Snow thermal conductivity changes: Sturm1997 and Jordan1991

[kvrigor]

This PR implements @AdrienDams snow thermal conductivity fixes in CLM5.

Damseaux, A., Matthes, H., Dutch, V. R., Wake, L., and Rutter, N.: Impact of snow thermal conductivity schemes on pan-Arctic permafrost dynamics in the Community Land Model version 5.0, The Cryosphere, 19, 1539–1558, https://doi.org/10.5194/tc-19-1539-2025, 2025.

New namelist parameters

These fixes allow changing the snow thermal conductivity per land unit type. New namelist switches must be added with defaults set to CLM6 defaults.

&clm_inparm
 snow_thermal_cond_method = 'Sturm1997'
 snow_thermal_cond_glc_method = 'Sturm1997'
 snow_thermal_cond_lake_method = 'Jordan1991'

Code changes

Changes were based from these upstream PRs:

• Introduce namelist option for thermal conductivity of snow: Jordan vs. Sturm ESCOMP/CTSM#2148
• User control over snow thermal conductivity scheme over glaciers ESCOMP/CTSM#3072

[jjokella]

Testing this PR

• @Buliao1
• ICOS-sites as point-scale testcases:
  • first test: FI-Hyy (best observations)
  • possibly later added due to large amount of snow: FI-Sod / CH-Dav
• check that Jordan1991 reproduces previous snow variables
• check effect of Sturm1997-snow-thermal-conductivity on fluxes
• paper using Sturm1997:

Dutch, V. R., et al. (2024). Simulating net ecosystem exchange under seasonal snow cover at an arctic tundra site. Biogeosciences, 21(3), 825–841. http://dx.doi.org/10.5194/bg-21-825-2024

TSMP2 branches that now include this PR:

• dev-pdaf-snow: https://github.com/HPSCTerrSys/TSMP2/tree/dev-pdaf-snow
• dev-pdaf-snow-params: https://github.com/HPSCTerrSys/TSMP2/tree/dev-pdaf-snow-params

Namelist parameters

• Jordan1991: Old eCLM defaults
• Sturm1997: Now introduced Snow thermal conductivity changes: Sturm1997 and Jordan1991 #101