What are the exact soil depths for the 10-layer (nlevsoi=10) PCT_SAND/PCT_CLAY in CLM5.0 surface dataset?

[chenyihui]

Dear scientists:

I am working with CLM5.0 surface dataset file:
surfdata_CMFD_TP_hist_78pfts_CMIP6_simyr2000_c260409.nc
In this file, I found that PCT_SAND and PCT_CLAY have 10 layers (nlevsoi=10).
However, the soil data I plan to use for replacement is the China Soil Dataset for Land Surface Modeling (Second Version), which only has 6 layers within 0–2 m depth:

• 0–5 cm
• 5–15 cm
• 15–30 cm
• 30–60 cm
• 60–100 cm
• 100–200 cm

I would like to interpolate or map my 6-layer data into the 10-layer structure of CLM to replace PCT_SAND and PCT_CLAY.
But I am not sure about the exact depth definition of the 10 soil layers in the CLM surface dataset.

My questions are:

1. How are the 10 soil layers (for nlevsoi=10) defined in terms of depth in CLM5.0 surface data?
2. In the CLM5.0 Technical Note, Section "2.2.2.1. Soil Layers" shows a 25-layer structure. Are these 10 layers simply the first 10 layers of that 25-layer table?
3. If not, is there any official or default depth definition for the 10-layer configuration that I can refer to?

Thank you for your help!

 

[oleson]

The CLM5 surface datasets do have nlevsoi=10 on them and the soil properties are defined accordingly. However, the code calculates the soil layer structure based on the namelist variable "soil_layerstruct", which by default is "20SL_8.5m". The resulting soil layer structure is provided in the technical note:

2.2. Surface Characterization, Vertical Discretization, and Model Input Requirements — ctsm CTSM master documentation

There should also be information on the soil layer structure in the lnd log file.

You can see how the soil layer structure is calculated in src/main/initVerticalMod.F90

The 10-layer properties are then mapped to the top 10 layers of the soil layer structure. Layers 11-20 use the properties of the 10th layer. You can see how this works in src/biogeophys/SoilHydrologyInitTimeConstMod.F90

 

[chenyihui]

The CLM5 surface datasets do have nlevsoi=10 on them and the soil properties are defined accordingly. However, the code calculates the soil layer structure based on the namelist variable "soil_layerstruct", which by default is "20SL_8.5m". The resulting soil layer structure is provided in the technical note:

2.2. Surface Characterization, Vertical Discretization, and Model Input Requirements — ctsm CTSM master documentation

There should also be information on the soil layer structure in the lnd log file.

You can see how the soil layer structure is calculated in src/main/initVerticalMod.F90

The 10-layer properties are then mapped to the top 10 layers of the soil layer structure. Layers 11-20 use the properties of the 10th layer. You can see how this works in src/biogeophys/SoilHydrologyInitTimeConstMod.F90

Thank you!