extraction fix

[kmdeck]

Purpose

Update root extraction so that it tends to zero as the soil dries or freezes.
We have the Darcy flux:
Flux = -K_eff [(psi_canopy - psi_soil)/(z_canopy -z_soil) + 1]

Previously: K_eff = [K_canopy(psi_soil) + K_canopy(psi_canopy)]/2.

Two things have changed: we now use the harmonic mean, and we replace K_canopy(psi_soil) with K_soil(psi_soil). Note that K_soil() and K_canopy() are two different functions.

Currently: K_eff = K_soil(psi_soil) * K_canopy(psi_canopy)/ [K_soil(psi_soil) + K_canopy(psi_canopy)]

So, if K_soil(psi_soil) -> 0, then K_eff -> 0, and the root extraction goes to zero consistently. Although as psi_soil ->0, K_canopy(psi_soil) ->0, it may not drop to zero quickly enough due to the differing functional forms.

Please see CLM:

which is different in that it uses conductances and has canopy -> root, but see Equation 11.16 (harmonic mean) and Equation 11.18 (K_soil in soil layer, i.e. K_soil(psi_soil))

Effect on NaNs:

Global run after soil evaporation fix (very similar to current main):

Global run after these changes:

To-do

Review

Content

1. Change the root extraction to depend on K_soil, and not K_plant(psi_soil). Note that this is only changed in the prognostic soil +canopy mode, and not the standalone canopy mode (prescribed soil). In the latter, we use K_plant(psi_soil) still.
2. Use the geometric mean to compute K_eff, and not arithmetic mean
3. Update tests

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• I have read and checked the items on the review checklist.

[juliasloan25]

Awesome!! This looks great, I just had a couple comments :)

[kmdeck]

Change the root extraction to depend on K_soil, and not K_plant(psi_soil). Note that this is only changed in the prognostic soil +canopy mode, and not the standalone canopy mode (prescribed soil). In the latter, we use K_plant(psi_soil) still.

It seems unusual to me to use slightly different equations for standalone vs integrated modes. Although maybe it doesn't make sense to evaluate K_soil with prescribed soil?

Yeah, I agree...it would entail changing the PrescribedSoil struct to include a function for K_soil(psi) as well, or a timeseries of Ksoil(t) which is consistent with psi_soil(t), which would be made up at this point. We dont really have a use case for it yet.

[braghiere]

Change the root extraction to depend on K_soil, and not K_plant(psi_soil). Note that this is only changed in the prognostic soil +canopy mode, and not the standalone canopy mode (prescribed soil). In the latter, we use K_plant(psi_soil) still.

It seems unusual to me to use slightly different equations for standalone vs integrated modes. Although maybe it doesn't make sense to evaluate K_soil with prescribed soil?

Yeah, I agree...it would entail changing the PrescribedSoil struct to include a function for K_soil(psi) as well, or a timeseries of Ksoil(t) which is consistent with psi_soil(t), which would be made up at this point. We dont really have a use case for it yet.

Agree. If it is not too difficult, maybe we can change the standalone as well? If it is a bit of work, we can leave it for now since we're focusing on canopy+soil development, which is more aligned to OKRs.

[braghiere]

It looks good to me. Left a few comments.

[juliasloan25]

Change the root extraction to depend on K_soil, and not K_plant(psi_soil). Note that this is only changed in the prognostic soil +canopy mode, and not the standalone canopy mode (prescribed soil). In the latter, we use K_plant(psi_soil) still.

It seems unusual to me to use slightly different equations for standalone vs integrated modes. Although maybe it doesn't make sense to evaluate K_soil with prescribed soil?

Yeah, I agree...it would entail changing the PrescribedSoil struct to include a function for K_soil(psi) as well, or a timeseries of Ksoil(t) which is consistent with psi_soil(t), which would be made up at this point. We dont really have a use case for it yet.

Agree. If it is not too difficult, maybe we can change the standalone as well? If it is a bit of work, we can leave it for now since we're focusing on canopy+soil development, which is more aligned to OKRs.

I think it makes sense to keep PrescribedSoil as-is for now, until we do have a use case that necessitates this change

[kmdeck]

Change the root extraction to depend on K_soil, and not K_plant(psi_soil). Note that this is only changed in the prognostic soil +canopy mode, and not the standalone canopy mode (prescribed soil). In the latter, we use K_plant(psi_soil) still.

It seems unusual to me to use slightly different equations for standalone vs integrated modes. Although maybe it doesn't make sense to evaluate K_soil with prescribed soil?

Yeah, I agree...it would entail changing the PrescribedSoil struct to include a function for K_soil(psi) as well, or a timeseries of Ksoil(t) which is consistent with psi_soil(t), which would be made up at this point. We dont really have a use case for it yet.

Agree. If it is not too difficult, maybe we can change the standalone as well? If it is a bit of work, we can leave it for now since we're focusing on canopy+soil development, which is more aligned to OKRs.

I think it makes sense to keep PrescribedSoil as-is for now, until we do have a use case that necessitates this change

Thanks guys! I updated an old issue to have this included: #159

[kmdeck]

@braghiere @juliasloan25 I will extend the run to 365 days (or document why we cant and open an issue, I forget why it didnt run before).

would this be ready to merge then? If so, if you approve it now Ill merge it after the last fix to set tf=365 days.

I would really like to rethink aspects of our plant hydraulics model thoroughly #159 , but for now want to move forward with what we have

[juliasloan25]

@braghiere @juliasloan25 I will extend the run to 365 days (or document why we cant and open an issue, I forget why it didnt run before).

would this be ready to merge then? If so, if you approve it now Ill merge it after the last fix to set tf=365 days.

I would really like to rethink aspects of our plant hydraulics model thoroughly #159 , but for now want to move forward with what we have

Yeah, looks good to me!

[braghiere]

Looks good. Thanks!