SUBROUTINE obs_depth (ng, tile, model)
!
!git $Id$
!svn $Id: obs_depth.F 1151 2023-02-09 03:08:53Z arango $
!================================================== Hernan G. Arango ===
!  Copyright (c) 2002-2023 The ROMS/TOMS Group                         !
!    Licensed under a MIT/X style license                              !
!    See License_ROMS.md                                               !
!=======================================================================
!                                                                      !
!  This routine proccess the observation vertical position, Zobs. If   !
!  the input position is in meters (Zobs < 0) instead of  fractional   !
!  level (Zobs > 0; 1 <= Zobs <= N),  zero out its Zobs value in all   !
!  nodes in group but itself to faciliate exchange between all tiles   !
!  with "mp_collect", after model extraction.                          !
!                                                                      !
!-----------------------------------------------------------------------
!
      USE mod_param
      USE mod_fourdvar
      USE mod_ncparam
      USE mod_scalars
!
      implicit none
!
!  Imported variable declarations.
!
      integer, intent(in) :: ng, tile, model
!
!  Local variable declarations.
!
      logical :: r_bound, u_bound, v_bound
      integer :: Mstr, Mend, iobs, itrc
      real(r8) :: IniVal = 0.0_r8
!
!-----------------------------------------------------------------------
!  Set lower and upper tile bounds and staggered variables bounds for
!  this horizontal domain partition.  Notice that if tile=-1, it will
!  set the values for the global grid.
!-----------------------------------------------------------------------
!
      integer :: Istr, IstrB, IstrP, IstrR, IstrT, IstrM, IstrU
      integer :: Iend, IendB, IendP, IendR, IendT
      integer :: Jstr, JstrB, JstrP, JstrR, JstrT, JstrM, JstrV
      integer :: Jend, JendB, JendP, JendR, JendT
      integer :: Istrm3, Istrm2, Istrm1, IstrUm2, IstrUm1
      integer :: Iendp1, Iendp2, Iendp2i, Iendp3
      integer :: Jstrm3, Jstrm2, Jstrm1, JstrVm2, JstrVm1
      integer :: Jendp1, Jendp2, Jendp2i, Jendp3
!
      Istr   =BOUNDS(ng) % Istr   (tile)
      IstrB  =BOUNDS(ng) % IstrB  (tile)
      IstrM  =BOUNDS(ng) % IstrM  (tile)
      IstrP  =BOUNDS(ng) % IstrP  (tile)
      IstrR  =BOUNDS(ng) % IstrR  (tile)
      IstrT  =BOUNDS(ng) % IstrT  (tile)
      IstrU  =BOUNDS(ng) % IstrU  (tile)
      Iend   =BOUNDS(ng) % Iend   (tile)
      IendB  =BOUNDS(ng) % IendB  (tile)
      IendP  =BOUNDS(ng) % IendP  (tile)
      IendR  =BOUNDS(ng) % IendR  (tile)
      IendT  =BOUNDS(ng) % IendT  (tile)
      Jstr   =BOUNDS(ng) % Jstr   (tile)
      JstrB  =BOUNDS(ng) % JstrB  (tile)
      JstrM  =BOUNDS(ng) % JstrM  (tile)
      JstrP  =BOUNDS(ng) % JstrP  (tile)
      JstrR  =BOUNDS(ng) % JstrR  (tile)
      JstrT  =BOUNDS(ng) % JstrT  (tile)
      JstrV  =BOUNDS(ng) % JstrV  (tile)
      Jend   =BOUNDS(ng) % Jend   (tile)
      JendB  =BOUNDS(ng) % JendB  (tile)
      JendP  =BOUNDS(ng) % JendP  (tile)
      JendR  =BOUNDS(ng) % JendR  (tile)
      JendT  =BOUNDS(ng) % JendT  (tile)
!
      Istrm3 =BOUNDS(ng) % Istrm3 (tile)            ! Istr-3
      Istrm2 =BOUNDS(ng) % Istrm2 (tile)            ! Istr-2
      Istrm1 =BOUNDS(ng) % Istrm1 (tile)            ! Istr-1
      IstrUm2=BOUNDS(ng) % IstrUm2(tile)            ! IstrU-2
      IstrUm1=BOUNDS(ng) % IstrUm1(tile)            ! IstrU-1
      Iendp1 =BOUNDS(ng) % Iendp1 (tile)            ! Iend+1
      Iendp2 =BOUNDS(ng) % Iendp2 (tile)            ! Iend+2
      Iendp2i=BOUNDS(ng) % Iendp2i(tile)            ! Iend+2 interior
      Iendp3 =BOUNDS(ng) % Iendp3 (tile)            ! Iend+3
      Jstrm3 =BOUNDS(ng) % Jstrm3 (tile)            ! Jstr-3
      Jstrm2 =BOUNDS(ng) % Jstrm2 (tile)            ! Jstr-2
      Jstrm1 =BOUNDS(ng) % Jstrm1 (tile)            ! Jstr-1
      JstrVm2=BOUNDS(ng) % JstrVm2(tile)            ! JstrV-2
      JstrVm1=BOUNDS(ng) % JstrVm1(tile)            ! JstrV-1
      Jendp1 =BOUNDS(ng) % Jendp1 (tile)            ! Jend+1
      Jendp2 =BOUNDS(ng) % Jendp2 (tile)            ! Jend+2
      Jendp2i=BOUNDS(ng) % Jendp2i(tile)            ! Jend+2 interior
      Jendp3 =BOUNDS(ng) % Jendp3 (tile)            ! Jend+3
!
!-----------------------------------------------------------------------
!  If distributed-memory and Zobs < 0, zero-out Zobs values in all
!  nodes but itself to facilitate exchages between tiles latter.
!-----------------------------------------------------------------------
!
!  Set starting index of obervation vectors for reading.  In weak
!  constraint, the entire observation data is loaded. Otherwise,
!  only the observation for the current time window are loaded
!  and started from vector index one.
!
      Mstr=NstrObs(ng)
      Mend=NendObs(ng)
!
!  Set observations depth (Zobs) to zero if not bounded in the current
!  parallel tile to facilitate global reduction in "mp_collect".
!
      DO iobs=Mstr,Mend
        r_bound=((rXmin(ng) .le.Xobs(iobs)).and.                        &
     &           (Xobs(iobs).lt.rXmax(ng))).and.                        &
     &          ((rYmin(ng) .le.Yobs(iobs)).and.                        &
     &           (Yobs(iobs).lt.rYmax(ng)))
        u_bound=((uXmin(ng) .le.Xobs(iobs)).and.                        &
     &           (Xobs(iobs).lt.uXmax(ng))).and.                        &
     &          ((uYmin(ng) .le.Yobs(iobs)).and.                        &
     &           (Yobs(iobs).lt.uYmax(ng)))
        v_bound=((vXmin(ng) .le.Xobs(iobs)).and.                        &
     &           (Xobs(iobs).lt.vXmax(ng))).and.                        &
     &          ((vYmin(ng) .le.Yobs(iobs)).and.                        &
     &           (Yobs(iobs).lt.vYmax(ng)))
        IF (.not.(r_bound.or.u_bound.or.v_bound)) THEN
          Zobs(iobs)=IniVal                              ! not bouded
        END IF
      END DO
!
      RETURN
      END SUBROUTINE obs_depth