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Added routine to calculate surface inundated fraction in polygonal tu…
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…ndra, but still needs work defining values for microtopographic parameters before it can be tested
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@chuckaustin
chuckaustin committed May 6, 2024
1 parent 735b5b2 commit fc8f584
Showing 1 changed file with 49 additions and 17 deletions.
66 changes: 49 additions & 17 deletions components/elm/src/biogeophys/CanopyHydrologyMod.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -783,7 +783,7 @@ subroutine FracH2OSfc(bounds, num_h2osfc, filter_h2osfc, &
! !USES:
use shr_const_mod , only : shr_const_pi
use shr_spfn_mod , only : erf => shr_spfn_erf
use landunit_varcon , only : istsoil, istcrop
use landunit_varcon , only : istsoil, istcrop, ispolygon
!
! !ARGUMENTS:
type(bounds_type) , intent(in) :: bounds
Expand All @@ -794,24 +794,28 @@ subroutine FracH2OSfc(bounds, num_h2osfc, filter_h2osfc, &
integer , intent(in), optional :: no_update ! flag to make calculation w/o updating variables
!
! !LOCAL VARIABLES:
integer :: c,f,l ! indices
integer :: c,f,l,k ! indices
real(r8):: d,fd,dfdd ! temporary variable for frac_h2oscs iteration
real(r8):: sigma ! microtopography pdf sigma in mm
real(r8):: swc ! surface water content in m
real(r8):: min_h2osfc
!-----------------------------------------------------------------------

associate( &
micro_sigma => col_pp%micro_sigma , & ! Input: [real(r8) (:) ] microtopography pdf sigma (m)

h2osno => col_ws%h2osno , & ! Input: [real(r8) (:) ] snow water (mm H2O)
excess_ice => col_ws%excess_ice , & ! Input: [real(r8) (:,:) ] excess ground ice [kg/m2]

h2osoi_liq => col_ws%h2osoi_liq , & ! Output: [real(r8) (:,:) ] liquid water (col,lyr) [kg/m2]
h2osfc => col_ws%h2osfc , & ! Output: [real(r8) (:) ] surface water (mm)
frac_sno => col_ws%frac_sno , & ! Output: [real(r8) (:) ] fraction of ground covered by snow (0 to 1)
frac_sno_eff => col_ws%frac_sno_eff , & ! Output: [real(r8) (:) ] eff. fraction of ground covered by snow (0 to 1)
frac_h2osfc => col_ws%frac_h2osfc , & ! Output: [real(r8) (:) ] col fractional area with surface water greater than zero
frac_h2osfc_act => col_ws%frac_h2osfc_act & ! Output: [real(r8) (:) ] col fractional area with surface water greater than zero
associate( &
micro_sigma => col_pp%micro_sigma , & ! Input: [real(r8) (:) ] microtopography pdf sigma (m)

iwp_microrel => col_pp%iwp_microrel , & ! Input: [real(r8) (:) ] ice wedge polygon microtopographic relief (m)
iwp_exclvol => col_pp%iwp_exclvol , & ! Input: [real(r8) (:) ] microtopography pdf sigma (m)
iwp_ddep => col_pp%iwp_ddep , & ! Input: [real(r8) (:) ] microtopography pdf sigma (m)

h2osno => col_ws%h2osno , & ! Input: [real(r8) (:) ] snow water (mm H2O)

h2osoi_liq => col_ws%h2osoi_liq , & ! Output: [real(r8) (:,:) ] liquid water (col,lyr) [kg/m2]
h2osfc => col_ws%h2osfc , & ! Output: [real(r8) (:) ] surface water (mm)
frac_sno => col_ws%frac_sno , & ! Output: [real(r8) (:) ] fraction of ground covered by snow (0 to 1)
frac_sno_eff => col_ws%frac_sno_eff , & ! Output: [real(r8) (:) ] eff. fraction of ground covered by snow (0 to 1)
frac_h2osfc => col_ws%frac_h2osfc , & ! Output: [real(r8) (:) ] col fractional area with surface water greater than zero
frac_h2osfc_act => col_ws%frac_h2osfc_act & ! Output: [real(r8) (:) ] col fractional area with surface water greater than zero
)

! arbitrary lower limit on h2osfc for safer numerics...
Expand All @@ -825,15 +829,42 @@ subroutine FracH2OSfc(bounds, num_h2osfc, filter_h2osfc, &
if (lun_pp%itype(l) == istsoil .or. lun_pp%itype(l) == istcrop) then

! Use newton-raphson method to iteratively determine frac_h20sfc
! based on amount of surface water storage (h2osfc) and
! microtopography variability (micro_sigma)
! based on amount of surface water storage (h2osfc) and
! microtopography variability (micro_sigma) if nonpolygonal, or
! amount of surface water (h2osfc) and microtopographic attributes
! (iwp_microrel, iwp_exclvol) if polygonal tundra

if (h2osfc(c) > min_h2osfc) then
! a cutoff is needed for numerical reasons...(nonconvergence after 5 iterations)

if lun_pp%ispolygon(l) then
! calculate water depth and inundation fraction if column is polygonal
swc = h2osfc(c)/1000 ! convert to m

if swc > iwp_microrel - iwp_exclvol then
d = swc + iwp_exclvol
else
d = 0.0
do k=1,10
fd = (2_r8*iwp_exclvol - iwp_microrel) * (d/iwp_microrel)**3_r8 &
+ (2_r8*iwp_microrel - 3_r8*iwp_exclvol) * (d/iwp_microrel)**2_r8 &
- swc
dfdd = (3_r8/iwp_microrel) * (2_r8*iwp_exclvol - iwp_microrel) * (d/iwp_microrel)**2_r8 &
+ (2_r8/iwp_microrel) * (2_r8*iwp_microrel - 3_r8*iwp_exclvol) * (d/iwp_microrel)
d = d - fd/dfdd
enddo
endif
!-- update the submerged areal fraction using the new d value
frac_h2osfc(c) = (3_r8/iwp_microrel) * (2_r8*iwp_exclvol - iwp_microrel) * (d/iwp_microrel)**2_r8 &
+ (2_r8/iwp_microrel) * (2_r8*iwp_microrel - 3_r8*iwp_exclvol) * (d/iwp_microrel)
endif

else
! calculate water depth and inudation fraction if column is non-polygonal
d=0.0

sigma=1.0e3 * micro_sigma(c) ! convert to mm
do l=1,10
do k=1,10
fd = 0.5*d*(1.0_r8+erf(d/(sigma*sqrt(2.0)))) &
+sigma/sqrt(2.0*shr_const_pi)*exp(-d**2/(2.0*sigma**2)) &
-h2osfc(c)
Expand All @@ -843,6 +874,7 @@ subroutine FracH2OSfc(bounds, num_h2osfc, filter_h2osfc, &
enddo
!-- update the submerged areal fraction using the new d value
frac_h2osfc(c) = 0.5*(1.0_r8+erf(d/(sigma*sqrt(2.0))))
endif

else
frac_h2osfc(c) = 0._r8
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