalgorithms on fast vector and subsequently parallel computers,\r\nallowing higher and higher resolution in space and\r\ntime. However, many of today&#8217;s popular modeling systems\r\ncan still be regarded as members of the first generation of\r\nocean models: at their core, rather similar geophysical fluid\r\ndynamics equations are solved numerically using a conservative\r\nfinite-difference method on a structured grid.\r\nToday, several aspects of structured-grid models could\r\nbenefit from significant upgrades, learning from major\r\nadvances in computational fluid dynamics. In particular, the\r\nuse of a structured grid limits the flexibility in the spatial\r\nresolution and does not allow one to take full advantage of\r\nnumerical algorithms such as finite volumes and finite\r\nelements, which can achieve their best performance when\r\nimplemented on unstructured meshes.\r\nEven though many of today&#8217;s complex marine modeling\r\nand data assimilation systems have evolved significantly\r\nsince Bryan&#8217;s prototype, it would be challenging to modify\r\nthem step-by-step from a structured-grid approach to an\r\nunstructured-grid one. Therefore, novel marine model\r\ndesign research is underway, paving the way for the second\r\ngeneration of ocean modeling systems. It is difficult to\r\npredict today if this new generation of ocean models will\r\nachieve its chief objective: widening the range of resolved\r\nscales of motion with increased efficiencies and accuracies,\r\npossibly allowing multi-resolution, multi-scale, and multidynamics\r\nnumerical simulations of marine flows, all\r\noccurring seamlessly within distributed computing environments.\r\nIn fact, hybrid approaches merging the advantages\r\nof structured and unstructured-grid modeling may be the\r\nway forward.\r\nWhether or not unstructured mesh approaches will\r\nprevail is all the more difficult to predict now that\r\nstructured mesh modelers have developed powerful solutions\r\nfor increasing the resolution when and where\r\nneeded. For instance, grid embedding is still a popular\r\nand useful method for enhancing model resolution. It can\r\ninvolve multiply nested domains and allows the relatively straightforward use of different dynamics or models in each\r\ndomain. Research is also underway for developing multigrid,\r\nwavelet, and other multi-scale decompositions for the\r\nnumerical solution of dynamical equations but also for the\r\nstudy of results, model evaluation or data assimilation.\r\nThis special issue presents a number of examples of the\r\nabovementioned developments. Ringler et al. examine the\r\npotential of spherical centroidal Voronoi tessellations for\r\nperforming multi-resolution simulations; they apply this\r\nmethod to the Greenland ice sheet and the North Atlantic\r\nOcean. Lambrechts et al. present a triangular mesh\r\ngeneration system and its applications to the World Ocean\r\nand various shelf seas, including the Great Barrier Reef,\r\nAustralia. Finite element models on unstructured grids are\r\ndescribed and utilized in several manuscripts. Bellafiore et\r\nal. study the Adriatic Sea and the Lagoon of Venice, while\r\nJones and Davies simulate tides and storm surges along the\r\nwestern coast of Britain. Danilov et al. assess two finite\r\nelement discretizations, i.e., a continuous element and a\r\nnon-conforming one, and compare the results of these\r\ndiscretizations with those of a finite-difference model. In\r\nHarig et al., the tsunami generated by the great Sumatra-Andaman earthquake of 26 December 2004 is simulated by\r\nmeans of a finite element model. Comparisons are carried\r\nout with various types of data as well as with the results of\r\na structured mesh model using a nested structured-grid\r\nsystem. A nested-grid ocean circulation model is also\r\nemployed by Yang and Sheng to carry out a process study\r\non the Inner Scotian Shelf, Canada, focusing on the\r\ncirculation induced by a tropical storm. Debreu and Blayo\r\npresent a detailed review of two-way embedding algorithms\r\nfor structured-grid models. Finally, Logutov develops a\r\nmulti-scale assimilation scheme for tidal data within the\r\nframework of a multiply nested structured-grid barotropic\r\ntidal modeling approach.\r\nAs illustrated by these manuscripts, the next generation\r\nof ocean modelers is motivated by a wide range of research\r\nopportunities over a rich spectrum of needs. Future progress\r\nwill involve fundamental and applied numerical and\r\ncomputational research as well as new multi-scale geophysical\r\nfluid modeling. Domains of ongoing interest range\r\nfrom estuaries to the global ocean, including coastal regions\r\nand shelf seas. New multi-scale modeling of physical as\r\nwell as biological, chemical or interdisciplinary processes\r\nwill flourish in the coming decades.\r\nWe are grateful to the authors for their contributions and\r\nto the chief-editor for his support in this endeavor. We are\r\nthankful to the reviewers for their time and help in assessing\r\nthe manuscripts submitted to this special issue. Eric\r\nDeleersnijder is a Research associate with the Belgian\r\nNational Fund for Scientific Research (FNRS); he is\r\nindebted to the Communaut Francaise de Belgique for its\r\nsupport through contract ARC 04\/09-316. Pierre Lermusiaux\r\nis grateful to the Office of Naval Research for support under\r\ngrant N00014-08-1-1097 to the Massachusetts Institute of\r\nTechnology.","protected":false},"excerpt":{"rendered":"<p>In 1969, the Journal of Computational Physics published a seminal article by K. Bryan presenting the first ocean general circulation model. Since then, many numerical studies of the World Ocean, as well as regional or coastal flows, used models directly or indirectly inspired by the work of Bryan and his colleagues. A number of these [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[32,37,28,38,5,59,54],"tags":[],"class_list":["post-801","post","type-post","status-publish","format-standard","hentry","category-numerical-ocean-modeling","category-applications-to-ocean-dynamics","category-multiscale-ocean-modeling","category-physical-oceanography","category-publications","category-papers-in-refereed-journals-physical-oceanography","category-papers-in-refereed-journals-multiscale-ocean-modeling"],"_links":{"self":[{"href":"https:\/\/mseas.mit.edu\/index.php?rest_route=\/wp\/v2\/posts\/801","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/mseas.mit.edu\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/mseas.mit.edu\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/mseas.mit.edu\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/mseas.mit.edu\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=801"}],"version-history":[{"count":8,"href":"https:\/\/mseas.mit.edu\/index.php?rest_route=\/wp\/v2\/posts\/801\/revisions"}],"predecessor-version":[{"id":5723,"href":"https:\/\/mseas.mit.edu\/index.php?rest_route=\/wp\/v2\/posts\/801\/revisions\/5723"}],"wp:attachment":[{"href":"https:\/\/mseas.mit.edu\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=801"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/mseas.mit.edu\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=801"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/mseas.mit.edu\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=801"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}