Creating a restart for a new ocean grid

This document describes the bootstrap method used to generate the initial conditions for the AGCM when introducing a new NEMO configuration (i.e. anything other than ORCA1, ORCA025, and eORCA1). This document assumes that the user has a general knowledge of running CanESM5.

  1. Ensure that you have a working NEMO, OMIP-style simulation that can at least run a few timesteps.

  2. save all the necessary input fields and and update the CanESM sequencing, perhaps specifying a new NEMO configuration, and CanESM5 runmode

  3. Create a new CanESM5 run in the typical way

  4. Modify canesm.cfg with the following - Update CanNEMO_CONFIG to the new configuration - Update the runmode to CanESM-init - debug=on to make sure the run directory is retained when the model crashes

  5. Run the model in the normal way. The model will likely crash at the end of the first timestep. This is expected because the ocean and atmosphere do not agree on the land mask.

  6. Navigate to the run directory under $CCRNTMP

  7. Copy the cpl_fland.nc (or cpl_fland_info.nc, depending on agcm version) file in the directory to a temporary scratch directory

  8. From the cpl_fland.nc (or cpl_fland_info.nc, depending on agcm version) file create a new file that contains the variable SRCF which is fraction of ocean in each grid cell.

    1. Use python, ncks, etc. to calculate 1-FLND and create a new netCDF file with the variable SRCF. For example,

      $ ncap2 -s “SRCF=1-fland_cpl” cpl_fland_info.nc cpl_srcf.nc

    2. (For spectral AGCM grid) Use ncks to expand the lon dimension to account for the longitudinal cycle. For example,

      $ ncks -h -O –msa_usr_rdr -d lon,0,127 -d lon,0 cpl_srcf.nc cpl_srcf.nc

    3. Use nc2ccc to convert this file to a CCCma-style file, for example,

      $ nc2ccc var=SRCF cpl_srcf.nc t63_to_eorca1_i_fland_caspian

  9. This file can then be passed to Vivek to create a new river routing file

  10. save both the new SRCF and river routing file

  11. Update CCCma_tools/cccjob_dir/lib/jobdefs/canesm_cgcm_jobdef (GEM) or CanESM_source_link/CONFIG/ESM/model_run_basefile_defaults.cfg (spectral)

    1. Change maskfile to the saved file with SRCF

    2. Change target to the new river routing file

  12. After all these changes, run the model again. This will run for a year and create a new useable restart.