3: Starting FHIST from spunup state in 1850#

By default the FHIST starts from a default initial condition in 1979, but you can start from another year and use initial conditions coming from a previous run.

Exercise: Customize your CAM history files

Create, configure, build and run a case called fhist.1850 with the compset FHIST at the resolution f09_f09_mg17 using the same history file output as in the control.

  • Use initialization datasets from a previous case.
    For instance, use the data from the run: b.e21.B1850.f19_g17.CMIP6-piControl-2deg.001 at year 321

  • Start model in 1850.

  • Run for 5 days.

Check your solution:

  • How can you check that there is a difference between the set up of this and your control?

  • How can you check that it is running the way you intended: using ssts & ghg forcings from time-varying, historical files?

  • What year is the model running?

Click here for hints

How do I start my run using initialization datasets from a previous run?

  • Look at chapter Modifify the run type. In that chapter, you learned different ways to start up the model, and how to use initial conditions/restart files from a different case to start up a hybrid case. Use that method for the current exercise.

  • Data from spun-up model runs can be found in inputdata (DIN_LOC_ROOT) .

How do I start my run in 1850?

  • Look at the description of the xml variable RUN_STARTDATE

How do I output 3 hourly instantaneous variables?

  • Use namelist variables: nhtfrq, mfilt, fincl.

  • For more information, look at the chapter:
    NAMELIST MODIFICATIONS -> Customize CAM output

I am getting an error: This compset and grid combination is untested in CESM

  • overide this error by adding --run-unsupported to the create_newcase command

Click here for the solution

# Set environment variables

Set environment variables with the commands:

tcsh

set CASENAME=fhist.1850
set CASEDIR=/glade/u/home/$USER/cases/$CASENAME
set RUNDIR=/glade/scratch/$USER/$CASENAME/run
set COMPSET=FHIST
set RESOLUTION=f19_f19_mg17

bash

export CASENAME=fhist.1850
export CASEDIR=/glade/u/home/$USER/cases/$CASENAME
export RUNDIR=/glade/scratch/$USER/$CASENAME/run
export COMPSET=FHIST
export RESOLUTION=f19_f19_mg17

# Create a new case

Create a new case with the command create_newcase:

cd /glade/work/$USER/code/my_cesm_code/cime/scripts/
./create_newcase --case $CASEDIR --res $RESOLUTION --compset $COMPSET --run-unsupported

# Change the job queue and account number

If needed, change job queue and account number.
For instance, to run in the queue regular and the project number P93300642

cd $CASEDIR
./xmlchange JOB_QUEUE=regular,PROJECT=P93300642

This step can be redone at anytime in the process.

# Setup

Invoke case.setup with the command:

cd $CASEDIR
./case.setup

# Customize namelists

Edit the file user_nl_cam and add the lines:

nhtfrq(2) = -3
mfilt(2) = 240
fincl2 = 'TS:I','PS:I', 'U850:I','T850:I','PRECT:I','LHFLX:I','SHFLX:I','FLNT:I','FLNS:I'

You can do this with a text editor. Alternatively, you can use the echo command:

echo "nhtfrq(2) = -3">> user_nl_cam    
echo "mfilt(2) = 240">> user_nl_cam
echo "fincl2 = 'TS:I','PS:I', 'U850:I','T850:I','PRECT:I','LHFLX:I','SHFLX:I','FLNT:I','FLNS:I'">> user_nl_cam
echo "">> user_nl_cam

You build the namelists with the command:

./preview_namelists

This step is optional as the script preview_namelists is automatically called by case.build and case.submit. But it is nice to check that your changes made their way into:

$CASEDIR/CaseDocs/atm_in

# change starting date and ref case

./xmlchange RUN_STARTDATE=1850-01-01  
./xmlchange RUN_REFCASE=b.e21.B1850.f19_g17.CMIP6-piControl-2deg.001
./xmlchange RUN_REFDATE=0321-01-01

# Set run length

If needed, change the run length. If you want to run 5 days, you don’t have to do this, as 5 days is the default.

./xmlchange STOP_N=5,STOP_OPTION=ndays

# Build and submit:

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

# Check your solution

When the run is completed, look at the history files into the archive directory.

(1) Check that your archive directory on cheyenne (The path will be different on other machines):

cd /glade/scratch/$USER/archive/$CASENAME/atm/hist
ls

As your run is only 5-day, there should be no monthly file (h0)

Notice that the start year is 1850.

(2) Look at the contents of the h1 files using ncdump.

  • The file should contain the instantaneous output in the file h1 for the variables:

        float FLNS(time, lat, lon) ;
                FLNS:Sampling_Sequence = "rad_lwsw" ;
                FLNS:units = "W/m2" ;
                FLNS:long_name = "Net longwave flux at surface" ;
        float FLNT(time, lat, lon) ;
                FLNT:Sampling_Sequence = "rad_lwsw" ;
                FLNT:units = "W/m2" ;
                FLNT:long_name = "Net longwave flux at top of model" ;
        float LHFLX(time, lat, lon) ;
                LHFLX:units = "W/m2" ;
                LHFLX:long_name = "Surface latent heat flux" ;
        float PRECT(time, lat, lon) ;
                PRECT:units = "m/s" ;
                PRECT:long_name = "Total (convective and large-scale) precipitation rate (liq + ice)" ;
        float PS(time, lat, lon) ;
                PS:units = "Pa" ;
                PS:long_name = "Surface pressure" ;
        float SHFLX(time, lat, lon) ;
                SHFLX:units = "W/m2" ;
                SHFLX:long_name = "Surface sensible heat flux" ;
        float T850(time, lat, lon) ;
                T850:units = "K" ;
                T850:long_name = "Temperature at 850 mbar pressure surface" ;
        float TS(time, lat, lon) ;
                TS:units = "K" ;
                TS:long_name = "Surface temperature (radiative)" ;
        float U850(time, lat, lon) ;
                U850:units = "m/s" ;
                U850:long_name = "Zonal wind at 850 mbar pressure surface" ;

Note that these variables have no cell_methods attribute becasue the output is instantaneous.