! SPDX-FileCopyrightText: FLEXPART 1998-2019, see flexpart_license.txt
! SPDX-License-Identifier: GPL-3.0-or-later

subroutine drydepokernel_nest(nunc,deposit,x,y,nage,kp)
  !                               i      i    i i  i
  !*****************************************************************************
  !                                                                            *
  !     Attribution of the deposition from an individual particle to the       *
  !     nested deposition fields using a uniform kernel with bandwidths        *
  !     dxoutn and dyoutn.                                                     *
  !                                                                            *
  !     Author: A. Stohl                                                       *
  !                                                                            *
  !     26 December 1996                                                       *
  !                                                                            *
  !      2 September 2004: Adaptation from drydepokernel.                      *
  !                                                                            *
  !*****************************************************************************
  !                                                                            *
  ! Variables:                                                                 *
  !                                                                            *
  ! nunc             uncertainty class of the respective particle              *
  ! nage             age class of the respective particle                      *
  ! deposit          amount (kg) to be deposited                               *
  !                                                                            *
  !*****************************************************************************

  use unc_mod
  use par_mod
  use com_mod

  implicit none

  real(dep_prec), dimension(maxspec) :: deposit
  real :: x,y,ddx,ddy,xl,yl,wx,wy,w
  integer :: ix,jy,ixp,jyp,ks,kp,nunc,nage



  xl=(x*dx+xoutshiftn)/dxoutn
  yl=(y*dy+youtshiftn)/dyoutn
  ix=int(xl)
  jy=int(yl)
  ddx=xl-real(ix)                   ! distance to left cell border
  ddy=yl-real(jy)                   ! distance to lower cell border

  if (ddx.gt.0.5) then
    ixp=ix+1
    wx=1.5-ddx
  else
    ixp=ix-1
    wx=0.5+ddx
  endif

  if (ddy.gt.0.5) then
    jyp=jy+1
    wy=1.5-ddy
  else
    jyp=jy-1
    wy=0.5+ddy
  endif


  ! Determine mass fractions for four grid points
  !**********************************************
    do ks=1,nspec

  if (DRYDEPSPEC(ks).and.(abs(deposit(ks)).gt.0)) then

  if ((ix.ge.0).and.(jy.ge.0).and.(ix.le.numxgridn-1).and. &
       (jy.le.numygridn-1)) then
    w=wx*wy
      drygriduncn(ix,jy,ks,kp,nunc,nage)= &
           drygriduncn(ix,jy,ks,kp,nunc,nage)+deposit(ks)*w
  endif

  if ((ixp.ge.0).and.(jyp.ge.0).and.(ixp.le.numxgridn-1).and. &
       (jyp.le.numygridn-1)) then
    w=(1.-wx)*(1.-wy)
      drygriduncn(ixp,jyp,ks,kp,nunc,nage)= &
           drygriduncn(ixp,jyp,ks,kp,nunc,nage)+deposit(ks)*w
  endif

  if ((ixp.ge.0).and.(jy.ge.0).and.(ixp.le.numxgridn-1).and. &
       (jy.le.numygridn-1)) then
    w=(1.-wx)*wy
      drygriduncn(ixp,jy,ks,kp,nunc,nage)= &
           drygriduncn(ixp,jy,ks,kp,nunc,nage)+deposit(ks)*w
  endif

  if ((ix.ge.0).and.(jyp.ge.0).and.(ix.le.numxgridn-1).and. &
       (jyp.le.numygridn-1)) then
    w=wx*(1.-wy)
      drygriduncn(ix,jyp,ks,kp,nunc,nage)= &
           drygriduncn(ix,jyp,ks,kp,nunc,nage)+deposit(ks)*w
  endif

  endif

    end do
end subroutine drydepokernel_nest