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A version to compute emissivity for different scenarios with fractional grid in coupled/uncoupled models #5

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This PR proposes an alternative solution on emissivity computation for different scenarios.
It checks if semis_ice(i) has non-zero values
(could come from RUC LSM for uncoupled model, or CICE for coupled
model). If yes, then uses them over ice fraction. If not, then computes ice emissivity using
either snow cover fraction (sncovr_ice) or snow depth.

for different scenarios. It checks of semis_ice(i) has non-zero values
(could come from RUC LSM for uncoupled model, or CICE for coupled
model), then use it over ice fraction. If not, then compute it using
either snow cover fraction (sncovr_ice) or snow depth.
hrgh = min(f_one,max(0.20,1.0577-1.1538e-3*hprif(i)))
fsno = asnow / (argh + asnow) * hrgh
fsnoi = min(f_one, fsno / (fraci(i)+fracl(i)))
sfcemis_ice = emsref(7)*(f_one-fsnoi) + emsref(8)*fsnoi
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Tanya,
There is one problem here. Note that in my version I save "sfcemis_ice" into semis_ice(i), as it is needed elsewhere. When we do this, it could potentially go through a different path in the above "if" loop when it is called another time.
Moorthi

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Moorthi,
I have changed the if statement to use semis_ice(i) with RUC lsm and CICE (for now other ice schemes or lake models do not provide semis_ice), and compute it in all other scenarios. Will this work now?

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Tanya,
It won't work. I think my original version is fine. The reason it won't work is because, when it is coupled to CICE6, it only takes care of sea-ice, not lake ice. That is the reason I was adding "lakefrac" in the logic so that if it is coupled and not RUClsm, then to compute emissivity for the lake ice the default way.
Moorthi

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Ok, let's go with your version. Thank you for merging RUC LSM clean-up version into your PR.

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@SMoorthi-emc I forgot to tell you that one thing will not work in your version with RUC LSM. The RUC ice model is turned on for ice on the ocean and lakes only when uncoupled from CICE or the lake model. Thus, if coupled to the lake model semis_ice(i) is not defined unless it is computed in the lake model (I think it is not the case for Flake). Therefore, with RUC LSM the "standard" method to compute semis_ice from snow depth should be applied it the lake model is turned on.

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Tanya,
If the model is coupled to CICE6, then with RUC LSM, the emissivity from CICE6 used? In this case, if "flake" is called for lake, then RUC LSM does not update emissivity right? If no lake model is used, the RUC LSM will calculate lake ice emissivity. If this is the case, I think I need to update the code (for now assuming that "flake" does not update ice emissivity)

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Moorthi, Yes to both questions. And yes, RUC LSM will calculate lake ice emissivity only if no lake model is used. Thank you!

@SMoorthi-emc
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SMoorthi-emc commented Oct 4, 2021 via email

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