**Evaluation of Structured and Unstructured Models for Application in Operational Ocean Forecasting in Nearshore Waters**

**Shannon Nudds 1,\*, Youyu Lu 1, Simon Higginson 1, Susan P. Haigh 2, Jean-Philippe Paquin 3, Mitchell O'Flaherty-Sproul 2, Stephanne Taylor 1, Hauke Blanken 4, Guillaume Marcotte 5, Gregory C. Smith 3, Natacha B. Bernier 3, Phillip MacAulay 6, Yongsheng Wu 1, Li Zhai 1, Xianmin Hu 1, Jérôme Chanut 7, Michael Dunphy 4, Frédéric Dupont 8, David Greenberg 1, Fraser J. M. Davidson 9 and Fred Page 2**


Received: 30 April 2020; Accepted: 26 June 2020; Published: 30 June 2020

**Abstract:** The oceanography sub-initiative of Canada's Oceans Protection Plan was tasked to develop high-resolution nearshore ocean models for enhanced marine safety and emergency response, fitting into the multi-scale, multi-level nested operational ocean forecasting systems. For decision making on eventual 24/7 operational support, two ocean models (a structured grid model, NEMO (Nucleus for European Modelling of the Ocean); and an unstructured grid model, FVCOM (Finite Volume Coastal Ocean Model), were evaluated. The evaluation process includes the selection of the study area, the requirements for model setup, and the evaluation metrics. The chosen study area, Saint John Harbour in the Bay of Fundy, features strong tides, significant river runoff and a narrow tidal-river channel. Both models were configured with the same sources of bathymetry and forcing data. FVCOM achieved 50–100 m horizontal resolution in the inner harbour and included wetting/drying. NEMO achieved 100 m resolution in the harbour with a three-level one-way nesting configuration. Statistical metrics showed that one-year simulations with both models achieved comparable accuracies against the observed tidal and non-tidal water levels and currents, temperature and salinity, and the trajectories of surface drifters, but the computational cost of FVCOM was significantly less than that of NEMO.

**Keywords:** coastal modelling; operational forecasting; model evaluation; inter-comparison; NEMO; FVCOM; Ocean Protection Plan
