NorShelf: A reanalysis and data-assimilative forecast model for the Norwegian Shelf Sea

Abstract. A regional ocean model setup with data assimilation (DA) for the shelf sea off Norway has been set up at the Norwegian Meteorologial Institute (MET Norway). The model domain includes the Skagerrak in the southeast, the northern parts of the North Sea, the Shelf sea off western Norway including the shelf slope, and parts of the Barents Sea in the north. NorShelf is based on the Regional Ocean Modeling System (ROMS) with a physical space 4D-variational (4D-Var) DA scheme. A horizontal model resolution of 2.4km has been chosen to suit the scale of the available observations, and to compromise the need to resolve high resolution eddy dynamics while confining nonlinearities that limit the 4D-Var DA capabilities. The model is intended as forecasting tool for ocean circulation and hydrography beyond the coastal area, including the entire shelf sea and the dynamics of the North Atlantic current at the shelf slope. This report  contains a full description of model configuration and examples of model hydrography and 4D-Var performance.