Move weight calculations inside IM2 block

E3SM-Project · Jan 9, 2025 · 874f2bc · 874f2bc
1 parent 259f0e0
commit 874f2bc
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Showing 2 changed files with 22 additions and 19 deletions.
diff --git a/components/elm/src/biogeophys/SoilHydrologyMod.F90 b/components/elm/src/biogeophys/SoilHydrologyMod.F90
@@ -244,21 +244,6 @@ subroutine SurfaceRunoff (bounds, num_hydrologyc, filter_hydrologyc, &
 
       end do
 
-      ! calculate the sum of column weights on each topounit for columns in the hydrologyc filter
-      ! This will be the istsoil, istcrop, and icol_road_perv subset of urban columns
-      ! First zero the topounit sum of weights. This zeros some multiple times, but no harm done.
-      do fc = 1, num_hydrologyc
-         c = filter_hydrologyc(fc)
-         t = col_pp%topounit(c)
-         top_pp%uphill_wt(t) = 0._r8
-      end do
-      ! Next sum the weights
-      do fc = 1, num_hydrologyc
-         c = filter_hydrologyc(fc)
-         t = col_pp%topounit(c)
-         top_pp%uphill_wt(t) = top_pp%uphill_wt(t) + col_pp%wttopounit(c)
-      end do
-
       ! remove stormflow and snow on h2osfc from qflx_top_soil
       do fc = 1, num_hydrologyc
          c = filter_hydrologyc(fc)
@@ -267,14 +252,32 @@ subroutine SurfaceRunoff (bounds, num_hydrologyc, filter_hydrologyc, &
          qflx_top_soil(c) = qflx_top_soil(c) + qflx_snow_h2osfc(c) + qflx_floodc(c)
       end do
 
-      ! flow from uphill topounit goes to top of soil for soil, crop, and pervious road columns
+      ! when using the subgrid hillslope lateral flow mechanism (IM2 from NGEE Arctic):
+      ! 1. calculate fraction of topounit flow that goes to each column
+      ! 2. Calculate the weighted flux from uphill (qflx_from_uphill) and add to qflx_top_soil 
       if (use_IM2_hillslope_hydrology) then
+         ! calculate the sum of column weights on each topounit for columns in the hydrologyc filter
+         ! This will be the istsoil, istcrop, and icol_road_perv subset of urban columns
+         ! First zero the topounit sum of weights. This zeros some multiple times, but no harm done.
+         do fc = 1, num_hydrologyc
+            c = filter_hydrologyc(fc)
+            t = col_pp%topounit(c)
+            top_pp%uphill_wt(t) = 0._r8
+         end do
+         ! Next sum the relevant column weights
+         do fc = 1, num_hydrologyc
+            c = filter_hydrologyc(fc)
+            t = col_pp%topounit(c)
+            top_pp%uphill_wt(t) = top_pp%uphill_wt(t) + col_pp%wttopounit(c)
+         end do
+
+         ! flow from uphill topounit goes to top of soil for soil, crop, and pervious road columns
          do fc = 1, num_hydrologyc
             c = filter_hydrologyc(fc)
             t = col_pp%topounit(c)
             qflx_from_uphill(c) = (col_pp%wttopounit(c)/top_pp%uphill_wt(t)) * (frac_from_uphill * top_ws%from_uphill(t)) / dtime
             qflx_top_soil(c) = qflx_top_soil(c) + qflx_from_uphill(c)
-        end do
+         end do
       endif
 
     end associate

diff --git a/components/elm/src/main/elm_varcon.F90 b/components/elm/src/main/elm_varcon.F90
@@ -226,9 +226,9 @@ module elm_varcon
   ! IM2 hillslope hydrology constants
   !------------------------------------------------------------------
   ! fraction of surface runoff fluxes that get transferred to downhill topounit
-  real(r8), public, parameter :: frac_to_downhill = 1.0  ! (fraction, valid values from 0.0 to 1.0)
+  real(r8), public, parameter :: frac_to_downhill = 1.0_r8  ! (fraction, valid values from 0.0 to 1.0)
   ! fraction of from_uphill water state that get transferred to columns on the topounit in each timestep
-  real(r8), public, parameter :: frac_from_uphill = 0.5  ! (fraction, valid values from 0.0 to 1.0)
+  real(r8), public, parameter :: frac_from_uphill = 0.5_r8  ! (fraction, valid values from 0.0 to 1.0)
 
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