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Interstitial bareground #1577

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f736477
remove unused total canopy area variable
glemieux Jun 14, 2026
5c852bb
rename canopy_fraction_pa to patch_fraction
glemieux Jun 14, 2026
ac12b45
add logic to receive interstitial bareground flag from HLM
glemieux Jun 14, 2026
9215893
update the boundary condition output for patch fraction
glemieux Jun 14, 2026
c20ceb3
add interstitial bareground logic to handle surface roughness and dis…
glemieux Jun 26, 2026
0837748
move weighting check outside of TCA check
glemieux Aug 11, 2026
8c2b11c
remove interstitial check from zero TCA option
glemieux Aug 11, 2026
fdbca10
add input bc for bareground roughness from the HLM
glemieux Aug 24, 2026
4045b45
update roughness length calculation to include bareground
glemieux Aug 24, 2026
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76 changes: 54 additions & 22 deletions biogeochem/EDCanopyStructureMod.F90
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Expand Up @@ -36,6 +36,7 @@ module EDCanopyStructureMod
use FatesInterfaceTypesMod , only : hlm_use_planthydro
use FatesInterfaceTypesMod , only : hlm_use_cohort_age_tracking
use FatesInterfaceTypesMod , only : hlm_use_sp
use FatesInterfaceTypesMod , only : hlm_use_interstitial_bareground
use FatesInterfaceTypesMod , only : numpft
use FatesInterfaceTypesMod, only : bc_in_type
use FatesPlantHydraulicsMod, only : UpdateH2OVeg,InitHydrCohort, RecruitWaterStorage
Expand Down Expand Up @@ -1328,7 +1329,7 @@ end subroutine leaf_area_profile

! ======================================================================================

subroutine update_hlm_dynamics(nsites,sites,fcolumn,bc_out)
subroutine update_hlm_dynamics(nsites,sites,fcolumn,bc_out,bc_in)

! ----------------------------------------------------------------------------------
! The purpose of this routine is to package output boundary conditions related
Expand All @@ -1345,22 +1346,25 @@ subroutine update_hlm_dynamics(nsites,sites,fcolumn,bc_out)
type(ed_site_type), intent(inout), target :: sites(nsites)
integer, intent(in) :: fcolumn(nsites)
type(bc_out_type), intent(inout) :: bc_out(nsites)
type(bc_in_type), intent(in) :: bc_in(nsites)

! Locals
type (fates_cohort_type) , pointer :: currentCohort
integer :: s, ifp, c, p
type (fates_patch_type) , pointer :: currentPatch
real(r8) :: bare_frac_area
real(r8) :: local_patch_fraction
real(r8) :: total_patch_area
real(r8) :: total_canopy_area
real(r8) :: total_patch_leaf_stem_area
real(r8) :: weight ! Weighting for cohort variables in patch

real(r8) :: weight ! Weighting for cohort variables in patch
real(r8) :: weighting_area ! Area to normalize against depending on insterstitial bareground handling
real(r8) :: bareground_fraction ! fraction of the patch that is bareground

do s = 1,nsites

total_patch_area = 0._r8
total_canopy_area = 0._r8
bc_out(s)%canopy_fraction_pa(:) = 0._r8
local_patch_fraction = 0._r8
bc_out(s)%patch_fraction(:) = 0._r8
bc_out(s)%dleaf_pa(:) = 0._r8
bc_out(s)%z0m_pa(:) = 0._r8
bc_out(s)%displa_pa(:) = 0._r8
Expand Down Expand Up @@ -1389,24 +1393,46 @@ subroutine update_hlm_dynamics(nsites,sites,fcolumn,bc_out)

bc_out(s)%hbot_pa(ifp) = max(0._r8, min(0.2_r8, bc_out(s)%htop_pa(ifp)- 1.0_r8))

! Use canopy-only crown area weighting for all cohorts in the patch to define the characteristic
! Roughness length and displacement height used by the HLM
! use total LAI + SAI to weight the leaft characteristic dimension
! Define the characteristic roughness length and displacement height used by the HLM
! Nominally, FATES uses canopy-only crown area weighting for all cohorts in the patch
! when the interstitial bareground is being collapsed into the HLM bareground patch.
! When we account for the bareground as part of the patch, the full area is accounted
! for in the calculation.
! If there is no canopy and we are considering the interstitial bareground we do
! something else.
! Use total LAI + SAI to weight the leaft characteristic dimension
! Avoid this if running in satellite phenology mode
! ----------------------------------------------------------------------------

! Set the are to be used for weighting against the cohort area
! If we are not using the interstitial bareground paradigm, simply
! use the patch area. Otherwise use the total canopy area.
weighting_area = currentPatch%total_canopy_area
if (hlm_use_interstitial_bareground .eq. ifalse) then
weighting_area = currentPatch%area
end if

if (currentPatch%total_canopy_area > nearzero) then
currentCohort => currentPatch%shortest
do while(associated(currentCohort))
if (currentCohort%canopy_layer .eq. 1) then
weight = min(1.0_r8,currentCohort%c_area/currentPatch%total_canopy_area)
weight = min(1.0_r8,currentCohort%c_area/weighting_area)
bc_out(s)%z0m_pa(ifp) = bc_out(s)%z0m_pa(ifp) + &
EDPftvarcon_inst%z0mr(currentCohort%pft) * currentCohort%height * weight
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bc_out(s)%displa_pa(ifp) = bc_out(s)%displa_pa(ifp) + &
EDPftvarcon_inst%displar(currentCohort%pft) * currentCohort%height * weight
endif
currentCohort => currentCohort%taller
end do

! If we are not using the interstitial bareground, we need to account for the bareground area
! fraction in calculating the roughness length. Here we mimic ZengWang 2007. This should
! eventually be replaced with a more robust approach that more accurately accounts for the
! the bareground fraction of the patch.
if (hlm_use_interstitial_bareground .eq. ifalse) then
bareground_fraction = (currentPatch%area - currentPatch%total_canopy_area) / currentPatch%area
bc_out(s)%z0m_pa(ifp) = exp(log(bc_out(s)%z0m_pa(ifp)) + bareground_fraction * log(bc_in(s)%z0mg))
end if

! for lai, scale to total LAI + SAI in patch. first add up all the LAI and SAI in the patch
total_patch_leaf_stem_area = 0._r8
Expand All @@ -1433,9 +1459,9 @@ subroutine update_hlm_dynamics(nsites,sites,fcolumn,bc_out)
endif
else
! if no canopy, then use dummy values (first PFT) of aerodynamic properties
bc_out(s)%z0m_pa(ifp) = EDPftvarcon_inst%z0mr(1) * bc_out(s)%htop_pa(ifp)
bc_out(s)%displa_pa(ifp) = EDPftvarcon_inst%displar(1) * bc_out(s)%htop_pa(ifp)
bc_out(s)%dleaf_pa(ifp) = EDPftvarcon_inst%dleaf(1)
bc_out(s)%z0m_pa(ifp) = EDPftvarcon_inst%z0mr(1) * bc_out(s)%htop_pa(ifp)
bc_out(s)%displa_pa(ifp) = EDPftvarcon_inst%displar(1) * bc_out(s)%htop_pa(ifp)
bc_out(s)%dleaf_pa(ifp) = EDPftvarcon_inst%dleaf(1)
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endif
! -----------------------------------------------------------------------------

Expand All @@ -1445,19 +1471,25 @@ subroutine update_hlm_dynamics(nsites,sites,fcolumn,bc_out)
! currentPatch%total_canopy_area/currentPatch%area is fraction of this patch cover by plants
! currentPatch%area/AREA is the fraction of the soil covered by this patch.

! If we are accounting for the interstitial bareground within the HLM bareground patch
! we use the projected total canopy area fraction as the output boundary condition.
! Otherwise we simply use the fraction of the area that the patch contributes to the given site.
if (hlm_use_interstitial_bareground == itrue) then
local_patch_fraction = min(1.0_r8,currentPatch%total_canopy_area/currentPatch%area)
else
local_patch_fraction = 1.0_r8
end if

if(currentPatch%area.gt.0.0_r8)then
bc_out(s)%canopy_fraction_pa(ifp) = &
min(1.0_r8,currentPatch%total_canopy_area/currentPatch%area)*(currentPatch%area/AREA)
bc_out(s)%patch_fraction(ifp) = local_patch_fraction*(currentPatch%area/AREA)
else
bc_out(s)%canopy_fraction_pa(ifp) = 0.0_r8
bc_out(s)%patch_fraction(ifp) = 0.0_r8
endif

bare_frac_area = (1.0_r8 - min(1.0_r8,currentPatch%total_canopy_area/currentPatch%area)) * &
bare_frac_area = (1.0_r8 - local_patch_fraction) * &
(currentPatch%area/AREA)

total_patch_area = total_patch_area + bc_out(s)%canopy_fraction_pa(ifp) + bare_frac_area

@glemieux glemieux Jun 14, 2026 •
edited
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Note that this is dead and duplicate code being removed. total_canopy_area wasn't being used downstream.


total_canopy_area = total_canopy_area + bc_out(s)%canopy_fraction_pa(ifp)
total_patch_area = total_patch_area + bc_out(s)%patch_fraction(ifp) + bare_frac_area

bc_out(s)%nocomp_pft_label_pa(ifp) = currentPatch%nocomp_pft_label

Expand All @@ -1484,7 +1516,7 @@ subroutine update_hlm_dynamics(nsites,sites,fcolumn,bc_out)
bc_out(s)%frac_veg_nosno_alb_pa(ifp) = 0.0_r8
end if

else ! nocomp or SP, and currentPatch%nocomp_pft_label .eq. 0
else ! nocomp or SP, (i.e.currentPatch%nocomp_pft_label .eq. 0

total_patch_area = total_patch_area + currentPatch%area/AREA

Expand All @@ -1511,7 +1543,7 @@ subroutine update_hlm_dynamics(nsites,sites,fcolumn,bc_out)
do while(associated(currentPatch))
ifp = currentPatch%patchno
if(currentPatch%nocomp_pft_label.ne.nocomp_bareground)then ! for vegetated patches only
bc_out(s)%canopy_fraction_pa(ifp) = bc_out(s)%canopy_fraction_pa(ifp)/total_patch_area
bc_out(s)%patch_fraction(ifp) = bc_out(s)%patch_fraction(ifp)/total_patch_area
endif ! veg patch
currentPatch => currentPatch%younger
end do
Expand Down
11 changes: 9 additions & 2 deletions main/FatesInterfaceMod.F90
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Expand Up @@ -411,7 +411,7 @@ subroutine zero_bcs(fates,s)
fates%bc_out(s)%dleaf_pa(:) = 0.0_r8
fates%bc_out(s)%nocomp_pft_label_pa(:) = 0

fates%bc_out(s)%canopy_fraction_pa(:) = 0.0_r8
fates%bc_out(s)%patch_fraction(:) = 0.0_r8
fates%bc_out(s)%frac_veg_nosno_alb_pa(:) = 0.0_r8

if (hlm_use_planthydro.eq.itrue) then
Expand Down Expand Up @@ -744,7 +744,7 @@ subroutine allocate_bcout(bc_out, nlevsoil_in, nlevdecomp_in)
allocate(bc_out%displa_pa(maxpatch_total))
allocate(bc_out%z0m_pa(maxpatch_total))

allocate(bc_out%canopy_fraction_pa(maxpatch_total))
allocate(bc_out%patch_fraction(maxpatch_total))
allocate(bc_out%frac_veg_nosno_alb_pa(maxpatch_total))

allocate(bc_out%nocomp_pft_label_pa(maxpatch_total))
Expand Down Expand Up @@ -1574,6 +1574,7 @@ subroutine set_fates_ctrlparms(tag,ival,rval,cval)
hlm_use_fixed_biogeog = unset_int
hlm_use_nocomp = unset_int
hlm_use_sp = unset_int
hlm_use_interstitial_bareground = unset_int
hlm_use_inventory_init = unset_int
hlm_use_dbh_init = unset_int
hlm_inventory_ctrl_file = 'unset'
Expand Down Expand Up @@ -2050,6 +2051,12 @@ subroutine set_fates_ctrlparms(tag,ival,rval,cval)
write(fates_log(),*) 'Transfering hlm_use_sp= ',ival,' to FATES'
end if

case('use_fates_interstitial_bareground')
hlm_use_interstitial_bareground = ival
if (fates_global_verbose()) then
write(fates_log(),*) 'Transfering hlm_use_interstitial_bareground= ',ival,' to FATES'
end if

case('use_planthydro')
hlm_use_planthydro = ival
if (fates_global_verbose()) then
Expand Down
16 changes: 12 additions & 4 deletions main/FatesInterfaceTypesMod.F90
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Expand Up @@ -225,6 +225,9 @@ module FatesInterfaceTypesMod
integer, public :: hlm_use_sp ! Flag to use FATES satellite phenology (LAI) mode
! 1 = TRUE, 0 = FALSE

integer, public :: hlm_use_interstitial_bareground ! Flag to use count the FATES interstitial bareground area
! with the HLM bareground patch
! 1 = TRUE, 0 = FALSE

! Flag specifying what types of history fields to allocate and prepare
! The "_dynam" refers to history fields that can be updated on the dynamics (daily) step
Expand Down Expand Up @@ -503,6 +506,9 @@ module FatesInterfaceTypesMod

! soil temperature (Kelvin)
real(r8), allocatable :: t_soisno_sl(:)

! surface roughness length, site bareground (m)
real(r8) :: z0mg

! Canopy Radiation Boundaries
! ---------------------------------------------------------------------------------
Expand Down Expand Up @@ -766,10 +772,12 @@ module FatesInterfaceTypesMod
real(r8), allocatable :: displa_pa(:) ! displacement height [m]
real(r8), allocatable :: dleaf_pa(:) ! leaf characteristic dimension/width/diameter [m]

real(r8), allocatable :: canopy_fraction_pa(:) ! Area fraction of each patch in the site
! Use most likely for weighting
! This is currently the projected canopy
! area of each patch [0-1]
real(r8), allocatable :: patch_fraction(:) ! Area fraction of each patch in the site
! Use most likely for weighting
! This is either the projected canopy
! area of each patch [0-1] or the actual
! are fraction that each patch contributes
! to the site

real(r8), allocatable :: frac_veg_nosno_alb_pa(:) ! This is not really a fraction
! this is actually binary based on if any
Expand Down