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Stomatal resistance incorrectly dependent on vegetation fraction #92

Open barlage opened 1 year ago

barlage commented 1 year ago

The radiation absorbed by the canopy is a grid quantity and therefore so is PAR (sunlit and shaded). When PAR is used to calculate stomatal resistance, this results in a vegetation fraction dependence on stomatal resistance. A quick test by dividing PAR by vegetation fraction in the inputs to stomatal resistance corrects this dependence so there are two possible solutions:

  1. remove the scaling of PAR before sending to stomatal resistance calculation
  2. a more general but larger solution (and I think preferable) is to remove the scaling on canopy absorbed radiation and apply it later when the grid average components are done at the end of the energy routine.
barlage commented 1 year ago

I will also note that in NoahMP PAR is used in the Noah scheme equivalent canres, while in Noah canres the input is total SWdown so the parameters likely need to be recalibrated for this difference.

jesusff commented 1 year ago

Dear @cenlinhe

you provided a fix for this (a7dd399) in the refactored code:

https://github.com/NCAR/noahmp/blob/107215a/src/ResistanceCanopyStomataBallBerryMod.F90#L98-L109

But I cannot find the corresponding code in the non-refactored code to mimic it. It should be around here:

https://github.com/NCAR/noahmp/blob/release-v4.5-WRF/src/module_sf_noahmplsm.F#L5076-L5085

but there was no index for shade/sunlit in the non-refactored code. We are trying to fix these issues for our CORDEX runs with WRF. Any hint is appreciated :-)

cenlinhe commented 1 year ago

@jesusff Sorry for the confusion. I have not included the update/fix in the non-refactored code yet. I will do it this week by updating the v4.5 branch.

cenlinhe commented 1 year ago

@jesusff I have fixed this issue in this commit in release-v4.5-WRF branch: https://github.com/NCAR/noahmp/commit/0fd17e50a3cbdb4ddd6ba00196927803f656fed0 The fix in v5.0 (included in release-v5.0.1) is in this commit: https://github.com/NCAR/noahmp/commit/a7dd399972fca4d477c43654d384287ad62114a2

jesusff commented 1 year ago

Thanks a lot @cenlinhe for the fixes to this and #91 in the old code. Much appreciated! We'll be testing them into long-term WRF runs.

cenlinhe commented 1 year ago

@jesusff I found a minor issue in my previous bug fix for this FVEG scaling. I updated the code further: https://github.com/NCAR/noahmp/commit/4ecebec7072e507ed7607012e5a89379348391bf