NEMO – Nucleus for European Modelling of the Ocean

What is NEMO?

NEMO (Nucleus for European Modelling of the Ocean, is is a state-of-the-art modelling framework for research activities and forecasting services in ocean and climate sciences. It is developed in a sustainable way by a European Consortium that includes CMCC, CNRS (France), Mercator Ocean International (France), NERC-NOC (UK)  and Metoffice UK.

The system consists of three principal engines:

  • NEMO-OCE, for modelling the blue ocean (thermo)dynamics and solving the primitive equations;
  • NEMO-ICE (SI3: Sea-Ice Integrated Initiative) for modelling the white ocean (thermo)dynamics, brine inclusions and subgrid-scale thickness variations
  • NEMO-TOP (Tracers in the Ocean Paradigm) for modelling the green ocean using (on,off)line oceanic tracers transport and biogeochemical processes

NEMO also includes specific software packages like:

  • AGRIF for creating embedded zooms seamlessly thanks to 2-way nesting,
  • XIOS for managing input/output in an optimal way,
  • OASIS, which provides coupling interfaces between NEMO and other Earth system components

and other utilities for (pre, post)-processing data to use for setting up a configuration or to analyze model results.

NEMO is distributed under a GNU GPL compatible free licence.

The NEMO system evolves through the improvement of the existing engines or the creation of new ones, the integration of new components and interfaces with other models, also facing challenges with the evolution of the computing architectures. These evolutions are driven by an annual work plan elaborated within the NEMO Consortium.

Since 2022, the NEMO system is distributed through NEMO GitLab Repository and uses Discourse forum for exchanging information with other NEMO developers and users.

How does CMCC contribute to and use NEMO?

A group of CMCC researchers participate in the NEMO System Team, actively contributing to High Performance Computing, Sea Ice, TOP and Air-Sea interaction working groups and related developments. They are:

CMCC Experts that participate in the Developers Committee are Dorotea Iovino and Momme Butenschön. Simona Masina is the CMCC Representative at the NEMO Steering Committee.

At CMCC, the following operational systems use NEMO:

  • CMCC Operational Seasonal Prediction System (SPS): the ocean module is based on NEMO v3.6 , at 1/4° horizontal resolution and 50 vertical levels for the global ocean, integrated into the Community Earth System Model (CESM) developed at NCAR;
  • Global Ocean Forecasting System (GOFS16), based on NEMOv3.4-LIM2, at 1/16° horizontal resolution and 98 vertical levels;
  • the CMCC Global Ocean Reanalyses System (CGLORS) based on NEMOv3.6-LIM2 at 1/4°horizontal resolution and 75 vertical levels, that consists of two different products v5 and v7, starting in 1980 and 1993 respectively, and extended twice a year;
  • Mediterranean Forecasting System (MedFS), based on NEMO v3.6 at 1/24° horizontal resolution and 141 vertical levels: NRT System (Clementi et al. 2017, 2021) and Reanalysis System (Escudier et al., 2021);
  • Black Sea Forecasting System (BSFS), based on NEMO v4.0.2 at 1/40° horizontal resolution and 121 vertical levels (Ciliberti et al., 2021a, 2021b);
  • Black Sea Reanalysis System, based on NEMO v3.6 at 1/36°x1/27° horizontal resolution and 31 vertical levels (Lima et al., 2021).

Climate oriented applications developed at CMCC are:

  • CMCC Earth System Model v2 (CMCC-ESM2, Lovato et al., 2022) participated in the CMIP6 intercomparison project: its ocean component is based on NEMO v3.6 at 1° horizontal resolution and 50 vertical levels;
  • CMCC global ocean configurations participated in OMIP1 and OMIP2 exercises with the NEMOv3.6 ocean component as part of CESM at 1° and 1/4° horizontal resolution with 75 vertical levels. The NEMOv3.6-LIM2 participated in the HighRes OMIP2 with the eddying ocean configuration GLOB16 system at 1/16° horizontal resolution and 98 vertical levels;
  • CMCC Coupled Model v2 (CMCC-CM2, Cherchi et a;. 2019) based on CESM with NEMOv3.6 as ocean model, participated in the CMIP6 with a 1° horizontal resolution (refinement at 1/3° near the equator) and 50 geopotential levels. Similar system with a global NEMOv3.6 ocean at 1/4° and 50 vertical levels contributed to the HighRes MIP.


Clementi, E., Pistoia, J., Delrosso, D., Mattia, G., Fratianni, C., Storto, A., Ciliberti, S., Lemieux, B., Fenu, E., Simoncelli, S., Drudi, M., Grandi, A., Padeletti, D., Di Pietro, P., Pinardi, N., (2017). A 1/24 degree resolution Mediterranean analysis and forecast modelling system for the Copernicus Marine Environment Monitoring Service. Extended abstract to the 8th EuroGOOS Conference, Bergen

Clementi, E., Aydogdu, A., Goglio, A. C., Pistoia, J., Escudier, R., Drudi, M., Grandi, A., Mariani, A., Lyubartsev, V., Lecci, R., Cretí, S., Coppini, G., Masina, S., & Pinardi, N. (2021). Mediterranean Sea Analysis and Forecast (CMEMS MED-Currents, EAS6 system) (Version 1) [Data set]. Copernicus Monitoring Environment Marine Service (CMEMS).

Escudier R., Clementi E., Cipollone A., Pistoia J., Drudi M., Grandi A., Lyubartsev V., Lecci R., Aydogdu A., Delrosso D., Omar M., Masina S., Coppini G., Pinardi N. 2021. A High Resolution Reanalysis for the Mediterranean Sea. Frontiers in Earth Science, Vol 9, pp 1060, DOI: 10.3389/feart.2021.702285.

Madec G. and NEMO System Team, “NEMO ocean engine”, Scientific Notes of Climate Modelling Center (27) – ISSN 1288-1619, Institut Pierre-Simon Laplace (IPSL)

NEMO Sea Ice Working Group, “Sea Ice modelling Integrated Initiative (SI3) – The NEMO sea ice engine”, Scientific Notes of Climate Modelling Center (31) – ISSN 1288-1619, Institut Pierre-Simon Laplace (IPSL)

NEMO TOP Working Group, “Tracer in Ocean Paradigm (TOP) – The NEMO passive tracer engine”, Scientific Notes of Climate Modelling Center (28) – ISSN 1288-1619, Institut Pierre-Simon Laplace (IPSL)

Iovino, D., Masina, S., Storto, A., Cipollone, A., and Stepanov, V. N.: A 1/16° eddying simulation of the global NEMO sea-ice–ocean system, Geosci. Model Dev., 9, 2665–2684,, 2016

Iovino, D., Masina, S., Fogli P.G.: Resolving Mesoscale Dynamics in Global Ocean. AGU Fall Meeting 2018. Washington DC, US.

Masina S., Cipollone A., Iovino D., Ciliberti S., Coppini G., Lecci R., Trotta F., Pinardi N. and  Baordo F.: GOFS16: A Global Ocean-Sea Ice Forecast System at Eddying Resolution OM21A-06 Ocean Science Meeting 2020, San Diego, CA.

Lovato, T., Peano, D. , Butenschön, M., Materia, S., Iovino, D., Scoccimarro, E., Fogli, P. G., Cherchi, A., Bellucci, A., Gualdi, S., Masina, S., Navarra, A., (2022). CMIP6 simulations with the CMCC Earth System Model (CMCC-ESM2). Journal of Advances in Modeling Earth Systems.

Epicoco, I., Mele, F., Mocavero, S., Chiarelli, M., D’Anca, A., Aloisio, G., Refactoring the Memory Access Pattern to Improve Computational Performance in NEMO, EGU 2020-9723

Epicoco, I., Mocavero, S., Mele, F., D’Anca, A., and Aloisio, G., New communication strategies in NEMO, EGU21-4762

Mele, F., Epicoco, I., Mocavero, Calvert, D., Bell, M., Preparing NEMO4.2, the new NEMO modeling framework for the next generation HPC infrastructures, EGU22-13484

Calvert, D., Bell, M., Mele, F., Epicoco, I., Masson, S., Glover, M., Madec, G., Loop blocking (“tiling”) in NEMO, EGU22-13438

Ciliberti, S. A., Jansen, E., Martins, D., Gunduz, M., Ilicak, M., Stefanizzi, L., Lecci, R., Cretí, S., Causio, S., Aydogdu, A., Lima, L., Palermo, F., Peneva, E. L., Coppini, G., Masina, S., Pinardi, N., & Palazov, A. (2021a). Black Sea Physical Analysis and Forecast (CMEMS BS-Currents, EAS4 system) (Version 1) [Data set]. Copernicus Monitoring Environment Marine Service (CMEMS).

Lima, L., Ciliberti, S.A., Aydogdu, A., Masina, S., Escudier, R., Cipollone, A., Azevedo, D., Causio, S., Peneva, E., Lecci, R., Clementi, E., Jansen, E., Ilicak, M., Creti’, S., Stefanizzi, L., Palermo, F., Coppini, G. (2021). Climate Signals in the Black Sea From a Multidecadal Eddy-Resolving Reanalysis. Front. Mar. Sci.,

Ciliberti, S., Jansen, E., Azevedo, D., Ilicak, M., Gunduz, M., Matreata, M., Lima, L., Aydogdu, A., Causio, S., Stefanizzi, L., Creti’, S., Lecci, R., Peneva, E., Masina, S., Coppini, G., Pinardi, N., Palazov, A. (2021b). Improving the accuracy of the Black Sea physics analysis and forecasting system in the framework of Copernicus Marine Service. 9th EuroGOOS International conference, Shom; Ifremer; EuroGOOS AISBL, May 2021, Brest, France. ffhal-03334309f

Storto, A., and Masina S. (2016): “C-GLORSv5: an improved multipurpose global ocean eddy- permitting physical reanalysis”. Earth System Science Data, 8 (2), 679–696.

Storto, A., Masina, S., Simoncelli, S. et al. The added value of the multi-system spread information for ocean heat content and steric sea level investigations in the CMEMS GREP ensemble reanalysis product. Clim Dyn 53, 287–312 (2019).

Cipollone, A., Storto, A., & Masina, S. (2020). Implementing a Parallel Version of a Variational Scheme in a Global Assimilation System at Eddy-Resolving Resolution, Journal of Atmospheric and Oceanic Technology, 37(10), 1865-1876


Stefania Ciliberti.

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