Exercise 2: Modify History Frequency

Exercise 2: Modify History Frequency#

Exercise: Create a daily history file#

Create a new case named i2000_bgc_hist_daily using the compset I2000Clm60BgcCrujra and resolution f19_f19_mt233.

By default CLM writes one monthly history file. Add a second history file that writes daily averages of TSA (2-m air temperature) and TLAI (leaf area index).

Click here for hints

How do I control the output?

Use CLM namelist variables:

hist_fincl1 and hist_fincl2
hist_nhtfrq
hist_mfilt

Remember that if hist_nhtfrq = 0, the file contains monthly averages, if hist_nhtfrq > 0, the output frequency is given as a number of model time steps, and if hist_nhtfrq < 0, the output frequency is given as a number of hours.

Think about: Each value in hist_nhtfrq and hist_mfilt lines up with a history file (the first is for h0, the second for h1). A negative hist_nhtfrq is interpreted as hours, and 0 means monthly. What does hist_mfilt control?

If you left hist_mfilt out and the daily file never appeared after a 1-month run, why might that be?

Click here for the solution

Create a new case

Create a new case i2000_bgc_hist_daily with the command:

cd /glade/u/home/$USER/code/my_clm_code/cime/scripts/

./create_newcase --case ~/cases/i2000_bgc_hist_daily \
  --compset I2000Clm60BgcCrujra \
  --res f19_f19_mt233 \
  --run-unsupported

Setup

Invoke case.setup with the command:

cd ~/cases/i2000_bgc_hist_daily
./case.setup

Customize namelists

Edit the file user_nl_clm and add the lines:

hist_fincl2 = 'TSA','TLAI'
hist_nhtfrq = 0,-24
hist_mfilt  = 1,31

Set run length

Change the run length:

./xmlchange STOP_N=1
./xmlchange STOP_OPTION=nmonths

Change the wallclock time, job queue, and account number

Change the wallclock time. If needed, change job queue and account number.
For instance, to run in the queue tutorial and the project number UESM0016 (You should use the project number given for this tutorial), use the command:

./xmlchange JOB_WALLCLOCK_TIME=01:00:00
./xmlchange JOB_QUEUE=tutorial
./xmlchange PROJECT=UESM0016 --force

Build and submit

Build the model and submit your job:

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

Look at your solution

When the run is complete, go to the archive directory:

cd /glade/derecho/scratch/$USER/archive/i2000_bgc_hist_daily/lnd/hist
ls

In CLM, history files are separated into averaged and instantaneous files using the suffixes a and i.

You should see files like:

- h0 
i2000_bgc_hist_daily.clm2.h0a.2000-01.nc
i2000_bgc_hist_daily.clm2.h0i.2000-01.nc

- h1
i2000_bgc_hist_daily.clm2.h1a.2000-01-02-00000.nc

The important files for this exercise are:

  • h0a: monthly averaged output

  • h1a: daily averaged output requested with fincl2 = 'TSA', 'TLAI'

For this exercise, focus on checking:

ncdump -h i2000_bgc_hist_daily.clm2.h1a.2000-01-02-00000.nc

The h1a files should contain the daily time-averaged fields. These variables should include:

double time_bounds(time, nbnd) ;
        time_bounds:long_name = "time interval endpoints" ;
        time_bounds:units = "days since 2000-01-01 00:00:00" ;
        time_bounds:calendar = "noleap" ;

float TLAI(time, lat, lon) ;
          TLAI:long_name = "total projected leaf area index" ;
          TLAI:units = "m^2/m^2" ;
          TLAI:cell_methods = "time: mean" ;
          TLAI:_FillValue = 1.e+36f ;
          TLAI:missing_value = 1.e+36f ;
          TLAI:landunit_mask = "unknown" ;
          
float TSA(time, lat, lon) ;
        TSA:long_name = "2m air temperature" ;
        TSA:units = "K" ;
        TSA:cell_methods = "time: mean" ;
        TSA:_FillValue = 1.e+36f ;
        TSA:missing_value = 1.e+36f ;
        TSA:landunit_mask = "unknown" ;

Check the number of time samples:

ncdump -h i2000_bgc_hist_daily.clm2.h1a.2000-01-02-00000.nc | grep time

The h1a file should contain 31 time samples.

You can also check file sizes with:

du -skh /glade/derecho/scratch/$USER/archive/i2000_bgc_hist_daily/lnd/hist/*
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