Exercise 2: Modify run type

Exercise 2: Modify run type#

Exercise: Modify the env_run.xml file

Branch from the end of Exercise 1 Part I to create a new case named “b.day2.2”.
Double the ocean coupling frequency (OCN_NCPL). Include an initial file as output data. Run for 1 month, then restart for 1 month.

Hint!

For a branch run, we need to set several variables related to the reference case in env_run.xml. To find variables applied to reference case (Branch and Hybrid runs), use ./xmlquery -p REF.
Ocean coupling frequency needs to be changed in env_run.xml, controlled by the variable OCN_NCPL. What is the default value of OCN_NCPL? Use xmlquery to find out! You may also take a look at the variable description in env_run.xml to learn more about the variable.
Make sure to update the walltime to match the run length.
Don’t forget to put restart files into the run directory $RUNDIR.
To include an initial file as output, we will need to modify the variable inithist in the atmospehre namelist user_nl_cam. We will learn more about this in the next chapter namelist modification.

Click here for the solution

1. Create your new case with the command:

    cd /glade/work/$USER/code/my_cesm_code/cime/scripts/
    ./create_newcase --case /glade/work/$USER/cases/b.day2.2 --res f19_g17 --compset B1850

2. In your case directory, change the run type to branch, and change the associated RUN_* variables:

    cd /glade/work/$USER/cases/b.day2.2
    ./xmlchange RUN_TYPE=branch
    ./xmlchange RUN_REFCASE=b.day2.1,RUN_REFDATE=0001-04-01,GET_REFCASE=FALSE

3. Set run time variables:

    ./xmlchange STOP_OPTION=nmonths,STOP_N=1,RESUBMIT=1,JOB_WALLCLOCK_TIME=02:00:00

4. Double ocean coupling frequency in `env_run.xml`:

    ./xmlchange OCN_NCPL=48

5. Set up the case, put the initial and restart files in the `$RUNDIR`:

    ./case.setup
    cp /glade/scratch/$USER/archive/b.day2.1/rest/0001-04-01-00000/*  /glade/scratch/$USER/b.day2.2/run/

6. To include an initial file at the end of the run, add the following lines to file `user_nl_cam`:

   inithist='ENDOFRUN'

7. Run ./preview_namelists:

    ./preview_namelists

6. Carry on to build and submit the run:

      qcmd -- ./case.build
      ./case.submit

Remember that qcmd is used on Cheyenne only.

After the job completes, go to the short term archive space and explore.