!> @file user_init_grid.f90
!--------------------------------------------------------------------------------------------------!
! This file is part of the PALM model system.
!
! PALM is free software: you can redistribute it and/or modify it under the terms of the GNU General
! Public License as published by the Free Software Foundation, either version 3 of the License, or
! (at your option) any later version.
!
! PALM is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the
! implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
! Public License for more details.
!
! You should have received a copy of the GNU General Public License along with PALM. If not, see
! <http://www.gnu.org/licenses/>.
!
! Copyright 1997-2021 Leibniz Universitaet Hannover
!--------------------------------------------------------------------------------------------------!
!
!
! Description:
! ------------
!> Execution of user-defined grid initializing actions
!--------------------------------------------------------------------------------------------------!
 SUBROUTINE user_init_grid( topo_3d )


    USE control_parameters

    USE indices

    USE kinds

    USE user

    IMPLICIT NONE

!    INTEGER(iwp)                                           ::  k_topo   !< topography top index
    INTEGER(iwp), DIMENSION(nzb:nzt+1,nysg:nyng,nxlg:nxrg) ::  topo_3d  !< 3D topography field

!    REAL(wp) ::  h_topo !< user-defined topography height

!
!-- Next line is to avoid compiler warning about unused variables. Please remove.
    IF ( topo_3d(nzb,nysg,nxlg) == 0 )  CONTINUE


!
!-- Here the user-defined grid initializing actions follow:

!
!-- Set the index array nzb_local for non-flat topography.
!-- Here consistency checks concerning domain size and periodicity are necessary
    SELECT CASE ( TRIM( topography ) )

       CASE ( 'flat', 'single_building', 'single_street_canyon', 'tunnel' )
!
!--       Not allowed here since these are the standard cases used in init_grid.

       CASE ( 'user_defined_topography_1' )
!
!--       Here the user can define their own topography.
!--       After definition, please remove the following three lines!
          message_string = 'topography "' // topography // '" not available yet'
          CALL message( 'user_init_grid', 'UI0005', 1, 2, 0, 6, 0 )
!
!--       The user is allowed to set surface-mounted as well as non-surface mounted topography
!--       (e.g. overhanging structures). For both, use 3D array topo_3d and set bit 0. The
!--       convention is: bit is zero inside topography, bit is 1 for atmospheric grid point.
!--       The following example shows how to prescribe sine-like topography along x-direction with
!--       amplitude of 10 * dz(1) and wavelength 10 * dy.
!           DO  i = nxlg, nxrg
!              h_topo = 10.0_wp * dz(1) * ( SIN( 3.14_wp * 0.5_wp) * i * dx / ( 5.0_wp * dy ) )**2
!
!              k_topo = MINLOC( ABS( zw - h_topo ), 1 ) - 1
!
!              topo_3d(k_topo+1:nzt+1,:,i) = IBSET( topo_3d(k_topo+1:nzt+1,:,i), 0 )
!           ENDDO
!
!           CALL exchange_horiz_int( topo_3d, nys, nyn, nxl, nxr, nzt, nbgp )

       CASE DEFAULT
!
!--       The DEFAULT case is reached if the parameter topography contains a wrong character string
!--       that is neither recognized in init_grid nor here in user_init_grid.
          message_string = 'unknown topography "' // topography // '"'
          CALL message( 'user_init_grid', 'UI0006', 1, 2, 0, 6, 0 )

    END SELECT

 END SUBROUTINE user_init_grid