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NEMO Reference Configuration

The SURF-NEMO platform uses the NEMO (Nucleus for European Modelling of the Ocean) model as its core ocean circulation component. A solid understanding of NEMO is helpful for advanced configuration and for a deeper interpretation of simulation results. For more information and official documentation, please visit the NEMO website.

The version of NEMO included within the SURF-NEMO Docker container is precompiled and ready to use, eliminating the need for manual compilation.

NEMO Version

Details:

NEMO Configuration for SURF

A customized NEMO configuration named SURF has been created including only the ocean (OCE) component. It is based on the ORCA2_ICE_PISCES reference configuration, with sea-ice and biogeochemistry components disabled by excluding the key_si3 and key_top preprocessor keys.

As part of the SURF-NEMO approach, the configuration process is designed to balance flexibility with automation. Users can specify key NEMO parameters via a user-friendly JSON configuration file, while other settings are either preconfigured with recommended defaults or dynamically computed at runtime. This design simplifies setup while supporting advanced customization.

For a complete list of user configurable parameters — both basic and advanced options — refer to the Configuration Section of this manual.

Source Code Customizations

The SURF configuration incorporates specific modifications to the NEMO source code. These customized subroutines are located in the MY_SRC directory within the NEMO source tree:

  • istate.F90, tdasshd.F90, dtauvd.F90: These subroutines have been extended to allow initialization of all prognostic variables, including zonal and meridional velocities and sea surface height (SSH), in addition to temperature and salinity fields. Two custom namelist sections — &namuvd and &namsshd — have been added to control this behavior through flags such as ln_uvd_init and ln_sshd_init. These customizations are particularly beneficial for short-term simulations, as they can reduce the model's spin-up period.

  • sbc_phy.F90, sbcblk.F90, sbcblk_algo_mfs.F90: These modules have been modified to allow the MFS bulk formulae to accept dew-point temperature.

The NEMO Namelist

NEMO is configured using plain text files called namelists, which define key aspects of the simulation, such as run duration, time-stepping, physical parameterizations, and numerical schemes. In addition to namelists, NEMO uses XML files used by the XIOS library to manage model output.

During the simulation step, SURF writes the namelist for each simulation day, based on the user configuration and on internally set defaults.

Below is the reference namelist_ref file, organized into tiles by section for easier browsing. More details for each parameter can be found in the NEMO manual.

In the namelist, the placeholders @@@ are replaced with the corresponding values from the SURF configuration file.

NEMO namelist

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DOMAINcfg namelist

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