Nemo-Nordic 2.0: operational marine forecast model for the Baltic Sea

Abstract. This paper describes Nemo-Nordic 2.0, an operational marine model for the Baltic Sea. The is used both near-real-time forecasts and hindcast purposes. It provides estimates of sea surface height, water temperature, salinity, velocity, as well ice concentration thickness. based on NEMO (Nucleus European Modelling Ocean) circulation previous 1.0 configuration by Hordoir et al. (2019). most notable updates include switch from version 3.6 to 4.0, updated bathymetry, revised bottom friction formulation. domain covers Sea North with approximately 1 nmi resolution. Vertical grid resolution has been increased 3 m in layer. In addition, numerical solver reduce artificial mixing improve representation inflow events. modeled SI3 instead LIM3. validated against level, salinity observations, chart data a 2-year simulation (October 2014 September 2016). level root mean square deviation (RMSD) typically within 10 cm throughout basin. Seasonal temperature variation captured, although exhibits negative bias −0.5 ∘C. Salinity RMSD below 1.5 g kg−1. captures major event its propagation Gotland Deep. assessment demonstrates that 2.0 can reproduce hydrographic features