soil4c_vr

[Chr]

Dear CLM Modellers,

I am currently performing a spinup for my domain (with an I2000BGCCROP compset) on CLM5, and wanted to verify the simulated soilC values from the restart file with measured data. I noted that there are three soilC variables: soil1c_vr, soil2c_vr, and soil3c_vr in 25 soil layers. I suppose that the numbers refer to the SOM pools described in Chapter 21 of the CLM5 Tech Note. I wonder, if there is also a soil4c_vr available. It is mentioned in the Tech Note, and I found it in the old variable list for CLM4.5, but couldnt find it in the current restart file.

If there is no soil4c_vr available, can I assume that the sum of soil1c_vr, soil2c_vr, and soil3c_vr for each layer is equal to total soilc_vr?

Thanks for your help.

 

[oleson]

There are two options for the decomposition submodel, the CLM-CN pool structure which is the default in CLM4.5 and has four soil carbon pools, or a second pool structure based on the Century model which is the default in CLM5 and has three soil carbon pools. In theory, one could use the CLM-CN pool structure in CLM5 by specifying the namelist variable use_century_decomp = .false. In practice, I'm not sure this has been tested.
So default CLM5 has three soil carbon pools. soil4c_vr would only be present if use_century_decomp = .false. (CLM4.5).
The sum of soil1c_vr, soil2c_vr, and soil3c_vr should be soilc_vr.

 

[Chr]

Thank you, now I understand it!