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How to output porosity, field capacity(FC), wilting point (WP) in CLM (SP mode) for single-point run!

Makduma Badhan

Makduma Zahan Badhan
New Member
Hi all,

I’m running a single-site CLM simulation in SP mode and need to obtain field capacity, wilting point, and porosity for each soil layer to calculate Soil Water Availability (SWA) for that different layer in that specific site. I’ve seen that watsat and watfc are listed among CLM history variables, and I’m wondering if these indeed are the correct variables to use for porosity and field capacity? and if so I can output these by adding them in user_nl_clm. However, I haven’t found any history variables related to wilting point (WP), so I’m unsure how to compute or extract wilting point values per soil layer. Given my limited experience modifying CLM code, I would appreciate expert advice on how best to obtain these parameters. Additionally, would it be better to calculate wilting point externally from soil texture data rather than trying to extract it from the model? Any guidance or suggestions would be very helpful at this point.

Thanks,
Makduma
 

slevis

Moderator
Staff member
@Makduma Badhan, you may find some answers in the documentation (and maybe you have been looking already):

This document explains how things are calculated in the code, so you can find whether watsat and watfc are what you expect. For example, searching for "porosity" got me to this section:
A quick search did not show me where to look for field capacity, so I hope that you have more time to search.

Searching for "wilt" got me to this section where you may find guidance for the calculation of WP:

Given your lack of experience with CLM code, you may find it easier to calculate WP externally. The final choice is yours of course.
 

Makduma Badhan

Makduma Zahan Badhan
New Member
@slevis or @oleson Can any of you help me? As I posted above, I'm running a single-point CTSM (CLM) simulation in SP mode and want to output the following soil hydraulic variables. I have a look at the technical note and these are the variables I want.
  • watsat (porosity at saturation)
  • watfc (field capacity)

I saw both variables listed in the CTSM history field documentation, so I added them to user_nl_clm like this:
fincl2 = 'watsat','watfc'

However, the run failed with this error (I just provided the error message:
htapes_fieldlist ERROR: watsat in fincl( 15 ) for history tape 2 not found
ENDRUN:
ERROR: ERROR in histFileMod.F90 at line 886

My questions:
  1. Why would apparently documented history variables like watsat and watfc not be recognized when added to user_nl_clm?
  2. Are these variables only available under specific model configurations or compile-time options?
  3. What is the correct method to output these values from CTSM? I need help to learn this. I tried searching CLM documentation and forum post, but no luck.
 

oleson

Keith Oleson
CSEG and Liaisons
Staff member
It looks like watsat and watfc output are only allowed if you are in "BGC" mode (and you are running in SP mode):

if (use_cn) then
this%watsat_col(begc:endc,:) = spval
call hist_addfld2d (fname='watsat', units='m^3/m^3', type2d='levgrnd', &
avgflag='A', long_name='water saturated', &
ptr_col=this%watsat_col, default='inactive')
end if

if (use_cn) then
this%watfc_col(begc:endc,:) = spval
call hist_addfld2d (fname='watfc', units='m^3/m^3', type2d='levgrnd', &
avgflag='A', long_name='water field capacity', &
ptr_col=this%watfc_col, default='inactive')
end if

I'm not sure of the purpose in limiting their output to BGC mode, but you could try commenting out the if statements and recompiling.

WATSAT is also output by default in the history fields but since it does not change over time it is only output on a monthly history file at the beginning of the simulation and on the first monthly history file upon a restart.

This conversation may also be helpful:

 
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