'Gamma_get_sm' turned off in MEGANV2.1 CLM4.5

[HazelMooney]

Model: cesm2.2.0 clm 4.5 meganv2.1
Enquiry: soil moisture activity factor

Describe your problem or question:
I have been investigating activity factors for my model runs using CLM4.5. Soil moisture is constant throughout and in the fortran code VOCEmissionMod.F90 we see that the soil moisture activity factor algorithms are commented out, and the activity factor is instead specified at gamma_sm = 1.0_r8
See screenshots attached. I have been unable to find guidance online as to why the calculation has been commented out in this version of the model, can you provide any guidance or references to help me understand this?

 

[oleson]

I don't know the history of that commented out code. I do know that MEGAN was recently updated and a new drought stress algorithm was implemented per this PR:

New updates on MEGANv2.1 by HuiWangWanderInGitHub · Pull Request #2588 · ESCOMP/CTSM

Description of changes We added new features to MEGANv2.1 for simulating isoprene emissions based on three recent studies conducted at the BAI lab in the University of California, Irvine. The first...

github.com

In it, gamma_sm was been changed to a function of btran:

gamma_sm = get_gamma_SM(btran(p))

However, there has been further conversation about low isoprene emissions perhaps partly as a result of that as indicated by the discussion in this issue:

Low MEGAN emissions in CESM3 · Issue #3016 · ESCOMP/CTSM

Using the latest beta cases, we are seeing a significant underestimation of biogenic emissions, when running a F-case with -bgc sp: beta02 was still OK, for example, isoprene emissions were around ...

github.com

 

[HazelMooney]

I don't know the history of that commented out code. I do know that MEGAN was recently updated and a new drought stress algorithm was implemented per this PR:

New updates on MEGANv2.1 by HuiWangWanderInGitHub · Pull Request #2588 · ESCOMP/CTSM

Description of changes We added new features to MEGANv2.1 for simulating isoprene emissions based on three recent studies conducted at the BAI lab in the University of California, Irvine. The first...

github.com

In it, gamma_sm was been changed to a function of btran:

gamma_sm = get_gamma_SM(btran(p))

However, there has been further conversation about low isoprene emissions perhaps partly as a result of that as indicated by the discussion in this issue:

Low MEGAN emissions in CESM3 · Issue #3016 · ESCOMP/CTSM

Using the latest beta cases, we are seeing a significant underestimation of biogenic emissions, when running a F-case with -bgc sp: beta02 was still OK, for example, isoprene emissions were around ...

github.com

Thank you for your reply. I am aware of the wider concerns regarding soil moisture and isoprene.

Due to the code being commented out, i am trying to turn it on to test it out, as per below:

! Activity factor for soil moisture: all species (commented out for now)
gamma_sm = get_gamma_SM(clayfrac(p), sandfrac(p), h2osoi_vol(c,:), h2osoi_ice(c,:), &
col%dz(c,:), soilstate_inst%bsw_col(c,:), watsat(c,:), sucsat(c,:), root_depth(patch%itype(p)))
!gamma_sm = 1.0_r8


Can you advise on using a modified VOCEmissionsModule.F90 file?

So far, i have copied the file to the /SourceMods/src.clm/ directory of my case, and then modified the SM code as shown above
However, at build, i am getting these errors for all of the required variables for the equation

error #6404: This name does not have a type, and must have an explicit type. [CLAYFRAC] gamma_sm = get_gamma_SM(clayfrac(p), sandfrac(p), h2osoi_vol(c,:), h2osoi_ice(c,:), &

i also see error #6200: A colon (:) is not valid in this context. gamma_sm = get_gamma_SM(clayfrac(p), sandfrac(p), h2osoi_vol(c,:), h2osoi_ice(c,:), &

error #6460: This is not a field name that is defined in the encompassing structure. [DZ] col%dz(c,:), soilstate_inst%bsw_col(c,:), watsat(c,:), sucsat(c,:), root_depth(patch%itype(p)))

 

[HazelMooney]

Thank you for your reply. I am aware of the wider concerns regarding soil moisture and isoprene.

Due to the code being commented out, i am trying to turn it on to test it out, as per below:

! Activity factor for soil moisture: all species (commented out for now)
gamma_sm = get_gamma_SM(clayfrac(p), sandfrac(p), h2osoi_vol(c,:), h2osoi_ice(c,:), &
col%dz(c,:), soilstate_inst%bsw_col(c,:), watsat(c,:), sucsat(c,:), root_depth(patch%itype(p)))
!gamma_sm = 1.0_r8


Can you advise on using a modified VOCEmissionsModule.F90 file?

So far, i have copied the file to the /SourceMods/src.clm/ directory of my case, and then modified the SM code as shown above
However, at build, i am getting these errors for all of the required variables for the equation

error #6404: This name does not have a type, and must have an explicit type. [CLAYFRAC] gamma_sm = get_gamma_SM(clayfrac(p), sandfrac(p), h2osoi_vol(c,:), h2osoi_ice(c,:), &

i also see error #6200: A colon (:) is not valid in this context. gamma_sm = get_gamma_SM(clayfrac(p), sandfrac(p), h2osoi_vol(c,:), h2osoi_ice(c,:), &

error #6460: This is not a field name that is defined in the encompassing structure. [DZ] col%dz(c,:), soilstate_inst%bsw_col(c,:), watsat(c,:), sucsat(c,:), root_depth(patch%itype(p)))

To add to the above, i have now identified that several of the required variables are not presently in vocemiss_inst
Can you advise who might be best to speak to about this soil moisture calculation being turned off in this version?

dz => col%dz , & ! Input: [real(r8) (:,:) ] depth of layer (m)

bsw => soilstate_inst%bsw_col , & ! Input: [real(r8) (:,:) ] Clapp and Hornberger "b" (nlevgrnd)

clayfrac => soilstate_inst%clayfrac_col , & ! Input: [real(r8) (:) ] fraction of soil that is clay

sandfrac => soilstate_inst%sandfrac_col , & ! Input: [real(r8) (:) ] fraction of soil that is sand

watsat => soilstate_inst%watsat_col , & ! Input: [real(r8) (:,:) ] volumetric soil water at saturation (porosity) (nlevgrnd)

sucsat => soilstate_inst%sucsat_col , & ! Input: [real(r8) (:,:) ] minimum soil suction (mm) (nlevgrnd)

h2osoi_vol => waterstate_inst%h2osoi_vol_col , & ! Input: [real(r8) (:,:) ] volumetric soil water (m3/m3)

h2osoi_ice => waterstate_inst%h2osoi_ice_col , & ! Input: [real(r8) (:,:) ] ice soil content (kg/m3)

 

[slevis]

I think your best bet is still to investigate the links that @oleson suggested above and look for possible contacts there.