Soil organic carbon storage at different soil depths

[tenghao]

Hello everyone

I found the total soil organic carbon (TOTSOMC), the total soil organic carbon at a depth of 1m (TOTSOMC_1m), and the soil carbon in the vertical direction (SOILC_vr) in the 1.2.5. CTSM History Fields of the CLM5.0 User’s Guide. If I want to output the soil organic carbon storage at custom soil layer depths, such as 0-30cm, 30-60cm, and 60-100cm, what changes should be made to the model?

 

[slevis]

Try the namelist variable soil_layerstruct_userdefined
If you search the Forums for soil_layerstruct_userdefined, I think you will find answers to similar questions.

 

[tenghao]

Thank you very much for your reply.

In the CESM2.2.2 CLM Namelist Definitions, I found "soil_layerstruct_userdefined" and "soil_layerstruct_userdefined_nlevsoi", but these two variables seem to only change the soil layer structure.

Then, how can the SOMC of different soil layers under custom settings be output?
For example: TOTSOMC_0-30cm (organic carbon in the 0-30cm soil layer), TOTSOMC_30-60cm (organic carbon in the 30-60cm soil layer), and TOTSOMC_60-100cm (organic carbon in the 60-100cm soil layer).

Do I need to add some variables in "user_nl_clm" or make some modifications to the relevant F90 files related to SOMC?

 

[slevis]

In my version I see output from 3D variables such as SOILC_vr, which stands for "vertically resolved" but I'm looking at very recent code.

If you do not see such output in your version, then you need to learn how to add new variables to history. I think the easiest way is to see how other variables get added to history and follow the same template.

 

[tenghao]

Yes, I have found this 3D variable SOILC_vr (gc/m3), and I have the following questions here:

(1) Does carbon in the SOILC_vr variable refer to organic carbon in the soil? Or does it refer to all the carbon in the soil?

(2) If SOILC_vr is the output I want, will the vertical resolved of SOILC_vr become the thickness of the custom soil layers when I set soil_layerstruct_userdefined、soil_layerstruct_userdefined in user_nl_clm to customize the soil layers?

(3) If I want to obtain the carbon storage of different soil layer thicknesses, the unit based on SOILC_vr is gc/m3, multiplied by the soil volume to obtain the carbon storage in the soil layer. Is this understanding correct?

Carbon storage (gc)=SOILC_vr (gc/m3 first layer soil) × soil volume (m3 first layer soil)

(4) If I want to obtain TOTSOMC for different soil layer thicknesses, what should I do? If SOILC_vr refers to organic carbon in the soil and its unit is (gc/m³), and the unit of TOTSOMC is (gc/m²), then

the organic carbon in different soil layers (gc/m²) = SOILC_vr (gc/m³) × soil layer thickness (m).

Is this correct?


Please forgive me if there are some elementary mistakes. I'm looking forward to your reply very much.

 

[slevis]

1) A good place to start is the documentation:

2.16. CN Pools — ctsm release-clm5.0 documentation

2) I'm pretty sure, yes, but it's worth trying it out and confirming.
3) Seems correct.
4) Also seems correct.

It's ok to make mistakes. It's part of the learning process.