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Glacier modifications in NoahMP to address GFSv17 biases #316

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Merged
grantfirl merged 8 commits into from
Sep 29, 2025
Merged

Glacier modifications in NoahMP to address GFSv17 biases #316

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5e4a9bb
change snow thermal conductivity to be same as in noahmp model
barlage Aug 28, 2025
571b871
add minimum snow depth for glacier to be 20cm by adding new snow
barlage Aug 28, 2025
ac768e4
change snow limit for glacier to be 600mm
barlage Aug 28, 2025
6454fba
remove snow albedo aging for glaciers
barlage Aug 28, 2025
d0f53cb
initialize glacier with 2m snow depth
barlage Sep 3, 2025
e0fd99e
keep snow depth and SWE constant over glaciers
barlage Sep 3, 2025
6e4abdc
Merge branch 'ufs/dev' into glacier_mods
barlage Sep 10, 2025
a008c65
Merge branch 'ufs/dev' into glacier_mods
barlage Sep 18, 2025
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6 changes: 2 additions & 4 deletions physics/Interstitials/UFS_SCM_NEPTUNE/GFS_phys_time_vary.fv3.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -533,10 +533,8 @@ subroutine GFS_phys_time_vary_init (
endif

if (vegtyp == 15) then ! land ice in MODIS/IGBP
if (weasd(ix) < 0.1_kind_phys) then
weasd(ix) = 0.1_kind_phys
snd = 0.01_kind_phys
endif
weasd(ix) = 600.0_kind_phys ! 600mm SWE for glacier
snd = 2.0_kind_phys ! 2m snow depth for glacier
endif

if (snd < 0.025_kind_phys ) then
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29 changes: 23 additions & 6 deletions physics/SFC_Models/Land/Noahmp/module_sf_noahmp_glacier.F90
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Expand Up @@ -785,8 +785,8 @@ subroutine csnow_glacier (isnow ,nsnow ,nsoil ,snice ,snliq ,dzsnso ,
do iz = isnow+1, 0
! tksno(iz) = 3.2217e-6*bdsnoi(iz)**2. ! stieglitz(yen,1965)
! tksno(iz) = 2e-2+2.5e-6*bdsnoi(iz)*bdsnoi(iz) ! anderson, 1976
! tksno(iz) = 0.35 ! constant
tksno(iz) = 2.576e-6*bdsnoi(iz)**2. + 0.074 ! verseghy (1991)
tksno(iz) = 0.35 ! constant
! tksno(iz) = 2.576e-6*bdsnoi(iz)**2. + 0.074 ! verseghy (1991)
! tksno(iz) = 2.22*(bdsnoi(iz)/1000.)**1.88 ! douvill(yen, 1981)
enddo

Expand Down Expand Up @@ -982,8 +982,8 @@ subroutine snowalb_bats_glacier (nband,cosz,fage,albsnd,albsni)
cf1=((1.+sl1)/(1.+sl2*cosz)-sl1)
fzen=amax1(cf1,0.)

albsni(1)=0.95*(1.-c1*fage)
albsni(2)=0.65*(1.-c2*fage)
albsni(1)=0.95 !*(1.-c1*fage) ! remove aging over glaciers
albsni(2)=0.65 !*(1.-c2*fage) ! remove aging over glaciers

albsnd(1)=albsni(1)+0.4*fzen*(1.-albsni(1)) ! vis direct
albsnd(2)=albsni(2)+0.4*fzen*(1.-albsni(2)) ! nir direct
Expand Down Expand Up @@ -2616,7 +2616,7 @@ subroutine snowwater_glacier (nsnow ,nsoil ,imelt ,dt ,sfctmp , & !in
! local
integer :: iz
real (kind=kind_phys) :: bdsnow !< bulk density of snow (kg/m3)
real (kind=kind_phys),parameter :: mwd = 100. !< maximum water depth (mm)
real (kind=kind_phys),parameter :: mwd = 600. !< maximum water depth (mm)
! ----------------------------------------------------------------------
snoflow = 0.0
ponding1 = 0.0
Expand Down Expand Up @@ -2650,6 +2650,23 @@ subroutine snowwater_glacier (nsnow ,nsoil ,imelt ,dt ,sfctmp , & !in
ponding1 ,ponding2 ,fsh , & !inout
qsnbot ) !out

!reset the glacier to 2m depth with 600mm SWE

isnow = -3
snice(-2) = 15.0
snice(-1) = 60.0
snice( 0) = 525.0
snliq(-2) = 0.0
snliq(-1) = 0.0
snliq( 0) = 0.0
if(stc( 0) < 100.0) stc( 0) = stc( 1) ! if the temperature is missing,
if(stc(-1) < 100.0) stc(-1) = stc( 0) ! set to layer below
if(stc(-2) < 100.0) stc(-2) = stc(-1) ! should not be necessary
dzsnso(-2)= 0.05
dzsnso(-1)= 0.20
dzsnso( 0)= 1.75
sneqv = 600.0

!set empty snow layers to zero

do iz = -nsnow+1, isnow
Expand All @@ -2662,7 +2679,7 @@ subroutine snowwater_glacier (nsnow ,nsoil ,imelt ,dt ,sfctmp , & !in

!to obtain equilibrium state of snow in glacier region

if(sneqv > mwd) then ! 100 mm -> maximum water depth
if(sneqv > mwd) then ! 600 mm -> maximum water depth
bdsnow = snice(0) / dzsnso(0)
snoflow = (sneqv - mwd)
snice(0) = snice(0) - snoflow
Expand Down