1: Control case: FHISTC_LTso

1: Control case: FHISTC_LTso#

In this exercise, you will create and run a control simulation using the FHISTC_LTso compset.

The FHISTC_LTso compset uses prescribed historical sea surface temperatures (SSTs), sea ice, and historical forcing data with the low-top atmosphere configuration.

You will also customize CAM history output to produce 3-hourly instantaneous fields interpolated on a lat/lon grid that can later be used to compare against sensitivity experiments.

`FHISTC_LTso` follows the AMIP protocol which is a standardized experimental protocol for global Atmospheric General Circulation Models (AGCMs).

For more information about the AMIP protocol and the HadSST data sets

Why This Control Case Matters

This control simulation will serve as the baseline for later experiments in this section. By keeping the compset, resolution, run length, and output variables consistent, you will be able to compare sensitivity experiments directly against this control case.

For example, later experiments may modify SSTs, forcing files, datasets, or model parameters. The control case allows you to identify which differences are caused by the experiment itself.

Exercise: Customize your CAM history files

Create, configure, build, and run a case called fhist.control using:

  • Compset: FHISTC_LTso

  • Resolution: ne16pg3_ne16pg3_mg17

Run the case for *5 days with 3-hourly instantaneous output for the following variables:

TS, PS, Z500, U850, U200, T850, T500, T200, CLDLOW, PRECT, LHFLX, SHFLX, FLNT, FLNS

In addition, configure the history files to be automatically interpolated to a regular 2° × 2° latitude-longitude grid.

You are also welcome to output additional variables of interest.

About the resolution for FHISTC_LTso

  • Supported resolution for this compset is ne30pg3_ne30pg3_mg17 This is approximately a 1-degree atmosphere and land grid.

  • During the tutorial, we recommend using ne16pg3_ne16pg3_mg17 This lower-resolution configuration runs faster and is better suited for short tutorial exercises.

Click here for hints

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

What if I get an unsupported-grid warning?*

You might be getting this error if the ne16pg3_ne16pg3_mg17 is not a supported resolution in the version of the model you are using.

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:

For tcsh users

set CASENAME=fhist.control
set CASEDIR=/glade/u/home/$USER/cases/$CASENAME
set RUNDIR=/glade/derecho/scratch/$USER/$CASENAME/run
set COMPSET=FHISTC_LTso
set RESOLUTION=ne16pg3_ne16pg3_mg17

For bash users

export CASENAME=fhist.control
export CASEDIR=/glade/u/home/$USER/cases/$CASENAME
export RUNDIR=/glade/derecho/scratch/$USER/$CASENAME/run
export COMPSET=FHISTC_LTso
export RESOLUTION=ne16pg3_ne16pg3_mg17

# Make a case directory

If needed create a directory cases into your home directory:

mkdir /glade/u/home/$USER/cases/

# Create a new case

Create a new case with the command create_newcase:

cd /glade/u/home/$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 tutorial and the project number UESM0014. You should use the project number given for this tutorial.

cd $CASEDIR
./xmlchange JOB_QUEUE=tutorial,PROJECT=UESM0014 --force

Use the project number provided for your tutorial. This step can be repeated at any time before submitting the case.

# 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'
interpolate_output(2) = .true.
interpolate_nlat(2)   =  91
interpolate_nlon(2)   = 180

This creates a second CAM history stream, h1, with 3-hourly instantaneous output.

You can edit the file with a text editor. Alternatively, you can add the lines using echo:

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 "interpolate_output(2) = .true.">> user_nl_cam    
echo "interpolate_nlat(2)   = 91">> user_nl_cam    
echo "interpolate_nlon(2)   = 180">> user_nl_cam    
echo "">> user_nl_cam

Build the namelists:

./preview_namelists

This step is optional because preview_namelists is automatically called by case.build and case.submit.

However, it is useful to check that your changes appear in:

$CASEDIR/CaseDocs/atm_in

# 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 complete, examine the history files in the archive directory.

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

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

As your run is only 5-day, there should be no monthly file (h0). You should see 3-hourly h1 files.

(2) Inspect the contents of the h1 files using ncdump.

ncdump -h f2000_control.cam.h1.0001-01-01-00000.nc

The filename may differ depending on the model start date, so you can also use:

ncdump -h *.cam.h1.*.nc

The file should contain instantaneous output for variables such as:

  • 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.

For more information about the AMIP protocol and the HadSST data sets