NEMO (Nucleus for European Modelling of the Ocean) is an ocean modelling framework which is composed of "engines" nested in an "environment". The "engines" provide numerical solutions of ocean, sea-ice, tracers and biochemistry equations and their related physics. The "environment" consists in reference configurations, pre- and post-processing tools, interface to the other components of the Earth system, user interface, computer dependent functions and documentation of the system.

NEMO allows several ocean related components of the Earth system to work together or separately (i.e "standalone mode"). It also allows a two-way nesting via the AGRIF software. It is interfaced with the other components of the Earth system (atmosphere, land surfaces, ...) via the OASIS coupler.

NEMO releases

The latest stable release of NEMO is the version 3.4.1 (Jan 2012). It includes five major components:

• the blue ocean (ocean dynamics, NEMO-OPA)
• the white ocean (sea-ice, NEMO-LIM)
• the green ocean (biogeochemistry, NEMO-TOP) ;
• the adaptative mesh refinement software (AGRIF) ;
• the assimilation component NEMO_TAM and NEMO-OBS
  

These engines can be run in standalone mode.
AGRIF package is implemented to use embedded sub-grids.

NEMO evolution

The NEMO system will evolve through the improvement of the existing "engines", the addition of "engines"coming from other models or their interface to NEMO, or the creation of new "engines", and the improvement and generalisation of the "environment".
These evolutions are driven by an annual work plan elaborated within the NEMO Consortium. Mid-terms objectives are elaborated within the NEMO community through the  "NEMO’s development strategy: consensus and open discussions" document, revised yearly since 2014.

After validation of the new developments, they are implemented in the shared reference. In order to ensure the reliability of the system, to allow projects to find the appropriate version and to keep track of the evolutions, NEMO is under SVN (Subversion control System). NEMO also uses Trac (tracking system for software development projects) to share information on the developments and eventual bugs.

The full description of NEMO is:

• Source codes: an ocean general circulation model (OPA_SRC), its assimilation component  (tangent linear and adjoint model TAM_SRC) and observation module (OBS), on/off-line ocean tracer and biochemistry models (TOP_SRC) and a sea-ice model (LIM_SRC).
• a built-in interface to the OASIS coupler and XIOS (input-output) library
• a set of reference configurations including a tri-3 polar global ocean (ORCA2). These are provided for illustrative purposes enabling one to verify that the code flow is correct
• scripts to compile, create executables and run the experiment on target platforms
• pre- and post-processing tools built on IDL (SAXO) to configure input files and analyse output files
• a configuration control system based on SVN
• on-line and off-line documentation of the model formulation and code

Target platforms

NEMO is intended to be a portable platform. It actually runs on a number of computers (target platforms).

Reference configurations

6 reference configurations are available for now, with their downloadable input files. These may evolve, depending on the area of interest of NEMO community and Consortium, following two main objectives: to allow the possibility to run a given configuration on a platform to be check that it works properly and to give a demonstrator to the user/project in order to build his own configuration.