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Fix Tsnice calculation #542

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Merged
eclare108213 merged 4 commits into from
Nov 3, 2025
Merged

Fix Tsnice calculation #542

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e9d626f
Fix Tsnice calculation
dabail10 Sep 19, 2025
1b47cf1
Fix some bug with Tsnice
dabail10 Sep 24, 2025
453743d
Add zero initialization for Tsnice in driver
dabail10 Sep 24, 2025
ba7a2d3
Fix the computation of Tsnice to be a straight line
dabail10 Oct 30, 2025
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7 changes: 3 additions & 4 deletions columnphysics/icepack_therm_vertical.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -375,12 +375,11 @@ subroutine thermo_vertical (dt, aicen, &
einter = einter + hilyr * zqin(k)
enddo ! k

Tsnice = c0
if ((hslyr+hilyr) > puny) then
if (hilyr > puny) then
if (hslyr > puny) then
Tsnice = (hslyr*zTsn(nslyr) + hilyr*zTin(1)) / (hslyr+hilyr)
Tsnice = Tsnice + aicen*((hslyr*zTsn(nslyr) + hilyr*zTin(1)) / (hslyr+hilyr))
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@NickSzapiro-NOAA NickSzapiro-NOAA Sep 22, 2025

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Can I check that I understand? Does this aicen factor get "canceled" in ice_history in:

! Only average for timesteps when ice present
if (avail_hist_fields(n)%avg_ice_present) then
   do j = jlo, jhi
   do i = ilo, ihi
      if (tmask(i,j,iblk)) then
            a2D(i,j,n,iblk) = &
            a2D(i,j,n,iblk)*avgct(ns)*ravgip(i,j)
      endif

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@dabail10 dabail10 Sep 22, 2025

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No, this is aggregating the category Tsnice into the grid cell Tsnice. The time averaging in ice_history.F90 will come in a CICE PR!

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@NickSzapiro-NOAA NickSzapiro-NOAA Sep 23, 2025

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Thanks! Then isn't a Tsnice = Tsnice/sum(aicen) factor missing? For example, for single category aicen almost puny

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@dabail10 dabail10 Sep 23, 2025

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Sorry this is so confusing. I should really call this:

Tsnice = sum(aicen(n)*Tsnicen(n)) for n=1,5

this is done for every point in space within icepack. The history averaging in CICE is then:

sum(aice(t)*Tsnice(t)) / sum(aice(t)), for t over the averaging period. The CICE changes are coming in a future PR!

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@anton-seaice anton-seaice Sep 23, 2025

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I'm also confused :)

Tsnice = sum(aicen(n)*Tsnicen(n)) for n=1,5

sum(aicen(n)) is not 1, so Tsnice ends up weighted by aice here right ?

... The history averaging in CICE is then:

sum(aice(t)*Tsnice(t)) / sum(aice(t)), for t over the averaging period. The CICE changes are coming in a future PR!

Doesn't this mean its weighted by aice twice ?

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@anton-seaice anton-seaice Sep 24, 2025 •
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Oh - maybe this line would be correct now:

worka(i,j) = aice(i,j,iblk)*(Tsnice(i,j,iblk)/aice_init(i,j,iblk)+Tffresh)

https://github.com/CICE-Consortium/CICE/blob/b01032506d71d86ca51cef8c3c28c1ab87532833/cicecore/cicedyn/analysis/ice_history.F90#L2768

the divide by aice_init corrects it for the aice weighting applied during thermo vertical

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@eclare108213 eclare108213 Sep 24, 2025 •
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No, this is aggregating the category Tsnice into the grid cell Tsnice.

This is true only if Tsnice=0 for the open water area. Assuming that, then the grid cell average Tavg = sum(aicen(n)*Tsnice(n))/sum(aicen(n)) =sum(aicen(n)*Tsnice(n))/1 where the sums are for n=0,ncat mathematically but only need to be taken for n=1,ncat in the code. Confusing, yes, but possibly okay here. (Explicit code comments to this effect would be helpful.) A better assumption for Tsnice for open water might be the ocean temperature. On the other hand, if the data request is for Tsnice only over the ice-covered area, then it had better be
sum(aicen(n)*Tsnice(n))/sum(aicen(n)) for n=1,ncat, where aicen might actually be aicen_init at this point in the code.

I'm generally suspicious of any 'mixed' ice area scaling using both aice and aice_init. Those will need to be considered on a case-by-case basis, in my opinion.

else
Tsnice = Tsf
Tsnice = Tsnice + aicen*Tsf
endif
endif

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1 change: 1 addition & 0 deletions configuration/driver/icedrv_flux.F90
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Expand Up @@ -688,6 +688,7 @@ subroutine init_history_therm
congel (:) = c0
frazil (:) = c0
snoice (:) = c0
Tsnice (:) = c0
dsnow (:) = c0
meltt (:) = c0
melts (:) = c0
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