boundary_impulse_tracer Module Reference

Detailed Description

Implements a boundary impulse response tracer to calculate Green's functions.

Boundary Impulse Response Tracer and Transit Time Distributions

Transit time distributions (TTD) are the Green's function solution of the passive tracer equation between the oceanic surface and interior. The name derives from the idea that the 'age' (e.g. time since last contact with the atmosphere) of a water parcel is best characterized as a distribution of ages because water parcels leaving the surface arrive at a particular interior point at different times. The more commonly used ideal age tracer is the first moment of the TTD, equivalently referred to as the mean age.

A boundary impulse response (BIR) is a passive tracer whose surface boundary condition is a rectangle function with width \(\Delta t\). In the case of unsteady flow, multiple BIRs, initiated at different times in the model can be used to infer the transit time distribution or Green's function between the oceanic surface and interior. In the case of steady or cyclostationary flow, a single BIR is sufficient.

In the References section, both the theoretical discussion of TTDs and BIRs are listed along with modeling studies which have this used framework in scientific investigations

Run-time parameters

-DO_BOUNDARY_IMPULSE_TRACER: Enables the boundary impulse tracer model -IMPULSE_SOURCE_TIME: Length of time that the surface layer acts as a source of the BIR tracer

References

and BIR Theory

-Holzer, M., and T.M. Hall, 2000: Transit-time and tracer-age distributions in geophysical flows. J. Atmos. Sci., 57, 3539-3558, doi:10.1175/1520-0469(2000)057<3539:TTATAD>2.0.CO;2. -T.W.N. Haine, H. Zhang, D.W. Waugh, M. Holzer, On transit-time distributions in unsteady circulation models, Ocean Modelling, Volume 21, Issues 1–2, 2008, Pages 35-45, ISSN 1463-5003 http://dx.doi.org/10.1016/j.ocemod.2007.11.004.

Modelling applications

-Peacock, S., and M. Maltrud (2006), Transit-time distributions in a global ocean model, J. Phys. Oceanogr., 36(3), 474–495, doi:10.1175/JPO2860.1. -Maltrud, M., Bryan, F. & Peacock, Boundary impulse response functions in a century-long eddying global ocean simulation, S. Environ Fluid Mech (2010) 10: 275. doi:10.1007/s10652-009-9154-3

Data Types
type	boundary_impulse_tracer_cs
	The control structure for the boundary impulse tracer package. More...

Functions/Subroutines
logical function, public	register_boundary_impulse_tracer (HI, GV, param_file, CS, tr_Reg, restart_CS)
	Read in runtime options and add boundary impulse tracer to tracer registry. More...
subroutine, public	initialize_boundary_impulse_tracer (restart, day, G, GV, h, diag, OBC, CS, sponge_CSp, tv)
	Initialize tracer from restart or set to 1 at surface to initialize. More...
subroutine, public	boundary_impulse_tracer_column_physics (h_old, h_new, ea, eb, fluxes, dt, G, GV, CS, tv, debug, evap_CFL_limit, minimum_forcing_depth)
	Apply source or sink at boundary and do vertical diffusion. More...
integer function, public	boundary_impulse_stock (h, stocks, G, GV, CS, names, units, stock_index)
	Calculate total inventory of tracer. More...
subroutine, public	boundary_impulse_tracer_surface_state (state, h, G, CS)
	This subroutine extracts the surface fields from this tracer package that are to be shared with the atmosphere in coupled configurations. This particular tracer package does not report anything back to the coupler. More...
subroutine, public	boundary_impulse_tracer_end (CS)
	Performs finalization of boundary impulse tracer. More...

Variables
integer, parameter	ntr_max = 1
	NTR_MAX is the maximum number of tracers in this module.

Function/Subroutine Documentation

boundary_impulse_stock()

integer function, public boundary_impulse_tracer::boundary_impulse_stock	(	real, dimension(szi_(g),szj_(g),szk_(g)), intent(in)	h,
		real, dimension(:), intent(out)	stocks,
		type(ocean_grid_type), intent(in)	G,
		type(verticalgrid_type), intent(in)	GV,
		type(boundary_impulse_tracer_cs), pointer	CS,
		character(len=*), dimension(:), intent(out)	names,
		character(len=*), dimension(:), intent(out)	units,
		integer, intent(in), optional	stock_index
	)

Calculate total inventory of tracer.

Parameters

[in]	g	The ocean's grid structure
[in]	gv	The ocean's vertical grid structure
[in]	h	Layer thicknesses [H ~> m or kg m-2]
[out]	stocks	the mass-weighted integrated amount of each tracer, in kg times concentration units [kg conc].
	cs	The control structure returned by a previous call to register_boundary_impulse_tracer.
[out]	names	The names of the stocks calculated.
[out]	units	The units of the stocks calculated.
[in]	stock_index	The coded index of a specific stock being sought.

Returns

Return value: the number of stocks calculated here.

Definition at line 285 of file boundary_impulse_tracer.F90.

  type(ocean_grid_type),                    intent(in   ) :: G    !< The ocean's grid structure
  type(verticalGrid_type),                  intent(in   ) :: GV   !< The ocean's vertical grid structure
  real, dimension(SZI_(G),SZJ_(G),SZK_(G)), intent(in   ) :: h    !< Layer thicknesses [H ~> m or kg m-2]
  real, dimension(:),                       intent(  out) :: stocks !< the mass-weighted integrated amount of each
                                                                  !! tracer, in kg times concentration units [kg conc].
  type(boundary_impulse_tracer_CS),         pointer       :: CS   !< The control structure returned by a previous
                                                                  !! call to register_boundary_impulse_tracer.
  character(len=*), dimension(:),           intent(  out) :: names  !< The names of the stocks calculated.
  character(len=*), dimension(:),           intent(  out) :: units  !< The units of the stocks calculated.
  integer, optional,                        intent(in   ) :: stock_index !< The coded index of a specific stock
                                                                  !! being sought.
  integer :: boundary_impulse_stock  !< Return value: the number of stocks calculated here.
 
! This function calculates the mass-weighted integral of all tracer stocks,
! returning the number of stocks it has calculated.  If the stock_index
! is present, only the stock corresponding to that coded index is returned.
 
  ! Local variables
  integer :: i, j, k, is, ie, js, je, nz, m
  is = g%isc ; ie = g%iec ; js = g%jsc ; je = g%jec ; nz = gv%ke
 
  boundary_impulse_stock = 0
  if (.not.associated(cs)) return
  if (cs%ntr < 1) return
 
  if (present(stock_index)) then ; if (stock_index > 0) then
    ! Check whether this stock is available from this routine.
 
    ! No stocks from this routine are being checked yet.  Return 0.
    return
  endif ; endif
 
  do m=1,1
    call query_vardesc(cs%tr_desc(m), name=names(m), units=units(m), caller="boundary_impulse_stock")
    units(m) = trim(units(m))//" kg"
    stocks(m) = 0.0
    do k=1,nz ; do j=js,je ; do i=is,ie
      stocks(m) = stocks(m) + cs%tr(i,j,k,m) * &
                           (g%mask2dT(i,j) * g%areaT(i,j) * h(i,j,k))
    enddo ; enddo ; enddo
    stocks(m) = gv%H_to_kg_m2 * stocks(m)
  enddo
 
  boundary_impulse_stock = cs%ntr
 

boundary_impulse_tracer_column_physics()

subroutine, public boundary_impulse_tracer::boundary_impulse_tracer_column_physics	(	real, dimension(szi_(g),szj_(g),szk_(g)), intent(in)	h_old,
		real, dimension(szi_(g),szj_(g),szk_(g)), intent(in)	h_new,
		real, dimension(szi_(g),szj_(g),szk_(g)), intent(in)	ea,
		real, dimension(szi_(g),szj_(g),szk_(g)), intent(in)	eb,
		type(forcing), intent(in)	fluxes,
		real, intent(in)	dt,
		type(ocean_grid_type), intent(in)	G,
		type(verticalgrid_type), intent(in)	GV,
		type(boundary_impulse_tracer_cs), pointer	CS,
		type(thermo_var_ptrs), intent(in)	tv,
		logical, intent(in)	debug,
		real, intent(in), optional	evap_CFL_limit,
		real, intent(in), optional	minimum_forcing_depth
	)

Apply source or sink at boundary and do vertical diffusion.

Parameters

[in]	g	The ocean's grid structure
[in]	gv	The ocean's vertical grid structure
[in]	h_old	Layer thickness before entrainment [H ~> m or kg m-2].
[in]	h_new	Layer thickness after entrainment [H ~> m or kg m-2].
[in]	ea	an array to which the amount of fluid entrained
[in]	eb	an array to which the amount of fluid entrained
[in]	fluxes	A structure containing pointers to thermodynamic and tracer forcing fields. Unused fields have NULL ptrs.
[in]	dt	The amount of time covered by this call [s]
	cs	The control structure returned by a previous call to register_boundary_impulse_tracer.
[in]	tv	A structure pointing to various thermodynamic variables
[in]	debug	If true calculate checksums
[in]	evap_cfl_limit	Limit on the fraction of the water that can be fluxed out of the top layer in a timestep [nondim]
[in]	minimum_forcing_depth	The smallest depth over which fluxes can be applied [m]

Definition at line 208 of file boundary_impulse_tracer.F90.

  type(ocean_grid_type),   intent(in) :: G    !< The ocean's grid structure
  type(verticalGrid_type), intent(in) :: GV   !< The ocean's vertical grid structure
  real, dimension(SZI_(G),SZJ_(G),SZK_(G)), &
                           intent(in) :: h_old !< Layer thickness before entrainment [H ~> m or kg m-2].
  real, dimension(SZI_(G),SZJ_(G),SZK_(G)), &
                           intent(in) :: h_new !< Layer thickness after entrainment [H ~> m or kg m-2].
  real, dimension(SZI_(G),SZJ_(G),SZK_(G)), &
                           intent(in) :: ea   !< an array to which the amount of fluid entrained
                                              !! from the layer above during this call will be
                                              !! added [H ~> m or kg m-2].
  real, dimension(SZI_(G),SZJ_(G),SZK_(G)), &
                           intent(in) :: eb   !< an array to which the amount of fluid entrained
                                              !! from the layer below during this call will be
                                              !! added [H ~> m or kg m-2].
  type(forcing),           intent(in) :: fluxes !< A structure containing pointers to thermodynamic
                                              !! and tracer forcing fields.  Unused fields have NULL ptrs.
  real,                    intent(in) :: dt   !< The amount of time covered by this call [s]
 type(boundary_impulse_tracer_CS),  pointer :: CS !< The control structure returned by a previous
                                              !! call to register_boundary_impulse_tracer.
  type(thermo_var_ptrs),   intent(in) :: tv   !< A structure pointing to various
                                              !! thermodynamic variables
  logical,                 intent(in) :: debug !< If true calculate checksums
  real,          optional, intent(in) :: evap_CFL_limit !< Limit on the fraction of the water that can
                                              !! be fluxed out of the top layer in a timestep [nondim]
  real,          optional, intent(in) :: minimum_forcing_depth !< The smallest depth over which
                                              !! fluxes can be applied [m]
 
!   This subroutine applies diapycnal diffusion and any other column
! tracer physics or chemistry to the tracers from this file.
! This is a simple example of a set of advected passive tracers.
 
! The arguments to this subroutine are redundant in that
!     h_new(k) = h_old(k) + ea(k) - eb(k-1) + eb(k) - ea(k+1)
 
  ! Local variables
  real :: Isecs_per_year = 1.0 / (365.0*86400.0)
  real :: year, h_total, scale, htot, Ih_limit
  integer :: secs, days
  integer :: i, j, k, is, ie, js, je, nz, m, k_max
  real, dimension(SZI_(G),SZJ_(G),SZK_(G)) :: h_work ! Used so that h can be modified
 
  is = g%isc ; ie = g%iec ; js = g%jsc ; je = g%jec ; nz = gv%ke
 
  if (.not.associated(cs)) return
  if (cs%ntr < 1) return
 
  ! This uses applyTracerBoundaryFluxesInOut, usually in ALE mode
  if (present(evap_cfl_limit) .and. present(minimum_forcing_depth)) then
    do k=1,nz ;do j=js,je ; do i=is,ie
      h_work(i,j,k) = h_old(i,j,k)
    enddo ; enddo ; enddo
    call applytracerboundaryfluxesinout(g, gv, cs%tr(:,:,:,1), dt, fluxes, h_work, &
      evap_cfl_limit, minimum_forcing_depth)
    call tracer_vertdiff(h_work, ea, eb, dt, cs%tr(:,:,:,1), g, gv)
  else
    call tracer_vertdiff(h_old, ea, eb, dt, cs%tr(:,:,:,1), g, gv)
  endif
 
  ! Set surface conditions
  do m=1,1
    if (cs%remaining_source_time>0.0) then
      do k=1,cs%nkml ; do j=js,je ; do i=is,ie
        cs%tr(i,j,k,m) = 1.0
      enddo ; enddo ; enddo
      cs%remaining_source_time = cs%remaining_source_time-dt
    else
      do k=1,cs%nkml ; do j=js,je ; do i=is,ie
        cs%tr(i,j,k,m) = 0.0
      enddo ; enddo ; enddo
    endif
 
  enddo
 

boundary_impulse_tracer_end()

subroutine, public boundary_impulse_tracer::boundary_impulse_tracer_end

(

type(boundary_impulse_tracer_cs), pointer

CS

)

Performs finalization of boundary impulse tracer.

Parameters

cs	The control structure returned by a previous call to register_boundary_impulse_tracer.

Definition at line 367 of file boundary_impulse_tracer.F90.

  type(boundary_impulse_tracer_CS), pointer :: CS   !< The control structure returned by a previous
                                                    !! call to register_boundary_impulse_tracer.
  integer :: m
 
  if (associated(cs)) then
    if (associated(cs%tr)) deallocate(cs%tr)
    deallocate(cs)
  endif

boundary_impulse_tracer_surface_state()

subroutine, public boundary_impulse_tracer::boundary_impulse_tracer_surface_state	(	type(surface), intent(inout)	state,
		real, dimension(szi_(g),szj_(g),szk_(g)), intent(in)	h,
		type(ocean_grid_type), intent(in)	G,
		type(boundary_impulse_tracer_cs), pointer	CS
	)

This subroutine extracts the surface fields from this tracer package that are to be shared with the atmosphere in coupled configurations. This particular tracer package does not report anything back to the coupler.

Parameters

[in]	g	The ocean's grid structure.
[in,out]	state	A structure containing fields that describe the surface state of the ocean.
[in]	h	Layer thickness [H ~> m or kg m-2].
	cs	The control structure returned by a previous call to register_boundary_impulse_tracer.

Definition at line 336 of file boundary_impulse_tracer.F90.

  type(ocean_grid_type),  intent(in)    :: G  !< The ocean's grid structure.
  type(surface),          intent(inout) :: state !< A structure containing fields that
                                              !! describe the surface state of the ocean.
  real, dimension(SZI_(G),SZJ_(G),SZK_(G)), &
                          intent(in)    :: h  !< Layer thickness [H ~> m or kg m-2].
  type(boundary_impulse_tracer_CS), pointer :: CS !< The control structure returned by a previous
                                              !! call to register_boundary_impulse_tracer.
 
  ! This particular tracer package does not report anything back to the coupler.
  ! The code that is here is just a rough guide for packages that would.
 
  integer :: m, is, ie, js, je, isd, ied, jsd, jed
  is = g%isc ; ie = g%iec ; js = g%jsc ; je = g%jec
  isd = g%isd ; ied = g%ied ; jsd = g%jsd ; jed = g%jed
 
  if (.not.associated(cs)) return
 
  if (cs%coupled_tracers) then
    do m=1,cs%ntr
      !   This call loads the surface values into the appropriate array in the
      ! coupler-type structure.
      call coupler_type_set_data(cs%tr(:,:,1,m), cs%ind_tr(m), ind_csurf, &
                   state%tr_fields, idim=(/isd, is, ie, ied/), &
                   jdim=(/jsd, js, je, jed/) )
    enddo
  endif
 

initialize_boundary_impulse_tracer()

subroutine, public boundary_impulse_tracer::initialize_boundary_impulse_tracer	(	logical, intent(in)	restart,
		type(time_type), intent(in), target	day,
		type(ocean_grid_type), intent(in)	G,
		type(verticalgrid_type), intent(in)	GV,
		real, dimension(szi_(g),szj_(g),szk_(g)), intent(in)	h,
		type(diag_ctrl), intent(in), target	diag,
		type(ocean_obc_type), pointer	OBC,
		type(boundary_impulse_tracer_cs), pointer	CS,
		type(sponge_cs), pointer	sponge_CSp,
		type(thermo_var_ptrs), intent(in)	tv
	)

Initialize tracer from restart or set to 1 at surface to initialize.

Parameters

[in]	restart	.true. if the fields have already been read from a restart file.
[in]	day	Time of the start of the run.
[in]	g	The ocean's grid structure
[in]	gv	The ocean's vertical grid structure
[in]	h	Layer thicknesses [H ~> m or kg m-2]
[in]	diag	A structure that is used to regulate diagnostic output.
	obc	This open boundary condition type specifies whether, where, and what open boundary conditions are used.
	cs	The control structure returned by a previous call to register_boundary_impulse_tracer.
	sponge_csp	Pointer to the control structure for the sponges.
[in]	tv	A structure pointing to various thermodynamic variables

Definition at line 152 of file boundary_impulse_tracer.F90.

  logical,                            intent(in) :: restart !< .true. if the fields have already
                                                         !! been read from a restart file.
  type(time_type),            target, intent(in) :: day  !< Time of the start of the run.
  type(ocean_grid_type),              intent(in) :: G    !< The ocean's grid structure
  type(verticalGrid_type),            intent(in) :: GV   !< The ocean's vertical grid structure
  real, dimension(SZI_(G),SZJ_(G),SZK_(G)), &
                                      intent(in) :: h    !< Layer thicknesses [H ~> m or kg m-2]
  type(diag_ctrl),            target, intent(in) :: diag !< A structure that is used to regulate
                                                         !! diagnostic output.
  type(ocean_OBC_type),               pointer    :: OBC  !< This open boundary condition type specifies
                                                         !! whether, where, and what open boundary
                                                         !! conditions are used.
  type(boundary_impulse_tracer_CS),   pointer    :: CS   !< The control structure returned by a previous
                                                         !! call to register_boundary_impulse_tracer.
  type(sponge_CS),                    pointer    :: sponge_CSp !< Pointer to the control structure for the sponges.
  type(thermo_var_ptrs),              intent(in) :: tv   !< A structure pointing to various
                                                         !! thermodynamic variables
  ! Local variables
  character(len=16) :: name     ! A variable's name in a NetCDF file.
  character(len=72) :: longname ! The long name of that variable.
  character(len=48) :: units    ! The dimensions of the variable.
  character(len=48) :: flux_units ! The units for age tracer fluxes, either
                                ! years m3 s-1 or years kg s-1.
  logical :: OK
  integer :: i, j, k, is, ie, js, je, isd, ied, jsd, jed, nz, m
  integer :: IsdB, IedB, JsdB, JedB
 
  if (.not.associated(cs)) return
  if (cs%ntr < 1) return
  is = g%isc ; ie = g%iec ; js = g%jsc ; je = g%jec ; nz = gv%ke
  isd = g%isd ; ied = g%ied ; jsd = g%jsd ; jed = g%jed
  isdb = g%IsdB ; iedb = g%IedB ; jsdb = g%JsdB ; jedb = g%JedB
 
  cs%Time => day
  cs%diag => diag
  name = "boundary_impulse"
 
  do m=1,cs%ntr
    call query_vardesc(cs%tr_desc(m), name=name, caller="initialize_boundary_impulse_tracer")
    if ((.not.restart) .or. (.not. &
        query_initialized(cs%tr(:,:,:,m), name, cs%restart_CSp))) then
      do k=1,cs%nkml ; do j=jsd,jed ; do i=isd,ied
        cs%tr(i,j,k,m) = 1.0
      enddo ; enddo ; enddo
    endif
  enddo ! Tracer loop
 
  if (associated(obc)) then
  ! Steal from updated DOME in the fullness of time.
  endif
 

register_boundary_impulse_tracer()

logical function, public boundary_impulse_tracer::register_boundary_impulse_tracer	(	type(hor_index_type), intent(in)	HI,
		type(verticalgrid_type), intent(in)	GV,
		type(param_file_type), intent(in)	param_file,
		type(boundary_impulse_tracer_cs), pointer	CS,
		type(tracer_registry_type), pointer	tr_Reg,
		type(mom_restart_cs), pointer	restart_CS
	)

Read in runtime options and add boundary impulse tracer to tracer registry.

Parameters

[in]	hi	A horizontal index type structure
[in]	gv	The ocean's vertical grid structure
[in]	param_file	A structure to parse for run-time parameters
	cs	The control structure returned by a previous call to register_boundary_impulse_tracer.
	tr_reg	A pointer that is set to point to the control structure for the tracer advection and diffusion module
	restart_cs	A pointer to the restart control structure

Definition at line 66 of file boundary_impulse_tracer.F90.

  type(hor_index_type),             intent(in   ) :: HI   !< A horizontal index type structure
  type(verticalGrid_type),          intent(in   ) :: GV   !< The ocean's vertical grid structure
  type(param_file_type),            intent(in   ) :: param_file !< A structure to parse for run-time parameters
  type(boundary_impulse_tracer_CS), pointer       :: CS   !< The control structure returned by a previous
                                                          !! call to register_boundary_impulse_tracer.
  type(tracer_registry_type),       pointer       :: tr_Reg !< A pointer that is set to point to the control
                                                          !! structure for the tracer advection and
                                                          !! diffusion module
  type(MOM_restart_CS),             pointer       :: restart_CS !< A pointer to the restart control structure
 
  ! Local variables
  character(len=40)  :: mdl = "boundary_impulse_tracer" ! This module's name.
  character(len=200) :: inputdir ! The directory where the input files are.
  character(len=48)  :: var_name ! The variable's name.
  character(len=3)   :: name_tag ! String for creating identifying boundary_impulse
  character(len=48)  :: flux_units ! The units for tracer fluxes, usually
                            ! kg(tracer) kg(water)-1 m3 s-1 or kg(tracer) s-1.
  ! This include declares and sets the variable "version".
#include "version_variable.h"
  real, pointer :: tr_ptr(:,:,:) => null()
  real, pointer :: rem_time_ptr => null()
  logical :: register_boundary_impulse_tracer
  integer :: isd, ied, jsd, jed, nz, m, i, j
  isd = hi%isd ; ied = hi%ied ; jsd = hi%jsd ; jed = hi%jed ; nz = gv%ke
 
  if (associated(cs)) then
    call mom_error(warning, "register_boundary_impulse_tracer called with an "// &
                             "associated control structure.")
    return
  endif
  allocate(cs)
 
  ! Read all relevant parameters and write them to the model log.
  call log_version(param_file, mdl, version, "")
  call get_param(param_file, mdl, "IMPULSE_SOURCE_TIME", cs%remaining_source_time, &
                 "Length of time for the boundary tracer to be injected "//&
                 "into the mixed layer. After this time has elapsed, the "//&
                 "surface becomes a sink for the boundary impulse tracer.", &
                 default=31536000.0)
  call get_param(param_file, mdl, "TRACERS_MAY_REINIT", cs%tracers_may_reinit, &
                 "If true, tracers may go through the initialization code "//&
                 "if they are not found in the restart files.  Otherwise "//&
                 "it is a fatal error if the tracers are not found in the "//&
                 "restart files of a restarted run.", default=.false.)
  cs%ntr = ntr_max
  allocate(cs%tr(isd:ied,jsd:jed,nz,cs%ntr)) ; cs%tr(:,:,:,:) = 0.0
 
  cs%nkml = max(gv%nkml,1)
 
  do m=1,cs%ntr
    ! This is needed to force the compiler not to do a copy in the registration
    ! calls.  Curses on the designers and implementers of Fortran90.
    cs%tr_desc(m) = var_desc(trim("boundary_impulse"), "kg kg-1", &
        "Boundary impulse tracer", caller=mdl)
    if (gv%Boussinesq) then ; flux_units = "kg kg-1 m3 s-1"
    else ; flux_units = "kg s-1" ; endif
 
    tr_ptr => cs%tr(:,:,:,m)
    call query_vardesc(cs%tr_desc(m), name=var_name, caller="register_boundary_impulse_tracer")
    ! Register the tracer for horizontal advection, diffusion, and restarts.
    call register_tracer(tr_ptr, tr_reg, param_file, hi, gv, tr_desc=cs%tr_desc(m), &
                         registry_diags=.true., flux_units=flux_units, &
                         restart_cs=restart_cs, mandatory=.not.cs%tracers_may_reinit)
 
    !   Set coupled_tracers to be true (hard-coded above) to provide the surface
    ! values to the coupler (if any).  This is meta-code and its arguments will
    ! currently (deliberately) give fatal errors if it is used.
    if (cs%coupled_tracers) &
      cs%ind_tr(m) = aof_set_coupler_flux(trim(var_name)//'_flux', &
          flux_type=' ', implementation=' ', caller="register_boundary_impulse_tracer")
  enddo
  ! Register remaining source time as a restart field
  rem_time_ptr => cs%remaining_source_time
  call register_restart_field(rem_time_ptr, "bir_remain_time", &
                              .not.cs%tracers_may_reinit, restart_cs, &
                              "Remaining time to apply BIR source", "s")
 
  cs%tr_Reg => tr_reg
  cs%restart_CSp => restart_cs
  register_boundary_impulse_tracer = .true.