2: Pre-Industrial Compset: F1850C_LTso

2: Pre-Industrial Compset: F1850C_LTso#

Understanding Pre-Industrial Simulations#

In the previous exercise, you created a control simulation using FHISTC_LTso, which uses time-varying historical sea surface temperatures, sea ice, greenhouse gases, aerosols, and other forcings.

In this exercise, you will run F1850C_LTso, a pre-industrial configuration. Unlike the historical compset, F1850C_LTso uses repeating climatological conditions representative of approximately the year 1850.

This type of simulation can be used as a baseline pre-industrial climate state for climate change studies because it represents Earth before major anthropogenic influences.

By comparing this simulation to the historical control, you will learn how CESM handles different forcing configurations and how to verify that your simulation is using the intended datasets.

Exercise: Run a Pre-Industrial Simulation

Create, configure, build, and run a case called f1850 using:

Compset: F1850C_LTso
Resolution: ne16pg3_ne16pg3_mg17

Use the same CAM history output settings as in the previous exercise and run for 5 days.

As you work through the exercise, consider the following questions:

How can you verify that this simulation is configured differently from your historical control case?
How can you determine which SST and forcing datasets are being used?
What model year is being simulated?
How does the model start date differ from the historical control case?

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

How can I verify which forcing datasets,SSTs, and start date are being used?

Look at the generated namelists:

$CASEDIR/CaseDocs/atm_in

You can also compare the SSTs between the historical and pre-industrial cases:

./xmlquery SSTICE_DATA_FILENAME

and the start date:

./xmlquery RUN_STARTDATE

I am getting an error: This compset and grid combination is untested in CESM You might be getting this error if the ne16pg3_ne16pg3_mg17 is not a supported resolution in teh version 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:

tcsh user

set CASENAME=f1850
set CASEDIR=/glade/u/home/$USER/cases/$CASENAME
set RUNDIR=/glade/derecho/scratch/$USER/$CASENAME/run
set COMPSET=F1850C_LTso
set RESOLUTION=ne16pg3_ne16pg3_mg17

bash user

export CASENAME=f1850
export CASEDIR=/glade/u/home/$USER/cases/$CASENAME
export RUNDIR=/glade/derecho/scratch/$USER/$CASENAME/run
export COMPSET=F1850C_LTso
export RESOLUTION=ne16pg3_ne16pg3_mg17

# 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

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

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 "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  

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 usefule to check that your changes made their way into:

$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

# Verify the Configuration

Before or after the run, compare key settings with your historical control case.

Check the Start Date

./xmlquery RUN_STARTDATE

Unlike the historical case, which starts in a modern historical year, the F1850C_LTso simulation should start at 0001 which is typically when using a pre-industrial repeating a single year.

Check the SST Dataset

You should find that:

fhist.control uses historical time-varying SST datasets.
f1850 uses pre-industrial climatological SST datasets representative of approximately 1850.

./xmlquery SSTICE_DATA_FILENAME

For the should see:

SSTICE_DATA_FILENAME: /glade/campaign/cesm/cesmdata/inputdata/atm/cam/sst/sst_HadOIBl_bc_1x1_clim_pi_c101029.nc

Compare Additional Forcing Datasets

Inspect the atmospheric namelist:

 $CASEDIR/CaseDocs/atm_in

Compare the forcing datasets used by: fhist.control f1850

Look for differences in:

Greenhouse gas concentrations
Aerosol forcing
…

These differences are the primary reason the two simulations represent different climate states.

# Check your solution

When the run is completed, look at the history files into 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)

Notice that the history file names begin in year 0001. This is different from fhist.control, which starts in a modern historical period.

(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 because the output is instantaneous.

# What Changed Relative to the Historical Control?

Compare the following between fhist.control and f1850:

RUN_STARTDATE
SST forcing datasets
Greenhouse gas concentrations
Aerosol forcing
Atmospheric chemistry forcing files
Sea-ice forcing datasets

Understanding these differences is one of the key goals of this exercise.

The atmospheric model and output settings are nearly identical between the two cases. The primary difference is the forcing environment: one represents the historical climate system, while the other represents pre-industrial conditions.

Setting	fhist.control	f1850.control	Why it matters
Compset	FHISTC_LTso	F1850C_LTso	Controls the forcing protocol
Resolution	ne16pg3_ne16pg3_mg17	ne16pg3_ne16pg3_mg17	Same model grid
Forcing Type	Historical, time-varying	Pre-industrial climatology	Main scientific difference
SST Dataset	Historical SSTs	Pre-industrial climatological SSTs	Changes atmospheric forcing
Sea Ice	Historical, time-varying	Pre-industrial climatology	Changes surface boundary conditions
Greenhouse Gases	Historical concentrations	1850 concentrations	Changes radiative forcing
Aerosols	Historical forcing	1850 forcing	Changes clouds and radiation
Start Date	Modern historical period	Year 0001	Different model calendar

2: Pre-Industrial Compset: F1850C_LTso

Contents

2: Pre-Industrial Compset: F1850C_LTso#

Understanding Pre-Industrial Simulations#