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Streaming Filter
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The filters and their target frequencies are no longer hard-coded.
Instead, multiple filters with tidal or arbitrary frequencies as
their target frequencies can be turned on. The filter names are
specified in MOM_input and must consist of two letters/numbers. If
the name of a filter is the same as the name of a tidal constituent,
then the corresponding tidal frequency will be used as its target
frequency. Otherwise, the user must specify the target frequency by
"FILTER_${FILTER_NAME}_OMEGA" in MOM_input.

The restarting capability has also been implemented. Because the
filtering is a point-wise operation, all variables are considered
as fields, even if they are velocity components.
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@c2xu
c2xu committed Dec 12, 2024
1 parent 78a7936 commit 70f8687
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94 changes: 28 additions & 66 deletions src/core/MOM_barotropic.F90
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Original file line number Diff line number Diff line change
Expand Up @@ -26,8 +26,7 @@ module MOM_barotropic
use MOM_restart, only : query_initialized, MOM_restart_CS
use MOM_self_attr_load, only : scalar_SAL_sensitivity
use MOM_self_attr_load, only : SAL_CS
use MOM_streaming_filter, only : Filt_register, Filt_accum, Filter_CS
use MOM_tidal_forcing, only : tidal_frequency
use MOM_streaming_filter, only : Filt_register, Filt_init, Filt_accum, Filter_CS
use MOM_time_manager, only : time_type, real_to_time, operator(+), operator(-)
use MOM_unit_scaling, only : unit_scale_type
use MOM_variables, only : BT_cont_type, alloc_bt_cont_type
Expand Down Expand Up @@ -250,10 +249,8 @@ module MOM_barotropic
logical :: linearized_BT_PV !< If true, the PV and interface thicknesses used
!! in the barotropic Coriolis calculation is time
!! invariant and linearized.
logical :: use_filter_m2 !< If true, apply streaming band-pass filter for detecting
!! instantaneous tidal signals.
logical :: use_filter_k1 !< If true, apply streaming band-pass filter for detecting
!! instantaneous tidal signals.
logical :: use_filter !< If true, use streaming band-pass filter to detect the
!! instantaneous tidal signals in the simulation.
logical :: use_wide_halos !< If true, use wide halos and march in during the
!! barotropic time stepping for efficiency.
logical :: clip_velocity !< If true, limit any velocity components that are
Expand Down Expand Up @@ -297,10 +294,8 @@ module MOM_barotropic
type(hor_index_type), pointer :: debug_BT_HI => NULL() !< debugging copy of horizontal index_type
type(SAL_CS), pointer :: SAL_CSp => NULL() !< Control structure for SAL
type(harmonic_analysis_CS), pointer :: HA_CSp => NULL() !< Control structure for harmonic analysis
type(Filter_CS) :: Filt_CS_um2, & !< Control structures for the M2 streaming filter
Filt_CS_vm2, & !< Control structures for the M2 streaming filter
Filt_CS_uk1, & !< Control structures for the K1 streaming filter
Filt_CS_vk1 !< Control structures for the K1 streaming filter
type(Filter_CS) :: Filt_CS_u, & !< Control structures for the streaming band-pass filter of ubt
Filt_CS_v !< Control structures for the streaming band-pass filter of vbt
logical :: module_is_initialized = .false. !< If true, module has been initialized

integer :: isdw !< The lower i-memory limit for the wide halo arrays.
Expand Down Expand Up @@ -608,8 +603,8 @@ subroutine btstep(U_in, V_in, eta_in, dt, bc_accel_u, bc_accel_v, forces, pbce,
DCor_v, & ! An averaged total thickness at v points [H ~> m or kg m-2].
Datv ! Basin depth at v-velocity grid points times the x-grid
! spacing [H L ~> m2 or kg m-1].
real, dimension(:,:), pointer :: um2, uk1, vm2, vk1
! M2 and K1 velocities from the output of streaming filters [m s-1]
real, dimension(:,:,:), pointer :: ufilt, vfilt
! Filtered velocities from the output of streaming filters [m s-1]
real, target, dimension(SZIW_(CS),SZJW_(CS)) :: &
eta, & ! The barotropic free surface height anomaly or column mass
! anomaly [H ~> m or kg m-2]
Expand Down Expand Up @@ -1598,15 +1593,9 @@ subroutine btstep(U_in, V_in, eta_in, dt, bc_accel_u, bc_accel_v, forces, pbce,
endif ; enddo ; enddo
endif

! Here is an example of how the filter equations are time stepped to determine the M2 and K1 velocities.
! The filters are initialized and registered in subroutine barotropic_init.
if (CS%use_filter_m2) then
call Filt_accum(ubt, um2, CS%Time, US, CS%Filt_CS_um2)
call Filt_accum(vbt, vm2, CS%Time, US, CS%Filt_CS_vm2)
endif
if (CS%use_filter_k1) then
call Filt_accum(ubt, uk1, CS%Time, US, CS%Filt_CS_uk1)
call Filt_accum(vbt, vk1, CS%Time, US, CS%Filt_CS_vk1)
if (CS%use_filter) then
call Filt_accum(ubt, ufilt, CS%Time, US, CS%Filt_CS_u)
call Filt_accum(vbt, vfilt, CS%Time, US, CS%Filt_CS_v)

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endif

! Zero out the arrays for various time-averaged quantities.
Expand Down Expand Up @@ -4984,6 +4973,12 @@ subroutine barotropic_init(u, v, h, eta, Time, G, GV, US, param_file, diag, CS,
endif ! len_trim(wave_drag_file) > 0
endif ! CS%linear_wave_drag

! Initialize streaming band-pass filters
if (CS%use_filter) then
call Filt_init(param_file, US, CS%Filt_CS_u, restart_CS)
call Filt_init(param_file, US, CS%Filt_CS_v, restart_CS)

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endif

CS%dtbt_fraction = 0.98 ; if (dtbt_input < 0.0) CS%dtbt_fraction = -dtbt_input

dtbt_tmp = -1.0
Expand Down Expand Up @@ -5268,9 +5263,8 @@ subroutine register_barotropic_restarts(HI, GV, US, param_file, CS, restart_CS)
! Local variables
type(vardesc) :: vd(3)
character(len=40) :: mdl = "MOM_barotropic" ! This module's name.
integer :: n_filters !< Number of streaming band-pass filters to be used in the simulation.
integer :: isd, ied, jsd, jed, IsdB, IedB, JsdB, JedB
real :: am2, ak1 !< Bandwidth parameters of the M2 and K1 streaming filters [nondim]
real :: om2, ok1 !< Target frequencies of the M2 and K1 streaming filters [rad T-1 ~> rad s-1]

isd = HI%isd ; ied = HI%ied ; jsd = HI%jsd ; jed = HI%jed
IsdB = HI%IsdB ; IedB = HI%IedB ; JsdB = HI%JsdB ; JedB = HI%JedB
Expand All @@ -5283,33 +5277,6 @@ subroutine register_barotropic_restarts(HI, GV, US, param_file, CS, restart_CS)
"sum(u dh_dt) while also correcting for truncation errors.", &
default=.false., do_not_log=.true.)

call get_param(param_file, mdl, "STREAMING_FILTER_M2", CS%use_filter_m2, &
"If true, turn on streaming band-pass filter for detecting "//&
"instantaneous tidal signals.", default=.false.)
call get_param(param_file, mdl, "STREAMING_FILTER_K1", CS%use_filter_k1, &
"If true, turn on streaming band-pass filter for detecting "//&
"instantaneous tidal signals.", default=.false.)
call get_param(param_file, mdl, "FILTER_ALPHA_M2", am2, &
"Bandwidth parameter of the streaming filter targeting the M2 frequency. "//&
"Must be positive. To turn off filtering, set FILTER_ALPHA_M2 <= 0.0.", &
default=0.0, units="nondim", do_not_log=.not.CS%use_filter_m2)
call get_param(param_file, mdl, "FILTER_ALPHA_K1", ak1, &
"Bandwidth parameter of the streaming filter targeting the K1 frequency. "//&
"Must be positive. To turn off filtering, set FILTER_ALPHA_K1 <= 0.0.", &
default=0.0, units="nondim", do_not_log=.not.CS%use_filter_k1)
call get_param(param_file, mdl, "TIDE_M2_FREQ", om2, &
"Frequency of the M2 tidal constituent. "//&
"This is only used if TIDES and TIDE_M2"// &
" are true, or if OBC_TIDE_N_CONSTITUENTS > 0 and M2"// &
" is in OBC_TIDE_CONSTITUENTS.", units="rad s-1", default=tidal_frequency("M2"), &
scale=US%T_to_s, do_not_log=.true.)
call get_param(param_file, mdl, "TIDE_K1_FREQ", ok1, &
"Frequency of the K1 tidal constituent. "//&
"This is only used if TIDES and TIDE_K1"// &
" are true, or if OBC_TIDE_N_CONSTITUENTS > 0 and K1"// &
" is in OBC_TIDE_CONSTITUENTS.", units="rad s-1", default=tidal_frequency("K1"), &
scale=US%T_to_s, do_not_log=.true.)

ALLOC_(CS%ubtav(IsdB:IedB,jsd:jed)) ; CS%ubtav(:,:) = 0.0
ALLOC_(CS%vbtav(isd:ied,JsdB:JedB)) ; CS%vbtav(:,:) = 0.0
if (CS%gradual_BT_ICs) then
Expand Down Expand Up @@ -5338,22 +5305,17 @@ subroutine register_barotropic_restarts(HI, GV, US, param_file, CS, restart_CS)
call register_restart_field(CS%dtbt, "DTBT", .false., restart_CS, &
longname="Barotropic timestep", units="seconds", conversion=US%T_to_s)

! Initialize and register streaming filters
if (CS%use_filter_m2) then
if (am2 > 0.0 .and. om2 > 0.0) then
call Filt_register(am2, om2, 'u', HI, CS%Filt_CS_um2)
call Filt_register(am2, om2, 'v', HI, CS%Filt_CS_vm2)
else
CS%use_filter_m2 = .false.
endif
endif
if (CS%use_filter_k1) then
if (ak1 > 0.0 .and. ok1 > 0.0) then
call Filt_register(ak1, ok1, 'u', HI, CS%Filt_CS_uk1)
call Filt_register(ak1, ok1, 'v', HI, CS%Filt_CS_vk1)
else
CS%use_filter_k1 = .false.
endif
! Initialize and register streaming band-pass filters
call get_param(param_file, mdl, "USE_FILTER", CS%use_filter, &
"If true, use streaming band-pass filters to detect the "//&
"instantaneous tidal signals in the simulation.", default=.false.)
call get_param(param_file, mdl, "N_FILTERS", n_filters, &
"Number of streaming band-pass filters to be used in the simulation.", &
default=0, do_not_log=.not.CS%use_filter)
if (n_filters<=0) CS%use_filter = .false.
if (CS%use_filter) then
call Filt_register(n_filters, 'ubt', 'u', HI, CS%Filt_CS_u, restart_CS)
call Filt_register(n_filters, 'vbt', 'v', HI, CS%Filt_CS_v, restart_CS)

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endif

end subroutine register_barotropic_restarts
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