DCSM-FM 0.5nm: a sixth-generation model for the NW European Shelf : 2022 release

Upon request of Rijkswaterstaat (RWS), Deltares has developed a sixth-generation hydrodynamic model of the Northwest European Shelf: the Dutch Continental Shelf Model – Flexible Mesh (DCSM-FM). This model is the latest in a line of DCSM models developed by RWS and Deltares and a successor to the fifth-generation WAQUA model DCSMv6. 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 the present model is part of a more comprehensive project in which sixth-generation models have been 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. Since the proposed applications on the North Sea pose a wide range of sometimes mutually exclusive demands on a model, two horizontal schematizations were proposed: a relatively coarse two-dimensional model (DCSM-FM 0.5nm) and a relatively fine schematization (DCSM-FM 100m) with further refinement in most Dutch coastal waters. DCSM-FM 0.5nm is primarily aimed at ensemble forecasting, but also forms a sound basis for a subsequent 3D model development, including temperature and salinity as state parameters. DCSM-FM 100m is primarily aimed at deterministic water level forecasting at HMC and WMCN-kust. The present report describes the model setup, calibration and validation of the relatively coarse, two-dimensional model DCSM-FM 0.5nm. A first version of this model was released in 2019. In 2022, this model was updated with respect to model bathymetry, tidal boundary forcing and meteorological forcing and numerous other adjustments and improvements. These changes, including a recalibration and revalidation are reflected in this current report.