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NGEE Arctic IM3: bug-fix for LAI fraction buried by snow #7406

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NGEE Arctic IM3: bug-fix for LAI fraction buried by snow #7406

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e82f1ec
Fix snow burial bug when bendresist < 1
rfiorella Mar 6, 2025
24f30e0
Addresses two bugs in the NGEE-Arctic IM3 code
rfiorella Mar 20, 2025
4a154c2
typo fix in endrun call
rfiorella Jul 2, 2025
33f5a88
Fix typo after correcting bad rebase
rfiorella Jul 5, 2025
7dbf7a2
lengthen snowveg-arctic test to highlight IM3 bending parameter bug
rfiorella Sep 18, 2025
0969135
update snowveg_arctic test to use Ld150 flag
rfiorella Sep 19, 2025
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2 changes: 1 addition & 1 deletion cime_config/tests.py
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Original file line number Diff line number Diff line change
Expand Up @@ -50,7 +50,7 @@
"ERS.f19_g16.I20TRGSWCNPRDCTCBC.elm-ctc_f19_g16_I20TRGSWCNPRDCTCBC",
"SMS_Ly2_P1x1.1x1_smallvilleIA.I20TRGSWCNPCROP.elm-lulcc_sville",
"ERS.r05_r05.ICNPRDCTCBC.elm-cbudget",
"ERS.ELM_USRDAT.I1850CNPRDCTCBC.elm-snowveg_arctic",
"ERS_Ld150.ELM_USRDAT.I1850CNPRDCTCBC.elm-snowveg_arctic",
"ERS.ELM_USRDAT.I1850CNPRDCTCBC.elm-usrpft_default_I1850CNPRDCTCBC",
"ERS.ELM_USRDAT.I1850CNPRDCTCBC.elm-usrpft_codetest_I1850CNPRDCTCBC",
"ERS.1x1_icycape.I1850GSWCNPRDCTCBC.elm-polygonal_tundra"
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13 changes: 8 additions & 5 deletions components/elm/src/biogeochem/VegStructUpdateMod.F90
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Expand Up @@ -236,16 +236,19 @@ subroutine VegStructUpdate(num_soilp, filter_soilp, &
! Wang and Zeng et al 2007.
! Taller vegetation (trees and shrubs) have been updated to use formulation similar to
! Sturm et al. 2005; Liston and Hiemstra, 2011; and Belke-Brea et al. 2020
if ( woody(ivt(p)) >= 1.0_r8 ) then
if ( woody(ivt(p)) == 1.0_r8 ) then
ol = min( max(snow_depth(c)-hbot(p), 0._r8), htop(p)-hbot(p))
fb = 1._r8 - (ol / max(1.e-06_r8, bendresist(ivt(p)) * (htop(p)-hbot(p)))) ** vegshape(ivt(p))
fb = (ol / max(1.e-06_r8, (htop(p)-hbot(p))))
else if (woody(ivt(p)) == 2.0_r8) then
ol = min( max(snow_depth(c)-bendresist(ivt(p))*hbot(p), 0._r8), (bendresist(ivt(p))*(htop(p)-hbot(p)))**vegshape(ivt(p)))
fb = (ol / max(1.e-06_r8, bendresist(ivt(p))*(htop(p)-hbot(p))**vegshape(ivt(p))))
else
fb = 1._r8 - max(min(snow_depth(c),0.2_r8),0._r8)/0.2_r8 ! 0.2m is assumed
fb = max(min(snow_depth(c),0.2_r8),0._r8)/0.2_r8 ! 0.2m is assumed
!depth of snow required for complete burial of grasses
endif

elai(p) = max(tlai(p)*fb, 0.0_r8)
esai(p) = max(tsai(p)*fb, 0.0_r8)
elai(p) = max(tlai(p)*(1._r8 - fb), 0.0_r8)
esai(p) = max(tsai(p)*(1._r8 - fb), 0.0_r8)

! Fraction of vegetation free of snow
if ((elai(p) + esai(p)) > 0._r8) then
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23 changes: 16 additions & 7 deletions components/elm/src/main/pftvarcon.F90
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Expand Up @@ -315,7 +315,7 @@ module pftvarcon
! NGEE Arctic snow-vegetation interactions
real(r8), allocatable :: bendresist(:) ! vegetation resistance to bending under snow loading, 0 to 1 (e.g., Liston and Hiemstra 2011; Sturm et al. 2005)
real(r8), allocatable :: vegshape(:) ! shape parameter to modify shrub burial by snow (1 = parabolic, 2 = hemispheric)
real(r8), allocatable :: stocking(:) ! stocking density for pft (stems / hectare)
real(r8), allocatable :: stocking(:) ! stocking density for pft (stems / hectare assumed on param file)
real(r8), allocatable :: taper(:) ! ratio of height:radius_breast_height (woody vegetation allometry)
logical :: taper_defaults ! set flag to use taper defaults if not on params file (necessary as import and set values are in different places)

Expand Down Expand Up @@ -1094,18 +1094,27 @@ subroutine pftconrd
if (.not. readv ) bendresist(:) = 1._r8
call ncd_io('vegshape', vegshape, 'read', ncid, readvar=readv, posNOTonfile=.true.)
if (.not. readv ) vegshape(:) = 1._r8
! check validity
! check validity
do i = 0, npft-1
if (bendresist(i) .gt. 1.0_r8 .or. bendresist(i) .le. 0._r8) then
call endrun(msg="Non-physical selection of bendresist parameter, set between 0 and 1"//errMsg(__FILE__, __LINE__))
end if
if (vegshape(i) .gt. 2.0_r8 .or. vegshape(i) .le. 0._r8) then
call endrun(msg="Non-physical selection of vegshape parameter, set between 0 and 2"//errMsg(__FILE__, __LINE__))
if (vegshape(i) .gt. 2.0_r8 .or. vegshape(i) .lt. 1._r8) then
call endrun(msg="Non-physical selection of vegshape parameter, set as 1 or 2"//errMsg(__FILE__, __LINE__))
end if
end do
end do

call ncd_io('stocking', stocking, 'read', ncid, readvar=readv, posNOTonfile=.true.)
if (.not. readv ) stocking(:) = 0.1_r8 ! convert previous default of 1000 stems/ha to stems/m2 as had been done in VegStructUpdateMod.F90
taper_defaults = .false.
if (.not. readv ) then
stocking(:) = 0.1_r8 ! convert previous default of 1000 stems/ha to stems/m2 as had been done in VegStructUpdateMod.F90
else
stocking(:) = stocking(:)/10000._r8 ! conversion from stems/ha to stems/m2 done here now
endif
if (any(stocking(:) .ge. 1000._r8 )) then
call endrun(msg="Non-physical selection of stocking density parameter, implies >1000 plants/m2"//errMsg(__FILE__, __LINE__))
endif

taper_defaults = .false.
call ncd_io('taper', taper, 'read', ncid, readvar=readv, posNOTonfile=.true.)
if (.not. readv ) then
taper(:) = 200._r8 ! pftnames not set to integers yet, so reassign further down.
Expand Down