Hardening and frost mortality schemes

[mariuslam]

Description:

This concerns the inclusion of a hardening scheme, which provides each PFT and site with a unique hardiness level. The hardiness level is updated every model day and depends on the daily mean temperature, 5 year running mean of the minimum yearly temperature index, PFTfreezetol parameter, daylength. The hardiness level is between -70 and -2 for all PFTs.

• If use_frost_hard=.true. -->The hardiness level is used to predict frost mortality instead of the fixed PFTfreezetol parameter.The magnitude of a frost event is given by the difference between the minimum temperature and the hardiness level, and frost occurs when the minimum temperature is below the hardiness level. --> Frost can now be experienced by all PFTs if temperature decreases faster than the acclimation rate of plants. Even PFTs with a PFTfreezetol of -80 might endure frost. The new implementation keeps the purpose of constraining PFT distribution as PFTfreezetol limits the hardiness level.

• If use_hydro_hard=.true. : The hardiness level is also used to constrain stomatal transpiration and hydraulic conductivity. The hardiness level reduces hydraulic failure mortality and modifies the PV curves. The hardening scheme may potentially (not in this PR) be used to modify plant phenology and more specifically the timing of leaf onset and offset.

Collaborators:

@huitang-earth, @rosiealice, @rgknox

Expectation of Answer Changes:

• frost_hard: While we keep the distribution purpose of the previous frost parametrization, now there is frost when there should be frost, --> total biomass levels are usually only slightly impacted
  --> Side effect of frost_hard: In the previous frost parametrization, damage started 5deg above the PFTfreezetol parameter, here it starts at the hardiness level and is maximum 5deg below the hardiness level. So PFTs with a freezetol of 2.5 will now have injury at -2 instead of 7.5, this might have some impacts on enhancing the growth of topical PFTs in the arctic region. However in a multi-PFT run they won't be competitive enough, and in single PFT runs, they do not grow much as much as extratropical PFTs.

• hydro_hard : Has major impacts of the biomass in northern regions as this prevents water fluxes during winter. Plants do not desiccate to the same extent as before and survive cold winters.

• I also changed FatesHydroWTFMod.F90 to not allow water potentials below -25Mpa.

Checklist:

• [ x] My change requires a change to the documentation.
• I have updated the in-code documentation .AND. (the technical note .OR. the wiki) accordingly.
• I have read the CONTRIBUTING document.
• FATES PASS/FAIL regression tests were run
• If answers were expected to change, evaluation was performed and provided

Test Results:

CTSM (or) E3SM (specify which) test hash-tag:

CTSM (or) E3SM (specify which) baseline hash-tag:

FATES baseline hash-tag:

Test Output:

[rgknox]

Thanks for submitting this work @mariuslam ! Exciting stuff! If you are available/amenable, we can coordinate a chat to take a detailed walk through the features in this PR and work out a path forward. For instance, we can help with resolving conflicts and merging your branch safely up to master. Will send you an email.

[mariuslam]

correct small differences in EDCohortDynamics

[mariuslam]

Hey @rgknox, I have cleaned the PR. I wonder if some of the changes made here are interesting to NCAR. If not I won't spend more time on it, but if yes I will be available for discussion and further modifications.
While this implementation is not supposed to impact warm regions of the world, it will considerably modify/enhance simulations over cold regions.
It is possible also to only merge the Frost or only the Hydro part. Or maybe consider only the changes of HydroWTFMod, or anything else.

[ekluzek]

Just pinging to check on the status here...

[glemieux]

Just pinging to check on the status here...

Cross posting here to note @rosiealice recent comment on #1130 (comment).