Parameters related to active layer thickness

[lucia]

Hello,
I am simulating the thickness of active layer, but I found that the thickness of active layer in some sites is much larger than the measured value. May I ask what parameters should I adjust to slow down its melting? I have been searching for parameters, but I have not found the appropriate parameters that are most likely to affect the thickness of active layer.Can you please give me some advise?

 

[slevis]

I'm not familiar with the Active Layer model, but I recommend starting in this file in your ctsm directory:
src/biogeophys/ActiveLayerMod.F90

 

[lucia]

slevis,thank you.This is very helpful for me and I'm going to look at this file

 

[oleson]

I wonder if the CLM5 PPE (perturbed parameter ensemble) can be of some help here. The work has not been published yet but results can be found here:

Diagnostics

If you navigate to the global mean link for ALTMAX (the maximum annual active layer thickness):

https://webext.cgd.ucar.edu/I2000/PPEn11_OAAT/figs/ALTMAX/ALTMAX_global_mean.png

I see that the parameter upplim_destruct (which corresponds to upplim_destruct_metamorph in your lnd_in, the upper limit for snow densification through destructive metamorphism) has the largest effect on ALTMAX. The "high-val" setting in the Control reduces ALTMAX. The default value for upplim_destruct_metamorph is 175 kg/m3 while the high-val setting is 250 kg/m3, so perhaps you could try that. The results show the global mean so your results will depend on the specific site you are simulating. For example, the results depend on biome as shown in this plot:

https://webext.cgd.ucar.edu/I2000/PPEn11_OAAT/figs/ALTMAX/ALTMAX_biome_mean.png