Nemo

Welcome to the Bristol Nemo Page!

Here are a few tips and comments based on Bristol's experiences compiling and running NEMO. Hopefully, you will find some useful.

Please take a look the official NEMO webpage before continuing with this page.

Projects using Nemo at Bristol

Amundsen Sea

Thinning of the Pine Island Glacier, West Antarctica, has been observed during the 1990s. It has been suggested that relatively warm water at the base of the ice shelf has triggered the thinning. The source of and mechanism driving this warm water is unknown.

We are constructing a regional model of the Amunsden Sea using Nemo to investigate ocean circulation close to Pine Island Bay. Input data at the sea surface and at the open boundaries are constructed using output data from the OCCAM global ocean model.

ORCA2_LIM test case

Nemo provides a test case, ORCA2_LIM, for a global ocean run coupled with the sea-ice model. The run simulates one year.

The configuration for ORCA2_LIM is downloaded through CVS when getting Nemo and the necessary forcing files are provided through a link on the Nemo website.

Region model

How to set up a regional model starting from the ORCA2_LIM test case:

1. Create a new configuration for the regional model.
   • In directory modipsl/config/ create a new directory AMUNDSEN, for example, and copy the contents of the ORCA2_LIM directory into AMUNDSEN.
   • Edit file fait_config in modipsl/modeles/UTIL/. Add \n AMUNDSEN to LIST = and add the line set -A DIR_AMUNSDEN OPA_SRC C1D_SRC NST_SRC.
2. Change CPP keys by editing BB_make.ldef in modipsl/config/AMUNDSEN/scripts/. Remove key_orca_r2 since you're not running a global model and add key_obc to invoke open boundary conditions instead.
3. TIP: modify tradmp.F90 in modipsl/modeles/NEMO/OPA_SRC/TRA/. Replace the line if (cp_cfg=="orca" .AND. (ndmp > 0 .OR. ndmp==-1)) then with if (ndmp > 0 .OR. ndmp==-1) then. If you don't make the change you'll get the error message tra_dmp: You should not have seen this print error?. With this change you can apply tracer damping as in the ORCA configurations (i.e. global models for various resolutions) without special treatment for particular areas such as the Mediterranean or the Red Sea that are grid dependent.
4. Set the new domain resolution in par_oce.F90 in modipsl/modeles/NEMO/OPA_SRC/. Parameters for the resolution are jpidta and jpjdta.
5. Set parameters in obc_oce.F90 and obc_par.F90 in modipsl/modeles/NEMO/OPA_SRC/OBC/.
   • obc_oce.F90: nbobc is the number of open boundaries, i.e. set to 1, 2, 3 or 4.
   • obc_par.F90: set logical parameter lp_obc_east to .true. if open boundary conditions are to be applied to part or all of the eastern face of the domain. Similarly for lp_obc_west, lp_obc_north and lp_obc_north.

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