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Snow cover fraction for Advancing Arctic Capabilities Programme #105

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1 change: 1 addition & 0 deletions CONTRIBUTORS.md
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Expand Up @@ -9,3 +9,4 @@
| ScottWales | Scott Wales | Bureau of Meteorology | 2026-02-16 |
| t00sa | Sam Clarke-Green | Met Office | 2026-02-27 |
| Pierre-siddall | Pierre Siddall| Met Office | 2026-02-06 |
| RichardEssery | Richard Essery | University of Edinburgh | 2026-04-18 |
9 changes: 9 additions & 0 deletions src/control/shared/fluxes.F90
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Expand Up @@ -95,6 +95,8 @@ MODULE fluxes_mod
! Surface FQW for sea-ice
REAL(KIND=real_jlslsm), ALLOCATABLE :: fsmc_pft(:,:)
! Moisture availability factor.
REAL(KIND=real_jlslsm), ALLOCATABLE :: fsnow(:,:)
! Snow cover fraction on tiles
REAL(KIND=real_jlslsm), ALLOCATABLE :: ftl_sicat(:,:,:)
! Surface FTL for sea-ice
REAL(KIND=real_jlslsm), ALLOCATABLE :: ftl_surft(:,:)
Expand Down Expand Up @@ -215,6 +217,8 @@ MODULE fluxes_mod
! Surface FQW for sea-ice
REAL(KIND=real_jlslsm), POINTER :: fsmc_pft(:,:)
! Moisture availability factor.
REAL(KIND=real_jlslsm), POINTER :: fsnow(:,:)
! Snow cover fraction on tiles
REAL(KIND=real_jlslsm), POINTER :: ftl_sicat(:,:,:)
! Surface FTL for sea-ice
REAL(KIND=real_jlslsm), POINTER :: ftl_surft(:,:)
Expand Down Expand Up @@ -340,6 +344,7 @@ SUBROUTINE fluxes_alloc(land_pts, t_i_length, t_j_length, &
ALLOCATE(fluxes_data%sub_surf_roff_gb(land_pts))
ALLOCATE(fluxes_data%surf_roff_gb(land_pts))
ALLOCATE(fluxes_data%alb_surft(land_pts,nsurft,4) )
ALLOCATE(fluxes_data%fsnow(land_pts,nsurft))
ALLOCATE(fluxes_data%tstar_ij(t_i_length,t_j_length))
ALLOCATE(fluxes_data%e_sea_ij(t_i_length,t_j_length))
ALLOCATE(fluxes_data%fsmc_pft(land_pts,npft))
Expand Down Expand Up @@ -383,6 +388,7 @@ SUBROUTINE fluxes_alloc(land_pts, t_i_length, t_j_length, &
fluxes_data%sub_surf_roff_gb(:) = 0.0
fluxes_data%surf_roff_gb(:) = 0.0
fluxes_data%alb_surft(:,:,:) = 0.0
fluxes_data%fsnow(:,:) = 0.0
fluxes_data%tstar_ij(:,:) = 0.0
fluxes_data%e_sea_ij(:,:) = 0.0
fluxes_data%fsmc_pft(:,:) = 0.0
Expand Down Expand Up @@ -459,6 +465,7 @@ SUBROUTINE fluxes_dealloc(fluxes_data)
DEALLOCATE(fluxes_data%sub_surf_roff_gb)
DEALLOCATE(fluxes_data%surf_roff_gb)
DEALLOCATE(fluxes_data%alb_surft)
DEALLOCATE(fluxes_data%fsnow)
DEALLOCATE(fluxes_data%tstar_ij)
DEALLOCATE(fluxes_data%e_sea_ij)
DEALLOCATE(fluxes_data%fsmc_pft)
Expand Down Expand Up @@ -541,6 +548,7 @@ SUBROUTINE fluxes_assoc(fluxes,fluxes_data)
fluxes%sub_surf_roff_gb => fluxes_data%sub_surf_roff_gb
fluxes%surf_roff_gb => fluxes_data%surf_roff_gb
fluxes%alb_surft => fluxes_data%alb_surft
fluxes%fsnow => fluxes_data%fsnow
fluxes%tstar_ij => fluxes_data%tstar_ij
fluxes%e_sea_ij => fluxes_data%e_sea_ij
fluxes%fsmc_pft => fluxes_data%fsmc_pft
Expand Down Expand Up @@ -619,6 +627,7 @@ SUBROUTINE fluxes_nullify(fluxes)
NULLIFY(fluxes%sub_surf_roff_gb)
NULLIFY(fluxes%surf_roff_gb)
NULLIFY(fluxes%alb_surft)
NULLIFY(fluxes%fsnow)
NULLIFY(fluxes%tstar_ij)
NULLIFY(fluxes%e_sea_ij)
NULLIFY(fluxes%fsmc_pft)
Expand Down
12 changes: 12 additions & 0 deletions src/control/shared/jules_radiation_mod.F90
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Expand Up @@ -116,6 +116,7 @@ SUBROUTINE check_jules_radiation()

USE ereport_mod, ONLY: ereport
USE jules_print_mgr, ONLY: jules_message
USE jules_snow_mod, ONLY: i_snow_tile

!-----------------------------------------------------------------------------
! Description:
Expand Down Expand Up @@ -157,6 +158,17 @@ SUBROUTINE check_jules_radiation()
CALL ereport("check_jules_radiation", errorstatus, jules_message)
END IF

! Required options if a separate snow tile is being used
IF ( ANY(i_snow_tile == 1) ) THEN
IF ( (.NOT. l_spec_albedo) .OR. l_embedded_snow .OR. &
(.NOT. l_snow_albedo) ) THEN
errorstatus = 1003
CALL ereport("check_jules_radiation", errorstatus, &
"l_spec_albedo = T, l_embedded_snow = F and l_snow_albedo = T" // &
"required if ANY i_snow_tile = 1")
END IF
END IF

!Can set the size of rad_nband
IF (l_spec_albedo) THEN
rad_nband = 2
Expand Down
29 changes: 27 additions & 2 deletions src/control/shared/jules_snow_mod.F90
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Expand Up @@ -71,6 +71,12 @@ MODULE jules_snow_mod
INTEGER :: &
i_snow_cond_parm = 0
! Parametrization scheme for snow conductivity

INTEGER :: &
i_snow_tile(nsurft_max)
! Tiles without (0) or with (1) separate energy balance
! for snow. Must be 0 on ice tiles
DATA i_snow_tile / nsurft_max * 0 /

!-----------------------------------------------------------------------------
! Parametrization of the rate of growth of snow grains
Expand Down Expand Up @@ -307,7 +313,7 @@ MODULE jules_snow_mod
NAMELIST / jules_snow/ &
! Switches
nsmax, l_snowdep_surf, l_rho_snow_corr, frac_snow_subl_melt, &
graupel_options, &
graupel_options,i_snow_tile, &
! Equitemperature metamorphism
l_et_metamorph, a_snow_et, b_snow_et, c_snow_et, rho_snow_et_crit, &
! Thermal conductivity of snow
Expand All @@ -333,7 +339,7 @@ SUBROUTINE check_jules_snow()

USE water_constants_mod, ONLY: tm

USE jules_surface_types_mod, ONLY: npft
USE jules_surface_types_mod, ONLY: ice, npft, ntype
USE jules_surface_mod, ONLY: l_aggregate
USE jules_vegetation_mod, ONLY: can_model

Expand Down Expand Up @@ -388,6 +394,25 @@ SUBROUTINE check_jules_snow()
END IF
END IF

! Check for inconsistencies if a separate snow tile is used
IF ( ANY(i_snow_tile == 1) ) THEN
! Tiles cannot be aggregated
IF ( l_aggregate ) THEN
CALL ereport(RoutineName, errorstatus, &
'l_aggregate = F required if ANY i_snow_tile = 1')
END IF
! The last surface type must be an ice tile
IF ( ice .NE. ntype ) THEN
CALL ereport(RoutineName, errorstatus, &
'ice = ntype required if ANY i_snow_tile = 1')
END IF
! The ice tile cannot be selected
IF ( i_snow_tile(ntype) == 1 ) THEN
CALL ereport(RoutineName, errorstatus, &
'i_snow_tile(ntype) = 1 is not permitted')
END IF
END IF

END SUBROUTINE check_jules_snow
#endif

Expand Down
10 changes: 6 additions & 4 deletions src/control/shared/surf_couple_explicit_mod.F90
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Expand Up @@ -554,8 +554,8 @@ SUBROUTINE surf_couple_explicit( &
!IN soil/vegetation/land surface data :
ainfo%land_index,nsurft,sm_levels,progs%canopy_surft,psparms%catch_surft, &
psparms%catch_snow_surft, psparms%hcon_soilt,jules_vars%ho2r2_orog_gb, &
flandg_tmp, &
progs%snow_surft,jules_vars%sil_orog_land_gb,psparms%smvccl_soilt, &
flandg_tmp, fluxes%fsnow, &
jules_vars%sil_orog_land_gb,psparms%smvccl_soilt, &
psparms%smvcst_soilt,psparms%smvcwt_soilt, &
psparms%sthf_soilt, psparms%sthu_soilt,psparms%z0_surft, &
psparms%z0h_bare_surft, psparms%z0m_soil_gb, &
Expand Down Expand Up @@ -636,9 +636,11 @@ SUBROUTINE surf_couple_explicit( &
urban_param%wrr_gb, &
!Fluxes (IN OUT)
fluxes%anthrop_heat_surft, &
!prognostics (IN)
!snow prognostics (IN)
progs%nsnow_surft, progs%sice_surft, progs%sliq_surft, &
progs%snowdepth_surft, progs%tsnow_surft, progs%ds_surft, &
progs%tsnow_surft, progs%ds_surft, &
!snow prognostics (IN OUT)
progs%snowdepth_surft, progs%snow_surft, &
!c_elevate (OUT)
jules_vars%surf_hgt_surft, jules_vars%lw_down_elevcorr_surft, &
!jules_vars_mod (OUT)
Expand Down
4 changes: 2 additions & 2 deletions src/control/shared/surf_couple_extra_mod.F90
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Expand Up @@ -703,9 +703,9 @@ SUBROUTINE surf_couple_extra( &
fluxes%melt_surft,fluxes%snowinc_surft, &
progs%smcl_soilt(:,:,1),psparms%sthf_soilt(:,:,1), &
fluxes%surf_htf_surft, progs%t_soil_soilt(:,:,1), &
progs%tsurf_elev_surft, progs%tstar_surft, &
progs%tsurf_elev_surft, progs%tstar_surft, psparms%z0_surft, &
psparms%smvcst_soilt(:,:,1), con_snow_wtrac, &
wtrac_jls%ei_surft, progs%rgrain_surft, &
wtrac_jls%ei_surft, fluxes%fsnow, progs%rgrain_surft, &
progs%rgrainl_surft, progs%rho_snow_grnd_surft, &
progs%sice_surft,progs%sliq_surft,progs%snow_grnd_surft, &
progs%snow_surft, progs%snowdepth_surft, progs%tsnow_surft, &
Expand Down
2 changes: 1 addition & 1 deletion src/control/shared/surf_couple_implicit_mod.F90
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Expand Up @@ -446,7 +446,7 @@ SUBROUTINE surf_couple_implicit( &
alpha1,ashtf_surft, &
jules_vars%dtrdz_charney_grid_1_ij,fracaero_t,fracaero_s, &
resfs,resft, rhokh_surft, &
fluxes%emis_surft,progs%snow_surft,dtstar_surft, &
fluxes%emis_surft,fluxes%fsnow,progs%snow_surft,dtstar_surft, &
! INOUT data :
progs%tstar_surft,fluxes%fqw_surft,fqw_1,ftl_1,fluxes%ftl_surft, &
sf_diag, &
Expand Down
2 changes: 1 addition & 1 deletion src/control/shared/surf_couple_radiation_mod.F90
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Expand Up @@ -248,7 +248,7 @@ SUBROUTINE surf_couple_radiation( &
progs%rgrain_surft, snow_surft, progs%tstar_surft, psparms%z0_surft, &
ainfo%frac_surft, &
!INTENT(OUT)
fluxes%alb_surft,albobs_sc_ij,fluxes%land_albedo_ij, &
fluxes%alb_surft,albobs_sc_ij,fluxes%fsnow,fluxes%land_albedo_ij, &
!New arguments replacing USE statements
!jules_vars_mod (IN OUT)
jules_vars%albobs_scaling_surft, &
Expand Down
14 changes: 14 additions & 0 deletions src/control/shared/tilepts_jls.F90
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Expand Up @@ -16,6 +16,8 @@ MODULE tilepts_mod
SUBROUTINE tilepts(land_pts,frac,surft_pts,surft_index,l_lice_point, &
l_lice_surft)

USE jules_snow_mod, ONLY: i_snow_tile

USE jules_surface_mod, ONLY: all_tiles, l_elev_land_ice

USE jules_surface_types_mod, ONLY: ntype, ice, elev_ice, elev_rock
Expand All @@ -41,6 +43,9 @@ SUBROUTINE tilepts(land_pts,frac,surft_pts,surft_index,l_lice_point, &
LOGICAL, INTENT(IN) :: l_lice_point(land_pts)
LOGICAL, INTENT(OUT) :: l_lice_surft(ntype)

LOGICAL :: snow_tile(land_pts)
! Indicates if a separate snow tile is used on a land point

LOGICAL :: use_tile ! Indicates if we will model the tile for the current
! land point

Expand All @@ -62,6 +67,7 @@ SUBROUTINE tilepts(land_pts,frac,surft_pts,surft_index,l_lice_point, &
!$OMP elev_ice, elev_rock, l_lice_point, l_lice_surft, &
!$OMP l_elev_land_ice, surft_pts ) &

@HelenRJohnson Helen Johnson (HelenRJohnson) Jul 10, 2026

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Suggested change
!$OMP l_elev_land_ice, surft_pts ) &
!$OMP l_elev_land_ice, surft_pts, i_snow_tile ) &

!$OMP PRIVATE( l, n, c, use_tile )

@HelenRJohnson Helen Johnson (HelenRJohnson) Jul 10, 2026

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Suggested change
!$OMP PRIVATE( l, n, c, use_tile )
!$OMP PRIVATE( l, n, c, use_tile, snow_tile )

snow_tile(:) = .FALSE.
DO n = 1,ntype
c = 0
l_lice_surft(n) = ( n == ice .OR. ANY(elev_ice == n) )
Expand All @@ -75,6 +81,14 @@ SUBROUTINE tilepts(land_pts,frac,surft_pts,surft_index,l_lice_point, &
! as this may be needed for on- or off-line icesheet coupling
IF (l_elev_land_ice .AND. l_lice_point(l) .AND. l_lice_surft(n)) &
use_tile = .TRUE.
! Ice tile can be used as a separate snow tile
IF (ANY(i_snow_tile == 1)) THEN
IF (i_snow_tile(n) == 1 .AND. frac(l,n) > 0.0) THEN
snow_tile(l) = .TRUE.
ELSE IF (n == ice .AND. snow_tile(l)) THEN
use_tile = .TRUE.
END IF
END IF
ELSE
! with all_tiles we do
! * All tiles except the ice/elevated tiles on non-land-ice points
Expand Down
23 changes: 14 additions & 9 deletions src/io/model_interface/extract_var.inc
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Expand Up @@ -76,7 +76,7 @@ USE sf_diags_mod, ONLY: &
sf_diag

USE jules_snow_mod, ONLY: &
canSnowTile
canSnowTile, i_snow_tile

USE overbank_inundation_mod, ONLY: &
frac_fplain_lp, frac_fplain_rp
Expand Down Expand Up @@ -1100,15 +1100,20 @@ CASE ( 'snow_depth_gb' )
cube = map_from_land(cube_land)

CASE ( 'snow_frac' )
! Sum frac over tiles with snow.
workspace_land(:) = 0.0
IF ( l_aggregate ) THEN
WHERE ( progs%snow_surft(:,1) + progs%snow_grnd_surft(:,1) > EPSILON(1.0) )
workspace_land(:) = 1.0
END WHERE
ELSE
workspace_land(:) = SUM(ainfo%frac_surft, 2, progs%snow_surft + &
progs%snow_grnd_surft > EPSILON(1.0))
IF (ANY(i_snow_tile == 1)) THEN
! Sum snow cover fractions on tiles
workspace_land(:) = SUM(fluxes%fsnow * ainfo%frac_surft(:,:),2)
ELSE
! Sum frac over tiles with snow.
IF ( l_aggregate ) THEN
WHERE ( progs%snow_surft(:,1) + progs%snow_grnd_surft(:,1) > EPSILON(1.0) )
workspace_land(:) = 1.0
END WHERE
ELSE
workspace_land(:) = SUM(ainfo%frac_surft, 2, progs%snow_surft + &
progs%snow_grnd_surft > EPSILON(1.0))
END IF
END IF
cube_land = cube_from_array(workspace_land)
cube = map_from_land(cube_land)
Expand Down
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