Exercise 3: Modifying DATM variables

Exercise 3: Modifying DATM variables#

Exercise: Change the atmospheric forcing years#

Create a new case named “i2000_forcing_years” using the same component set as in the Change component set chapter, e.g., i2000_fates_sp.basics.

Before running, use xmlquery to look at the current forcing settings:

./xmlquery DATM_YR_START,DATM_YR_END,DATM_YR_ALIGN

Then use xmlchange to make the model cycle over a different block of forcing years. Set DATM_YR_START to 2005 and DATM_YR_END to 2009. Set DATM_YR_ALIGN to the year your run starts (the year in RUN_STARTDATE), so that the first model year uses the 2005 forcing.

Run the case for 1 year.

Think about: What would happen if your run were longer than 5 years? What does DATM_YR_ALIGN control that DATM_YR_START does not?

Hint!

The data atmosphere (DATM) reads a fixed block of forcing years and cycles through them over the course of your run. Three variables control this:

  • DATM_YR_START: the first year of forcing data to use.

  • DATM_YR_END: the last year of forcing data to use.

  • DATM_YR_ALIGN: the model year that is matched to DATM_YR_START.

For example, for a run that starts in model year 2000 with DATM_YR_START=2005, DATM_YR_END=2009, and DATM_YR_ALIGN=2000, model year 2000 is forced with 2005 data, model year 2001 with 2006 data, and so on up to model year 2004 with 2009 data. In model year 2005 the forcing wraps back around to 2005.

Click here for the solution

  1. From the script directory, create your case:

    cd /glade/u/home/$USER/code/my_clm_code/cime/scripts/
    ./create_newcase --case /glade/u/home/$USER/cases/i2000_forcing_years --res f19_f19_mt233 --compset I1850Clm60SpCrujra --run-unsupported

  1. In your case directory, change the runtime variables:

    cd /glade/u/home/$USER/cases/i2000_forcing_years
    ./xmlchange DATM_YR_START=2005
    ./xmlchange DATM_YR_END=2009
    ./xmlchange DATM_YR_ALIGN=2000
    ./xmlchange STOP_N=1
    ./xmlchange STOP_OPTION='nyears'
    ./xmlchange JOB_WALLCLOCK_TIME=1:00:00
    ./xmlchange JOB_QUEUE=tutorial --force

  1. Set up the case:

    ./case.setup

  1. Continue to build and submit:

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

Remember that qcmd is used on Derecho only.

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