Question about stem area index in CLM5.0

[Qi Qi]

Hi, everyone. I'm trying to do some experiments based on the changes on the stem area index (SAI/Ls). I noticed that in the document of CLM5.0 the stem area index was described as ''Prescribed plant functional type (PFT) stem area index is derived from PFT leaf area index phenology combined with the methods of Zeng et al. (2002)'.
However, the stem area index in the Zeng et al. (2002) is set to a minimum value of 1 to most plant functional types, which is inconsistent with the Monthly_SAI output in CLM5.0. It seems that the SAI in CLM5.0 is generated after the normalization but I could not find the eassy to clarify this assumption. Is there any supporting information about this topic?
Many thanks!

Zeng, X., Shaikh, M., Dai, Y., Dickinson, R.E., Myneni, R., 2002. Coupling of the Common Land Model to the NCAR Community Climate Model. J. Climate 15, 1832–1854. Coupling of the Common Land Model to the NCAR Community Climate Model

 

[slevis]

I searched in the CLM5 Technical Note and found this section talking about the stem area:

2.2. Surface Characterization, Vertical Discretization, and Model Input Requirements — ctsm release-clm5.0 documentation

Searching on that page for the string "stem" I found two possible explanations for values lower than expected:
1) "The leaf and stem area indices are adjusted for vertical burying by snow" shown in history fields ELAI and ESAI (instead of TLAI and TSAI).
2) "Prescribed PFT stem area index is derived from PFT leaf area index phenology combined with the methods of Zeng et al. (2002)." I can't tell you offhand the effect of phenology, but it may explain the lower values than expected. You may find an answer in the Phenology section of the Technical Note or you could look through the code.

Also, if you looked at grid-cell averaged TSAI or ESAI in the model output, then you may be averaging parts of the grid cell with no (or lower) stem area.

 

[Qi Qi]

I searched in the CLM5 Technical Note and found this section talking about the stem area:

2.2. Surface Characterization, Vertical Discretization, and Model Input Requirements — ctsm release-clm5.0 documentation

Searching on that page for the string "stem" I found two possible explanations for values lower than expected:
1) "The leaf and stem area indices are adjusted for vertical burying by snow" shown in history fields ELAI and ESAI (instead of TLAI and TSAI).
2) "Prescribed PFT stem area index is derived from PFT leaf area index phenology combined with the methods of Zeng et al. (2002)." I can't tell you offhand the effect of phenology, but it may explain the lower values than expected. You may find an answer in the Phenology section of the Technical Note or you could look through the code.

Also, if you looked at grid-cell averaged TSAI or ESAI in the model output, then you may be averaging parts of the grid cell with no (or lower) stem area.

Thanks for your reply!
I would check the code and the technical note more detailedly.