coord_sigma.F90

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!> Regrid columns for the sigma coordinate
module coord_sigma
 
! This file is part of MOM6. See LICENSE.md for the license.
 
use mom_error_handler, only : mom_error, fatal
 
implicit none ; private
 
!> Control structure containing required parameters for the sigma coordinate
type, public :: sigma_cs ; private
 
  !> Number of levels
  integer :: nk
 
  !> Minimum thickness allowed for layers
  real :: min_thickness
 
  !> Target coordinate resolution, nondimensional
  real, allocatable, dimension(:) :: coordinateresolution
end type sigma_cs
 
public init_coord_sigma, set_sigma_params, build_sigma_column, end_coord_sigma
 
contains
 
!> Initialise a sigma_CS with pointers to parameters
subroutine init_coord_sigma(CS, nk, coordinateResolution)
  type(sigma_cs),     pointer    :: cs !< Unassociated pointer to hold the control structure
  integer,            intent(in) :: nk !< Number of layers in the grid
  real, dimension(:), intent(in) :: coordinateresolution !< Nominal coordinate resolution [nondim]
 
  if (associated(cs)) call mom_error(fatal, "init_coord_sigma: CS already associated!")
  allocate(cs)
  allocate(cs%coordinateResolution(nk))
 
  cs%nk                   = nk
  cs%coordinateResolution = coordinateresolution
end subroutine init_coord_sigma
 
!> This subroutine deallocates memory in the control structure for the coord_sigma module
subroutine end_coord_sigma(CS)
  type(sigma_cs), pointer :: cs !< Coordinate control structure
 
  ! nothing to do
  if (.not. associated(cs)) return
  deallocate(cs%coordinateResolution)
  deallocate(cs)
end subroutine end_coord_sigma
 
!> This subroutine can be used to set the parameters for the coord_sigma module
subroutine set_sigma_params(CS, min_thickness)
  type(sigma_cs), pointer    :: cs !< Coordinate control structure
  real, optional, intent(in) :: min_thickness !< Minimum allowed thickness [H ~> m or kg m-2]
 
  if (.not. associated(cs)) call mom_error(fatal, "set_sigma_params: CS not associated")
 
  if (present(min_thickness)) cs%min_thickness = min_thickness
end subroutine set_sigma_params
 
 
!> Build a sigma coordinate column
subroutine build_sigma_column(CS, depth, totalThickness, zInterface)
  type(sigma_cs),           intent(in)    :: cs !< Coordinate control structure
  real,                     intent(in)    :: depth !< Depth of ocean bottom (positive [H ~> m or kg m-2])
  real,                     intent(in)    :: totalthickness !< Column thickness (positive [H ~> m or kg m-2])
  real, dimension(CS%nk+1), intent(inout) :: zinterface !< Absolute positions of interfaces [H ~> m or kg m-2]
 
  ! Local variables
  integer :: k
 
  zinterface(cs%nk+1) = -depth
  do k = cs%nk,1,-1
    zinterface(k) = zinterface(k+1) + (totalthickness * cs%coordinateResolution(k))
    ! Adjust interface position to accommodate inflating layers
    ! without disturbing the interface above
    if (zinterface(k) < (zinterface(k+1) + cs%min_thickness)) then
      zinterface(k) = zinterface(k+1) + cs%min_thickness
    endif
  enddo
end subroutine build_sigma_column
 
end module coord_sigma