Variables in CLM

Hello, everyone:

I am now using CLM version 5.0.35 to change the soil thermal conductivity. In some literatures, the change of soil thermal conductivity needs to use the mass fraction of mineral soil, the volume fraction of mineral soil and the mass fraction of organic matter. In this regard, I have some questions about the variables in CLM as follows:


Question 1:About organic matter

I found the om_frac variable in SoilStateInitTimeConstMod.F90, whose long name is organic matter fraction. Is the om_frac variable the volume fraction of organic matter or the mass fraction of organic matter? In SoilStateInitTimeConstMod.F90, om_frac = organic3d(g,1)/organic _ max, where organic 3d (g, 1) is the density of organic matter in surfdata, it seems that the om _ frac variable seems to be the mass fraction of organic matter. Is this my correct understanding?

Question 2: About mineral soil.

In SoilStateInitTimeConstMod.F90, there are:


(1._r8-om_frac) is a fraction of mineral soil, which refers to the mass fraction of mineral soil or the volume fraction of mineral soil? If om_frac is the mass fraction of organic matter, then (1._r8-om_frac) should be the mass fraction of mineral soil. In the change of soil thermal conductivity, the volume fraction of mineral soil is needed. How should this be converted? Or is there any literature to refer to?

A good place to look for answers is the Technical Note:
The Technical Note explains the code in detail and includes references to the supporting bibliography that you can look up for additional information.

When I looked at CLM Tech Note, I found something different from the technical document in the F90 file.


In the soil evaporation resistance module, I compared the technical document (on the left side of the picture) with the contents in SurfaceResistanceMod.F90 (about 366-382 lines, on the right side of the picture).There are the following questions:


(1)Does the soil evaporation resistance operate only in Non-Vegetated Surfaces? Does the soil evaporation resistance not operate if the surface is covered with vegetation?


(2) I would like to confirm that what is in the left side of the picture is correctly corresponding to what is in the right side of the picture? If not, which F90 file is the soil evaporation impedance in?


(3) If it is correct, why is place 1 in the picture not the same as place 2 in the picture? The 1 in the picture is the square of the air filled pore space, and the 2 in the picture is eps*d0. The 2 in the picture should be eps*eps in order to be equal to the 1 in the picture.


(4) The 3 places in the picture are not the same as the 4 places in the picture; the 4 places in the picture are dg*d0 to be able to be the same as the 3 places, but unfortunately they are not.


(5) Is the 5 places in the picture (*1.e3) for the purpose of converting units? and what does the 6 places (+20._r8) mean?


Very much looking forward to your answers

Good luck!

Pinging @swensosc