Customize CLM output#

In this section, we will cover:

  • how to change the output frequency

  • how to control the number of time samples written to a history file

  • how to output extra variables

  • how to output extra history files

This can be achieved with 3 namelist variables:

  • hist_nhtfrq:: output frequency of the history file

  • hist_mfilt: number of samples on each history file

  • hist_fincl: adding variables and auxiliary history files

Customizing CLM output frequency: hist_nhtfrq#

We can change the output frequency with the namelist variable hist_nhtfrq

  • If hist_nhtfrq=0, the file will be a monthly average

  • If hist_nhtfrq>0, frequency is input as number of timesteps.

  • If hist_nhtfrq<0, frequency is input as number of hours.

For instance,

     hist_nhtfrq = -24

means daily output

     hist_nhtfrq = 24

means output every 24 timesteps

Evaluate your understanding

How do you modify the CLM output to output 3-hourly data ?

Click here for the solution

Add the following line to user_nl_clm:

    hist_nhtfrq = -3

Add extra variables and history files: hist_fincl#

You can output up to 10 history files:h0, h1, …, h9.

To control the list of fields in the history files, use the namelist variable hist_fincl

  • hist_fincl1 controls the fields in h0

  • hist_fincl2 controls the fields in h1

  • …

  • hist_fincl10 controls the fields in h9

For example, to add the field ‘TG’ to the h0 file, use the line:

     hist_fincl1 = 'TG'
Evaluate your understanding

What is the namelist setting to add a monthly history h1 with the variables ‘TG’, ‘TV’ and a daily history h2 with the variables ‘TG’, ‘TV’. Output 10 time samples in h1 and h2 ?

Click here for the solution

Modify env_run.xml with the command:

    ./xmlchange STOP_N=nmonths, STOP_OPTION=1

Add the following lines to user_nl_cam:

    hist_nhtfrq = 0, 0, -24 
    hist_mfilt = 1, 10, 10 
    hist_fincl2 = 'TG', 'TV' 
    hist_fincl3 = 'TG', 'TV'

Customizing CLM history files: hist_mfilt#

To control the number of time samples in the history file, we use the variable hist_mfilt.
This variable specifies is the maximum number of time samples written to a history file.

For example, if we want to have 10 time samples on each history file, we can set the namelist variable as follows:

     hist_mfilt = 10

To output daily data in a single file for a 1-year run, we can use the following values:

    hist_nhtfrq = -24   
    hist_mfilt = 365

If we want to output daily data with only 1 time sample per file, we can set the variables as follows:

    hist_nhtfrq = -24
    hist_mfilt = 1

NB: we cannot change mfilt for monthly frequency. For monthly frequency, we always have: hist_mfilt = 1

Evaluate your understanding

What is the setting to generate CLM 3-hourly data for a month-long simulation that will create a file every day?

Click here for the solution

Modify env_run.xml with the command:

    ./xmlchange STOP_N=nmonths, STOP_OPTION=1

Add the following line to user_nl_cam:

    hist_nhtfrq = -3
    hist_mfilt = 8

Averaging flag for the fincl variables#

Using a “:” following a field gives the averaging flag for the output field.

Valid flags are:

  • A ==> Average

  • I ==> Instantaneous

  • M ==> Minimum

  • X ==> Maximum

  • SUM ==> Sum

For instance, the line:

     hist_fincl1  = 'TLAI:M'

is used to add the minimum of TLAI to the file h0

Evaluate your understanding

What happens if we set in user_nl_clm:

    hist_fincl2 = 'TG', 'TV' 
    hist_fincl3 = 'TG', 'TV' 
    hist_fincl4 = 'TG', 'TV'
    hist_fincl5 = 'TG', 'TV' 
    hist_nhtfrq = 0, -24, -6, -1, 1
Click here for the solution

In addition to the monthly history file h0, we output 4 extra history files with daily, six-hourly, hourly, and every time-step values of TG and TV (leaving the primary history h0 files as monthly).