Supergrid

About

The supergrid is created using ORCA_gridgen which relies on the NEMO ocean modelling framework to generate tripolar grids for MOM6. For a complete description of the code, please check this user guide. The original code has been modified to create an supergrid (ocean_hgrid.nc), in addition to the defaults files for NEMO (coordinates.nc and coordinates_north.nc).

TODO: describe what else was modified… parallel, u point at the Equator, etc

Usage

File param.f90 has the modifications needed to generate the nominal 1/4 degree resolution grid (tx1_4); The original (default) configuration used for ORCA1 is also included for comparison (file param.f90.ori and trop.f90.ori). A simple diff of the files can be used to check what has been changed to create tx1_4:

diff param.f90 param.f90.ori

The code is intended to compile under any compliant Fortran 90 compiler. It must be compiled with a flag that promotes reals to 8 bytes. It must be linked with the NetCDF F90 library. To compile ORCA_gridgen on Casper, load the following modules:

module load intel/19.1.1
module load netcdf/4.8.1

Then type:

cd ORCA_gridgen
make clean
make

This should create an executable called “tripole.exe”. Next, type the following:

./tripole.exe

This should create three NetCDF files: ocean_hgrid.nc, coordinates.nc and coordinates_north.nc. For MOM6, we only use ocean_hgrid.nc.

This supergrid extends far South to accomodate ice shelves, when desired. This configuration will not include ice shelves and, therefore, we will trim the supergrid to reduce the amount of grid points on land.

python trim_south.py

This should create ocean_hgrid_trimmed.nc.