ELAI is above 0 even if the plant is totally covered by snow

[huitang-earth]

It has been noted in the code that this is an artifact. I think it is time to remove it :)

https://github.com/NGEET/fates/blob/1723d1443a2bc84f15f9b4e6e637592b49790971/biogeochem/EDCanopyStructureMod.F90#L2064

https://github.com/NGEET/fates/blob/1723d1443a2bc84f15f9b4e6e637592b49790971/biogeochem/EDCanopyStructureMod.F90#L2103

@rosiealice, @ckoven , @rgknox : I suspect this might also have some (perhaps small but notice-able) impacts on albedo of FATES-SP simulation.

Just an example of elai from FATES-SP (winter ELAI is 0.1 when it is totally buried by snow).

[huitang-earth]

Sorry, just noticed that this has been raised in #733 and #739. I am curious what is the status now? Will this artificial value be removed in the near future?

[rgknox]

@huitang-earth we did try to integrate this change thereby removing the artificial floor on lai, but for reasons still unknown, it was not passing regression tests. My guess is that somewhere there is a divide by zero, or some math function that does not like zero LAI

[rosiealice]

I wonder if we -just- changed the ELAI cap to 0, and not TLAI, whether that would cause the same problem?

Le jeu. 3 juin 2021 à 17:28, Ryan Knox @.***> a écrit :

@huitang-earth https://github.com/huitang-earth we did try to integrate this change thereby removing the artificial floor on lai, but for reasons still unknown, it was not passing regression tests. My guess is that somewhere there is a divide by zero, or some math function that does not like zero LAI

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[rosiealice]

FWIW, I tried only changing the elai and esai to 0 in the https://github.com/NGEET/fates/pull/750 branch and it it runs OK for the 4x5 degrees. Which test was it that failed @rgknox? I think this might also be causing some of the residual CLM5-SP vs FATES-SP errors I see in snowy places.

[rgknox]

I think the details are described here: https://github.com/NGEET/fates/pull/739

[rgknox]

In that implementation, ai_min was set above zero for all for lai value stem/leaf/effective/total