Development of a sixth generation model for the NW European Shelf (DCSM-FM 0.5nm) : model setup, calibration and validation

Upon request of Rijkswaterstaat (RWS) Deltares has developed a sixth-generation hydrodynamic model of the Northwest European Shelf. Specifically, this model covers the North Sea and adjacent shallow seas and estuaries in the Netherlands, such as the Wadden Sea, the Ems-Dollard estuary, the Western Scheldt and the Eastern Scheldt. The development of this model (DCSM-FM) is part of a more comprehensive project in which sixth-generation models are developed for all waters managed and maintained by RWS. An important difference with the previous fifth generation models is the use of the D-HYDRO Suite, the new software framework for modelling free surface flows, which was first released in 2015 and allows for the use of unstructured grids. While the previous generation models for the same area were specifically aimed at an optimal representation of water levels for operational forecasting under daily and storm surge conditions, for the sixth-generation model(s) the scope is wider. This model should also be suitable to use for e.g. water quality and ecology studies, oil spill modelling, search and rescue and to provide three-dimensional (3D) boundary conditions (including temperature and salinity) for detailed models of e.g. the Haringvliet and Rhine-Meuse Delta (RMM). The above applications pose a wide range and sometimes mutually exclusive demands on a model. Therefore, two horizontal schematizations were proposed: 1. DCSM-FM 0.5nm: a relatively coarse schematization (minimum grid size of 800-900 m in Dutch waters), primarily aimed at ensemble-based probability forecasting, but also forming a sound basis for a future three-dimensional model development including temperature and salinity as state parameters. 2. DCSM-FM 100m: a relatively fine schematization with a minimum resolution of -100 m in some Dutch waters (such as the Wadden Sea) to be used for accurate (operational) water level forecasting. This model will be a based on the model in item 1a, but with refinement where required. The present report deals with the development of the relatively coarse two-dimensional DCSM-FM model (DCSM-FM 0.5nm).