Abstract: This paper presents a novel method to select the optimal combination of grid resolution and number of
Lagrangian elements (LEs) required in numerical modelling of oil concentrations at sea. A sensitivity analysis in
terms of grid resolution and the number of LEs, was carried out to understand the uncertainty that these userdependent parameters introduce in the numerical results. A dataset of 211,200 simulations performed under 400 metocean patterns, 6 initial volumes, 11 grid resolutions, and different numbers of LEs (100 to 500,000), was used to analyze the sensitivity of the model along different Thresholds of Concern. Results show the importance of a correct selection of the number of LEs and the grid resolution in Lagrangian modelling of surface oil concentrations. The method proposed will allow selecting the optimal combination of these parameters to find an optimal balance between the accuracy and the computational cost of the simulation.
