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

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

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b642b22
This commit proposes an alternative solution on emissivity computation
tanyasmirnova Sep 30, 2021
1e35ea7
Changed the "if" statement when semis_ice(i) is used.
tanyasmirnova Sep 30, 2021
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32 changes: 14 additions & 18 deletions physics/radiation_surface.f
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Original file line number Diff line number Diff line change
Expand Up @@ -956,26 +956,22 @@ subroutine setemis &
if ( icy(i) ) then !-- ice emissivity

!-- complete or fractional ice
if (lsm == lsm_noahmp) then
if (.not. cplice .or. lakefrac(i) > f_zero) then
if (sncovr_ice(i) > f_zero) then
sfcemis_ice = emsref(7) * (f_one-sncovr_ice(i)) &
if (semis_ice(i) > f_zero) then
sfcemis_ice = semis_ice(i) ! output from RUC lsm or CICE (with snow effect)
else
!-- compute ice emissivity with snow effect for uncoupled lake or sea ice
if (sncovr_ice(i) > f_zero) then
sfcemis_ice = emsref(7) * (f_one-sncovr_ice(i)) &
& + emsref(8) * sncovr_ice(i)
elseif (snowf(i) > f_zero) then
asnow = 0.02*snowf(i)
argh = min(0.50, max(.025,0.01*zorlf(i)))
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
endif
semis_ice(i) = sfcemis_ice
else
sfcemis_ice = semis_ice(i) ! output from CICE
elseif (snowf(i) > f_zero) then
asnow = 0.02*snowf(i)
argh = min(0.50, max(.025,0.01*zorlf(i)))
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!

endif
elseif (lsm == lsm_ruc) then
sfcemis_ice = semis_ice(i) ! output from lsm (with snow effect)
endif ! lsm check
endif
endif ! icy

!-- land emissivity
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