Workflow changes between NorESM2 and NorESM3

1. checkout_externals vs. git-fleximod
2. rpointer file format
3. archive and compress job scripts

checkout_externals vs. git-fleximod

• Discussion page: NorESM #599
• See ./bin/git-fleximod --help for further info and options.
• Developed at NCAR: https://github.com/ESMCI/git-fleximod

The tag noresm2_5_alpha08 replaces checkout_externals with git-fleximod for checkoing out NorESM source code. Related to this change, external components are now defined in the .gitmodules files instead of the Externals.cfg file.

Updating components managed by git-fleximod

Updating a NorESM component tag has two goals:

• Commit NorESM (top level) so that all component submodules are recorded in the desired state. That is, running git checkout --recurse-submodules <new_tag> at the top level should checkout the NorESM tree to the correct state.
• Document the correct tag(s) by updating the fxtag entries in the top-level .gitmodules file

This procedure should always work:

1. In your NorESM clone, create a new update-BLOM-tag branch and fully check it out (git checkout -b update-blom-tag NorESM/noresm_develop && ./bin/git-fleximod update --optional).
   • git submodule status should be 'clean' (the first column is blank for all submodules).
2. In components/blom, checkout the new tag and run git submodule update.
   • git submodule status should be clean.
3. At the top level, update the fxtag value in the blom submodule section of the .gitmodules file with the new BLOM tag.
4. Run git commit -a -m 'Updated BLOM tag to rev.x.y.z.q'.
5. Push this to your fork and open a PR.

The rpointer (restart) filename format

The restart file rpointer.<component> used to be a file pointing to the latest restart file for each component. In NorESM3 this filename now includes a timestamp, and a new file is created for each set of restart files instead of overwriting the existing file. The reference timestamp is controled by the xmlcange option DRV_RESTART_POINTER.

Example script setting timestamp (month 12, year 1):

## Copy YEAR-001 restart files to run directory 
RESTCASE=${RESTCASE:-"n1850.ne16_tn14.noresm3_0_beta03b-run6_yr001.20251029"} 
RESTDIR=${RESTDIR:-"/cluster/work/users/${USER}/archive/${RESTCASE}/rest"} 
RESTDATE=${RESTDATE:-"0001-12-01"} 
cp ${RESTDIR}/${RESTDATE}-00000/* ${RUNDIR} 
 
# restart settings 
./xmlchange RUN_TYPE=branch 
./xmlchange RUN_REFCASE=${RESTCASE} 
./xmlchange RUN_REFDATE=${RESTDATE}  
./xmlchange DRV_RESTART_POINTER="rpointer.cpl.${RESTDATE}-00000"

Archive and compress job scripts

In NorESM2, the archive and compression scripts were run together in a single case.st_archive job. For NorESM3 these processes are in two separate jobs, case.st_arcive and case.compress, hence each simulation job spawns 3 tasks instead of 2 tasks in the HPC queue system. This does not have much practical implications from a user perspective, except that each of these tasks have their own task_count, tasks_per_node and walltime parameters.