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Add option to read MLE Frontal-Length Scale via file
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Introduced the `MLE_FRONT_LENGTH_FROM_FILE` parameter to allow specifying
a spatially and temporally varying MLE frontal-length scale via netCDF file.

Also added a new diagnostic, `mle_fl`, to save the frontal-length scale used
in the mixed-layer restratification parameterization.
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@gustavo-marques
gustavo-marques committed Jan 7, 2025
1 parent 544377e commit 217816c
Showing 1 changed file with 68 additions and 5 deletions.
73 changes: 68 additions & 5 deletions src/parameterizations/lateral/MOM_mixed_layer_restrat.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -9,12 +9,15 @@ module MOM_mixed_layer_restrat
use MOM_diag_mediator, only : diag_update_remap_grids
use MOM_domains, only : pass_var, To_West, To_South, Omit_Corners
use MOM_error_handler, only : MOM_error, FATAL, WARNING
use MOM_file_parser, only : get_param, log_version, param_file_type
use MOM_file_parser, only : get_param, log_param, log_version, param_file_type
use MOM_file_parser, only : openParameterBlock, closeParameterBlock
use MOM_forcing_type, only : mech_forcing, find_ustar
use MOM_grid, only : ocean_grid_type
use MOM_hor_index, only : hor_index_type
use MOM_interpolate, only : init_external_field, time_interp_external, time_interp_external_init
use MOM_interpolate, only : external_field
use MOM_intrinsic_functions, only : cuberoot
use MOM_io, only : slasher
use MOM_lateral_mixing_coeffs, only : VarMix_CS
use MOM_restart, only : register_restart_field, query_initialized, MOM_restart_CS
use MOM_unit_scaling, only : unit_scale_type
Expand Down Expand Up @@ -48,6 +51,7 @@ module MOM_mixed_layer_restrat
!! upscaling of buoyancy gradients that is otherwise represented
!! by the parameter FOX_KEMPER_ML_RESTRAT_COEF. If MLE_FRONT_LENGTH is
!! non-zero, it is recommended to set FOX_KEMPER_ML_RESTRAT_COEF=1.0.
logical :: fl_from_file !< If true, read the MLE front-length scale from a netCDF file.
logical :: MLE_use_PBL_MLD !< If true, use the MLD provided by the PBL parameterization.
!! if false, MLE will calculate a MLD based on a density difference
!! based on the parameter MLE_DENSITY_DIFF.
Expand Down Expand Up @@ -94,6 +98,9 @@ module MOM_mixed_layer_restrat

type(diag_ctrl), pointer :: diag !< A structure that is used to regulate the
!! timing of diagnostic output.
type(external_field) :: sbc_fl !< A handle used in time interpolation of
!! front-lenght scales read from a file.
type(time_type), pointer :: Time => NULL() !< A pointer to the ocean model's clock.
logical :: use_Stanley_ML !< If true, use the Stanley parameterization of SGS T variance
real :: ustar_min !< A minimum value of ustar in thickness units to avoid numerical
!! problems [H T-1 ~> m s-1 or kg m-2 s-1]
Expand Down Expand Up @@ -123,6 +130,7 @@ module MOM_mixed_layer_restrat
integer :: id_ustar = -1
integer :: id_bflux = -1
integer :: id_lfbod = -1
integer :: id_mle_fl = -1
!>@}

end type mixedlayer_restrat_CS
Expand Down Expand Up @@ -207,7 +215,8 @@ subroutine mixedlayer_restrat_OM4(h, uhtr, vhtr, tv, forces, dt, h_MLD, VarMix,
htot_fast, & ! The sum of the thicknesses of layers in the mixed layer [H ~> m or kg m-2]
Rml_av_fast, & ! Negative g_Rho0 times the average mixed layer density or G_Earth
! times the average specific volume [L2 H-1 T-2 ~> m s-2 or m4 kg-1 s-2]
MLD_slow, & ! Mixed layer depth actually used in MLE restratification parameterization [H ~> m or kg m-2]
MLD_slow, & ! Mixed layer depth actually used in MLE restratification parameterization [H ~> m or kg m-2]
mle_fl_2d, & ! MLE frontal lengh-scale [H ~> m or kg m-2]
htot_slow, & ! The sum of the thicknesses of layers in the mixed layer [H ~> m or kg m-2]
Rml_av_slow ! Negative g_Rho0 times the average mixed layer density or G_Earth
! times the average specific volume [L2 H-1 T-2 ~> m s-2 or m4 kg-1 s-2]
Expand Down Expand Up @@ -257,6 +266,7 @@ subroutine mixedlayer_restrat_OM4(h, uhtr, vhtr, tv, forces, dt, h_MLD, VarMix,
real :: I_LFront ! The inverse of the frontal length scale [L-1 ~> m-1]
real :: vonKar_x_pi2 ! A scaling constant that is approximately the von Karman constant times
! pi squared [nondim]
character(len=128) :: mesg
logical :: line_is_empty, keep_going, res_upscale
integer, dimension(2) :: EOSdom ! The i-computational domain for the equation of state
integer :: i, j, k, is, ie, js, je, Isq, Ieq, Jsq, Jeq, nz
Expand Down Expand Up @@ -338,7 +348,21 @@ subroutine mixedlayer_restrat_OM4(h, uhtr, vhtr, tv, forces, dt, h_MLD, VarMix,
h_neglect = GV%H_subroundoff
if (CS%front_length>0.) then
res_upscale = .true.
I_LFront = 1. / CS%front_length
do j=js-1,je+1 ; do i=is-1,ie+1
mle_fl_2d(i,j) = CS%front_length
enddo ; enddo
elseif (CS%front_length == 0. .and. CS%fl_from_file) then
res_upscale = .true.
call time_interp_external(CS%sbc_fl, CS%Time, mle_fl_2d, turns=G%HI%turns)
call pass_var(mle_fl_2d, G%domain, halo=1)
do j=js,je ; do i=is,ie
if ((G%mask2dT(i,j) > 0.0) .and. (mle_fl_2d(i,j) < 0.0)) then
write(mesg,'(" Time_interp negative MLE frontal-lenght scale of ",(1pe12.4)," at i,j = ",&
& 2(i3), "lon/lat = ",(1pe12.4)," E ", (1pe12.4), " N.")') &
mle_fl_2d(i,j), i, j, G%geoLonT(i,j), G%geoLatT(i,j)
call MOM_error(FATAL, "MOM_mixed_layer_restrat mixedlayer_restrat_OM4: "//trim(mesg))
endif
enddo ; enddo
else
res_upscale = .false.
endif
Expand Down Expand Up @@ -458,6 +482,8 @@ subroutine mixedlayer_restrat_OM4(h, uhtr, vhtr, tv, forces, dt, h_MLD, VarMix,
u_star = max(CS%ustar_min, 0.5*(U_star_2d(i,j) + U_star_2d(i+1,j)))

absf = 0.5*(abs(G%CoriolisBu(I,J-1)) + abs(G%CoriolisBu(I,J)))
! Compute I_LFront = 1 / (frontal length scale) [m-1]
I_LFront = 2. / ( mle_fl_2d(i,j) + mle_fl_2d(i+1,j) )
! If needed, res_scaling_fac = min( ds, L_d ) / l_f
if (res_upscale) res_scaling_fac = &
( sqrt( 0.5 * ( (G%dxCu(I,j)**2) + (G%dyCu(I,j)**2) ) ) * I_LFront ) &
Expand Down Expand Up @@ -543,7 +569,8 @@ subroutine mixedlayer_restrat_OM4(h, uhtr, vhtr, tv, forces, dt, h_MLD, VarMix,
!$OMP do
do J=js-1,je ; do i=is,ie
u_star = max(CS%ustar_min, 0.5*(U_star_2d(i,j) + U_star_2d(i,j+1)))

! Compute I_LFront = 1 / (frontal length scale) [m-1]
I_LFront = 2. / ( mle_fl_2d(i,j) + mle_fl_2d(i,j+1) )
absf = 0.5*(abs(G%CoriolisBu(I-1,J)) + abs(G%CoriolisBu(I,J)))
! If needed, res_scaling_fac = min( ds, L_d ) / l_f
if (res_upscale) res_scaling_fac = &
Expand Down Expand Up @@ -652,6 +679,7 @@ subroutine mixedlayer_restrat_OM4(h, uhtr, vhtr, tv, forces, dt, h_MLD, VarMix,
if (CS%id_Rml > 0) call post_data(CS%id_Rml, Rml_av_fast, CS%diag)
if (CS%id_uDml > 0) call post_data(CS%id_uDml, uDml_diag, CS%diag)
if (CS%id_vDml > 0) call post_data(CS%id_vDml, vDml_diag, CS%diag)
if (CS%id_mle_fl > 0) call post_data(CS%id_mle_fl, mle_fl_2d, CS%diag)

if (CS%id_uml > 0) then
do J=js,je ; do i=is-1,ie
Expand Down Expand Up @@ -1572,7 +1600,7 @@ end function growth_time

!> Initialize the mixed layer restratification module
logical function mixedlayer_restrat_init(Time, G, GV, US, param_file, diag, CS, restart_CS)
type(time_type), intent(in) :: Time !< Current model time
type(time_type), target, intent(in) :: Time !< Current model time
type(ocean_grid_type), intent(inout) :: G !< Ocean grid structure
type(verticalGrid_type), intent(in) :: GV !< Ocean vertical grid structure
type(unit_scale_type), intent(in) :: US !< A dimensional unit scaling type
Expand All @@ -1589,6 +1617,12 @@ logical function mixedlayer_restrat_init(Time, G, GV, US, param_file, diag, CS,
! temperature variance [nondim]
integer :: default_answer_date ! The default setting for the various ANSWER_DATE flags
! This include declares and sets the variable "version".
character(len=200) :: inputdir ! The directory where NetCDF input files
character(len=240) :: mle_fl_filename ! A file from which chl_a concentrations are to be read.
character(len=128) :: mle_fl_file ! Data containing MLE front-lenght scale. Used
! when reading from file.
character(len=32) :: fl_varname ! Name of front-lenght scale variable in mle_fl_file.

# include "version_variable.h"
integer :: i, j

Expand All @@ -1604,6 +1638,7 @@ logical function mixedlayer_restrat_init(Time, G, GV, US, param_file, diag, CS,
if (.not. mixedlayer_restrat_init) return

CS%initialized = .true.
CS%Time => Time

! Nonsense values to cause problems when these parameters are not used
CS%MLE_MLD_decay_time = -9.e9*US%s_to_T
Expand All @@ -1613,6 +1648,7 @@ logical function mixedlayer_restrat_init(Time, G, GV, US, param_file, diag, CS,
CS%MLE_MLD_stretch = -9.e9
CS%use_Stanley_ML = .false.
CS%use_Bodner = .false.
CS%fl_from_file = .false.

call get_param(param_file, mdl, "DEBUG", CS%debug, default=.false., do_not_log=.true.)
call get_param(param_file, mdl, "DEFAULT_ANSWER_DATE", default_answer_date, &
Expand Down Expand Up @@ -1735,6 +1771,29 @@ logical function mixedlayer_restrat_init(Time, G, GV, US, param_file, diag, CS,
"by the parameter FOX_KEMPER_ML_RESTRAT_COEF. If MLE_FRONT_LENGTH is "//&
"non-zero, it is recommended to set FOX_KEMPER_ML_RESTRAT_COEF=1.0.",&
units="m", default=0.0, scale=US%m_to_L)
call get_param(param_file, mdl, "MLE_FRONT_LENGTH_FROM_FILE", CS%fl_from_file, &
"If true, the MLE front-lenght scale is read from a file.", default=.false.)
if (CS%fl_from_file) then
call time_interp_external_init()

call get_param(param_file, mdl, "INPUTDIR", inputdir, default=".")
call get_param(param_file, mdl, "MLE_FL_FILE", mle_fl_file, &
"MLE_FL_FILE is the file containing MLE front-lenght scale. "//&
"It is used when MLE_FRONT_LENGTH_FROM_FILE is true.", fail_if_missing=.true.)
mle_fl_filename = trim(slasher(inputdir))//trim(mle_fl_file)
call log_param(param_file, mdl, "INPUTDIR/MLE_FL_FILE", mle_fl_filename)
call get_param(param_file, mdl, "FL_VARNAME", fl_varname, &
"Name of MLE front-lenght scale variable in MLE_FL_FILE.", default='mle_fl')
if (modulo(G%Domain%turns, 4) /= 0) then
CS%sbc_fl = init_external_field(mle_fl_filename, trim(fl_varname), MOM_domain=G%Domain%domain_in)
else
CS%sbc_fl = init_external_field(mle_fl_filename, trim(fl_varname), MOM_domain=G%Domain)
endif
endif
if (CS%fl_from_file .and. CS%front_length>0.0) call MOM_error(FATAL, "mixedlayer_restrat_init: "// &
"MLE_FRONT_LENGTH_FROM_FILE cannot be true when MLE_FRONT_LENGTH > 0.0. "// &
"If you want to use MLE_FRONT_LENGTH, set MLE_FRONT_LENGTH_FROM_FILE to false." // &
"If you want to use MLE_FRONT_LENGTH_FROM_FILE, set MLE_FRONT_LENGTH to 0.0.")
call get_param(param_file, mdl, "MLE_USE_PBL_MLD", CS%MLE_use_PBL_MLD, &
"If true, the MLE parameterization will use the mixed-layer "//&
"depth provided by the active PBL parameterization. If false, "//&
Expand Down Expand Up @@ -1838,6 +1897,10 @@ logical function mixedlayer_restrat_init(Time, G, GV, US, param_file, diag, CS,
CS%id_lfbod = register_diag_field('ocean_model', 'lf_bodner', diag%axesT1, Time, &
'Front length in Bodner mixed layer restratificiation parameterization', &
'm', conversion=US%L_to_m)
else
CS%id_mle_fl = register_diag_field('ocean_model', 'mle_fl', diag%axesT1, Time, &
'Frontal length scale used in the mixed layer restratificiation parameterization', &
'm', conversion=US%L_to_m)
endif

! If MLD_filtered is being used, we need to update halo regions after a restart
Expand Down

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