!-------------------------------------- LICENCE BEGIN ------------------------------------
!Environment Canada - Atmospheric Science and Technology License/Disclaimer,
!                     version 3; Last Modified: May 7, 2008.
!This is free but copyrighted software; you can use/redistribute/modify it under the terms
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!
!
!  X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X
!

      subroutine invlap(psol,prhs,cdgrid,ldmean) 6,1
!
!**s/r invlap  - Invert Laplacian.
!
!
!Author  : Luc Fillion - MSC - 1 Oct 04.
!Revision:
!  : Luc Fillion - ARMA/EC - 7 May 2008
!       - Include setting the mean value of the field to zero using ldmean as argument.
!     -------------------
!
!Arguments
!
      IMPLICIT NONE
!
#include "taglam4d.cdk"
#include "comdim.cdk"
#include "comlun.cdk"
      logical ldmean
      character*1 cdgrid
      real*8 psol(ni,nj)
      real*8 prhs(ni,nj)
!
      integer ji,jj,jk
      real*8 zsum,zcon 
!
!!
      zcon=0.0
      call invhelmc(psol,zcon,prhs,cdgrid)
!
      if(ldmean) then
        zsum=0.
        do ji=1,ni
          do jj=1,nj
            zsum=zsum+psol(ji,jj)
          enddo
        enddo
        zcon=zsum/(ni*nj)
        do ji=1,ni
          do jj=1,nj
            psol(ji,jj)=psol(ji,jj)-zcon
          enddo
        enddo
      endif
!
      return
      end