Preprints
https://doi.org/10.5194/gmd-2021-101
https://doi.org/10.5194/gmd-2021-101

Submitted as: model description paper 25 May 2021

Submitted as: model description paper | 25 May 2021

Review status: this preprint is currently under review for the journal GMD.

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

Tuomas Kärnä1, Patrik Ljungemyr2, Saeed Falahat2, Ida Ringgaard3, Lars Axell2, Vasily Korabel3, Jens Murawski3, Ilja Maljutenko4, Anja Lindenthal5, Simon Jandt-Scheelke5, Svetlana Verjovkina4, Ina Lorkowski5, Priidik Lagemaa4, Jun She3, Laura Tuomi1, Adam Nord2, and Vibeke Huess3 Tuomas Kärnä et al.
  • 1Finnish Meteorological Institute, Helsinki, Finland
  • 2Swedish Meteorological and Hydrological Institute, Norrköping, Sweden
  • 3Danish Meteorological Institute, Copenhagen, Denmark
  • 4Tallinn University of Technology, Tallinn, Estonia
  • 5Bundesamt für Seeschifffahrt und Hydrographie, Hamburg, Germany

Abstract. This paper describes Nemo-Nordic 2.0, an operational marine forecast model for the Baltic Sea. The model is based on the NEMO (Nucleus for European Modelling of the Ocean) circulation model and the previous Nemo-Nordic 1.0 configuration by Hordoir et al. [Geosci. Model Dev., 12, 363–386, 2019]. The most notable updates include the switch from NEMO version 3.6 to 4.0, updated model bathymetry and revised bottom friction formulation. The model domain covers the Baltic and the North Seas with approximately 1 nautical mile resolution. Vertical grid resolution has been increased from 3 to 1 m in the surface layer. In addition, the numerical solver configuration has been revised to reduce artificial mixing to improve the representation of inflow events. Sea-ice is modeled with the SI3 model instead of LIM3. The model is validated against sea level, water temperature and salinity observations, as well as Baltic Sea ice chart data for a two-year hindcast simulation. Sea level root mean square deviation (RMSD) is typically within 10 cm throughout the Baltic basin. Seasonal sea surface temperature variation is well captured, although the model exhibits a negative bias of approximately −0.5 °C. Salinity RMSD is typically below 1.5 g/kg. The model captures the 2014 Major Baltic Inflow event and its propagation to the Gotland Deep. The skill analysis demonstrates that Nemo-Nordic 2.0 can reproduce the hydrographic features of the Baltic Sea.

Tuomas Kärnä et al.

Status: open (until 21 Jul 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse

Tuomas Kärnä et al.

Tuomas Kärnä et al.

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Short summary
The model covers the Baltic and the North Seas with approximately 1 nautical mile resolution. We validate the model's performance against sea level, water temperature, and salinity observations, as well as sea ice charts. The skill analysis demonstrates that Nemo-Nordic 2.0 can reproduce the hydrographic features of the Baltic Sea.