Contents 1 Ocean Modelling with ICOM 2 ICOM: Model design and methodology 3 Applications of ICOM 4 Publications relating to ICOM 5 ICOM Release

Ocean Modelling with ICOM

Ocean modelling within the group is performed with the the Imperial College Ocean Model, ICOM.

ICOM is a three-dimensional non-hydrostatic parallel ocean model which uses control volume finite element discretisation methods on meshes which may be unstructured in all three dimensions and which may also adapt to optimally resolve solution dynamics.

This model in being developed in collaboration with the University of Oxford, the National Oceanography Centre Southampton, and the Proudman Oceanographic Laboratory Liverpool - see who's who to meet the team.

ICOM: Model design and methodology

ICOM has been developed with heavy emphasis on the following design attributes:

• It will be able to conform accurately to coastlines, and to ocean floor topography so that, in particular, dense water can flow down slope in a non-diffusive way, in contrast to the way in which down slope flow is traditionally treated in models with a Cartesian vertical coordinate;
• Employ an unstructured mesh with non-uniform resolution, so that regions of steep topography, high dynamical activity, or specific interest can be modelled at a higher horizontal and vertical resolution than is required by the large-scale flow;
• Employ mesh adaptivity to automatically resolve fine-scale features as they develop, and to minimise computational cost by reducing resolution where possible;
• Be non-hydrostatic, to cope with steep topography, in which the ratio of vertical to horizontal scales may not be sufficiently small to allow hydrostatic models to give an accurate description of the flow;
• Be robust under typical and extreme oceanographic conditions, in particular to represent states of geostrophic and hydrostatic balance accurately in large-scale dynamics;
• Not be constrained by a rigid lid, so that surface tides can be simulated in shallow, on-shelf regions and the interaction between barotropic and baroclinic tides, and between tides and other flows, such as eddies and slope currents, can be modelled accurately;
• Take implicit time steps, so that unreasonably small time steps are not imposed on global-scale model integration by either (a) surface and internal gravity wave speeds, and (b) regions in which a fine mesh is employed to resolve sharp topographic features;
• Minimise the extent to which truncation errors induce artificial flow in the neighbourhood of steep topography - a problem encountered by sigma-coordinate models;
• Take advantage of load-balanced domain decomposition algorithms, in order to run on parallel machines with distributed memory;
• Employ inversion methods based upon an adjoint model to assimilate observed data into simulations and improve predictive capabilities;
• Use the adjoint model to perform sensitivity studies to determine the role of parameters in model prediction.
• Use a Cartesian coordinate system that does not have the pole or singularity issues associated with Latitude-Longitude grids for example.

Applications of ICOM

• Comparisons with laboratory experiments
• Western boundary currents
• Flow over topography
• Open ocean deep convection
• Gravity currents
• Internal wave breaking
• Salt fingering
• Optimised bathymetry representation
• Tidal modelling
• Tsunami modelling
• North Atlantic thermohaline circulation
• Water World / Aqua Planet
• Wetting and Drying

Publications relating to ICOM

Further information on ICOM may be found in the following publications.

1. Ford R, Pain CC, Piggott MD, et al, A nonhydrostatic finite-element model for three-dimensional stratified oceanic flows. Part I: model formulation, Monthly Weather Review, 2004, Vol: 132, Pages: 2816 - 2831, ISSN: 0027-0644, doi:10.1175/MWR2824.1
2. Ford R, Pain CC, Piggott MD, et al, A nonhydrostatic finite-element model for three-dimensional stratified oceanic flows. Part II: model validation, Monthly Weather Review, 2004, Vol: 132, Pages: 2832 - 2844, ISSN: 0027-0644, doi:10.1175/MWR2825.1
3. Fang F, Pain CC, Piggott MD, et al, Adjoint data assimilation into a 3D unstructured mesh coastal finite element model, In: Spaulding ML, editor, 8th international conference on estuarine and coastal modeling, Monterey, CA, 3 - 5 November 2003, New York, Amer Soc Civil Engineers, 2004, Pages: 308 - 324, ISBN: 0-7844-0734-7
4. Pain CC, Piggott MD, Goddard AJH, et al, Three-dimensional unstructured mesh ocean modelling, Ocean Modelling, 2005, Vol: 10, Pages: 5 - 33, ISSN: 1463-5003, doi:10.1016/j.ocemod.2004.07.005
5. Piggott MD, Pain CC, Gorman GJ, et al, h, r, and hr adaptivity with applications in numerical ocean modelling, Ocean Modelling, 2005, Vol: 10, Pages: 95 - 113, ISSN: 1463-5003, doi:10.1016/j.ocemod.2004.07.007
6. Fang F, Pain CC, Piggott MD, et al, An adaptive mesh adjoint data assimilation method applied to free surface flows, International Journal for Numerical Methods in Fluids, 2005, Vol: 47, Pages: 995 - 1001, ISSN: 0271-2091, doi:10.1002/fld.865
7. Wells MR, Allison PA, Hampson GJ, et al, Modelling ancient tides: the Upper Carboniferous epi-continental seaway of Northwest Europe, Sedimentology, 2005, Vol: 52, Pages: 715 - 735, ISSN: 0037-0746, doi:10.1111/j.1365-3091.2005.00718.x
8. Wells MR, Allison PA, Piggott MD, et al, Large sea, small tides: the Late Carboniferous seaway of NW Europe, Journal of the Geological Society, 2005, Vol: 162, Pages: 417 - 420, ISSN: 0016-7649, doi:10.1144/0016-764904-128
9. Power PW, Pain CC, Piggott MD, et al, Adjoint a posteriori error measures for anisotropic mesh optimisation, Computer and Mathematics with Applications, 2006, Vol: 53, No. 8-9, Pages: 1213-1242, doi:10.1016/j.camwa.2006.11.003
10. Wells MR, Allison PA, Piggott MD, et al, Discussion on large sea, small tides: the Late Carboniferous seaway of NW Europe, Journal of the Geological Society, 2006, Vol: 163, Pages: 893 - 895, ISSN: 0016-7649, doi:10.1144/0016-76492006-045
11. Gorman GJ, Piggott MD, Pain CC, Optimisation based bathymetry approximation through constrained unstructured mesh adaptivity, Ocean Modelling, 2006, Vol: 12, Pages: 436 - 452, ISSN: 1463-5003, doi:10.1016/j.ocemod.2005.09.004
12. Power PW, Piggott MD, Fang F, et al, Adjoint goal-based error norms for adaptive mesh ocean modelling, Ocean Modelling, 2006, Vol: 15, Pages: 3 - 38, doi:10.1016/j.ocemod.2006.05.001
13. Fang F, Piggott MD, Pain CC, et al, An adaptive mesh adjoint data assimilation method, Ocean Modelling, 2006, Vol: 15, Pages: 39 - 55, doi:10.1016/j.ocemod.2006.02.002
14. Gorman GJ, Piggott MD, Pain CC, Shoreline approximation for unstructured mesh generation, Computers & Geosciences, 2007, Vol: 33, Pages: 666-677. doi:10.1016/j.cageo.2006.09.007
15. Wells MR, Allison PA, Piggott MD, Gorman GJ, et al, Numerical modelling of tides in the late Pennsylvanian midcontinent seaway of North America with implications for hydrography and sedimentation, Journal of Sedimentary Research, 2007, Vol: 77, Pages: 843 - 865, doi:10.2110/jsr.2007.075
16. Gorman GJ, Piggott MD, Wells MR, Pain CC, Allison PA, A systematic approach to unstructured mesh generation for ocean modelling using GMT and Terreno, Computers and Geosciences 34, 1721-1731, 2008 doi:10.1016/j.cageo.2007.06.014
17. Wells MR, Allison PA, Hampson GJ, Piggott MD, et al, Investigating tides in the Early Pennsylvanian Seaway of NW Eurasia using the Imperial College Ocean Model, Geological Association of Canada Special Paper 48, 363 - 387, 2008
18. Piggott MD, Pain CC, Gorman GJ, Marshall DP, Killworth PD, Unstructured adaptive meshes for ocean modeling, in Ocean Modeling in an Eddying Regime, Geophysical Monograph Series, American Geophysical Union, Hecht and Hasumi Eds., 383–408, 2008. http://www.agu.org/cgi-bin/agubooks?book=OSGM1774429
19. Piggott MD, Gorman GJ, Pain CC, Allison PA, Candy AS, Martin BT, Wells MR, A new computational framework for multi-scale ocean modelling based on adapting unstructured meshes, Institute for Computational Fluid Dynamics, CD, 12 pages, 2007.
20. Soufflet Y, Killworth PD, Pain CC, Piggott MD, Mindel J, Hanert E, Moving mesh methods for ocean modelling, Institute for Computational Fluid Dynamics, 2007.
21. Piggott MD, Pain CC, Gorman GJ, et al, Multi-scale ocean modelling with adaptive unstructured grids, CLIVAR Exchanges - Ocean model development and assessment, No. 42 (Vol 12(3)), Pages: 21-23, 2007, http://eprints.soton.ac.uk/47576/
22. Cotter CJ, Gorman GJ, Diagnostic tools for 3D unstructured oceanographic data. Ocean Modelling, Volume 20 Pages 170–182, 2008.
23. Piggott MD, Gorman GJ, Pain CC, Allison PA, Candy AS, Martin BT, Wells MR, A new computational framework for multi-scale ocean modelling based on adapting unstructured meshes, International Journal for Numerical Methods in Fluids, 2008, Vol: 56, Pages: 1003 - 1015, doi:10.1002/fld.1663
24. Gorman GJ, Pain CC, Umpleby AP, Piggott MD, Combined parallel tetrahedral mesh optimisation and dynamic load-balancing, Comp. Methods Appl. Mech. Engrg., in review.
25. Shaw B, Ambraseys NN, England PC, Floyd MA, Gorman GJ, Higham TFG, Jackson JA, Nocquet J-M, Pain CC, Piggott MD, Eastern Mediterranean tectonics and tsunami hazard inferred from the AD 365 earthquake, Nature Geoscience 1, 268 - 276, 2008, doi:10.1038/ngeo151.
26. Gorman GJ, Pain CC, Piggott MD, Umpleby AP, Farrell PE, Maddison JR, 2009: Interleaved parallel tetrahedral mesh optimisation and dynamic load-balancing, Adaptive Modeling and Simulation 2009, 101-104, Bouillard Ph, Diez P (eds.), CIMNE.
27. Farrell PE, Piggott MD, Pain CC, Gorman GJ, Wilson CR, Conservative interpolation between unstructured meshes via supermesh construction, Comp. Meth. Appl. Mech. Eng., 198, 2632-2642, 2009. doi:10.1016/j.cma.2009.03.004.
28. Ham DA, Farrell PE, Gorman GJ, Maddison JR, Wilson CR, Kramer SC, Shipton J, Collins GS, CotterCJ, Piggott MD, Spud 1.0: generalising and automating the user interfaces of scientific computer models, Geosci. Model Dev., 2, 33-42, 2009. http://www.geosci-model-dev.net/2/33/2009/gmd-2-33-2009.html.
29. Farrell PE, Piggott MD, Gorman GJ, Automated continuous verification and validation for numerical simulation. Internal Report.
30. Slingo J, Bates K, Nikiforakis N, Piggott M, Roberts M, Shaffrey L, Stevens I, Vidale P, Weller H, Developing the next generation climate system models: challenges and achievements, Phil. Trans. R. Soc. A., 367, 815-831, 2009. doi:10.1098/rsta.2008.0207.
31. Fang F, Pain CC, Navon IM, Gorman GJ, Piggott MD, Allison PA, Farrell PE, Goddard AJH, POD reduced order unstructured mesh ocean modelling method for moderate Reynolds number flows, Ocean Modelling 28, 127-136, 2009. doi:10.1016/j.ocemod.2008.12.006
32. Fang F, Pain CC, Navon IM, Piggott MD, Gorman GJ, Allison PA, Goddard AJH, Reduced order modelling of an adaptive mesh ocean model, International Journal for Numerical Methods in Fluids 59, 827-851, 2009. doi:10.1002/fld.1841.
33. Ham DA, Pain CC, Hanert E, Pietrzak J, Schröter J, Special Issue: The sixth international workshop on unstructured mesh numerical modelling of coastal, shelf and ocean flows. Imperial College London, September 19-21, 2007, Ocean Modelling, Volume 28, Issues 1-3, The Sixth International Workshop on Unstructured Mesh Numerical Modelling of Coastal, Shelf and Ocean Flows, 2009, Page 1, ISSN 1463-5003, doi:10.1016/j.ocemod.2009.02.005.
34. Cotter CJ, Ham DA, Pain CC, A mixed discontinuous/continuous finite element pair for shallow-water ocean modelling, Ocean Modelling, Volume 26, 2009, pages 86-90. http://dx.doi.org/10.1016/j.ocemod.2008.09.002.
35. Cotter CJ, Ham DA, Pain CC, Reich S, LBB stability of a mixed discontinuous/continuous Galerkin finite element pair, Journal of Computational Physics, Volume 228, 2009, pages 336-348. http://dx.doi.org/10.1016/j.jcp.2008.09.014.
36. Mitchell, AJ, Ulicny, D, Hampson, GJ, Allison, PA, Gorman, GJ, Piggott, MD, Wells, MR, Pain, CC, Modelling tidal current-induced bed shear stress and palaeocirculation in an epicontinental seaway: the Bohemian Cretaceous Basin, Central Europe, Sedimentology, in press, 2009. doi:10.1111/j.1365-3091.2009.01082.x
37. Piggott MD, Farrell PE, Wilson CR, Gorman GJ, Pain CC, Anisotropic mesh adaptivity for multi-scale ocean modelling, Phil. Trans. R. Soc. A 367, no. 1907, 4591-4611, 2009. doi:10.1098/rsta.2009.0155
38. Fang F, Pain CC, Navon IM, Gorman GJ, Piggott MD, Allison PA, Goddard AJH, A POD goal-oriented error measure for mesh optimization, International Journal for Numerical Methods in Fluids, in press, 2009. doi:10.1002/fld.2182

ICOM Release

ICOM is being developed as an open source project. The model and code will be released in due course. If you would like to be kept up to date with developments and future releases please register your interest by sending an email to m.d.piggott@imperial.ac.uk.

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