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implement spatially varying decay rates for internal tides leakage #794

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Merged
merged 4 commits into from
Jan 14, 2025
Merged

implement spatially varying decay rates for internal tides leakage #794

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0eed080
add option to specify horizontally varying decay
Dec 30, 2024
3011919
extend to vertical modes
Jan 2, 2025
0e7f5f4
fix comments
Jan 13, 2025
7e2db9a
corrected description of decay_rate array
Jan 14, 2025
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46 changes: 41 additions & 5 deletions src/parameterizations/lateral/MOM_internal_tides.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -152,8 +152,10 @@ module MOM_internal_tides
integer :: En_restart_power !< A power factor of 2 by which to multiply the energy in restart [nondim]
type(time_type), pointer :: Time => NULL() !< A pointer to the model's clock.
character(len=200) :: inputdir !< directory to look for coastline angle file
real :: decay_rate !< A constant rate at which internal tide energy is
!! lost to the interior ocean internal wave field [T-1 ~> s-1].
real, allocatable, dimension(:,:,:,:) :: decay_rate_2d !< rate at which internal tide energy is
!! lost to the interior ocean internal wave field
!! as a function of longitude, latitude, frequency
!! and vertical mode [T-1 ~> s-1].
real :: cdrag !< The bottom drag coefficient [nondim].
real :: drag_min_depth !< The minimum total ocean thickness that will be used in the denominator
!! of the quadratic drag terms for internal tides when
Expand All @@ -174,6 +176,8 @@ module MOM_internal_tides
!! internal tide energy [H Z2 T-2 ~> m3 s-2 or J m-2]
logical :: apply_residual_drag
!< If true, apply sink from residual term of reflection/transmission.
logical :: use_2d_decay_rate
!< If true, use a spatially varying decay rate for each harmonic.
real, allocatable :: En(:,:,:,:,:)
!< The internal wave energy density as a function of (i,j,angle,frequency,mode)
!! integrated within an angular and frequency band [H Z2 T-2 ~> m3 s-2 or J m-2]
Expand Down Expand Up @@ -677,7 +681,7 @@ subroutine propagate_int_tide(h, tv, Nb, Rho_bot, dt, G, GV, US, inttide_input_C
! Calculate loss rate and apply loss over the time step ; apply the same drag timescale
! to each En component (technically not correct; fix later)
En_b = CS%En(i,j,a,fr,m) ! save previous value
En_a = CS%En(i,j,a,fr,m) / (1.0 + (dt * CS%decay_rate)) ! implicit update
En_a = CS%En(i,j,a,fr,m) / (1.0 + (dt * CS%decay_rate_2d(i,j,fr,m))) ! implicit update
CS%TKE_leak_loss(i,j,a,fr,m) = (En_b - En_a) * I_dt ! compute exact loss rate [H Z2 T-3 ~> m3 s-3 or W m-2]
CS%En(i,j,a,fr,m) = En_a ! update value
enddo ; enddo ; enddo ; enddo ; enddo
Expand Down Expand Up @@ -3386,6 +3390,9 @@ subroutine internal_tides_init(Time, G, GV, US, param_file, diag, CS)
real :: kappa_itides ! characteristic topographic wave number [L-1 ~> m-1]
real, dimension(:,:), allocatable :: ridge_temp ! array for temporary storage of flags
! of cells with double-reflecting ridges [nondim]
real, dimension(:,:), allocatable :: tmp_decay ! a temp array to store decay rates [T-1 ~> s-1]
real :: decay_rate ! A constant rate at which internal tide energy is
! lost to the interior ocean internal wave field [T-1 ~> s-1].
logical :: use_int_tides, use_temperature
logical :: om4_remap_via_sub_cells ! Use the OM4-era ramap_via_sub_cells for calculating the EBT structure
real :: IGW_c1_thresh ! A threshold first mode internal wave speed below which all higher
Expand All @@ -3411,7 +3418,7 @@ subroutine internal_tides_init(Time, G, GV, US, param_file, diag, CS)
character(len=200) :: filename
character(len=200) :: refl_angle_file
character(len=200) :: refl_pref_file, refl_dbl_file, trans_file
character(len=200) :: h2_file
character(len=200) :: h2_file, decay_file
character(len=80) :: rough_var ! Input file variable names

character(len=240), dimension(:), allocatable :: energy_fractions
Expand Down Expand Up @@ -3546,10 +3553,13 @@ subroutine internal_tides_init(Time, G, GV, US, param_file, diag, CS)
call get_param(param_file, mdl, "MAX_TKE_TO_KD", CS%max_TKE_to_Kd, &
"Limiter for TKE_to_Kd.", &
units="", default=1e9, scale=US%Z_to_m*US%s_to_T**2)
call get_param(param_file, mdl, "INTERNAL_TIDE_DECAY_RATE", CS%decay_rate, &
call get_param(param_file, mdl, "INTERNAL_TIDE_DECAY_RATE", decay_rate, &
"The rate at which internal tide energy is lost to the "//&
"interior ocean internal wave field.", &
units="s-1", default=0.0, scale=US%T_to_s)
call get_param(param_file, mdl, "USE_2D_INTERNAL_TIDE_DECAY_RATE", CS%use_2d_decay_rate, &
"If true, use a spatially varying decay rate for leakage loss in the "// &
"internal tide code.", default=.false.)
call get_param(param_file, mdl, "INTERNAL_TIDE_VOLUME_BASED_CFL", CS%vol_CFL, &
"If true, use the ratio of the open face lengths to the "//&
"tracer cell areas when estimating CFL numbers in the "//&
Expand Down Expand Up @@ -3679,6 +3689,32 @@ subroutine internal_tides_init(Time, G, GV, US, param_file, diag, CS)
allocate(CS%TKE_itidal_loss_glo_dt(num_freq,num_mode), source=0.0)
allocate(CS%TKE_residual_loss_glo_dt(num_freq,num_mode), source=0.0)
allocate(CS%TKE_input_glo_dt(num_freq,num_mode), source=0.0)
allocate(CS%decay_rate_2d(isd:ied,jsd:jed,num_freq,num_mode), source=0.0)
allocate(tmp_decay(isd:ied,jsd:jed), source=0.0)

if (CS%use_2d_decay_rate) then
call get_param(param_file, mdl, "ITIDES_DECAY_FILE", decay_file, &
"The path to the file containing the decay rates "//&
"for internal tides with USE_2D_INTERNAL_TIDE_DECAY_RATE.", &
fail_if_missing=.true.)
do m=1,num_mode ; do fr=1,num_freq
! read 2d field for each harmonic
filename = trim(CS%inputdir) // trim(decay_file)
write(var_name, '("decay_rate_freq",i1,"_mode",i1)') fr, m
call MOM_read_data(filename, var_name, tmp_decay, G%domain, scale=US%T_to_s)
do j=G%jsc,G%jec ; do i=G%isc,G%iec
CS%decay_rate_2d(i,j,fr,m) = tmp_decay(i,j)
enddo ; enddo
enddo ; enddo
else
do m=1,num_mode ; do fr=1,num_freq ; do j=G%jsc,G%jec ; do i=G%isc,G%iec
CS%decay_rate_2d(i,j,fr,m) = decay_rate
enddo ; enddo ; enddo ; enddo
endif

do m=1,num_mode
call pass_var(CS%decay_rate_2d(:,:,:,m), G%domain)
enddo

! Compute the fixed part of the bottom drag loss from baroclinic modes
call get_param(param_file, mdl, "H2_FILE", h2_file, &
Expand Down
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