!$Id: ac_sulf.F90 10 2007-08-09 12:43:01Z acosce $
!! =========================================================================
!! INCA - INteraction with Chemistry and Aerosols
!! 
!! Copyright Laboratoire des Sciences du Climat et de l'Environnement (LSCE)
!! 	     Unite mixte CEA-CNRS-UVSQ
!! 
!! Contributors to this INCA subroutine:
!! 
!! Stacy Walters, NCAR, stacy@ucar.edu 
!! 
!! Anne Cozic, LSCE, anne.cozic@cea.fr
!! Yann Meurdesoif, LSCE, yann.meurdesoif@cea.fr
!! 
!! This software is a computer program whose purpose is to simulate the 
!! atmospheric gas phase and aerosol composition. The model is designed to be
!! used within a transport model or a general circulation model. This version 
!! of INCA was designed to be coupled to the LMDz GCM. LMDz-INCA accounts
!! for emissions, transport (resolved and sub-grid scale), photochemical 
!! transformations, and scavenging (dry deposition and washout) of chemical 
!! species and aerosols interactively in the GCM. Several versions of the INCA
!! model are currently used depending on the envisaged applications with the 
!! chemistry-climate model. 
!! 
!! This software is governed by the CeCILL  license under French law and
!! abiding by the rules of distribution of free software.  You can  use, 
!! modify and/ or redistribute the software under the terms of the CeCILL
!! license as circulated by CEA, CNRS and INRIA at the following URL
!! "http://www.cecill.info". 
!! 
!! As a counterpart to the access to the source code and  rights to copy,
!! modify and redistribute granted by the license, users are provided only
!! with a limited warranty  and the software's author,  the holder of the
!! economic rights,  and the successive licensors  have only  limited
!! liability. 
!! 
!! In this respect, the user's attention is drawn to the risks associated
!! with loading,  using,  modifying and/or developing or reproducing the
!! software by the user in light of its specific status of free software,
!! that may mean  that it is complicated to manipulate,  and  that  also
!! therefore means  that it is reserved for developers  and  experienced
!! professionals having in-depth computer knowledge. Users are therefore
!! encouraged to load and test the software's suitability as regards their
!! requirements in conditions enabling the security of their systems and/or 
!! data to be ensured and,  more generally, to use and operate it in the 
!! same conditions as regards security. 
!! 
!! The fact that you are presently reading this means that you have had
!! knowledge of the CeCILL license and that you accept its terms.
!! =========================================================================


SUBROUTINE FINDPLB( x, nx, xval, index )
  !-----------------------------------------------------------------------
  ! 	... "find periodic lower bound"
  ! 	Search the input array for the lower bound of the interval that
  ! 	contains the input value.  The returned index satifies:
  ! 	x(index) .le. xval .lt. x(index+1)
  ! 	Assume the array represents values in one cycle of a periodic coordinate.
  ! 	So, if xval .lt. x(1), then index=nx.
  ! Stacy Walters, NCAR, 1998.
  !-----------------------------------------------------------------------
  USE PRINT_INCA
  IMPLICIT NONE

  !-----------------------------------------------------------------------
  !	... Dummy args
  !-----------------------------------------------------------------------
  INTEGER, INTENT(in) ::  nx
  INTEGER, INTENT(out) ::  index
  REAL, INTENT(in) ::  x(nx)         ! strictly increasing array
  REAL, INTENT(in) ::  xval

  !-----------------------------------------------------------------------
  !	... Local variables
  !-----------------------------------------------------------------------
  INTEGER :: i

  IF( xval < x(1) .OR. xval >= x(nx) ) THEN
      index = nx
      RETURN
  END IF

  DO i = 2,nx
    IF( xval < x(i) ) THEN
        index = i - 1
        EXIT
    END IF
  END DO

END SUBROUTINE FINDPLB

subroutine LININTP( npts, t1, t2, tint, f1, f2, fint )
!-----------------------------------------------------------------------
! 	... Linearly interpolate between f1(t1) and f2(t2) to fint(tint)
! Stacy Walters, NCAR, 1998.
!-----------------------------------------------------------------------

  implicit none

!-----------------------------------------------------------------------
! 	... Dummy args
!-----------------------------------------------------------------------
  integer, intent(in) ::  npts
  real, intent(in) ::  t1               ! time level of f1
  real, intent(in) :: t2               ! time level of f2
  real, intent(in) :: tint             ! interpolant time
  real, intent(in) :: f1(npts)         ! field at time t1
  real, intent(in) :: f2(npts)         ! field at time t2
  real, intent(out) :: fint(npts)       ! field at time tint
  
!-----------------------------------------------------------------------
! 	... Local variables
!-----------------------------------------------------------------------
  integer :: i
  real :: factor
  
  factor = (tint - t1) / (t2 - t1)

  do i = 1, npts
     fint(i) = f1(i) + ( f2(i) - f1(i) )*factor
  end do
  
end subroutine LININTP