NEMO – Nucleus for European Modelling of the Ocean

NEMO (Nucleus for European Modelling of the Ocean, is a pan-European community ocean-modeling framework owned and maintained by a consortium of institutes including the CMCC. It is in use in a wide variety of applications whose prime objectives are oceanographic and climate research, operational ocean forecasts and seasonal weather forecasts.
The system consists of three principal engines

  • OPA (Océan Parallélisé), the blue ocean, for modeling the ocean dynamics;
  • LIM (Louvain-la-Neuve Sea Ice Model), the white ocean, for modeling sea-ice thermodynamics and dynamics;
  • TOP (Tracer in the Ocean Paradigm), the green ocean, for modeling marine biogeochemistry.

NEMO also includes the AGRIF package for adaptive grid refinement and assimilation components (tangent linear and adjoint models TAM, observational operator OBS, and application of the analysis increment ASM).
NEMO can also be interfaced to a number of other components such as atmospheric models or alternative models of sea-ice and biogeochemistry, to enable Earth system modeling. Engines are nested in environments, which involve, for instance, reference configurations, pre- and post-processing tools, interface to other Earth-System components and documentation of the system.
NEMO is available as a source code and agreement of the free license.

The NEMO system evolve through the improvement of the existing engines or the creation of new ones, the addition of new components coming from other models and their interface to NEMO, and the improvement and generalization of the environment. These evolutions are driven by an annual work plan elaborated within the NEMO Consortium.
All CMCC research of climate and ocean are based on the ocean general circulation model OPA. It is a finite difference, hydrostatic, primitive equation ocean general circulation model, with a free sea surface and a non-linear equation of state. OPA describes the distribution of variables in a 3D Arakawa C grid centered at tracer points. Prognostic variables (directly solved by the model equations) are the temperature, the salinity, the sea surface height and the 3D velocity fields.


  • Madec, G. and the NEMO team, 2012: “NEMO ocean engine”. Note du Pole de modélisation de l’Institut Pierre-Simon Laplace, France, No 27 ISSN No 1288-1619.
  • RP0247 – GLOB16, the CMCC global mesoscale-eddying ocean



Dorotea Iovino.

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