source: palm/trunk/SOURCE/pmc_interface_mod.f90 @ 3820

!> @file pmc_interface_mod.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 1997-2019 Leibniz Universitaet Hannover
!------------------------------------------------------------------------------!
!
! Current revisions:
! ------------------
! 
! 
! Former revisions:
! -----------------
! $Id: pmc_interface_mod.f90 3819 2019-03-27 11:01:36Z forkel $
! Adjustable anterpolation buffer introduced on all nest boundaries, it is controlled
! by the new nesting_parameters parameter anterpolation_buffer_width.
! 
! 3804 2019-03-19 13:46:20Z hellstea
! Anterpolation domain is lowered from kct-1 to kct-3 to avoid exessive       
! kinetic energy from building up in CBL flows.
! 
! 3803 2019-03-19 13:44:40Z hellstea
! A bug fixed in lateral boundary interpolations. Dimension of val changed from  
! 5 to 3 in pmci_setup_parent and pmci_setup_child.
! 
! 3794 2019-03-15 09:36:33Z raasch
! two remaining unused variables removed
! 
! 3792 2019-03-14 16:50:07Z hellstea
! Interpolations improved. Large number of obsolete subroutines removed.
! All unused variables removed. 
! 
! 3741 2019-02-13 16:24:49Z hellstea
! Interpolations and child initialization adjusted to handle set ups with child 
! pe-subdomain dimension not integer divisible by the grid-spacing ratio in the 
! respective direction. Set ups with pe-subdomain dimension smaller than the 
! grid-spacing ratio in the respective direction are now forbidden.
! 
! 3708 2019-01-30 12:58:13Z hellstea
! Checks for parent / child grid line matching introduced.
! Interpolation of nest-boundary-tangential velocity components revised.
! 
! 3697 2019-01-24 17:16:13Z hellstea
! Bugfix: upper k-bound in the child initialization interpolation 
! pmci_interp_1sto_all corrected.
! Copying of the nest boundary values into the redundant 2nd and 3rd ghost-node 
! layers is added to the pmci_interp_1sto_*-routines.
! 
! 3681 2019-01-18 15:06:05Z hellstea
! Linear interpolations are replaced by first order interpolations. The linear 
! interpolation routines are still included but not called. In the child 
! inititialization the interpolation is also changed to 1st order and the linear
! interpolation is not kept.
! Subroutine pmci_map_fine_to_coarse_grid is rewritten.
! Several changes in pmci_init_anterp_tophat.
! Child's parent-grid arrays (uc, vc,...) are made non-overlapping on the PE-
! subdomain boundaries in order to allow grid-spacing ratios higher than nbgp. 
! Subroutine pmci_init_tkefactor is removed as unnecessary.
! 
! 3655 2019-01-07 16:51:22Z knoop
! Remove unused variable simulated_time
! 
! 3636 2018-12-19 13:48:34Z raasch
! nopointer option removed
! 
! 3592 2018-12-03 12:38:40Z suehring
! Number of coupled arrays is determined dynamically (instead of a fixed value
! of 32)
! 
! 3524 2018-11-14 13:36:44Z raasch
! declaration statements rearranged to avoid compile time errors
! 
! 3484 2018-11-02 14:41:25Z hellstea
! Introduction of reversibility correction to the interpolation routines in order to 
! guarantee mass and scalar conservation through the nest boundaries. Several errors 
! are corrected and pmci_ensure_nest_mass_conservation is permanently removed. 
! 
! 3274 2018-09-24 15:42:55Z knoop
! Modularization of all bulk cloud physics code components
! 
! 3241 2018-09-12 15:02:00Z raasch
! unused variables removed
! 
! 3217 2018-08-29 12:53:59Z suehring
! Revise calculation of index bounds for array index_list, prevent compiler 
! (cray) to delete the loop at high optimization level.  
! 
! 3215 2018-08-29 09:58:59Z suehring
! Apply an additional switch controlling the nesting of chemical species
! 
! 3209 2018-08-27 16:58:37Z suehring
! Variable names for nest_bound_x replaced by bc_dirichlet_x.
! Remove commented prints into debug files.
! 
! 3182 2018-07-27 13:36:03Z suehring
! dz was replaced by dz(1)
! 
! 3049 2018-05-29 13:52:36Z Giersch
! Error messages revised
! 
! 3045 2018-05-28 07:55:41Z Giersch
! Error messages revised
! 
! 3022 2018-05-18 11:12:35Z suehring
! Minor fix - working precision added to real number
! 
! 3021 2018-05-16 08:14:20Z maronga
! Bugfix: variable lcr was defined as INTENT(OUT) instead of INTENT(INOUT)
! 
! 3020 2018-05-14 10:45:48Z hellstea
! Bugfix in pmci_define_loglaw_correction_parameters
! 
! 3001 2018-04-20 12:27:13Z suehring
! Bugfix, replace MERGE function by an if-condition in the anterpolation (in 
! order to avoid floating-point exceptions).
! 
! 2997 2018-04-19 13:35:17Z suehring
! Mask topography grid points in anterpolation
! 
! 2984 2018-04-18 11:51:30Z hellstea
! Bugfix in the log-law correction initialization. Pivot node cannot any more be 
! selected from outside the subdomain in order to prevent array under/overflows.
! 
! 2967 2018-04-13 11:22:08Z raasch
! bugfix: missing parallel cpp-directives added
! 
! 2951 2018-04-06 09:05:08Z kanani
! Add log_point_s for pmci_model_configuration
! 
! 2938 2018-03-27 15:52:42Z suehring
! - Nesting for RANS mode implemented
!    - Interpolation of TKE onto child domain only if both parent and child are 
!      either in LES mode or in RANS mode
!    - Interpolation of dissipation if both parent and child are in RANS mode
!      and TKE-epsilon closure is applied
!    - Enable anterpolation of TKE and dissipation rate in case parent and 
!      child operate in RANS mode
!
! - Some unused variables removed from ONLY list
! - Some formatting adjustments for particle nesting
! 
! 2936 2018-03-27 14:49:27Z suehring
! Control logics improved to allow nesting also in cases with
! constant_flux_layer = .F. or constant_diffusion = .T.
! 
! 2895 2018-03-15 10:26:12Z hellstea
! Change in the nest initialization (pmci_interp_tril_all). Bottom wall BC is no
! longer overwritten.
! 
! 2868 2018-03-09 13:25:09Z hellstea
! Local conditional Neumann conditions for one-way coupling removed.  
! 
! 2853 2018-03-05 14:44:20Z suehring
! Bugfix in init log-law correction.
! 
! 2841 2018-02-27 15:02:57Z knoop
! Bugfix: wrong placement of include 'mpif.h' corrected
! 
! 2812 2018-02-16 13:40:25Z hellstea
! Bugfixes in computation of the interpolation loglaw-correction parameters
! 
! 2809 2018-02-15 09:55:58Z schwenkel
! Bugfix for gfortran: Replace the function C_SIZEOF with STORAGE_SIZE
! 
! 2806 2018-02-14 17:10:37Z thiele
! Bugfixing Write statements
! 
! 2804 2018-02-14 16:57:03Z thiele
! preprocessor directive for c_sizeof in case of __gfortran added
! 
! 2803 2018-02-14 16:56:32Z thiele
! Introduce particle transfer in nested models.
! 
! 2795 2018-02-07 14:48:48Z hellstea
! Bugfix in computation of the anterpolation under-relaxation functions. 
! 
! 2773 2018-01-30 14:12:54Z suehring
! - Nesting for chemical species
! - Bugfix in setting boundary condition at downward-facing walls for passive
!   scalar
! - Some formatting adjustments
! 
! 2718 2018-01-02 08:49:38Z maronga
! Corrected "Former revisions" section
! 
! 2701 2017-12-15 15:40:50Z suehring
! Changes from last commit documented
! 
! 2698 2017-12-14 18:46:24Z suehring
! Bugfix in get_topography_top_index
!
! 2696 2017-12-14 17:12:51Z kanani
! Change in file header (GPL part)
! - Bugfix in init_tke_factor (MS)
! 
! 2669 2017-12-06 16:03:27Z raasch
! file extension for nested domains changed to "_N##",
! created flag file in order to enable combine_plot_fields to process nest data
! 
! 2663 2017-12-04 17:40:50Z suehring
! Bugfix, wrong coarse-grid index in init_tkefactor used.
! 
! 2602 2017-11-03 11:06:41Z hellstea
! Index-limit related bug (occurred with nesting_mode='vertical') fixed in
! pmci_interp_tril_t. Check for too high nest domain added in pmci_setup_parent.   
! Some cleaning up made. 
! 
! 2582 2017-10-26 13:19:46Z hellstea
! Resetting of e within buildings / topography in pmci_parent_datatrans removed
! as unnecessary since e is not anterpolated, and as incorrect since it overran
! the default Neumann condition (bc_e_b). 
! 
! 2359 2017-08-21 07:50:30Z hellstea
! A minor indexing error in pmci_init_loglaw_correction is corrected. 
! 
! 2351 2017-08-15 12:03:06Z kanani
! Removed check (PA0420) for nopointer version
! 
! 2350 2017-08-15 11:48:26Z kanani
! Bugfix and error message for nopointer version.
! 
! 2318 2017-07-20 17:27:44Z suehring
! Get topography top index via Function call 
! 
! 2317 2017-07-20 17:27:19Z suehring
! Set bottom boundary condition after anterpolation.
! Some variable description added.
! 
! 2293 2017-06-22 12:59:12Z suehring
! In anterpolation, exclude grid points which are used for interpolation. 
! This avoids the accumulation of numerical errors leading to increased 
! variances for shallow child domains.  
! 
! 2292 2017-06-20 09:51:42Z schwenkel
! Implementation of new microphysic scheme: cloud_scheme = 'morrison' 
! includes two more prognostic equations for cloud drop concentration (nc)  
! and cloud water content (qc). 
! 
! 2285 2017-06-15 13:15:41Z suehring
! Consider multiple pure-vertical nest domains in overlap check
! 
! 2283 2017-06-14 10:17:34Z suehring
! Bugfixes in inititalization of log-law correction concerning 
! new topography concept
! 
! 2281 2017-06-13 11:34:50Z suehring
! Bugfix, add pre-preprocessor directives to enable non-parrallel mode
! 
! 2241 2017-06-01 13:46:13Z hellstea
! A minor indexing error in pmci_init_loglaw_correction is corrected.
! 
! 2240 2017-06-01 13:45:34Z hellstea
!
! 2232 2017-05-30 17:47:52Z suehring
! Adjustments to new topography concept
! 
! 2229 2017-05-30 14:52:52Z hellstea
! A minor indexing error in pmci_init_anterp_tophat is corrected.
! 
! 2174 2017-03-13 08:18:57Z maronga
! Added support for cloud physics quantities, syntax layout improvements. Data
! transfer of qc and nc is prepared but currently deactivated until both
! quantities become prognostic variables.
! Some bugfixes.
! 
! 2019 2016-09-30 13:40:09Z hellstea
! Bugfixes mainly in determining the anterpolation index bounds. These errors 
! were detected when first time tested using 3:1 grid-spacing.
! 
! 2003 2016-08-24 10:22:32Z suehring
! Humidity and passive scalar also separated in nesting mode 
! 
! 2000 2016-08-20 18:09:15Z knoop
! Forced header and separation lines into 80 columns
! 
! 1938 2016-06-13 15:26:05Z hellstea
! Minor clean-up.
! 
! 1901 2016-05-04 15:39:38Z raasch
! Initial version of purely vertical nesting introduced.
! Code clean up. The words server/client changed to parent/child.
!
! 1900 2016-05-04 15:27:53Z raasch
! unused variables removed
!
! 1894 2016-04-27 09:01:48Z raasch
! bugfix: pt interpolations are omitted in case that the temperature equation is
! switched off
!
! 1892 2016-04-26 13:49:47Z raasch
! bugfix: pt is not set as a data array in case that the temperature equation is
! switched off with neutral = .TRUE.
!
! 1882 2016-04-20 15:24:46Z hellstea
! The factor ijfc for nfc used in anterpolation is redefined as 2-D array 
! and precomputed in pmci_init_anterp_tophat. 
! 
! 1878 2016-04-19 12:30:36Z hellstea
! Synchronization rewritten, logc-array index order changed for cache
! optimization
!
! 1850 2016-04-08 13:29:27Z maronga
! Module renamed
!
!
! 1808 2016-04-05 19:44:00Z raasch
! MPI module used by default on all machines
!
! 1801 2016-04-05 13:12:47Z raasch
! bugfix for r1797: zero setting of temperature within topography does not work
! and has been disabled
!
! 1797 2016-03-21 16:50:28Z raasch
! introduction of different datatransfer modes,
! further formatting cleanup, parameter checks added (including mismatches
! between root and nest model settings),
! +routine pmci_check_setting_mismatches
! comm_world_nesting introduced
!
! 1791 2016-03-11 10:41:25Z raasch
! routine pmci_update_new removed,
! pmc_get_local_model_info renamed pmc_get_model_info, some keywords also
! renamed,
! filling up redundant ghost points introduced,
! some index bound variables renamed,
! further formatting cleanup
!
! 1783 2016-03-06 18:36:17Z raasch
! calculation of nest top area simplified,
! interpolation and anterpolation moved to seperate wrapper subroutines
!
! 1781 2016-03-03 15:12:23Z raasch
! _p arrays are set zero within buildings too, t.._m arrays and respective
! settings within buildings completely removed
!
! 1779 2016-03-03 08:01:28Z raasch
! only the total number of PEs is given for the domains, npe_x and npe_y
! replaced by npe_total, two unused elements removed from array
! parent_grid_info_real,
! array management changed from linked list to sequential loop
!
! 1766 2016-02-29 08:37:15Z raasch
! modifications to allow for using PALM's pointer version,
! +new routine pmci_set_swaplevel
!
! 1764 2016-02-28 12:45:19Z raasch
! +cpl_parent_id,
! cpp-statements for nesting replaced by __parallel statements,
! errors output with message-subroutine,
! index bugfixes in pmci_interp_tril_all,
! some adjustments to PALM style
!
! 1762 2016-02-25 12:31:13Z hellstea
! Initial revision by A. Hellsten
!
! Description:
! ------------
! Domain nesting interface routines. The low-level inter-domain communication   
! is conducted by the PMC-library routines.
!
! @todo Remove array_3d variables from USE statements thate not used in the 
!       routine
! @todo Data transfer of qc and nc is prepared but not activated
!------------------------------------------------------------------------------!
 MODULE pmc_interface

    USE ISO_C_BINDING


    USE arrays_3d,                                                             &
        ONLY:  diss, diss_2, dzu, dzw, e, e_p, e_2, nc, nc_2, nc_p, nr, nr_2,  &
               pt, pt_2, q, q_2, qc, qc_2, qr, qr_2, s, s_2,                   &
               u, u_p, u_2, v, v_p, v_2, w, w_p, w_2, zu, zw

    USE control_parameters,                                                    &
        ONLY:  air_chemistry, bc_dirichlet_l, bc_dirichlet_n, bc_dirichlet_r,  &
               bc_dirichlet_s, child_domain,                                   &
               constant_diffusion, constant_flux_layer,                        &
               coupling_char, dt_3d, dz, humidity, message_string,             &
               neutral, passive_scalar, rans_mode, rans_tke_e,                 &
               roughness_length, topography, volume_flow

    USE chem_modules,                                                          &
        ONLY:  nspec

    USE chemistry_model_mod,                                                   &
        ONLY:  chem_species, nest_chemistry, spec_conc_2

    USE cpulog,                                                                &
        ONLY:  cpu_log, log_point_s

    USE grid_variables,                                                        &
        ONLY:  dx, dy

    USE indices,                                                               &
        ONLY:  nbgp, nx, nxl, nxlg, nxlu, nxr, nxrg, ny, nyn, nyng, nys, nysg, &
               nysv, nz, nzb, nzt, wall_flags_0

    USE bulk_cloud_model_mod,                                                  &
        ONLY: bulk_cloud_model, microphysics_morrison, microphysics_seifert

    USE particle_attributes,                                                   &
        ONLY:  particle_advection

    USE kinds

#if defined( __parallel )
#if !defined( __mpifh )
    USE MPI
#endif

    USE pegrid,                                                                &
        ONLY:  collective_wait, comm1dx, comm1dy, comm2d, myid, myidx, myidy,  &
               numprocs, pdims, pleft, pnorth, pright, psouth, status

    USE pmc_child,                                                             &
        ONLY:  pmc_childinit, pmc_c_clear_next_array_list,                     &
               pmc_c_getnextarray, pmc_c_get_2d_index_list, pmc_c_getbuffer,   &
               pmc_c_putbuffer, pmc_c_setind_and_allocmem,                     &
               pmc_c_set_dataarray, pmc_set_dataarray_name

    USE pmc_general,                                                           &
        ONLY:  da_namelen

    USE pmc_handle_communicator,                                               &
        ONLY:  pmc_get_model_info, pmc_init_model, pmc_is_rootmodel,           &
               pmc_no_namelist_found, pmc_parent_for_child, m_couplers

    USE pmc_mpi_wrapper,                                                       &
        ONLY:  pmc_bcast, pmc_recv_from_child, pmc_recv_from_parent,           &
               pmc_send_to_child, pmc_send_to_parent

    USE pmc_parent,                                                            &
        ONLY:  pmc_parentinit, pmc_s_clear_next_array_list, pmc_s_fillbuffer,  &
               pmc_s_getdata_from_buffer, pmc_s_getnextarray,                  &
               pmc_s_setind_and_allocmem, pmc_s_set_active_data_array,         &
               pmc_s_set_dataarray, pmc_s_set_2d_index_list

#endif

    USE surface_mod,                                                           &
        ONLY:  get_topography_top_index_ji, surf_def_h, surf_lsm_h, surf_usm_h

    IMPLICIT NONE

#if defined( __parallel )
#if defined( __mpifh )
    INCLUDE "mpif.h"
#endif
#endif

    PRIVATE
!
!-- Constants
    INTEGER(iwp), PARAMETER ::  child_to_parent = 2   !<
    INTEGER(iwp), PARAMETER ::  parent_to_child = 1   !<
    INTEGER(iwp), PARAMETER ::  interpolation_scheme_lrsn  = 2  !< Interpolation scheme to be used on lateral boundaries (maybe to be made user parameter)
    INTEGER(iwp), PARAMETER ::  interpolation_scheme_t     = 3  !< Interpolation scheme to be used on top boundary (maybe to be made user parameter)
!
!-- Coupler setup
    INTEGER(iwp), SAVE      ::  comm_world_nesting    !<
    INTEGER(iwp), SAVE      ::  cpl_id  = 1           !<
    CHARACTER(LEN=32), SAVE ::  cpl_name              !<
    INTEGER(iwp), SAVE      ::  cpl_npe_total         !<
    INTEGER(iwp), SAVE      ::  cpl_parent_id         !<
!
!-- Control parameters
    CHARACTER(LEN=7), SAVE ::  nesting_datatransfer_mode = 'mixed'  !< steering parameter for data-transfer mode
    CHARACTER(LEN=8), SAVE ::  nesting_mode = 'two-way'             !< steering parameter for 1- or 2-way nesting
    INTEGER(iwp),     SAVE ::  anterpolation_buffer_width = 2       !< Boundary buffer width for anterpolation
    
    LOGICAL, SAVE ::  nested_run = .FALSE.  !< general switch
    LOGICAL       ::  rans_mode_parent = .FALSE. !< mode of parent model (.F. - LES mode, .T. - RANS mode)
!
!-- Geometry
    REAL(wp), SAVE, DIMENSION(:), ALLOCATABLE, PUBLIC ::  coord_x            !<
    REAL(wp), SAVE, DIMENSION(:), ALLOCATABLE, PUBLIC ::  coord_y            !<
    REAL(wp), SAVE, PUBLIC                            ::  lower_left_coord_x !<
    REAL(wp), SAVE, PUBLIC                            ::  lower_left_coord_y !<
!
!-- Children's parent-grid arrays
    INTEGER(iwp), SAVE, DIMENSION(5), PUBLIC    ::  coarse_bound        !< subdomain index bounds for children's parent-grid arrays
    INTEGER(iwp), SAVE, DIMENSION(4), PUBLIC    ::  coarse_bound_aux    !< subdomain index bounds for allocation of index-mapping and other auxiliary arrays
    INTEGER(iwp), SAVE, DIMENSION(4), PUBLIC    ::  coarse_bound_w      !< subdomain index bounds for children's parent-grid work arrays

    REAL(wp), SAVE, DIMENSION(:,:,:), ALLOCATABLE, TARGET ::  dissc !< Parent-grid array on child domain - dissipation rate
    REAL(wp), SAVE, DIMENSION(:,:,:), ALLOCATABLE, TARGET ::  ec    !< Parent-grid array on child domain - SGS TKE
    REAL(wp), SAVE, DIMENSION(:,:,:), ALLOCATABLE, TARGET ::  ptc   !< Parent-grid array on child domain - potential temperature
    REAL(wp), SAVE, DIMENSION(:,:,:), ALLOCATABLE, TARGET ::  uc    !< Parent-grid array on child domain - velocity component u
    REAL(wp), SAVE, DIMENSION(:,:,:), ALLOCATABLE, TARGET ::  vc    !< Parent-grid array on child domain - velocity component v
    REAL(wp), SAVE, DIMENSION(:,:,:), ALLOCATABLE, TARGET ::  wc    !< Parent-grid array on child domain - velocity component w
    REAL(wp), SAVE, DIMENSION(:,:,:), ALLOCATABLE, TARGET ::  q_c   !< Parent-grid array on child domain - 
    REAL(wp), SAVE, DIMENSION(:,:,:), ALLOCATABLE, TARGET ::  qcc   !< Parent-grid array on child domain - 
    REAL(wp), SAVE, DIMENSION(:,:,:), ALLOCATABLE, TARGET ::  qrc   !< Parent-grid array on child domain - 
    REAL(wp), SAVE, DIMENSION(:,:,:), ALLOCATABLE, TARGET ::  nrc   !< Parent-grid array on child domain - 
    REAL(wp), SAVE, DIMENSION(:,:,:), ALLOCATABLE, TARGET ::  ncc   !< Parent-grid array on child domain - 
    REAL(wp), SAVE, DIMENSION(:,:,:), ALLOCATABLE, TARGET ::  sc    !< Parent-grid array on child domain - 
    INTEGER(idp), SAVE, DIMENSION(:,:), ALLOCATABLE, TARGET, PUBLIC ::  nr_partc    !<
    INTEGER(idp), SAVE, DIMENSION(:,:), ALLOCATABLE, TARGET, PUBLIC ::  part_adrc   !<

    REAL(wp), SAVE, DIMENSION(:,:,:,:), ALLOCATABLE, TARGET ::  chem_spec_c !< Parent-grid array on child domain - chemical species
!
!-- Grid-spacing ratios.
    INTEGER(iwp), SAVE ::  igsr     !< Integer grid-spacing ratio in i-direction 
    INTEGER(iwp), SAVE ::  jgsr     !< Integer grid-spacing ratio in j-direction 
    INTEGER(iwp), SAVE ::  kgsr     !< Integer grid-spacing ratio in k-direction
!
!-- Global parent-grid index bounds
    INTEGER(iwp), SAVE ::  iplg     !< Leftmost parent-grid array ip index of the whole child domain
    INTEGER(iwp), SAVE ::  iprg     !< Rightmost parent-grid array ip index of the whole child domain
    INTEGER(iwp), SAVE ::  jpsg     !< Southmost parent-grid array jp index of the whole child domain
    INTEGER(iwp), SAVE ::  jpng     !< Northmost parent-grid array jp index of the whole child domain
!
!-- Local parent-grid index bounds (to be moved here from pmci_setup_child)
!-- EXPLAIN WHY SEVERAL SETS OF PARENT-GRID INDEX BOUNDS ARE NEEDED.
    
!
!-- Highest prognostic parent-grid k-indices.
    INTEGER(iwp), SAVE ::  kcto     !< Upper bound for k in anterpolation of variables other than w.
    INTEGER(iwp), SAVE ::  kctw     !< Upper bound for k in anterpolation of w.
!
!-- Child-array indices to be precomputed and stored for anterpolation.
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:) ::  iflu   !< child index indicating left bound of parent grid box on u-grid
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:) ::  ifuu   !< child index indicating right bound of parent grid box on u-grid
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:) ::  iflo   !< child index indicating left bound of parent grid box on scalar-grid
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:) ::  ifuo   !< child index indicating right bound of parent grid box on scalar-grid
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:) ::  jflv   !< child index indicating south bound of parent grid box on v-grid
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:) ::  jfuv   !< child index indicating north bound of parent grid box on v-grid
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:) ::  jflo   !< child index indicating south bound of parent grid box on scalar-grid
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:) ::  jfuo   !< child index indicating north bound of parent grid box on scalar-grid
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:) ::  kflw   !< child index indicating lower bound of parent grid box on w-grid
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:) ::  kfuw   !< child index indicating upper bound of parent grid box on w-grid
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:) ::  kflo   !< child index indicating lower bound of parent grid box on scalar-grid
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:) ::  kfuo   !< child index indicating upper bound of parent grid box on scalar-grid
!
!-- Number of fine-grid nodes inside coarse-grid ij-faces
!-- to be precomputed for anterpolation.
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:,:,:) ::  ijkfc_u  !< number of child grid boxes contribution to a parent grid box, u-grid
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:,:,:) ::  ijkfc_v  !< number of child grid boxes contribution to a parent grid box, v-grid
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:,:,:) ::  ijkfc_w  !< number of child grid boxes contribution to a parent grid box, w-grid
    INTEGER(iwp), SAVE, ALLOCATABLE, DIMENSION(:,:,:) ::  ijkfc_s  !< number of child grid boxes contribution to a parent grid box, scalar-grid
!    
!-- Work arrays for interpolation and user-defined type definitions for horizontal work-array exchange    
    REAL(wp), DIMENSION(:,:,:), ALLOCATABLE :: workarrc_lr
    REAL(wp), DIMENSION(:,:,:), ALLOCATABLE :: workarrc_sn
    REAL(wp), DIMENSION(:,:,:), ALLOCATABLE :: workarrc_t
    INTEGER(iwp) :: workarrc_lr_exchange_type
    INTEGER(iwp) :: workarrc_sn_exchange_type
    INTEGER(iwp) :: workarrc_t_exchange_type_x
    INTEGER(iwp) :: workarrc_t_exchange_type_y
 
    INTEGER(iwp), DIMENSION(3)          ::  parent_grid_info_int    !<
    REAL(wp), DIMENSION(7)              ::  parent_grid_info_real   !<
    REAL(wp), DIMENSION(2)              ::  zmax_coarse             !<

    TYPE parentgrid_def
       INTEGER(iwp)                        ::  nx                 !<
       INTEGER(iwp)                        ::  ny                 !<
       INTEGER(iwp)                        ::  nz                 !<
       REAL(wp)                            ::  dx                 !<
       REAL(wp)                            ::  dy                 !<
       REAL(wp)                            ::  dz                 !<
       REAL(wp)                            ::  lower_left_coord_x !<
       REAL(wp)                            ::  lower_left_coord_y !<
       REAL(wp)                            ::  xend               !<
       REAL(wp)                            ::  yend               !<
       REAL(wp), DIMENSION(:), ALLOCATABLE ::  coord_x            !<
       REAL(wp), DIMENSION(:), ALLOCATABLE ::  coord_y            !<
       REAL(wp), DIMENSION(:), ALLOCATABLE ::  dzu                !<
       REAL(wp), DIMENSION(:), ALLOCATABLE ::  dzw                !<
       REAL(wp), DIMENSION(:), ALLOCATABLE ::  zu                 !<
       REAL(wp), DIMENSION(:), ALLOCATABLE ::  zw                 !<
    END TYPE parentgrid_def

    TYPE(parentgrid_def), SAVE, PUBLIC     ::  cg                 !< change to pg
!
!-- Variables for particle coupling
    TYPE, PUBLIC :: childgrid_def
       INTEGER(iwp)                        ::  nx                   !<
       INTEGER(iwp)                        ::  ny                   !<
       INTEGER(iwp)                        ::  nz                   !<
       REAL(wp)                            ::  dx                   !<
       REAL(wp)                            ::  dy                   !<
       REAL(wp)                            ::  dz                   !<
       REAL(wp)                            ::  lx_coord, lx_coord_b !<
       REAL(wp)                            ::  rx_coord, rx_coord_b !<
       REAL(wp)                            ::  sy_coord, sy_coord_b !<
       REAL(wp)                            ::  ny_coord, ny_coord_b !<
       REAL(wp)                            ::  uz_coord, uz_coord_b !<
    END TYPE childgrid_def

    TYPE(childgrid_def), SAVE, ALLOCATABLE, DIMENSION(:), PUBLIC :: childgrid !<

    INTEGER(idp),ALLOCATABLE,DIMENSION(:,:),PUBLIC,TARGET    :: nr_part  !<
    INTEGER(idp),ALLOCATABLE,DIMENSION(:,:),PUBLIC,TARGET    :: part_adr !<

   
    INTERFACE pmci_boundary_conds
       MODULE PROCEDURE pmci_boundary_conds
    END INTERFACE pmci_boundary_conds
    
    INTERFACE pmci_check_setting_mismatches
       MODULE PROCEDURE pmci_check_setting_mismatches
    END INTERFACE

    INTERFACE pmci_child_initialize
       MODULE PROCEDURE pmci_child_initialize
    END INTERFACE

    INTERFACE pmci_synchronize
       MODULE PROCEDURE pmci_synchronize
    END INTERFACE

    INTERFACE pmci_datatrans
       MODULE PROCEDURE pmci_datatrans
    END INTERFACE pmci_datatrans

    INTERFACE pmci_init
       MODULE PROCEDURE pmci_init
    END INTERFACE

    INTERFACE pmci_modelconfiguration
       MODULE PROCEDURE pmci_modelconfiguration
    END INTERFACE

    INTERFACE pmci_parent_initialize
       MODULE PROCEDURE pmci_parent_initialize
    END INTERFACE

    INTERFACE get_number_of_childs
       MODULE PROCEDURE get_number_of_childs
    END  INTERFACE get_number_of_childs

    INTERFACE get_childid
       MODULE PROCEDURE get_childid
    END  INTERFACE get_childid

    INTERFACE get_child_edges
       MODULE PROCEDURE get_child_edges
    END  INTERFACE get_child_edges

    INTERFACE get_child_gridspacing
       MODULE PROCEDURE get_child_gridspacing
    END  INTERFACE get_child_gridspacing

    INTERFACE pmci_set_swaplevel
       MODULE PROCEDURE pmci_set_swaplevel
    END INTERFACE pmci_set_swaplevel

    PUBLIC child_to_parent, comm_world_nesting, cpl_id, nested_run,                                 &
           nesting_datatransfer_mode, nesting_mode, parent_to_child, rans_mode_parent

    PUBLIC pmci_boundary_conds
    PUBLIC pmci_child_initialize
    PUBLIC pmci_datatrans
    PUBLIC pmci_init
    PUBLIC pmci_modelconfiguration
    PUBLIC pmci_parent_initialize
    PUBLIC pmci_synchronize
    PUBLIC pmci_set_swaplevel
    PUBLIC get_number_of_childs, get_childid, get_child_edges, get_child_gridspacing


 CONTAINS


 SUBROUTINE pmci_init( world_comm )

    USE control_parameters,                                                    &
        ONLY:  message_string

    IMPLICIT NONE

    INTEGER(iwp), INTENT(OUT) ::  world_comm   !<

#if defined( __parallel )

    INTEGER(iwp) ::  pmc_status   !<


    CALL pmc_init_model( world_comm, nesting_datatransfer_mode, nesting_mode,  &
                         anterpolation_buffer_width, pmc_status )

    IF ( pmc_status == pmc_no_namelist_found )  THEN
!
!--    This is not a nested run
       world_comm = MPI_COMM_WORLD
       cpl_id     = 1
       cpl_name   = ""

       RETURN

    ENDIF
!
!-- Check steering parameter values
    IF ( TRIM( nesting_mode ) /= 'one-way'  .AND.                              &
         TRIM( nesting_mode ) /= 'two-way'  .AND.                              &
         TRIM( nesting_mode ) /= 'vertical' )                                  &
    THEN
       message_string = 'illegal nesting mode: ' // TRIM( nesting_mode )
       CALL message( 'pmci_init', 'PA0417', 3, 2, 0, 6, 0 )
    ENDIF

    IF ( TRIM( nesting_datatransfer_mode ) /= 'cascade'  .AND.                 &
         TRIM( nesting_datatransfer_mode ) /= 'mixed'    .AND.                 &
         TRIM( nesting_datatransfer_mode ) /= 'overlap' )                      &
    THEN
       message_string = 'illegal nesting datatransfer mode: '                  &
                        // TRIM( nesting_datatransfer_mode )
       CALL message( 'pmci_init', 'PA0418', 3, 2, 0, 6, 0 )
    ENDIF
!
!-- Set the general steering switch which tells PALM that its a nested run
    nested_run = .TRUE.
!
!-- Get some variables required by the pmc-interface (and in some cases in the
!-- PALM code out of the pmci) out of the pmc-core
    CALL pmc_get_model_info( comm_world_nesting = comm_world_nesting,          &
                             cpl_id = cpl_id, cpl_parent_id = cpl_parent_id,   &
                             cpl_name = cpl_name, npe_total = cpl_npe_total,   &
                             lower_left_x = lower_left_coord_x,                &
                             lower_left_y = lower_left_coord_y )
!
!-- Set the steering switch which tells the models that they are nested (of
!-- course the root domain (cpl_id = 1) is not nested)
    IF ( cpl_id >= 2 )  THEN
       child_domain = .TRUE.
       WRITE( coupling_char, '(A2,I2.2)') '_N', cpl_id
    ENDIF

!
!-- Message that communicators for nesting are initialized.
!-- Attention: myid has been set at the end of pmc_init_model in order to
!-- guarantee that only PE0 of the root domain does the output.
    CALL location_message( 'finished', .TRUE. )
!
!-- Reset myid to its default value
    myid = 0
#else
!
!-- Nesting cannot be used in serial mode. cpl_id is set to root domain (1)
!-- because no location messages would be generated otherwise.
!-- world_comm is given a dummy value to avoid compiler warnings (INTENT(OUT)
!-- should get an explicit value)
    cpl_id     = 1
    nested_run = .FALSE.
    world_comm = 1
#endif

 END SUBROUTINE pmci_init



 SUBROUTINE pmci_modelconfiguration

    IMPLICIT NONE

    INTEGER(iwp) ::  ncpl   !<  number of nest domains

#if defined( __parallel )
    CALL location_message( 'setup the nested model configuration', .FALSE. )
    CALL cpu_log( log_point_s(79), 'pmci_model_config', 'start' )
!
!-- Compute absolute coordinates for all models
    CALL pmci_setup_coordinates
!
!-- Determine the number of coupled arrays
    CALL pmci_num_arrays
!
!-- Initialize the child (must be called before pmc_setup_parent)
    CALL pmci_setup_child
!
!-- Initialize PMC parent
    CALL pmci_setup_parent
!
!-- Check for mismatches between settings of master and child variables
!-- (e.g., all children have to follow the end_time settings of the root master)
    CALL pmci_check_setting_mismatches
!
!-- Set flag file for combine_plot_fields for precessing the nest output data
    OPEN( 90, FILE='3DNESTING', FORM='FORMATTED' )
    CALL pmc_get_model_info( ncpl = ncpl )
    WRITE( 90, '(I2)' )  ncpl
    CLOSE( 90 )

    CALL cpu_log( log_point_s(79), 'pmci_model_config', 'stop' )
    CALL location_message( 'finished', .TRUE. )
#endif

 END SUBROUTINE pmci_modelconfiguration



 SUBROUTINE pmci_setup_parent

#if defined( __parallel )
    IMPLICIT NONE

    CHARACTER(LEN=32) ::  myname
    
    INTEGER(iwp) ::  child_id           !<
    INTEGER(iwp) ::  ierr               !<
    INTEGER(iwp) ::  k                  !<
    INTEGER(iwp) ::  m                  !<
    INTEGER(iwp) ::  mid                !<
    INTEGER(iwp) ::  mm                 !<
    INTEGER(iwp) ::  n = 1              !< Running index for chemical species
    INTEGER(iwp) ::  nest_overlap       !<
    INTEGER(iwp) ::  nomatch            !<
    INTEGER(iwp) ::  nx_cl              !<
    INTEGER(iwp) ::  ny_cl              !<
    INTEGER(iwp) ::  nz_cl              !<
    INTEGER(iwp), DIMENSION(3) ::  val  !< Array for receiving the child-grid dimensions
    REAL(wp), DIMENSION(:), ALLOCATABLE ::  ch_xl   !<
    REAL(wp), DIMENSION(:), ALLOCATABLE ::  ch_xr   !<    
    REAL(wp), DIMENSION(:), ALLOCATABLE ::  ch_ys   !<
    REAL(wp), DIMENSION(:), ALLOCATABLE ::  ch_yn   !<
    REAL(wp) ::  cl_height        !< 
    REAL(wp) ::  dx_cl            !<
    REAL(wp) ::  dy_cl            !<
    REAL(wp) ::  dz_cl            !<
    REAL(wp) ::  left_limit       !<
    REAL(wp) ::  north_limit      !<
    REAL(wp) ::  right_limit      !<
    REAL(wp) ::  south_limit      !<
    REAL(wp) ::  xez              !<
    REAL(wp) ::  yez              !<
    REAL(wp), DIMENSION(5) ::  fval                      !< Array for receiving the child-grid spacings etc 
    REAL(wp), DIMENSION(:), ALLOCATABLE ::  cl_coord_x   !<
    REAL(wp), DIMENSION(:), ALLOCATABLE ::  cl_coord_y   !<

!
!   Initialize the pmc parent
    CALL pmc_parentinit
!
!-- Corners of all children of the present parent
    IF ( ( SIZE( pmc_parent_for_child ) - 1 > 0 ) .AND. myid == 0 )  THEN 
       ALLOCATE( ch_xl(1:SIZE( pmc_parent_for_child ) - 1) )
       ALLOCATE( ch_xr(1:SIZE( pmc_parent_for_child ) - 1) )
       ALLOCATE( ch_ys(1:SIZE( pmc_parent_for_child ) - 1) )
       ALLOCATE( ch_yn(1:SIZE( pmc_parent_for_child ) - 1) )
    ENDIF
    IF ( ( SIZE( pmc_parent_for_child ) - 1 > 0 ) )  THEN
       ALLOCATE( childgrid(1:SIZE( pmc_parent_for_child ) - 1) )
    ENDIF
!
!-- Get coordinates from all children
    DO  m = 1, SIZE( pmc_parent_for_child ) - 1

       child_id = pmc_parent_for_child(m)

       IF ( myid == 0 )  THEN

          CALL pmc_recv_from_child( child_id, val,  SIZE(val),  0, 123, ierr )
          CALL pmc_recv_from_child( child_id, fval, SIZE(fval), 0, 124, ierr )
         
          nx_cl     = val(1)
          ny_cl     = val(2)
          dx_cl     = fval(3)
          dy_cl     = fval(4)
          dz_cl     = fval(5)
          cl_height = fval(1)

          nz_cl = nz
!
!--       Find the highest nest level in the parent grid for the reduced z
!--       transfer
          DO  k = 1, nz                 
!AH  Let's try to make the parent-grid arrays higher by one parent dz 
!AH             IF ( zw(k) > fval(1) )  THEN
             IF ( zw(k) > fval(1)+dz(1) )  THEN
                nz_cl = k
                EXIT
             ENDIF
          ENDDO

!AH  Let's make the parent-grid arrays higher by one parent dz 
!AH          zmax_coarse = fval(1:2)
!AH          cl_height   = fval(1)
          zmax_coarse(1) = fval(1) + dz(1)
          zmax_coarse(2) = fval(2) + dz(1)
          cl_height   = fval(1) + dz(1)
!AH

!    
!--       Get absolute coordinates from the child
          ALLOCATE( cl_coord_x(-nbgp:nx_cl+nbgp) )
          ALLOCATE( cl_coord_y(-nbgp:ny_cl+nbgp) )
         
          CALL pmc_recv_from_child( child_id, cl_coord_x, SIZE( cl_coord_x ),  &
               0, 11, ierr )
          CALL pmc_recv_from_child( child_id, cl_coord_y, SIZE( cl_coord_y ),  &
               0, 12, ierr )
         
          parent_grid_info_real(1) = lower_left_coord_x
          parent_grid_info_real(2) = lower_left_coord_y
          parent_grid_info_real(3) = dx
          parent_grid_info_real(4) = dy
          parent_grid_info_real(5) = lower_left_coord_x + ( nx + 1 ) * dx
          parent_grid_info_real(6) = lower_left_coord_y + ( ny + 1 ) * dy
          parent_grid_info_real(7) = dz(1)

          parent_grid_info_int(1)  = nx
          parent_grid_info_int(2)  = ny
          parent_grid_info_int(3)  = nz_cl
!
!--       Check that the child domain matches parent domain. 
          nomatch = 0
          IF ( nesting_mode == 'vertical' )  THEN
             right_limit = parent_grid_info_real(5)
             north_limit = parent_grid_info_real(6)
             IF ( ( cl_coord_x(nx_cl+1) /= right_limit ) .OR.                  &
                  ( cl_coord_y(ny_cl+1) /= north_limit ) )  THEN
                nomatch = 1
             ENDIF
          ELSE       
!
!--       Check that the child domain is completely inside the parent domain. 
             xez = ( nbgp + 1 ) * dx 
             yez = ( nbgp + 1 ) * dy 
             left_limit  = lower_left_coord_x + xez
             right_limit = parent_grid_info_real(5) - xez
             south_limit = lower_left_coord_y + yez
             north_limit = parent_grid_info_real(6) - yez
             IF ( ( cl_coord_x(0) < left_limit )        .OR.                   &
                  ( cl_coord_x(nx_cl+1) > right_limit ) .OR.                   &
                  ( cl_coord_y(0) < south_limit )       .OR.                   &
                  ( cl_coord_y(ny_cl+1) > north_limit ) )  THEN
                nomatch = 1
             ENDIF
          ENDIF
!             
!--       Child domain must be lower than the parent domain such
!--       that the top ghost layer of the child grid does not exceed 
!--       the parent domain top boundary.
          IF ( cl_height > zw(nz) ) THEN
             nomatch = 1
          ENDIF
!
!--       Check that parallel nest domains, if any, do not overlap.
          nest_overlap = 0
          IF ( SIZE( pmc_parent_for_child ) - 1 > 0 )  THEN
             ch_xl(m) = cl_coord_x(-nbgp)
             ch_xr(m) = cl_coord_x(nx_cl+nbgp)
             ch_ys(m) = cl_coord_y(-nbgp)
             ch_yn(m) = cl_coord_y(ny_cl+nbgp)

             IF ( m > 1 )  THEN
                DO mm = 1, m - 1
                   mid = pmc_parent_for_child(mm)
!
!--                Check only different nest levels
                   IF (m_couplers(child_id)%parent_id /= m_couplers(mid)%parent_id)  THEN
                      IF ( ( ch_xl(m) < ch_xr(mm) .OR.                         &
                             ch_xr(m) > ch_xl(mm) )  .AND.                     &
                           ( ch_ys(m) < ch_yn(mm) .OR.                         &
                             ch_yn(m) > ch_ys(mm) ) )  THEN
                         nest_overlap = 1
                      ENDIF
                   ENDIF
                ENDDO
             ENDIF
          ENDIF

          CALL set_child_edge_coords

          DEALLOCATE( cl_coord_x )
          DEALLOCATE( cl_coord_y )
!
!--       Send information about operating mode (LES or RANS) to child. This will be 
!--       used to control TKE nesting and setting boundary conditions properly.
          CALL pmc_send_to_child( child_id, rans_mode, 1, 0, 19, ierr )  
!
!--       Send coarse grid information to child
          CALL pmc_send_to_child( child_id, parent_grid_info_real,             &
                                   SIZE( parent_grid_info_real ), 0, 21,       &
                                   ierr )
          CALL pmc_send_to_child( child_id, parent_grid_info_int,  3, 0,       &
                                   22, ierr )
!
!--       Send local grid to child
          CALL pmc_send_to_child( child_id, coord_x, nx+1+2*nbgp, 0, 24,       &
                                   ierr )
          CALL pmc_send_to_child( child_id, coord_y, ny+1+2*nbgp, 0, 25,       &
                                   ierr )
!
!--       Also send the dzu-, dzw-, zu- and zw-arrays here
          CALL pmc_send_to_child( child_id, dzu, nz_cl+1, 0, 26, ierr )
          CALL pmc_send_to_child( child_id, dzw, nz_cl+1, 0, 27, ierr )
          CALL pmc_send_to_child( child_id, zu,  nz_cl+2, 0, 28, ierr )
          CALL pmc_send_to_child( child_id, zw,  nz_cl+2, 0, 29, ierr )

       ENDIF

       CALL MPI_BCAST( nomatch, 1, MPI_INTEGER, 0, comm2d, ierr )
       IF ( nomatch /= 0 )  THEN
          WRITE ( message_string, * )  'nested child domain does ',            &
                                       'not fit into its parent domain'
          CALL message( 'pmci_setup_parent', 'PA0425', 3, 2, 0, 6, 0 )
       ENDIF
  
       CALL MPI_BCAST( nest_overlap, 1, MPI_INTEGER, 0, comm2d, ierr )
       IF ( nest_overlap /= 0  .AND.  nesting_mode /= 'vertical' )  THEN
          WRITE ( message_string, * )  'nested parallel child domains overlap'
          CALL message( 'pmci_setup_parent', 'PA0426', 3, 2, 0, 6, 0 )
       ENDIF
      
       CALL MPI_BCAST( nz_cl, 1, MPI_INTEGER, 0, comm2d, ierr )

       CALL MPI_BCAST( childgrid(m), STORAGE_SIZE(childgrid(1))/8, MPI_BYTE, 0, comm2d, ierr )
!
!--    TO_DO: Klaus: please give a comment what is done here
       CALL pmci_create_index_list
!
!--    Include couple arrays into parent content
!--    The adresses of the PALM 2D or 3D array (here server coarse grid) which are candidates
!--    for coupling are stored once into the pmc context. While data transfer, the array do not
!--    have to be specified again
       CALL pmc_s_clear_next_array_list
       DO  WHILE ( pmc_s_getnextarray( child_id, myname ) )
          IF ( INDEX( TRIM( myname ), 'chem_' ) /= 0 )  THEN             
             CALL pmci_set_array_pointer( myname, child_id = child_id,         &
                                          nz_cl = nz_cl, n = n )
             n = n + 1
          ELSE
             CALL pmci_set_array_pointer( myname, child_id = child_id,         &
                                          nz_cl = nz_cl )
          ENDIF
       ENDDO

       CALL pmc_s_setind_and_allocmem( child_id )
    ENDDO

    IF ( ( SIZE( pmc_parent_for_child ) - 1 > 0 ) .AND. myid == 0 )  THEN 
       DEALLOCATE( ch_xl )
       DEALLOCATE( ch_xr )
       DEALLOCATE( ch_ys )
       DEALLOCATE( ch_yn )
    ENDIF

 CONTAINS


    SUBROUTINE pmci_create_index_list

       IMPLICIT NONE

       INTEGER(iwp) ::  i                  !<
       INTEGER(iwp) ::  ic                 !<
       INTEGER(iwp) ::  ierr               !<
       INTEGER(iwp) ::  j                  !<
       INTEGER(iwp) ::  k                  !<
       INTEGER(iwp) ::  npx                !<
       INTEGER(iwp) ::  npy                !<
       INTEGER(iwp) ::  nrx                !<
       INTEGER(iwp) ::  nry                !<
       INTEGER(iwp) ::  px                 !<
       INTEGER(iwp) ::  py                 !<
       INTEGER(iwp) ::  parent_pe          !<

       INTEGER(iwp), DIMENSION(2) ::  scoord             !<
       INTEGER(iwp), DIMENSION(2) ::  size_of_array      !<

       INTEGER(iwp), DIMENSION(:,:), ALLOCATABLE  ::  coarse_bound_all   !<
       INTEGER(iwp), DIMENSION(:,:), ALLOCATABLE  ::  index_list         !<

       IF ( myid == 0 )  THEN
!          
!--       TO_DO: Klaus: give more specific comment what size_of_array stands for
          CALL pmc_recv_from_child( child_id, size_of_array, 2, 0, 40, ierr )
          ALLOCATE( coarse_bound_all(size_of_array(1),size_of_array(2)) )
          CALL pmc_recv_from_child( child_id, coarse_bound_all,                &
                                    SIZE( coarse_bound_all ), 0, 41, ierr )
!
!--       Compute size of index_list.
          ic = 0         
          DO  k = 1, size_of_array(2)           ! Replace k by some other letter
             ic = ic + ( coarse_bound_all(4,k) - coarse_bound_all(3,k) + 1 ) * &
                       ( coarse_bound_all(2,k) - coarse_bound_all(1,k) + 1 )
          ENDDO

          ALLOCATE( index_list(6,ic) )

          CALL MPI_COMM_SIZE( comm1dx, npx, ierr )
          CALL MPI_COMM_SIZE( comm1dy, npy, ierr )
!
!--       Nrx is the same for all PEs and so is nry, thus there is no need to compute
!--       them separately for each PE.
          nrx = nxr - nxl + 1
          nry = nyn - nys + 1
          ic  = 0
!
!--       Loop over all children PEs
          DO  k = 1, size_of_array(2)           ! Replace k by some other letter
!
!--          Area along y required by actual child PE
             DO  j = coarse_bound_all(3,k), coarse_bound_all(4,k)  !: j = jcs, jcn of PE# k 
!
!--             Area along x required by actual child PE
                DO  i = coarse_bound_all(1,k), coarse_bound_all(2,k)  !: i = icl, icr of PE# k 

                   px = i / nrx
                   py = j / nry
                   scoord(1) = px
                   scoord(2) = py
                   CALL MPI_CART_RANK( comm2d, scoord, parent_pe, ierr )
                  
                   ic = ic + 1
!
!--                First index in parent array
                   index_list(1,ic) = i - ( px * nrx ) + 1 + nbgp
!
!--                Second index in parent array
                   index_list(2,ic) = j - ( py * nry ) + 1 + nbgp
!
!--                x index of child coarse grid
                   index_list(3,ic) = i - coarse_bound_all(1,k) + 1
!
!--                y index of child coarse grid
                   index_list(4,ic) = j - coarse_bound_all(3,k) + 1
!
!--                PE number of child
                   index_list(5,ic) = k - 1
!
!--                PE number of parent
                   index_list(6,ic) = parent_pe

                ENDDO
             ENDDO
          ENDDO
!
!--       TO_DO: Klaus: comment what is done here
          CALL pmc_s_set_2d_index_list( child_id, index_list(:,1:ic) )

       ELSE
!
!--       TO_DO: Klaus: comment why this dummy allocation is required
          ALLOCATE( index_list(6,1) )
          CALL pmc_s_set_2d_index_list( child_id, index_list )
       ENDIF

       DEALLOCATE(index_list)

     END SUBROUTINE pmci_create_index_list



     SUBROUTINE set_child_edge_coords
        IMPLICIT  NONE

        INTEGER(iwp) :: nbgp_lpm = 1

        nbgp_lpm = min(nbgp_lpm, nbgp)

        childgrid(m)%nx = nx_cl
        childgrid(m)%ny = ny_cl
        childgrid(m)%nz = nz_cl
        childgrid(m)%dx = dx_cl
        childgrid(m)%dy = dy_cl
        childgrid(m)%dz = dz_cl

        childgrid(m)%lx_coord   = cl_coord_x(0)
        childgrid(m)%lx_coord_b = cl_coord_x(-nbgp_lpm)
        childgrid(m)%rx_coord   = cl_coord_x(nx_cl)+dx_cl
        childgrid(m)%rx_coord_b = cl_coord_x(nx_cl+nbgp_lpm)+dx_cl
        childgrid(m)%sy_coord   = cl_coord_y(0)
        childgrid(m)%sy_coord_b = cl_coord_y(-nbgp_lpm)
        childgrid(m)%ny_coord   = cl_coord_y(ny_cl)+dy_cl
        childgrid(m)%ny_coord_b = cl_coord_y(ny_cl+nbgp_lpm)+dy_cl
        childgrid(m)%uz_coord   = zmax_coarse(2)
        childgrid(m)%uz_coord_b = zmax_coarse(1)

     END SUBROUTINE set_child_edge_coords

#endif
 END SUBROUTINE pmci_setup_parent



 SUBROUTINE pmci_setup_child

#if defined( __parallel )
    IMPLICIT NONE

    CHARACTER(LEN=da_namelen) ::  myname     !< 
    INTEGER(iwp) ::  ierr       !< MPI error code
    INTEGER(iwp) ::  icl        !< Left index limit for children's parent-grid arrays
    INTEGER(iwp) ::  icla       !< Left index limit for allocation of index-mapping and other auxiliary arrays
    INTEGER(iwp) ::  iclw       !< Left index limit for children's parent-grid work arrays
    INTEGER(iwp) ::  icr        !< Left index limit for children's parent-grid arrays
    INTEGER(iwp) ::  icra       !< Right index limit for allocation of index-mapping and other auxiliary arrays
    INTEGER(iwp) ::  icrw       !< Right index limit for children's parent-grid work arrays
    INTEGER(iwp) ::  jcn        !< North index limit for children's parent-grid arrays
    INTEGER(iwp) ::  jcna       !< North index limit for allocation of index-mapping and other auxiliary arrays
    INTEGER(iwp) ::  jcnw       !< North index limit for children's parent-grid work arrays
    INTEGER(iwp) ::  jcs        !< South index limit for children's parent-grid arrays
    INTEGER(iwp) ::  jcsa       !< South index limit for allocation of index-mapping and other auxiliary arrays
    INTEGER(iwp) ::  jcsw       !< South index limit for children's parent-grid work arrays
    INTEGER(iwp) ::  n          !< Running index for number of chemical species
    INTEGER(iwp), DIMENSION(3) ::  val  !< Array for sending the child-grid dimensions to parent 
    REAL(wp) ::  xcs        !<
    REAL(wp) ::  xce        !<
    REAL(wp) ::  ycs        !<
    REAL(wp) ::  yce        !<

    REAL(wp), DIMENSION(5) ::  fval     !< Array for sending the child-grid spacings etc to parent 
                                             
!
!-- Child setup
!-- Root model does not have a parent and is not a child, therefore no child setup on root model
    IF ( .NOT. pmc_is_rootmodel() )  THEN

       CALL pmc_childinit
!
!--    The arrays, which actually will be exchanged between child and parent
!--    are defined Here AND ONLY HERE.
!--    If a variable is removed, it only has to be removed from here.
!--    Please check, if the arrays are in the list of POSSIBLE exchange arrays
!--    in subroutines:
!--    pmci_set_array_pointer (for parent arrays)
!--    pmci_create_child_arrays (for child arrays)
       CALL pmc_set_dataarray_name( 'coarse', 'u'  ,'fine', 'u',  ierr )
       CALL pmc_set_dataarray_name( 'coarse', 'v'  ,'fine', 'v',  ierr )
       CALL pmc_set_dataarray_name( 'coarse', 'w'  ,'fine', 'w',  ierr )
!
!--    Set data array name for TKE. Please note, nesting of TKE is actually
!--    only done if both parent and child are in LES or in RANS mode. Due to 
!--    design of model coupler, however, data array names must be already 
!--    available at this point.
       CALL pmc_set_dataarray_name( 'coarse', 'e'  ,'fine', 'e',  ierr )
!
!--    Nesting of dissipation rate only if both parent and child are in RANS
!--    mode and TKE-epsilo closure is applied. Please so also comment for TKE
!--    above.
       CALL pmc_set_dataarray_name( 'coarse', 'diss'  ,'fine', 'diss',  ierr )

       IF ( .NOT. neutral )  THEN
          CALL pmc_set_dataarray_name( 'coarse', 'pt' ,'fine', 'pt', ierr )
       ENDIF

       IF ( humidity )  THEN

          CALL pmc_set_dataarray_name( 'coarse', 'q'  ,'fine', 'q',  ierr )

          IF ( bulk_cloud_model  .AND.  microphysics_morrison )  THEN
            CALL pmc_set_dataarray_name( 'coarse', 'qc'  ,'fine', 'qc',  ierr )  
            CALL pmc_set_dataarray_name( 'coarse', 'nc'  ,'fine', 'nc',  ierr ) 
          ENDIF

          IF ( bulk_cloud_model  .AND.  microphysics_seifert )  THEN
             CALL pmc_set_dataarray_name( 'coarse', 'qr'  ,'fine', 'qr',  ierr )
             CALL pmc_set_dataarray_name( 'coarse', 'nr'  ,'fine', 'nr',  ierr ) 
          ENDIF
     
       ENDIF

       IF ( passive_scalar )  THEN
          CALL pmc_set_dataarray_name( 'coarse', 's'  ,'fine', 's',  ierr )
       ENDIF

       IF( particle_advection )  THEN
          CALL pmc_set_dataarray_name( 'coarse', 'nr_part'  ,'fine',           &
               'nr_part',  ierr )
          CALL pmc_set_dataarray_name( 'coarse', 'part_adr'  ,'fine',          &
               'part_adr',  ierr )
       ENDIF
       
       IF ( air_chemistry  .AND.  nest_chemistry )  THEN
          DO  n = 1, nspec
             CALL pmc_set_dataarray_name( 'coarse',                            &
                                          'chem_' //                           &
                                          TRIM( chem_species(n)%name ),        &
                                         'fine',                               &
                                          'chem_' //                           &
                                          TRIM( chem_species(n)%name ),        &
                                          ierr )
          ENDDO 
       ENDIF

       CALL pmc_set_dataarray_name( lastentry = .TRUE. )
!
!--    Send grid to parent
       val(1)  = nx
       val(2)  = ny
       val(3)  = nz
       fval(1) = zw(nzt+1)
       fval(2) = zw(nzt)
       fval(3) = dx
       fval(4) = dy
       fval(5) = dz(1)

       IF ( myid == 0 )  THEN

          CALL pmc_send_to_parent( val, SIZE( val ), 0, 123, ierr )
          CALL pmc_send_to_parent( fval, SIZE( fval ), 0, 124, ierr )
          CALL pmc_send_to_parent( coord_x, nx + 1 + 2 * nbgp, 0, 11, ierr )
          CALL pmc_send_to_parent( coord_y, ny + 1 + 2 * nbgp, 0, 12, ierr )

          CALL pmc_recv_from_parent( rans_mode_parent, 1, 0, 19, ierr )
!
!--       Receive Coarse grid information.
          CALL pmc_recv_from_parent( parent_grid_info_real,                    &
                                     SIZE(parent_grid_info_real), 0, 21, ierr )
          CALL pmc_recv_from_parent( parent_grid_info_int,  3, 0, 22, ierr )

       ENDIF

       CALL MPI_BCAST( parent_grid_info_real, SIZE(parent_grid_info_real),     &
                       MPI_REAL, 0, comm2d, ierr )
       CALL MPI_BCAST( parent_grid_info_int, 3, MPI_INTEGER, 0, comm2d, ierr )

       cg%dx = parent_grid_info_real(3)
       cg%dy = parent_grid_info_real(4)
       cg%dz = parent_grid_info_real(7)
       cg%nx = parent_grid_info_int(1)
       cg%ny = parent_grid_info_int(2)
       cg%nz = parent_grid_info_int(3)
!
!--    Get parent coordinates on coarse grid
       ALLOCATE( cg%coord_x(-nbgp:cg%nx+nbgp) )
       ALLOCATE( cg%coord_y(-nbgp:cg%ny+nbgp) )
       ALLOCATE( cg%dzu(1:cg%nz+1) )
       ALLOCATE( cg%dzw(1:cg%nz+1) )
       ALLOCATE( cg%zu(0:cg%nz+1) )
       ALLOCATE( cg%zw(0:cg%nz+1) )
!
!--    Get coarse grid coordinates and values of the z-direction from the parent
       IF ( myid == 0)  THEN
          CALL pmc_recv_from_parent( cg%coord_x, cg%nx+1+2*nbgp, 0, 24, ierr )
          CALL pmc_recv_from_parent( cg%coord_y, cg%ny+1+2*nbgp, 0, 25, ierr )
          CALL pmc_recv_from_parent( cg%dzu, cg%nz+1, 0, 26, ierr )
          CALL pmc_recv_from_parent( cg%dzw, cg%nz+1, 0, 27, ierr )
          CALL pmc_recv_from_parent( cg%zu, cg%nz+2, 0, 28, ierr )
          CALL pmc_recv_from_parent( cg%zw, cg%nz+2, 0, 29, ierr )
       ENDIF
!
!--    Broadcast this information
       CALL MPI_BCAST( cg%coord_x, cg%nx+1+2*nbgp, MPI_REAL, 0, comm2d, ierr )
       CALL MPI_BCAST( cg%coord_y, cg%ny+1+2*nbgp, MPI_REAL, 0, comm2d, ierr )
       CALL MPI_BCAST( cg%dzu, cg%nz+1, MPI_REAL, 0, comm2d, ierr )
       CALL MPI_BCAST( cg%dzw, cg%nz+1, MPI_REAL, 0, comm2d, ierr )
       CALL MPI_BCAST( cg%zu, cg%nz+2,  MPI_REAL, 0, comm2d, ierr )
       CALL MPI_BCAST( cg%zw, cg%nz+2,  MPI_REAL, 0, comm2d, ierr )
       CALL MPI_BCAST( rans_mode_parent, 1, MPI_LOGICAL, 0, comm2d, ierr )
!
!--    Find the index bounds for the nest domain in the coarse-grid index space
       CALL pmci_map_fine_to_coarse_grid
!
!--    TO_DO: Klaus give a comment what is happening here
       CALL pmc_c_get_2d_index_list
!
!--    Include couple arrays into child content
!--    TO_DO: Klaus: better explain the above comment (what is child content?)
       CALL  pmc_c_clear_next_array_list

       n = 1
       DO  WHILE ( pmc_c_getnextarray( myname ) )
!--       Note that cg%nz is not the original nz of parent, but the highest
!--       parent-grid level needed for nesting.
!--       Please note, in case of chemical species an additional parameter
!--       need to be passed, which is required to set the pointer correctly
!--       to the chemical-species data structure. Hence, first check if current
!--       variable is a chemical species. If so, pass index id of respective
!--       species and increment this subsequently.
          IF ( INDEX( TRIM( myname ), 'chem_' ) /= 0 )  THEN             
             CALL pmci_create_child_arrays ( myname, icl, icr, jcs, jcn, cg%nz, n )
             n = n + 1
          ELSE
             CALL pmci_create_child_arrays ( myname, icl, icr, jcs, jcn, cg%nz )
          ENDIF
       ENDDO
       CALL pmc_c_setind_and_allocmem
!
!--    Precompute the index-mapping arrays
       CALL pmci_define_index_mapping
!
!--    Check that the child and parent grid lines do match 
       CALL pmci_check_grid_matching 

    ENDIF

 CONTAINS


    SUBROUTINE pmci_map_fine_to_coarse_grid
!
!--    Determine index bounds of interpolation/anterpolation area in the coarse
!--    grid index space
       IMPLICIT NONE

       INTEGER(iwp), DIMENSION(5,numprocs) ::  coarse_bound_all     !< Transfer array for parent-grid index bounds
       INTEGER(iwp), DIMENSION(4)          ::  parent_bound_global  !< Transfer array for global parent-grid index bounds
       INTEGER(iwp), DIMENSION(2)          ::  size_of_array        !<
       INTEGER(iwp) :: i        !< 
       INTEGER(iwp) :: iauxl    !<
       INTEGER(iwp) :: iauxr    !<
       INTEGER(iwp) :: ijaux    !< 
       INTEGER(iwp) :: j        !<
       INTEGER(iwp) :: jauxs    !<
       INTEGER(iwp) :: jauxn    !< 
       REAL(wp) ::  xexl        !< Parent-grid array exceedance behind the left edge of the child PE subdomain
       REAL(wp) ::  xexr        !< Parent-grid array exceedance behind the right edge of the child PE subdomain 
       REAL(wp) ::  yexs        !< Parent-grid array exceedance behind the south edge of the child PE subdomain
       REAL(wp) ::  yexn        !< Parent-grid array exceedance behind the north edge of the child PE subdomain

!
!--    Determine the anterpolation index limits. If at least half of the 
!--    parent-grid cell is within the current child sub-domain, then it 
!--    is included in the current sub-domain's anterpolation domain. 
!--    Else the parent-grid cell is included in the neighbouring subdomain's 
!--    anterpolation domain, or not included at all if we are at the outer 
!--    edge of the child domain.
!
!--    Left
       IF  ( bc_dirichlet_l )  THEN
          xexl  = 2 * cg%dx
          iauxl = 0
       ELSE
          xexl  = 0.0_wp
          iauxl = 1
       ENDIF
       xcs     = coord_x(nxl) - xexl
       DO  i = 0, cg%nx
          IF ( cg%coord_x(i) + 0.5_wp * cg%dx >= xcs )  THEN
             icl = MAX( 0, i )
             EXIT
          ENDIF
       ENDDO
!
!--    Right
       IF  ( bc_dirichlet_r )  THEN
          xexr  = 2 * cg%dx
          iauxr = 0  
       ELSE
          xexr  = 0.0_wp
          iauxr = 1  
       ENDIF
       xce  = coord_x(nxr+1) + xexr
       DO  i = cg%nx, 0 , -1
          IF ( cg%coord_x(i) + 0.5_wp * cg%dx <= xce )  THEN
             icr = MIN( cg%nx, MAX( icl, i ) )
             EXIT
          ENDIF
       ENDDO
!
!--    South
       IF  ( bc_dirichlet_s )  THEN
          yexs  = 2 * cg%dy
          jauxs = 0  
       ELSE
          yexs  = 0.0_wp
          jauxs = 1  
       ENDIF
       ycs  = coord_y(nys) - yexs
       DO  j = 0, cg%ny
          IF ( cg%coord_y(j) + 0.5_wp * cg%dy >= ycs )  THEN
             jcs = MAX( 0, j )
             EXIT
          ENDIF
       ENDDO
!
!--    North
       IF  ( bc_dirichlet_n )  THEN
          yexn  = 2 * cg%dy
          jauxn = 0
       ELSE
          yexn  = 0.0_wp
          jauxn = 1
       ENDIF
       yce  = coord_y(nyn+1) + yexn
       DO  j = cg%ny, 0 , -1
          IF ( cg%coord_y(j) + 0.5_wp * cg%dy <= yce )  THEN
             jcn = MIN( cg%ny, MAX( jcs, j ) )
             EXIT
          ENDIF
       ENDDO
!
!--    Make sure that the indexing is contiguous (no gaps, no overlaps) 
#if defined( __parallel )
       IF ( nxl == 0 )  THEN
          CALL MPI_SEND( icr, 1, MPI_INTEGER, pright, 717, comm2d, ierr )
       ELSE IF ( nxr == nx )  THEN
          CALL MPI_RECV( ijaux, 1, MPI_INTEGER, pleft, 717, comm2d, status, ierr )
          icl = ijaux + 1
       ELSE
          CALL MPI_SEND( icr, 1, MPI_INTEGER, pright, 717, comm2d, ierr )
          CALL MPI_RECV( ijaux, 1, MPI_INTEGER, pleft, 717, comm2d, status, ierr ) 
          icl = ijaux + 1
       ENDIF
       IF ( nys == 0 )  THEN
          CALL MPI_SEND( jcn, 1, MPI_INTEGER, pnorth, 719, comm2d, ierr )
       ELSE IF ( nyn == ny )  THEN
          CALL MPI_RECV( ijaux, 1, MPI_INTEGER, psouth, 719, comm2d, status, ierr )
          jcs = ijaux + 1
       ELSE
          CALL MPI_SEND( jcn, 1, MPI_INTEGER, pnorth, 719, comm2d, ierr )
          CALL MPI_RECV( ijaux, 1, MPI_INTEGER, psouth, 719, comm2d, status, ierr ) 
          jcs = ijaux + 1
       ENDIF
#endif       

       WRITE(9,"('Pmci_map_fine_to_coarse_grid. Parent-grid array bounds: ',4(i4,2x))") icl, icr, jcs, jcn
       FLUSH(9)

       coarse_bound(1) = icl
       coarse_bound(2) = icr
       coarse_bound(3) = jcs
       coarse_bound(4) = jcn
       coarse_bound(5) = myid
!
!--    The following index bounds are used for allocating index mapping and some other auxiliary arrays
       coarse_bound_aux(1) = icl - iauxl
       coarse_bound_aux(2) = icr + iauxr
       coarse_bound_aux(3) = jcs - jauxs
       coarse_bound_aux(4) = jcn + jauxn
!
!--    Note that MPI_Gather receives data from all processes in the rank order
!--    This fact is exploited in creating the index list in pmci_create_index_list
       CALL MPI_GATHER( coarse_bound, 5, MPI_INTEGER, coarse_bound_all, 5,     &
                        MPI_INTEGER, 0, comm2d, ierr )

       IF ( myid == 0 )  THEN
          size_of_array(1) = SIZE( coarse_bound_all, 1 )
          size_of_array(2) = SIZE( coarse_bound_all, 2 )
          CALL pmc_send_to_parent( size_of_array, 2, 0, 40, ierr )
          CALL pmc_send_to_parent( coarse_bound_all, SIZE( coarse_bound_all ), &
               0, 41, ierr )
!
!--       Determine the global parent-grid index bounds       
          parent_bound_global(1) = MINVAL( coarse_bound_all(1,:) )
          parent_bound_global(2) = MAXVAL( coarse_bound_all(2,:) )
          parent_bound_global(3) = MINVAL( coarse_bound_all(3,:) )
          parent_bound_global(4) = MAXVAL( coarse_bound_all(4,:) )
       ENDIF
!
!--    Broadcat the global parent-grid index bounds to all current child processes
       CALL MPI_BCAST( parent_bound_global, 4, MPI_INTEGER, 0, comm2d, ierr )
       iplg = parent_bound_global(1)
       iprg = parent_bound_global(2)
       jpsg = parent_bound_global(3)
       jpng = parent_bound_global(4)
       WRITE(9,"('Pmci_map_fine_to_coarse_grid. Global parent-grid index bounds iplg, iprg, jpsg, jpng: ',4(i4,2x))") iplg, iprg, jpsg, jpng
       FLUSH(9)
       
    END SUBROUTINE pmci_map_fine_to_coarse_grid

     
      
    SUBROUTINE pmci_define_index_mapping
!
!--    Precomputation of the mapping of the child- and parent-grid indices.

       IMPLICIT NONE

       INTEGER(iwp) ::  i         !< Child-grid index
       INTEGER(iwp) ::  ii        !< Parent-grid index
       INTEGER(iwp) ::  istart    !<
       INTEGER(iwp) ::  ir        !<
       INTEGER(iwp) ::  iw        !< Child-grid index limited to -1 <= iw <= nx+1
       INTEGER(iwp) ::  j         !< Child-grid index
       INTEGER(iwp) ::  jj        !< Parent-grid index
       INTEGER(iwp) ::  jstart    !<
       INTEGER(iwp) ::  jr        !<
       INTEGER(iwp) ::  jw        !< Child-grid index limited to -1 <= jw <= ny+1
       INTEGER(iwp) ::  k         !< Child-grid index
       INTEGER(iwp) ::  kk        !< Parent-grid index
       INTEGER(iwp) ::  kstart    !<
       INTEGER(iwp) ::  kw        !< Child-grid index limited to kw <= nzt+1
     
!
!--    Allocate child-grid work arrays for interpolation.
       igsr = NINT( cg%dx / dx, iwp )
       jgsr = NINT( cg%dy / dy, iwp )
       kgsr = NINT( cg%dzw(1) / dzw(1), iwp )
       WRITE(9,"('igsr, jgsr, kgsr: ',3(i3,2x))") igsr, jgsr, kgsr
       FLUSH(9)
!       
!--    Determine index bounds for the parent-grid work arrays for
!--    interpolation and allocate them.
       CALL pmci_allocate_workarrays
!       
!--    Define the MPI-datatypes for parent-grid work array 
!--    exchange between the PE-subdomains.
       CALL pmci_create_workarray_exchange_datatypes
!
!--    First determine kcto and kctw which refer to the uppermost 
!--    coarse-grid levels below the child top-boundary level.
       kk = 0
       DO  WHILE ( cg%zu(kk) <= zu(nzt) )
          kk = kk + 1
       ENDDO
       kcto = kk - 1

       kk = 0
       DO  WHILE ( cg%zw(kk) <= zw(nzt-1) )
          kk = kk + 1
       ENDDO
       kctw = kk - 1

       WRITE(9,"('kcto, kctw = ', 2(i3,2x))") kcto, kctw
       FLUSH(9)
       
       icla = coarse_bound_aux(1)
       icra = coarse_bound_aux(2)
       jcsa = coarse_bound_aux(3)
       jcna = coarse_bound_aux(4)
       ALLOCATE( iflu(icla:icra) )
       ALLOCATE( iflo(icla:icra) )
       ALLOCATE( ifuu(icla:icra) )
       ALLOCATE( ifuo(icla:icra) )
       ALLOCATE( jflv(jcsa:jcna) )
       ALLOCATE( jflo(jcsa:jcna) )
       ALLOCATE( jfuv(jcsa:jcna) )
       ALLOCATE( jfuo(jcsa:jcna) )       
       ALLOCATE( kflw(0:cg%nz+1) )
       ALLOCATE( kflo(0:cg%nz+1) )
       ALLOCATE( kfuw(0:cg%nz+1) )
       ALLOCATE( kfuo(0:cg%nz+1) )
       ALLOCATE( ijkfc_u(0:cg%nz+1,jcsa:jcna,icla:icra) )
       ALLOCATE( ijkfc_v(0:cg%nz+1,jcsa:jcna,icla:icra) )
       ALLOCATE( ijkfc_w(0:cg%nz+1,jcsa:jcna,icla:icra) )
       ALLOCATE( ijkfc_s(0:cg%nz+1,jcsa:jcna,icla:icra) )

       ijkfc_u = 0
       ijkfc_v = 0
       ijkfc_w = 0
       ijkfc_s = 0
!
!--    i-indices of u for each ii-index value
       istart = nxlg
       DO  ii = icla, icra
!
!--       The parent and child grid lines do always match in x, hence we 
!--       use only the local k,j-child-grid plane for the anterpolation.
          i = istart
          DO WHILE ( coord_x(i) < cg%coord_x(ii) .AND. i < nxrg )
             i = i + 1
          ENDDO
          iflu(ii) = MIN( MAX( i, nxlg ), nxrg )
          ifuu(ii) = iflu(ii)
          istart   = iflu(ii)
!
!--       Print out the index bounds for checking and debugging purposes
          WRITE(9,"('pmci_define_index_mapping, ii, iflu, ifuu: ', 3(i4,2x))")    &
               ii, iflu(ii), ifuu(ii)
          FLUSH(9)
       ENDDO
       WRITE(9,*)
!
!--    i-indices of others for each ii-index value
       istart = nxlg
       DO  ii = icla, icra
          i = istart
          DO  WHILE ( ( coord_x(i) + 0.5_wp * dx < cg%coord_x(ii) )  .AND.     &
                      ( i < nxrg ) )
             i  = i + 1
          ENDDO
          iflo(ii) = MIN( MAX( i, nxlg ), nxrg )
          ir = i
          DO  WHILE ( ( coord_x(ir) + 0.5_wp * dx <= cg%coord_x(ii) + cg%dx )  &
                      .AND.  ( i < nxrg+1 ) )
             i  = i + 1
             ir = MIN( i, nxrg )
          ENDDO
          ifuo(ii) = MIN( MAX( i-1, iflo(ii) ), nxrg )
          istart = iflo(ii)
!
!--       Print out the index bounds for checking and debugging purposes
          WRITE(9,"('pmci_define_index_mapping, ii, iflo, ifuo: ', 3(i4,2x))")    &
               ii, iflo(ii), ifuo(ii)
          FLUSH(9)
       ENDDO
       WRITE(9,*)
!
!--    j-indices of v for each jj-index value
       jstart = nysg
       DO  jj = jcsa, jcna
!
!--       The parent and child grid lines do always match in y, hence we 
!--       use only the local k,i-child-grid plane for the anterpolation.
          j = jstart
          DO WHILE ( coord_y(j) < cg%coord_y(jj) .AND. j < nyng )
             j = j + 1
          ENDDO
          jflv(jj) = MIN( MAX( j, nysg ), nyng )
          jfuv(jj) = jflv(jj)
          jstart   = jflv(jj)
!
!--       Print out the index bounds for checking and debugging purposes
          WRITE(9,"('pmci_define_index_mapping, jj, jflv, jfuv: ', 3(i4,2x))")    &
               jj, jflv(jj), jfuv(jj)
          FLUSH(9)
       ENDDO
       WRITE(9,*)
!
!--    j-indices of others for each jj-index value
       jstart = nysg
       DO  jj = jcsa, jcna
          j = jstart
          DO  WHILE ( ( coord_y(j) + 0.5_wp * dy < cg%coord_y(jj) )  .AND.     &
                      ( j < nyng ) )
             j  = j + 1
          ENDDO
          jflo(jj) = MIN( MAX( j, nysg ), nyng )
          jr = j
          DO  WHILE ( ( coord_y(jr) + 0.5_wp * dy <= cg%coord_y(jj) + cg%dy )  &
                      .AND.  ( j < nyng+1 ) )
             j  = j + 1
             jr = MIN( j, nyng )
          ENDDO
          jfuo(jj) = MIN( MAX( j-1, jflo(jj) ), nyng )
          jstart = jflo(jj)
!
!--       Print out the index bounds for checking and debugging purposes
          WRITE(9,"('pmci_define_index_mapping, jj, jflo, jfuo: ', 3(i4,2x))")    &
               jj, jflo(jj), jfuo(jj)
          FLUSH(9)
       ENDDO
       WRITE(9,*)
!
!--    k-indices of w for each kk-index value
!--    Note that anterpolation index limits are needed also for the top boundary 
!--    ghost cell level because they are used also in the interpolation.
       kstart  = 0
       kflw(0) = 0
       kfuw(0) = 0
       DO kk = 1, cg%nz+1
!
!--       The parent and child grid lines do always match in z, hence we 
!--       use only the local j,i-child-grid plane for the anterpolation.
          k = kstart
          DO WHILE ( ( zw(k) < cg%zw(kk) )  .AND.  ( k < nzt+1 ) )
             k = k + 1
          ENDDO
          kflw(kk) = MIN( MAX( k, 1 ), nzt + 1 )
          kfuw(kk) = kflw(kk)
          kstart   = kflw(kk)
!
!--       Print out the index bounds for checking and debugging purposes
          WRITE(9,"('pmci_define_index_mapping, kk, kflw, kfuw: ', 4(i4,2x), 2(e12.5,2x))") &
               kk, kflw(kk), kfuw(kk), nzt,  cg%zu(kk), cg%zw(kk)
          FLUSH(9)
       ENDDO
       WRITE(9,*)
!
!--    k-indices of others for each kk-index value
       kstart  = 0
       kflo(0) = 0
       kfuo(0) = 0
!
!--    Note that anterpolation index limits are needed also for the top boundary 
!--    ghost cell level because they are used also in the interpolation.
       DO  kk = 1, cg%nz+1
          k = kstart
          DO  WHILE ( ( zu(k) < cg%zw(kk-1) )  .AND.  ( k <= nzt ) )
             k = k + 1
          ENDDO
          kflo(kk) = MIN( MAX( k, 1 ), nzt + 1 )
          DO  WHILE ( ( zu(k) <= cg%zw(kk) )  .AND.  ( k <= nzt+1 ) )
             k = k + 1
             IF ( k > nzt + 1 ) EXIT  ! This EXIT is to prevent zu(k) from flowing over.
          ENDDO
          kfuo(kk) = MIN( MAX( k-1, kflo(kk) ), nzt + 1 )
          kstart = kflo(kk)
       ENDDO
!
!--    Set the k-index bounds separately for the parent-grid cells cg%nz and cg%nz+1       
!--    although they are not actually needed.
       kflo(cg%nz)   = nzt+1    
       kfuo(cg%nz)   = nzt+kgsr 
       kflo(cg%nz+1) = nzt+kgsr 
       kfuo(cg%nz+1) = nzt+kgsr 
!
!--    Print out the index bounds for checking and debugging purposes
       DO  kk = 1, cg%nz+1
          WRITE(9,"('pmci_define_index_mapping, kk, kflo, kfuo: ', 4(i4,2x), 2(e12.5,2x))") &
               kk, kflo(kk), kfuo(kk), nzt,  cg%zu(kk), cg%zw(kk)
          FLUSH(9)
       ENDDO
       WRITE(9,*)
!
!--    Precomputation of number of fine-grid nodes inside parent-grid cells.
!--    Note that ii, jj, and kk are parent-grid indices. 
!--    This information is needed in anterpolation and in reversibility 
!--    correction in interpolation. 
       DO  ii = icla, icra
          DO  jj = jcsa, jcna
             DO kk = 0, cg%nz+1
!
!--             u-component
                DO  i = iflu(ii), ifuu(ii)
                   iw = MAX( MIN( i, nx+1 ), -1 )
                   DO  j = jflo(jj), jfuo(jj)
                      jw = MAX( MIN( j, ny+1 ), -1 )
                      DO  k = kflo(kk), kfuo(kk)
                         kw = MIN( k, nzt+1 )                
                         ijkfc_u(kk,jj,ii) = ijkfc_u(kk,jj,ii)                  &
                              + MERGE( 1, 0, BTEST( wall_flags_0(kw,jw,iw), 1 ) )
                      ENDDO
                   ENDDO
                ENDDO
!
!--             v-component 
                DO  i = iflo(ii), ifuo(ii)
                   iw = MAX( MIN( i, nx+1 ), -1 )
                   DO  j = jflv(jj), jfuv(jj)
                      jw = MAX( MIN( j, ny+1 ), -1 )
                      DO  k = kflo(kk), kfuo(kk)
                         kw = MIN( k, nzt+1 )                                        
                         ijkfc_v(kk,jj,ii) = ijkfc_v(kk,jj,ii)                  &
                              + MERGE( 1, 0, BTEST( wall_flags_0(kw,jw,iw), 2 ) )
                      ENDDO
                   ENDDO
                ENDDO
!
!--             scalars
                DO  i = iflo(ii), ifuo(ii)
                   iw = MAX( MIN( i, nx+1 ), -1 )
                   DO  j = jflo(jj), jfuo(jj)
                      jw = MAX( MIN( j, ny+1 ), -1 )
                      DO  k = kflo(kk), kfuo(kk)
                         kw = MIN( k, nzt+1 )
                         ijkfc_s(kk,jj,ii) = ijkfc_s(kk,jj,ii)                  &
                              + MERGE( 1, 0, BTEST( wall_flags_0(kw,jw,iw), 0 ) )
                      ENDDO
                   ENDDO
                ENDDO
!
!--             w-component 
                DO  i = iflo(ii), ifuo(ii)
                   iw = MAX( MIN( i, nx+1 ), -1 )
                   DO  j = jflo(jj), jfuo(jj)
                      jw = MAX( MIN( j, ny+1 ), -1 )
                      DO  k = kflw(kk), kfuw(kk)
                         kw = MIN( k, nzt+1 )
                         ijkfc_w(kk,jj,ii) = ijkfc_w(kk,jj,ii) + MERGE( 1, 0,   &
                              BTEST( wall_flags_0(kw,jw,iw), 3 ) )
                      ENDDO
                   ENDDO
                ENDDO

             ENDDO  ! kk        
          ENDDO  ! jj
       ENDDO  ! ii

    END SUBROUTINE pmci_define_index_mapping
    


    SUBROUTINE pmci_allocate_workarrays
!
!--    Allocate parent-grid work-arrays for interpolation
       IMPLICIT NONE

!
!--    Determine and store the PE-subdomain dependent index bounds
       IF  ( bc_dirichlet_l )  THEN
          iclw = icl + 1
       ELSE
          iclw = icl - 1
       ENDIF

       IF  ( bc_dirichlet_r )  THEN
          icrw = icr - 1
       ELSE
          icrw = icr + 1
       ENDIF

       IF  ( bc_dirichlet_s )  THEN
          jcsw = jcs + 1
       ELSE
          jcsw = jcs - 1
       ENDIF

       IF  ( bc_dirichlet_n )  THEN
          jcnw = jcn - 1
       ELSE
          jcnw = jcn + 1
       ENDIF
    
       coarse_bound_w(1) = iclw
       coarse_bound_w(2) = icrw
       coarse_bound_w(3) = jcsw
       coarse_bound_w(4) = jcnw
!
!--    Left and right boundaries.
       ALLOCATE( workarrc_lr(0:cg%nz+1,jcsw:jcnw,0:2) )
!
!--    South and north boundaries.
       ALLOCATE( workarrc_sn(0:cg%nz+1,0:2,iclw:icrw) )
!
!--    Top boundary.
!AH       ALLOCATE( workarrc_t(0:2,jcsw:jcnw,iclw:icrw) )
       ALLOCATE( workarrc_t(-2:3,jcsw:jcnw,iclw:icrw) )

    END SUBROUTINE pmci_allocate_workarrays



    SUBROUTINE pmci_create_workarray_exchange_datatypes
!
!--    Define specific MPI types for workarrc-exhchange.
       IMPLICIT NONE

#if defined( __parallel )       
!
!--    For the left and right boundaries
       CALL MPI_TYPE_VECTOR( 3, cg%nz+2, (jcnw-jcsw+1)*(cg%nz+2), MPI_REAL,     &
            workarrc_lr_exchange_type, ierr )
       CALL MPI_TYPE_COMMIT( workarrc_lr_exchange_type, ierr )
!
!--    For the south and north boundaries
       CALL MPI_TYPE_VECTOR( 1, 3*(cg%nz+2), 3*(cg%nz+2), MPI_REAL,             &
            workarrc_sn_exchange_type, ierr )
       CALL MPI_TYPE_COMMIT( workarrc_sn_exchange_type, ierr )
!
!--    For the top-boundary x-slices
!AH       CALL MPI_TYPE_VECTOR( icrw-iclw+1, 3, 3*(jcnw-jcsw+1), MPI_REAL,         &
!AH            workarrc_t_exchange_type_x, ierr )
       CALL MPI_TYPE_VECTOR( icrw-iclw+1, 6, 6*(jcnw-jcsw+1), MPI_REAL,         &
            workarrc_t_exchange_type_x, ierr )
       CALL MPI_TYPE_COMMIT( workarrc_t_exchange_type_x, ierr )
!
!--    For the top-boundary y-slices
!AH       CALL MPI_TYPE_VECTOR( 1, 3*(jcnw-jcsw+1), 3*(jcnw-jcsw+1), MPI_REAL,     &
!AH            workarrc_t_exchange_type_y, ierr )
       CALL MPI_TYPE_VECTOR( 1, 6*(jcnw-jcsw+1), 6*(jcnw-jcsw+1), MPI_REAL,     &
            workarrc_t_exchange_type_y, ierr )
       CALL MPI_TYPE_COMMIT( workarrc_t_exchange_type_y, ierr )
#endif
       
    END SUBROUTINE pmci_create_workarray_exchange_datatypes



    SUBROUTINE pmci_check_grid_matching 
!
!--    Check that the grid lines of child and parent do match.
!--    Also check that the child subdomain width is not smaller than 
!--    the parent grid spacing in the respective direction. 
       IMPLICIT NONE
       REAL(wp), PARAMETER :: tolefac = 1.0E-6_wp      !< Relative tolerence for grid-line matching
       REAL(wp) :: pesdwx                              !< Child subdomain width in x-direction 
       REAL(wp) :: pesdwy                              !< Child subdomain width in y-direction 
       REAL(wp) :: tolex                               !< Tolerance for grid-line matching in x-direction
       REAL(wp) :: toley                               !< Tolerance for grid-line matching in y-direction
       REAL(wp) :: tolez                               !< Tolerance for grid-line matching in z-direction
       INTEGER(iwp) :: non_matching_lower_left_corner  !< Flag for non-matching lower left corner
       INTEGER(iwp) :: non_int_gsr_x                   !< Flag for non-integer grid-spacing ration in x-direction
       INTEGER(iwp) :: non_int_gsr_y                   !< Flag for non-integer grid-spacing ration in y-direction
       INTEGER(iwp) :: non_int_gsr_z                   !< Flag for non-integer grid-spacing ration in z-direction
       INTEGER(iwp) :: too_narrow_pesd_x               !< Flag for too narrow pe-subdomain in x-direction
       INTEGER(iwp) :: too_narrow_pesd_y               !< Flag for too narrow pe-subdomain in y-direction


       non_matching_lower_left_corner = 0
       non_int_gsr_x = 0
       non_int_gsr_y = 0
       non_int_gsr_z = 0
       too_narrow_pesd_x = 0
       too_narrow_pesd_y = 0

       IF  ( myid == 0 )  THEN

          tolex = tolefac * dx
          toley = tolefac * dy
          tolez = tolefac * MINVAL( dzw )
!
!--       First check that the child grid lower left corner matches the paren grid lines.
          IF  ( MOD( lower_left_coord_x, cg%dx ) > tolex ) non_matching_lower_left_corner = 1
          IF  ( MOD( lower_left_coord_y, cg%dy ) > toley ) non_matching_lower_left_corner = 1
!
!--       Then check that the grid-spacing ratios in each direction are integer valued.    
          IF  ( MOD( cg%dx, dx ) > tolex )  non_int_gsr_x = 1
          IF  ( MOD( cg%dy, dy ) > toley )  non_int_gsr_y = 1
          DO  n = 0, kctw+1
             IF  ( ABS( cg%zw(n) - zw(kflw(n)) ) > tolez )  non_int_gsr_z = 1
          ENDDO

          pesdwx = REAL( nxr - nxl + 1, KIND=wp )
          IF  ( pesdwx / REAL( igsr, KIND=wp ) < 1.0_wp )  too_narrow_pesd_x = 1
          pesdwy = REAL( nyn - nys + 1, KIND=wp )
          IF  ( pesdwy / REAL( jgsr, KIND=wp ) < 1.0_wp )  too_narrow_pesd_y = 1
                          
       ENDIF

       CALL MPI_BCAST( non_matching_lower_left_corner, 1, MPI_INTEGER, 0,       &
            comm2d, ierr )
       IF  ( non_matching_lower_left_corner > 0 )  THEN
          WRITE ( message_string, * )  'nested child domain lower left ',       &
               'corner must match its parent grid lines'
          CALL message( 'pmci_check_grid_matching', 'PA0414', 3, 2, 0, 6, 0 )
       ENDIF

       CALL MPI_BCAST( non_int_gsr_x, 1, MPI_INTEGER, 0, comm2d, ierr )
       IF  ( non_int_gsr_x > 0 )  THEN
          WRITE ( message_string, * )  'nesting grid-spacing ratio ',           &
               '( parent dx / child dx ) must have an integer value'
          CALL message( 'pmci_check_grid_matching', 'PA0416', 3, 2, 0, 6, 0 )
       ENDIF

       CALL MPI_BCAST( non_int_gsr_y, 1, MPI_INTEGER, 0, comm2d, ierr )
       IF  ( non_int_gsr_y > 0 )  THEN
          WRITE ( message_string, * )  'nesting grid-spacing ratio ',           &
               '( parent dy / child dy ) must have an integer value'
          CALL message( 'pmci_check_grid_matching', 'PA0416', 3, 2, 0, 6, 0 )
       ENDIF

       CALL MPI_BCAST( non_int_gsr_z, 1, MPI_INTEGER, 0, comm2d, ierr )
       IF  ( non_int_gsr_z > 0 )  THEN
          WRITE ( message_string, * )  'nesting grid-spacing ratio ',           &
               '( parent dz / child dz ) must have an integer value for each z-level'
          CALL message( 'pmci_check_grid_matching', 'PA0416', 3, 2, 0, 6, 0 )
       ENDIF    

       CALL MPI_BCAST( too_narrow_pesd_x, 1, MPI_INTEGER, 0, comm2d, ierr )
       IF  ( too_narrow_pesd_x > 0 )  THEN
          WRITE ( message_string, * )  'child subdomain width in x-direction ',    &
               'must not be smaller than its parent grid dx. Change the PE-grid ', &
               'setting (npex, npey) to satisfy this requirement.'  
          CALL message( 'pmci_check_grid_matching', 'PA0587', 3, 2, 0, 6, 0 )
       ENDIF
 
       CALL MPI_BCAST( too_narrow_pesd_y, 1, MPI_INTEGER, 0, comm2d, ierr )
       IF  ( too_narrow_pesd_y > 0 )  THEN
          WRITE ( message_string, * )  'child subdomain width in y-direction ',    &
               'must not be smaller than its parent grid dy. Change the PE-grid ', &
               'setting (npex, npey) to satisfy this requirement.'  
          CALL message( 'pmci_check_grid_matching', 'PA0587', 3, 2, 0, 6, 0 )
       ENDIF       

     END SUBROUTINE pmci_check_grid_matching

#endif  
 END SUBROUTINE pmci_setup_child



 SUBROUTINE pmci_setup_coordinates

#if defined( __parallel )
    IMPLICIT NONE

    INTEGER(iwp) ::  i   !<
    INTEGER(iwp) ::  j   !<

!
!-- Create coordinate arrays.
    ALLOCATE( coord_x(-nbgp:nx+nbgp) )
    ALLOCATE( coord_y(-nbgp:ny+nbgp) )
     
    DO  i = -nbgp, nx + nbgp
       coord_x(i) = lower_left_coord_x + i * dx
    ENDDO

    DO  j = -nbgp, ny + nbgp
       coord_y(j) = lower_left_coord_y + j * dy
    ENDDO

#endif
 END SUBROUTINE pmci_setup_coordinates

!------------------------------------------------------------------------------!
! Description:
! ------------
!> In this subroutine the number of coupled arrays is determined. 
!------------------------------------------------------------------------------! 
  SUBROUTINE pmci_num_arrays  
               
#if defined( __parallel ) 
    USE pmc_general,                                                           &
        ONLY:  pmc_max_array

    IMPLICIT NONE
!
!-- The number of coupled arrays depends on the model settings. At least
!-- 5 arrays need to be coupled (u, v, w, e, diss).  Please note, actually
!-- e and diss (TKE and dissipation rate) are only required if RANS-RANS
!-- nesting is applied, but memory is allocated nevertheless. This is because
!-- the information whether they are needed or not is retrieved at a later
!-- point in time. In case e and diss are not needed, they are also not 
!-- exchanged between parent and child. 
    pmc_max_array = 5
!
!-- pt
    IF ( .NOT. neutral )  pmc_max_array = pmc_max_array + 1
    
    IF ( humidity )  THEN
!
!--    q
       pmc_max_array = pmc_max_array + 1
!
!--    qc, nc
       IF ( bulk_cloud_model  .AND.  microphysics_morrison )                   &
          pmc_max_array = pmc_max_array + 2
!
!--    qr, nr
       IF ( bulk_cloud_model  .AND.  microphysics_seifert )                    &
          pmc_max_array = pmc_max_array + 2
    ENDIF
!
!-- s
    IF ( passive_scalar )  pmc_max_array = pmc_max_array + 1
!
!-- nr_part, part_adr
    IF ( particle_advection )  pmc_max_array = pmc_max_array + 2
!
!-- Chemistry, depends on number of species
    IF ( air_chemistry  .AND.  nest_chemistry )                                &
       pmc_max_array = pmc_max_array + nspec
#endif
    
 END SUBROUTINE pmci_num_arrays



 SUBROUTINE pmci_set_array_pointer( name, child_id, nz_cl, n )

    IMPLICIT NONE

    INTEGER(iwp), INTENT(IN)          ::  child_id    !<
    INTEGER(iwp), INTENT(IN)          ::  nz_cl       !<
    INTEGER(iwp), INTENT(IN),OPTIONAL ::  n           !< index of chemical species

    CHARACTER(LEN=*), INTENT(IN) ::  name             !<

#if defined( __parallel )
    INTEGER(iwp) ::  ierr                            !< MPI error code

    REAL(wp), POINTER, DIMENSION(:,:)     ::  p_2d        !<
    REAL(wp), POINTER, DIMENSION(:,:,:)   ::  p_3d        !<
    REAL(wp), POINTER, DIMENSION(:,:,:)   ::  p_3d_sec    !<
    INTEGER(idp), POINTER, DIMENSION(:,:) ::  i_2d        !<


    NULLIFY( p_3d )
    NULLIFY( p_2d )
    NULLIFY( i_2d )
!
!-- List of array names, which can be coupled.
!-- In case of 3D please change also the second array for the pointer version
    IF ( TRIM(name) == "u"          )  p_3d => u
    IF ( TRIM(name) == "v"          )  p_3d => v
    IF ( TRIM(name) == "w"          )  p_3d => w
    IF ( TRIM(name) == "e"          )  p_3d => e
    IF ( TRIM(name) == "pt"         )  p_3d => pt
    IF ( TRIM(name) == "q"          )  p_3d => q
    IF ( TRIM(name) == "qc"         )  p_3d => qc
    IF ( TRIM(name) == "qr"         )  p_3d => qr
    IF ( TRIM(name) == "nr"         )  p_3d => nr
    IF ( TRIM(name) == "nc"         )  p_3d => nc
    IF ( TRIM(name) == "s"          )  p_3d => s
    IF ( TRIM(name) == "diss"       )  p_3d => diss   
    IF ( TRIM(name) == "nr_part"    )  i_2d => nr_part
    IF ( TRIM(name) == "part_adr"   )  i_2d => part_adr
    IF ( INDEX( TRIM(name), "chem_" ) /= 0 )  p_3d => chem_species(n)%conc
!
!-- Next line is just an example for a 2D array (not active for coupling!)
!-- Please note, that z0 has to be declared as TARGET array in modules.f90
!    IF ( TRIM(name) == "z0" )    p_2d => z0
    IF ( TRIM(name) == "u"    )  p_3d_sec => u_2
    IF ( TRIM(name) == "v"    )  p_3d_sec => v_2
    IF ( TRIM(name) == "w"    )  p_3d_sec => w_2
    IF ( TRIM(name) == "e"    )  p_3d_sec => e_2
    IF ( TRIM(name) == "pt"   )  p_3d_sec => pt_2
    IF ( TRIM(name) == "q"    )  p_3d_sec => q_2
    IF ( TRIM(name) == "qc"   )  p_3d_sec => qc_2
    IF ( TRIM(name) == "qr"   )  p_3d_sec => qr_2
    IF ( TRIM(name) == "nr"   )  p_3d_sec => nr_2
    IF ( TRIM(name) == "nc"   )  p_3d_sec => nc_2
    IF ( TRIM(name) == "s"    )  p_3d_sec => s_2
    IF ( TRIM(name) == "diss" )  p_3d_sec => diss_2
    IF ( INDEX( TRIM(name), "chem_" ) /= 0 )  p_3d_sec => spec_conc_2(:,:,:,n)

    IF ( ASSOCIATED( p_3d ) )  THEN
       CALL pmc_s_set_dataarray( child_id, p_3d, nz_cl, nz,                    &
                                 array_2 = p_3d_sec )
    ELSEIF ( ASSOCIATED( p_2d ) )  THEN
       CALL pmc_s_set_dataarray( child_id, p_2d )
    ELSEIF ( ASSOCIATED( i_2d ) )  THEN
       CALL pmc_s_set_dataarray( child_id, i_2d )
    ELSE
!
!--    Give only one message for the root domain
       IF ( myid == 0  .AND.  cpl_id == 1 )  THEN

          message_string = 'pointer for array "' // TRIM( name ) //            &
                           '" can''t be associated'
          CALL message( 'pmci_set_array_pointer', 'PA0117', 3, 2, 0, 6, 0 )
       ELSE
!
!--       Avoid others to continue
          CALL MPI_BARRIER( comm2d, ierr )
       ENDIF

   ENDIF

#endif
END SUBROUTINE pmci_set_array_pointer



INTEGER FUNCTION get_number_of_childs ()     ! Change the name to "get_number_of_children"

   IMPLICIT NONE

#if defined( __parallel )
   get_number_of_childs = SIZE( pmc_parent_for_child ) - 1
#else
   get_number_of_childs = 0
#endif

   RETURN

END FUNCTION get_number_of_childs


INTEGER FUNCTION get_childid (id_index)

   IMPLICIT NONE

   INTEGER,INTENT(IN)                 :: id_index

#if defined( __parallel )
   get_childid = pmc_parent_for_child(id_index)
#else
   get_childid = 0
#endif

   RETURN

END FUNCTION get_childid



SUBROUTINE  get_child_edges (m, lx_coord, lx_coord_b, rx_coord, rx_coord_b,    &
                               sy_coord, sy_coord_b, ny_coord, ny_coord_b,     &
                               uz_coord, uz_coord_b)
   IMPLICIT NONE
   INTEGER,INTENT(IN)             ::  m
   REAL(wp),INTENT(OUT)           ::  lx_coord, lx_coord_b
   REAL(wp),INTENT(OUT)           ::  rx_coord, rx_coord_b
   REAL(wp),INTENT(OUT)           ::  sy_coord, sy_coord_b
   REAL(wp),INTENT(OUT)           ::  ny_coord, ny_coord_b
   REAL(wp),INTENT(OUT)           ::  uz_coord, uz_coord_b

   lx_coord = childgrid(m)%lx_coord
   rx_coord = childgrid(m)%rx_coord
   sy_coord = childgrid(m)%sy_coord
   ny_coord = childgrid(m)%ny_coord
   uz_coord = childgrid(m)%uz_coord

   lx_coord_b = childgrid(m)%lx_coord_b
   rx_coord_b = childgrid(m)%rx_coord_b
   sy_coord_b = childgrid(m)%sy_coord_b
   ny_coord_b = childgrid(m)%ny_coord_b
   uz_coord_b = childgrid(m)%uz_coord_b

END SUBROUTINE get_child_edges



SUBROUTINE  get_child_gridspacing( m, dx,dy,dz )

   IMPLICIT NONE
   INTEGER,INTENT(IN)             ::  m
   REAL(wp),INTENT(OUT)           ::  dx,dy
   REAL(wp),INTENT(OUT),OPTIONAL  ::  dz

   dx = childgrid(m)%dx
   dy = childgrid(m)%dy
   IF(PRESENT(dz))   THEN
      dz = childgrid(m)%dz
   ENDIF

END SUBROUTINE get_child_gridspacing



SUBROUTINE pmci_create_child_arrays( name, is, ie, js, je, nzc, n  )

    IMPLICIT NONE

    CHARACTER(LEN=*), INTENT(IN) ::  name    !<

    INTEGER(iwp), INTENT(IN) ::  ie      !<
    INTEGER(iwp), INTENT(IN) ::  is      !<
    INTEGER(iwp), INTENT(IN) ::  je      !<
    INTEGER(iwp), INTENT(IN) ::  js      !<
    INTEGER(iwp), INTENT(IN) ::  nzc     !<  nzc is cg%nz, but note that cg%nz is not the original nz of parent, but the highest parent-grid level needed for nesting.

    INTEGER(iwp), INTENT(IN), OPTIONAL ::  n  !< number of chemical species

#if defined( __parallel )
    INTEGER(iwp) ::  ierr    !<

    REAL(wp), POINTER,DIMENSION(:,:)       ::  p_2d    !<
    REAL(wp), POINTER,DIMENSION(:,:,:)     ::  p_3d    !<
    INTEGER(idp), POINTER,DIMENSION(:,:)   ::  i_2d    !<


    NULLIFY( p_3d )
    NULLIFY( p_2d )
    NULLIFY( i_2d )
!
!-- List of array names, which can be coupled
    IF ( TRIM( name ) == "u" )  THEN
       IF ( .NOT. ALLOCATED( uc ) )  ALLOCATE( uc(0:nzc+1,js:je,is:ie) )
       p_3d => uc
    ELSEIF ( TRIM( name ) == "v" )  THEN
       IF ( .NOT. ALLOCATED( vc ) )  ALLOCATE( vc(0:nzc+1,js:je,is:ie) )
       p_3d => vc
    ELSEIF ( TRIM( name ) == "w" )  THEN
       IF ( .NOT. ALLOCATED( wc ) )  ALLOCATE( wc(0:nzc+1,js:je,is:ie) )
       p_3d => wc
    ELSEIF ( TRIM( name ) == "e" )  THEN
       IF ( .NOT. ALLOCATED( ec ) )  ALLOCATE( ec(0:nzc+1,js:je,is:ie) )
       p_3d => ec
    ELSEIF ( TRIM( name ) == "diss" )  THEN
       IF ( .NOT. ALLOCATED( dissc ) )  ALLOCATE( dissc(0:nzc+1,js:je,is:ie) )
       p_3d => dissc
    ELSEIF ( TRIM( name ) == "pt")  THEN
       IF ( .NOT. ALLOCATED( ptc ) )  ALLOCATE( ptc(0:nzc+1,js:je,is:ie) )
       p_3d => ptc
    ELSEIF ( TRIM( name ) == "q")  THEN
       IF ( .NOT. ALLOCATED( q_c ) )  ALLOCATE( q_c(0:nzc+1,js:je,is:ie) )
       p_3d => q_c
    ELSEIF ( TRIM( name ) == "qc")  THEN
       IF ( .NOT. ALLOCATED( qcc ) )  ALLOCATE( qcc(0:nzc+1,js:je,is:ie) )
       p_3d => qcc
    ELSEIF ( TRIM( name ) == "qr")  THEN
       IF ( .NOT. ALLOCATED( qrc ) )  ALLOCATE( qrc(0:nzc+1,js:je,is:ie) )
       p_3d => qrc
    ELSEIF ( TRIM( name ) == "nr")  THEN
       IF ( .NOT. ALLOCATED( nrc ) )  ALLOCATE( nrc(0:nzc+1,js:je,is:ie) )
       p_3d => nrc
    ELSEIF ( TRIM( name ) == "nc")  THEN
       IF ( .NOT. ALLOCATED( ncc ) )  ALLOCATE( ncc(0:nzc+1,js:je,is:ie) )
       p_3d => ncc
    ELSEIF ( TRIM( name ) == "s")  THEN
       IF ( .NOT. ALLOCATED( sc ) )  ALLOCATE( sc(0:nzc+1,js:je,is:ie) )
       p_3d => sc
    ELSEIF ( TRIM( name ) == "nr_part") THEN
       IF ( .NOT. ALLOCATED( nr_partc ) )  ALLOCATE( nr_partc(js:je,is:ie) )
       i_2d => nr_partc
    ELSEIF ( TRIM( name ) == "part_adr") THEN
       IF ( .NOT. ALLOCATED( part_adrc ) )  ALLOCATE( part_adrc(js:je,is:ie) )
       i_2d => part_adrc
    ELSEIF ( TRIM( name(1:5) ) == "chem_" )  THEN
       IF ( .NOT. ALLOCATED( chem_spec_c ) )                                   &
          ALLOCATE( chem_spec_c(0:nzc+1,js:je,is:ie,1:nspec) )
       p_3d => chem_spec_c(:,:,:,n)
    !ELSEIF (trim(name) == "z0") then
       !IF (.not.allocated(z0c))  allocate(z0c(js:je, is:ie))
       !p_2d => z0c
    ENDIF

    IF ( ASSOCIATED( p_3d ) )  THEN
       CALL pmc_c_set_dataarray( p_3d )
    ELSEIF ( ASSOCIATED( p_2d ) )  THEN
       CALL pmc_c_set_dataarray( p_2d )
    ELSEIF ( ASSOCIATED( i_2d ) )  THEN
       CALL pmc_c_set_dataarray( i_2d )
    ELSE
!
!--    Give only one message for the first child domain
       IF ( myid == 0  .AND.  cpl_id == 2 )  THEN

          message_string = 'pointer for array "' // TRIM( name ) //            &
                           '" can''t be associated'
          CALL message( 'pmci_create_child_arrays', 'PA0170', 3, 2, 0, 6, 0 )
       ELSE
!
!--       Prevent others from continuing
          CALL MPI_BARRIER( comm2d, ierr )
       ENDIF
    ENDIF

#endif
 END SUBROUTINE pmci_create_child_arrays



 SUBROUTINE pmci_parent_initialize

!
!-- Send data for the children in order to let them create initial 
!-- conditions by interpolating the parent-domain fields.
#if defined( __parallel )
    IMPLICIT NONE

    INTEGER(iwp) ::  child_id    !<
    INTEGER(iwp) ::  m           !<
    REAL(wp) ::  waittime        !<


    DO  m = 1, SIZE( pmc_parent_for_child ) - 1
       child_id = pmc_parent_for_child(m)
       CALL pmc_s_fillbuffer( child_id, waittime=waittime )
    ENDDO

#endif
 END SUBROUTINE pmci_parent_initialize



 SUBROUTINE pmci_child_initialize

!
!-- Create initial conditions for the current child domain by interpolating 
!-- the parent-domain fields.
#if defined( __parallel )
    IMPLICIT NONE

    INTEGER(iwp) ::  i          !<
    INTEGER(iwp) ::  icl        !<
    INTEGER(iwp) ::  icla       !<
    INTEGER(iwp) ::  iclw       !<
    INTEGER(iwp) ::  icr        !<
    INTEGER(iwp) ::  icra       !<
    INTEGER(iwp) ::  icrw       !<
    INTEGER(iwp) ::  j          !<
    INTEGER(iwp) ::  jcn        !<
    INTEGER(iwp) ::  jcna       !<
    INTEGER(iwp) ::  jcnw       !<
    INTEGER(iwp) ::  jcs        !<
    INTEGER(iwp) ::  jcsa       !<
    INTEGER(iwp) ::  jcsw       !<
    INTEGER(iwp) ::  k          !< 
    INTEGER(iwp) ::  n          !< running index for chemical species
    REAL(wp) ::  waittime       !<

!
!-- Root model is never anyone's child
    IF ( cpl_id > 1 )  THEN
!
!--    Child domain boundaries in the parent index space
       icl  = coarse_bound(1)
       icr  = coarse_bound(2)
       jcs  = coarse_bound(3)
       jcn  = coarse_bound(4)
       icla = coarse_bound_aux(1)
       icra = coarse_bound_aux(2)
       jcsa = coarse_bound_aux(3)
       jcna = coarse_bound_aux(4)
       iclw = coarse_bound_w(1)
       icrw = coarse_bound_w(2)
       jcsw = coarse_bound_w(3)
       jcnw = coarse_bound_w(4)

!
!--    Get data from the parent
       CALL pmc_c_getbuffer( waittime = waittime )
!
!--    The interpolation.
       CALL pmci_interp_1sto_all ( u, uc, kcto, iflu, ifuu, jflo, jfuo, kflo, kfuo, 'u' )
       CALL pmci_interp_1sto_all ( v, vc, kcto, iflo, ifuo, jflv, jfuv, kflo, kfuo, 'v' )
       CALL pmci_interp_1sto_all ( w, wc, kctw, iflo, ifuo, jflo, jfuo, kflw, kfuw, 'w' )

       IF ( (        rans_mode_parent  .AND.         rans_mode )  .OR.                              &
            (  .NOT. rans_mode_parent  .AND.  .NOT.  rans_mode  .AND.                               &
               .NOT. constant_diffusion ) )  THEN
          CALL pmci_interp_1sto_all ( e, ec, kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, 'e' )
       ENDIF

       IF ( rans_mode_parent  .AND.  rans_mode  .AND.  rans_tke_e )  THEN
          CALL pmci_interp_1sto_all ( diss, dissc, kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, 's' )
       ENDIF

       IF ( .NOT. neutral )  THEN
          CALL pmci_interp_1sto_all ( pt, ptc, kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, 's' )
       ENDIF

       IF ( humidity )  THEN

          CALL pmci_interp_1sto_all ( q, q_c, kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, 's' )

          IF ( bulk_cloud_model  .AND.  microphysics_morrison )  THEN
             CALL pmci_interp_1sto_all ( qc, qcc, kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, 's' ) 
             CALL pmci_interp_1sto_all ( nc, ncc, kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, 's' )   
          ENDIF

          IF ( bulk_cloud_model  .AND.  microphysics_seifert )  THEN
             CALL pmci_interp_1sto_all ( qr, qrc, kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, 's' )
             CALL pmci_interp_1sto_all ( nr, nrc, kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, 's' )
          ENDIF

       ENDIF

       IF ( passive_scalar )  THEN
          CALL pmci_interp_1sto_all ( s, sc, kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, 's' )
       ENDIF

       IF ( air_chemistry  .AND.  nest_chemistry )  THEN
          DO  n = 1, nspec
             CALL pmci_interp_1sto_all ( chem_species(n)%conc, chem_spec_c(:,:,:,n),                &
                                         kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, 's' )
          ENDDO
       ENDIF

       IF ( topography /= 'flat' )  THEN
!
!--       Inside buildings set velocities and TKE back to zero.
!--       Other scalars (pt, q, s, km, kh, p, sa, ...) are ignored at present,
!--       maybe revise later.
          DO   i = nxlg, nxrg
             DO   j = nysg, nyng
                DO  k = nzb, nzt
                   u(k,j,i)   = MERGE( u(k,j,i), 0.0_wp,                       &
                                       BTEST( wall_flags_0(k,j,i), 1 ) )
                   v(k,j,i)   = MERGE( v(k,j,i), 0.0_wp,                       &
                                       BTEST( wall_flags_0(k,j,i), 2 ) )
                   w(k,j,i)   = MERGE( w(k,j,i), 0.0_wp,                       &
                                       BTEST( wall_flags_0(k,j,i), 3 ) )
!                    e(k,j,i)   = MERGE( e(k,j,i), 0.0_wp,                       &
!                                        BTEST( wall_flags_0(k,j,i), 0 ) )
                   u_p(k,j,i) = MERGE( u_p(k,j,i), 0.0_wp,                     &
                                       BTEST( wall_flags_0(k,j,i), 1 ) )
                   v_p(k,j,i) = MERGE( v_p(k,j,i), 0.0_wp,                     &
                                       BTEST( wall_flags_0(k,j,i), 2 ) )
                   w_p(k,j,i) = MERGE( w_p(k,j,i), 0.0_wp,                     &
                                       BTEST( wall_flags_0(k,j,i), 3 ) )
!                    e_p(k,j,i) = MERGE( e_p(k,j,i), 0.0_wp,                     &
!                                        BTEST( wall_flags_0(k,j,i), 0 ) )
                ENDDO
             ENDDO
          ENDDO
       ENDIF
    ENDIF


 CONTAINS


    SUBROUTINE pmci_interp_1sto_all( f, fc, kct, ifl, ifu, jfl, jfu, kfl, kfu, var )
!
!--    Interpolation of the internal values for the child-domain initialization
       IMPLICIT NONE

       REAL(wp), DIMENSION(nzb:nzt+1,nysg:nyng,nxlg:nxrg), INTENT(INOUT) :: f  !< Child-grid array 
       REAL(wp), DIMENSION(0:cg%nz+1,jcs:jcn,icl:icr), INTENT(IN) :: fc        !< Parent-grid array
       INTEGER(iwp) :: kct                                    !< The parent-grid index in z-direction just below the boundary value node
       INTEGER(iwp), DIMENSION(icla:icra), INTENT(IN) ::  ifl !< Indicates start index of child cells belonging to certain parent cell - x direction
       INTEGER(iwp), DIMENSION(icla:icra), INTENT(IN) ::  ifu !< Indicates end index of child cells belonging to certain parent cell - x direction
       INTEGER(iwp), DIMENSION(jcsa:jcna), INTENT(IN) ::  jfl !< Indicates start index of child cells belonging to certain parent cell - y direction
       INTEGER(iwp), DIMENSION(jcsa:jcna), INTENT(IN) ::  jfu !< Indicates end index of child cells belonging to certain parent cell - y direction
       INTEGER(iwp), DIMENSION(0:cg%nz+1), INTENT(IN) ::  kfl !< Indicates start index of child cells belonging to certain parent cell - z direction
       INTEGER(iwp), DIMENSION(0:cg%nz+1), INTENT(IN) ::  kfu !< Indicates end index of child cells belonging to certain parent cell - z direction
       CHARACTER(LEN=1), INTENT(IN) :: var                    !< Variable symbol: 'u', 'v', 'w' or 's'
!
!--    Local variables:
       INTEGER(iwp) ::  i        !<
       INTEGER(iwp) ::  ib       !<
       INTEGER(iwp) ::  ie       !<
       INTEGER(iwp) ::  ifirst   !<
       INTEGER(iwp) ::  ilast    !<
       INTEGER(iwp) ::  j        !<
       INTEGER(iwp) ::  jb       !<
       INTEGER(iwp) ::  je       !<
       INTEGER(iwp) ::  jfirst   !<
       INTEGER(iwp) ::  jlast    !<
       INTEGER(iwp) ::  k        !<
       INTEGER(iwp) ::  l        !<
       INTEGER(iwp) ::  lb       !<
       INTEGER(iwp) ::  le       !<
       INTEGER(iwp) ::  m        !<
       INTEGER(iwp) ::  mb       !<
       INTEGER(iwp) ::  me       !<
       INTEGER(iwp) ::  n        !<


       lb = icl
       le = icr
       mb = jcs
       me = jcn
       ifirst = nxl
       ilast  = nxr
       jfirst = nys
       jlast  = nyn

       IF ( nesting_mode /= 'vertical' )  THEN
          IF ( bc_dirichlet_l )  THEN
             lb     = icl + 1
             ifirst = nxl - 1
!
!--          For u, nxl is a ghost node, but not for the other variables
             IF ( var == 'u' )  THEN
                lb     = icl + 2
                ifirst = nxl
             ENDIF
          ENDIF
          IF ( bc_dirichlet_s )  THEN
             mb     = jcs + 1
             jfirst = nys - 1 
!
!--          For v, nys is a ghost node, but not for the other variables
             IF ( var == 'v' )  THEN
                mb     = jcs + 2
                jfirst = nys
             ENDIF
          ENDIF
          IF ( bc_dirichlet_r )  THEN
             le    = icr - 1
             ilast = nxr + 1 
          ENDIF
          IF ( bc_dirichlet_n )  THEN
             me    = jcn - 1
             jlast = nyn + 1
          ENDIF
       ENDIF      

       f(:,:,:) = 0.0_wp

       IF  ( var == 'u' )  THEN

          ib = ifl(lb) 
          ie = ifl(le+1) - 1
          jb = jfl(mb)
          je = jfu(me)
          DO  l = lb, le
             DO  m = mb, me
                DO n = 0, kct + 1 

                   DO  i = ifl(l), ifl(l+1)-1
                      DO  j = jfl(m), jfu(m)
                         DO  k = kfl(n), MIN( kfu(n), nzt+1 )
                            f(k,j,i) = fc(n,m,l)
                         ENDDO
                      ENDDO
                   ENDDO
                   
                ENDDO
             ENDDO
          ENDDO

       ELSE IF  ( var == 'v' )  THEN

          ib = ifl(lb) 
          ie = ifu(le)
          jb = jfl(mb)
          je = jfl(me+1) - 1
          DO  l = lb, le
             DO  m = mb, me
                DO n = 0, kct + 1  

                   DO i = ifl(l), ifu(l)
                      DO  j = jfl(m), jfl(m+1)-1
                         DO  k = kfl(n), MIN( kfu(n), nzt+1 )
                            f(k,j,i) = fc(n,m,l) 
                         ENDDO
                      ENDDO
                   ENDDO

                ENDDO
             ENDDO
          ENDDO

       ELSE IF  ( var == 'w' )  THEN

          ib = ifl(lb) 
          ie = ifu(le)
          jb = jfl(mb)
          je = jfu(me)
          DO  l = lb, le
             DO  m = mb, me
                DO n = 1, kct + 1  

                   DO i = ifl(l), ifu(l)
                      DO  j = jfl(m), jfu(m)
                         f(nzb,j,i) = 0.0_wp   ! Because the n-loop starts from n=1 instead of 0
                         DO  k = kfu(n-1)+1, kfu(n) 
                            f(k,j,i) = fc(n,m,l)
                         ENDDO
                      ENDDO
                   ENDDO
                   
                ENDDO
             ENDDO
          ENDDO

       ELSE   ! scalars

          ib = ifl(lb) 
          ie = ifu(le)
          jb = jfl(mb)
          je = jfu(me)
          DO  l = lb, le
             DO  m = mb, me
                DO n = 0, kct + 1
                                      
                   DO i = ifl(l), ifu(l)
                      DO  j = jfl(m), jfu(m)                         
                         DO  k = kfl(n), MIN( kfu(n), nzt+1 )
                            f(k,j,i) = fc(n,m,l)
                         ENDDO
                      ENDDO
                   ENDDO
                   
                ENDDO
             ENDDO
          ENDDO

       ENDIF  ! var
!
!--    If the subdomain i- and/or j-dimension (nx/npex and/or ny/npey) is 
!--    not integer divisible by the grid spacing ratio in its direction,
!--    the above loops will return with unfilled gaps in the initial fields.
!--    These gaps, if present, are filled here.  
       IF  ( ib > ifirst )  THEN
          DO  i = ifirst, ib-1
             f(:,:,i) = f(:,:,ib)
          ENDDO
       ENDIF
       IF  ( ie < ilast )  THEN
          DO  i = ie+1, ilast
             f(:,:,i) = f(:,:,ie)
          ENDDO
       ENDIF
       IF  ( jb > jfirst )  THEN
          DO  j = jfirst, jb-1
             f(:,j,:) = f(:,jb,:)
          ENDDO
       ENDIF
       IF  ( je < jlast )  THEN
          DO  j = je+1, jlast
             f(:,j,:) = f(:,je,:)
          ENDDO
       ENDIF

    END SUBROUTINE pmci_interp_1sto_all

#endif
 END SUBROUTINE pmci_child_initialize



 SUBROUTINE pmci_check_setting_mismatches
!
!-- Check for mismatches between settings of master and child variables
!-- (e.g., all children have to follow the end_time settings of the root model).
!-- The root model overwrites variables in the other models, so these variables
!-- only need to be set once in file PARIN.

#if defined( __parallel )

    USE control_parameters,                                                    &
        ONLY:  dt_restart, end_time, message_string, restart_time, time_restart

    IMPLICIT NONE

    INTEGER ::  ierr

    REAL(wp) ::  dt_restart_root
    REAL(wp) ::  end_time_root
    REAL(wp) ::  restart_time_root
    REAL(wp) ::  time_restart_root

!
!-- Check the time to be simulated.
!-- Here, and in the following, the root process communicates the respective
!-- variable to all others, and its value will then be compared with the local
!-- values.
    IF ( pmc_is_rootmodel() )  end_time_root = end_time
    CALL MPI_BCAST( end_time_root, 1, MPI_REAL, 0, comm_world_nesting, ierr )

    IF ( .NOT. pmc_is_rootmodel() )  THEN
       IF ( end_time /= end_time_root )  THEN
          WRITE( message_string, * )  'mismatch between root model and ',      &
               'child settings:& end_time(root) = ', end_time_root,            &
               '& end_time(child) = ', end_time, '& child value is set',       &
               ' to root value'
          CALL message( 'pmci_check_setting_mismatches', 'PA0419', 0, 1, 0, 6, &
                        0 )
          end_time = end_time_root
       ENDIF
    ENDIF
!
!-- Same for restart time
    IF ( pmc_is_rootmodel() )  restart_time_root = restart_time
    CALL MPI_BCAST( restart_time_root, 1, MPI_REAL, 0, comm_world_nesting, ierr )

    IF ( .NOT. pmc_is_rootmodel() )  THEN
       IF ( restart_time /= restart_time_root )  THEN
          WRITE( message_string, * )  'mismatch between root model and ',      &
               'child settings: & restart_time(root) = ', restart_time_root,   &
               '& restart_time(child) = ', restart_time, '& child ',           &
               'value is set to root value'
          CALL message( 'pmci_check_setting_mismatches', 'PA0419', 0, 1, 0, 6, &
                        0 )
          restart_time = restart_time_root
       ENDIF
    ENDIF
!
!-- Same for dt_restart
    IF ( pmc_is_rootmodel() )  dt_restart_root = dt_restart
    CALL MPI_BCAST( dt_restart_root, 1, MPI_REAL, 0, comm_world_nesting, ierr )

    IF ( .NOT. pmc_is_rootmodel() )  THEN
       IF ( dt_restart /= dt_restart_root )  THEN
          WRITE( message_string, * )  'mismatch between root model and ',      &
               'child settings: & dt_restart(root) = ', dt_restart_root,       &
               '& dt_restart(child) = ', dt_restart, '& child ',               &
               'value is set to root value'
          CALL message( 'pmci_check_setting_mismatches', 'PA0419', 0, 1, 0, 6, &
                        0 )
          dt_restart = dt_restart_root
       ENDIF
    ENDIF
!
!-- Same for time_restart
    IF ( pmc_is_rootmodel() )  time_restart_root = time_restart
    CALL MPI_BCAST( time_restart_root, 1, MPI_REAL, 0, comm_world_nesting, ierr )

    IF ( .NOT. pmc_is_rootmodel() )  THEN
       IF ( time_restart /= time_restart_root )  THEN
          WRITE( message_string, * )  'mismatch between root model and ',      &
               'child settings: & time_restart(root) = ', time_restart_root,   &
               '& time_restart(child) = ', time_restart, '& child ',           &
               'value is set to root value'
          CALL message( 'pmci_check_setting_mismatches', 'PA0419', 0, 1, 0, 6, &
                        0 )
          time_restart = time_restart_root
       ENDIF
    ENDIF

#endif

 END SUBROUTINE pmci_check_setting_mismatches



 SUBROUTINE pmci_synchronize

#if defined( __parallel )
!
!-- Unify the time steps for each model and synchronize using 
!-- MPI_ALLREDUCE with the MPI_MIN operator over all processes using 
!-- the global communicator MPI_COMM_WORLD.
   
   IMPLICIT NONE

   INTEGER(iwp)           :: ierr  !<
   REAL(wp), DIMENSION(1) :: dtl   !<
   REAL(wp), DIMENSION(1) :: dtg   !<

   
   dtl(1) = dt_3d 
   CALL MPI_ALLREDUCE( dtl, dtg, 1, MPI_REAL, MPI_MIN, MPI_COMM_WORLD, ierr )
   dt_3d  = dtg(1)

#endif
 END SUBROUTINE pmci_synchronize
                


 SUBROUTINE pmci_set_swaplevel( swaplevel )

!
!-- After each Runge-Kutta sub-timestep, alternately set buffer one or buffer
!-- two active

    IMPLICIT NONE

    INTEGER(iwp), INTENT(IN) ::  swaplevel  !< swaplevel (1 or 2) of PALM's
                                            !< timestep

    INTEGER(iwp)            ::  child_id    !<
    INTEGER(iwp)            ::  m           !<

#if defined( __parallel )
    DO  m = 1, SIZE( pmc_parent_for_child )-1
       child_id = pmc_parent_for_child(m)
       CALL pmc_s_set_active_data_array( child_id, swaplevel )
    ENDDO
#endif
 END SUBROUTINE pmci_set_swaplevel



 SUBROUTINE pmci_datatrans( local_nesting_mode )
!
!-- This subroutine controls the nesting according to the nestpar 
!-- parameter nesting_mode (two-way (default) or one-way) and the 
!-- order of anterpolations according to the nestpar parameter 
!-- nesting_datatransfer_mode (cascade, overlap or mixed (default)).
!-- Although nesting_mode is a variable of this model, pass it as 
!-- an argument to allow for example to force one-way initialization 
!-- phase.
!-- Note that interpolation ( parent_to_child ) must always be carried 
!-- out before anterpolation ( child_to_parent ).

    IMPLICIT NONE

    CHARACTER(LEN=*), INTENT(IN) ::  local_nesting_mode


    IF ( TRIM( local_nesting_mode ) == 'one-way' )  THEN

       CALL pmci_child_datatrans( parent_to_child )
       CALL pmci_parent_datatrans( parent_to_child )

    ELSE

       IF( nesting_datatransfer_mode == 'cascade' )  THEN

          CALL pmci_child_datatrans( parent_to_child )
          CALL pmci_parent_datatrans( parent_to_child )

          CALL pmci_parent_datatrans( child_to_parent )
          CALL pmci_child_datatrans( child_to_parent )

       ELSEIF( nesting_datatransfer_mode == 'overlap')  THEN

          CALL pmci_parent_datatrans( parent_to_child )
          CALL pmci_child_datatrans( parent_to_child )

          CALL pmci_child_datatrans( child_to_parent )
          CALL pmci_parent_datatrans( child_to_parent )

       ELSEIF( TRIM( nesting_datatransfer_mode ) == 'mixed' )  THEN

          CALL pmci_parent_datatrans( parent_to_child )
          CALL pmci_child_datatrans( parent_to_child )

          CALL pmci_parent_datatrans( child_to_parent )
          CALL pmci_child_datatrans( child_to_parent )

       ENDIF

    ENDIF

 END SUBROUTINE pmci_datatrans



 SUBROUTINE pmci_parent_datatrans( direction )

    IMPLICIT NONE

    INTEGER(iwp), INTENT(IN) ::  direction   !<

#if defined( __parallel )
    INTEGER(iwp) ::  child_id    !<
    INTEGER(iwp) ::  i           !<
    INTEGER(iwp) ::  j           !<
    INTEGER(iwp) ::  k           !<
    INTEGER(iwp) ::  m           !<


    DO  m = 1, SIZE( pmc_parent_for_child ) - 1
       child_id = pmc_parent_for_child(m)
       IF ( direction == parent_to_child )  THEN
          CALL cpu_log( log_point_s(71), 'pmc parent send', 'start' )
          CALL pmc_s_fillbuffer( child_id )
          CALL cpu_log( log_point_s(71), 'pmc parent send', 'stop' )
       ELSE
!
!--       Communication from child to parent
          CALL cpu_log( log_point_s(72), 'pmc parent recv', 'start' )
          child_id = pmc_parent_for_child(m)
          CALL pmc_s_getdata_from_buffer( child_id )
          CALL cpu_log( log_point_s(72), 'pmc parent recv', 'stop' )
!
!--       The anterpolated data is now available in u etc
          IF ( topography /= 'flat' )  THEN
!
!--          Inside buildings/topography reset velocities back to zero.
!--          Scalars (pt, q, s, km, kh, p, sa, ...) are ignored at
!--          present, maybe revise later.
!--          Resetting of e is removed as unnecessary since e is not 
!--          anterpolated, and as incorrect since it overran the default 
!--          Neumann condition (bc_e_b). 
             DO   i = nxlg, nxrg
                DO   j = nysg, nyng
                   DO  k = nzb, nzt+1
                      u(k,j,i)  = MERGE( u(k,j,i), 0.0_wp,                     &
                                         BTEST( wall_flags_0(k,j,i), 1 ) )
                      v(k,j,i)  = MERGE( v(k,j,i), 0.0_wp,                     &
                                         BTEST( wall_flags_0(k,j,i), 2 ) )
                      w(k,j,i)  = MERGE( w(k,j,i), 0.0_wp,                     &
                                         BTEST( wall_flags_0(k,j,i), 3 ) )
!
!--                 TO_DO: zero setting of temperature within topography creates
!--                       wrong results
!                   pt(nzb:nzb_s_inner(j,i),j,i) = 0.0_wp
!                   IF ( humidity  .OR.  passive_scalar )  THEN
!                      q(nzb:nzb_s_inner(j,i),j,i) = 0.0_wp
!                   ENDIF
                   ENDDO
                ENDDO
             ENDDO
          ENDIF
       ENDIF
    ENDDO

#endif
 END SUBROUTINE pmci_parent_datatrans



 SUBROUTINE pmci_child_datatrans( direction )

    IMPLICIT NONE

    INTEGER(iwp), INTENT(IN) ::  direction  !< Transfer direction: parent_to_child or child_to_parent

#if defined( __parallel )
    INTEGER(iwp) ::  icl         !< Parent-grid array index bound, left
    INTEGER(iwp) ::  icr         !< Parent-grid array index bound, right
    INTEGER(iwp) ::  jcn         !< Parent-grid array index bound, north
    INTEGER(iwp) ::  jcs         !< Parent-grid array index bound, south
    INTEGER(iwp) ::  icla        !< Auxiliary-array (index-mapping etc) index bound, left
    INTEGER(iwp) ::  icra        !< Auxiliary-array (index-mapping etc) index bound, right
    INTEGER(iwp) ::  jcna        !< Auxiliary-array (index-mapping etc) index bound, north
    INTEGER(iwp) ::  jcsa        !< Auxiliary-array (index-mapping etc) index bound, south
    INTEGER(iwp) ::  iclw        !< Parent-grid work array index bound, left
    INTEGER(iwp) ::  icrw        !< Parent-grid work array index bound, right
    INTEGER(iwp) ::  jcnw        !< Parent-grid work array index bound, north
    INTEGER(iwp) ::  jcsw        !< Parent-grid work array index bound, south

    REAL(wp), DIMENSION(1) ::  dtl         !< Time step size


    dtl = dt_3d
    IF ( cpl_id > 1 )  THEN
!
!--    Child domain boundaries in the parent indice space.
       icl  = coarse_bound(1)
       icr  = coarse_bound(2)
       jcs  = coarse_bound(3)
       jcn  = coarse_bound(4)
       icla = coarse_bound_aux(1)
       icra = coarse_bound_aux(2)
       jcsa = coarse_bound_aux(3)
       jcna = coarse_bound_aux(4)
       iclw = coarse_bound_w(1)
       icrw = coarse_bound_w(2)
       jcsw = coarse_bound_w(3)
       jcnw = coarse_bound_w(4)

       IF ( direction == parent_to_child )  THEN
    
          CALL cpu_log( log_point_s(73), 'pmc child recv', 'start' )
          CALL pmc_c_getbuffer( )
          CALL cpu_log( log_point_s(73), 'pmc child recv', 'stop' )

          CALL cpu_log( log_point_s(75), 'pmc interpolation', 'start' )
          CALL pmci_interpolation
          CALL cpu_log( log_point_s(75), 'pmc interpolation', 'stop' )
     
       ELSE
!
!--       direction == child_to_parent
          CALL cpu_log( log_point_s(76), 'pmc anterpolation', 'start' )
          CALL pmci_anterpolation
          CALL cpu_log( log_point_s(76), 'pmc anterpolation', 'stop' )

          CALL cpu_log( log_point_s(74), 'pmc child send', 'start' )
          CALL pmc_c_putbuffer( )
          CALL cpu_log( log_point_s(74), 'pmc child send', 'stop' )

       ENDIF
    ENDIF

  CONTAINS

   
    SUBROUTINE pmci_interpolation

!
!--    A wrapper routine for all interpolation actions
      
       IMPLICIT NONE

       INTEGER(iwp) ::  ibgp       !< index running over the nbgp boundary ghost points in i-direction
       INTEGER(iwp) ::  jbgp       !< index running over the nbgp boundary ghost points in j-direction
       INTEGER(iwp) ::  n          !< running index for number of chemical species
      
!
!--    In case of vertical nesting no interpolation is needed for the
!--    horizontal boundaries
       IF ( nesting_mode /= 'vertical' )  THEN
!
!--       Left border pe:
          IF ( bc_dirichlet_l )  THEN

             CALL pmci_interp_1sto_lr( u, uc, kcto, jflo, jfuo, kflo, kfuo, 'l', 'u' )
             CALL pmci_interp_1sto_lr( v, vc, kcto, jflv, jfuv, kflo, kfuo, 'l', 'v' )
             CALL pmci_interp_1sto_lr( w, wc, kctw, jflo, jfuo, kflw, kfuw, 'l', 'w' )

             IF ( (        rans_mode_parent  .AND.         rans_mode )  .OR.                        &
                  (  .NOT. rans_mode_parent  .AND.  .NOT.  rans_mode  .AND.                         &
                     .NOT. constant_diffusion ) )  THEN
!                CALL pmci_interp_1sto_lr( e, ec, kcto, jflo, jfuo, kflo, kfuo, 'l', 'e' )
!
!--             Interpolation of e is replaced by the Neumann condition. 
                DO ibgp = -nbgp, -1
                   e(nzb:nzt,nys:nyn,ibgp) = e(nzb:nzt,nys:nyn,0)
                ENDDO

             ENDIF

             IF ( rans_mode_parent  .AND.  rans_mode  .AND.  rans_tke_e )  THEN
                CALL pmci_interp_1sto_lr( diss, dissc, kcto, jflo, jfuo, kflo, kfuo, 'l', 's' )
             ENDIF

             IF ( .NOT. neutral )  THEN
                CALL pmci_interp_1sto_lr( pt, ptc, kcto, jflo, jfuo, kflo, kfuo, 'l', 's' )
             ENDIF

             IF ( humidity )  THEN

                CALL pmci_interp_1sto_lr( q, q_c, kcto, jflo, jfuo, kflo, kfuo, 'l', 's' )

                IF ( bulk_cloud_model  .AND.  microphysics_morrison )  THEN
                   CALL pmci_interp_1sto_lr( qc, qcc, kcto, jflo, jfuo, kflo, kfuo, 'l', 's' )  
                   CALL pmci_interp_1sto_lr( nc, ncc, kcto, jflo, jfuo, kflo, kfuo, 'l', 's' )          
                ENDIF

                IF ( bulk_cloud_model  .AND.  microphysics_seifert )  THEN
                   CALL pmci_interp_1sto_lr( qr, qrc, kcto, jflo, jfuo, kflo, kfuo, 'l', 's' ) 
                   CALL pmci_interp_1sto_lr( nr, nrc, kcto, jflo, jfuo, kflo, kfuo, 'l', 's' )             
                ENDIF

             ENDIF

             IF ( passive_scalar )  THEN
                CALL pmci_interp_1sto_lr( s, sc, kcto, jflo, jfuo, kflo, kfuo, 'l', 's' )
             ENDIF

             IF ( air_chemistry  .AND.  nest_chemistry )  THEN
                DO  n = 1, nspec
                   CALL pmci_interp_1sto_lr( chem_species(n)%conc, chem_spec_c(:,:,:,n),            &
                        kcto, jflo, jfuo, kflo, kfuo, 'l', 's' )
                ENDDO
             ENDIF

          ENDIF
!
!--       Right border pe
          IF ( bc_dirichlet_r )  THEN
             
             CALL pmci_interp_1sto_lr( u, uc, kcto, jflo, jfuo, kflo, kfuo, 'r', 'u' )
             CALL pmci_interp_1sto_lr( v, vc, kcto, jflv, jfuv, kflo, kfuo, 'r', 'v' )
             CALL pmci_interp_1sto_lr( w, wc, kctw, jflo, jfuo, kflw, kfuw, 'r', 'w' )

             IF ( (        rans_mode_parent  .AND.         rans_mode )  .OR.                        &
                  (  .NOT. rans_mode_parent  .AND.  .NOT.  rans_mode  .AND.                         &
                     .NOT. constant_diffusion ) )  THEN
!                CALL pmci_interp_1sto_lr( e, ec, kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, 'r', 'e' )
!
!--             Interpolation of e is replaced by the Neumann condition. 
                DO ibgp = nx+1, nx+nbgp
                   e(nzb:nzt,nys:nyn,ibgp) = e(nzb:nzt,nys:nyn,nx)
                ENDDO
             ENDIF

             IF ( rans_mode_parent  .AND.  rans_mode  .AND.  rans_tke_e )  THEN
                CALL pmci_interp_1sto_lr( diss, dissc, kcto, jflo, jfuo, kflo, kfuo, 'r', 's' )

             ENDIF

             IF ( .NOT. neutral )  THEN
                CALL pmci_interp_1sto_lr( pt, ptc, kcto, jflo, jfuo, kflo, kfuo, 'r', 's' )
             ENDIF

             IF ( humidity )  THEN
                CALL pmci_interp_1sto_lr( q, q_c, kcto, jflo, jfuo, kflo, kfuo, 'r', 's' )

                IF ( bulk_cloud_model  .AND.  microphysics_morrison )  THEN
                   CALL pmci_interp_1sto_lr( qc, qcc, kcto, jflo, jfuo, kflo, kfuo, 'r', 's' ) 
                   CALL pmci_interp_1sto_lr( nc, ncc, kcto, jflo, jfuo, kflo, kfuo, 'r', 's' )
                ENDIF

                IF ( bulk_cloud_model  .AND.  microphysics_seifert )  THEN
                   CALL pmci_interp_1sto_lr( qr, qrc, kcto, jflo, jfuo, kflo, kfuo, 'r', 's' ) 
                   CALL pmci_interp_1sto_lr( nr, nrc, kcto, jflo, jfuo, kflo, kfuo, 'r', 's' ) 
                ENDIF

             ENDIF

             IF ( passive_scalar )  THEN
                CALL pmci_interp_1sto_lr( s, sc, kcto, jflo, jfuo, kflo, kfuo, 'r', 's' )
             ENDIF

             IF ( air_chemistry  .AND.  nest_chemistry )  THEN
                DO  n = 1, nspec
                   CALL pmci_interp_1sto_lr( chem_species(n)%conc, chem_spec_c(:,:,:,n),            &
                        kcto, jflo, jfuo, kflo, kfuo, 'r', 's' )
                ENDDO
             ENDIF
          ENDIF
!
!--       South border pe
          IF ( bc_dirichlet_s )  THEN

             CALL pmci_interp_1sto_sn( v, vc, kcto, iflo, ifuo, kflo, kfuo, 's', 'v' )
             CALL pmci_interp_1sto_sn( w, wc, kctw, iflo, ifuo, kflw, kfuw, 's', 'w' )
             CALL pmci_interp_1sto_sn( u, uc, kcto, iflu, ifuu, kflo, kfuo, 's', 'u' )

             IF ( (        rans_mode_parent  .AND.         rans_mode )  .OR.   &
                  (  .NOT. rans_mode_parent  .AND.  .NOT.  rans_mode  .AND.    &
                     .NOT. constant_diffusion ) )  THEN
!                CALL pmci_interp_1sto_sn( e, ec, kcto, iflo, ifuo, kflo, kfuo, 's', 'e' )
!
!--             Interpolation of e is replaced by the Neumann condition. 
                DO jbgp = -nbgp, -1
                   e(nzb:nzt,jbgp,nxl:nxr) = e(nzb:nzt,0,nxl:nxr)
                ENDDO
             ENDIF

             IF ( rans_mode_parent  .AND.  rans_mode  .AND.  rans_tke_e )  THEN
                CALL pmci_interp_1sto_sn( diss, dissc, kcto, iflo, ifuo, kflo, kfuo, 's', 's' )
             ENDIF

             IF ( .NOT. neutral )  THEN
                CALL pmci_interp_1sto_sn( pt, ptc, kcto, iflo, ifuo, kflo, kfuo, 's', 's' )
             ENDIF

             IF ( humidity )  THEN
                CALL pmci_interp_1sto_sn( q, q_c, kcto, iflo, ifuo, kflo, kfuo, 's', 's' )

                IF ( bulk_cloud_model  .AND.  microphysics_morrison )  THEN
                   CALL pmci_interp_1sto_sn( qc, qcc, kcto, iflo, ifuo, kflo, kfuo, 's', 's' )
                   CALL pmci_interp_1sto_sn( nc, ncc, kcto, iflo, ifuo, kflo, kfuo, 's', 's' )
                ENDIF

                IF ( bulk_cloud_model  .AND.  microphysics_seifert )  THEN
                   CALL pmci_interp_1sto_sn( qr, qrc, kcto, iflo, ifuo, kflo, kfuo, 's', 's' )
                   CALL pmci_interp_1sto_sn( nr, nrc, kcto, iflo, ifuo, kflo, kfuo, 's', 's' )
                ENDIF

             ENDIF

             IF ( passive_scalar )  THEN
                CALL pmci_interp_1sto_sn( s, sc, kcto, iflo, ifuo, kflo, kfuo, 's', 's' )
             ENDIF

             IF ( air_chemistry  .AND.  nest_chemistry )  THEN
                DO  n = 1, nspec
                   CALL pmci_interp_1sto_sn( chem_species(n)%conc, chem_spec_c(:,:,:,n),            &
                        kcto, iflo, ifuo, kflo, kfuo, 's', 's' )
                ENDDO
             ENDIF
          ENDIF
!
!--       North border pe
          IF ( bc_dirichlet_n )  THEN
             
             CALL pmci_interp_1sto_sn( v, vc, kcto, iflo, ifuo, kflo, kfuo, 'n', 'v' )
             CALL pmci_interp_1sto_sn( w, wc, kctw, iflo, ifuo, kflw, kfuw, 'n', 'w' )
             CALL pmci_interp_1sto_sn( u, uc, kcto, iflu, ifuu, kflo, kfuo, 'n', 'u' )

             IF ( (        rans_mode_parent  .AND.         rans_mode )  .OR.                        & 
                  (  .NOT. rans_mode_parent  .AND.  .NOT.  rans_mode  .AND.                         &
                     .NOT. constant_diffusion ) )  THEN
!                CALL pmci_interp_1sto_sn( e, ec, kcto, iflo, ifuo, kflo, kfuo, 'n', 'e' )
!
!--             Interpolation of e is replaced by the Neumann condition. 
                DO jbgp = ny+1, ny+nbgp
                   e(nzb:nzt,jbgp,nxl:nxr) = e(nzb:nzt,ny,nxl:nxr)
                ENDDO
             ENDIF

             IF ( rans_mode_parent  .AND.  rans_mode  .AND.  rans_tke_e )  THEN
                CALL pmci_interp_1sto_sn( diss, dissc, kcto, iflo, ifuo, kflo, kfuo, 'n', 's' )
             ENDIF

             IF ( .NOT. neutral )  THEN
                CALL pmci_interp_1sto_sn( pt, ptc, kcto, iflo, ifuo, kflo, kfuo, 'n', 's' )
             ENDIF

             IF ( humidity )  THEN
                CALL pmci_interp_1sto_sn( q, q_c, kcto, iflo, ifuo, kflo, kfuo, 'n', 's' )

                IF ( bulk_cloud_model  .AND.  microphysics_morrison )  THEN
                   CALL pmci_interp_1sto_sn( qc, qcc, kcto, iflo, ifuo, kflo, kfuo, 'n', 's' )
                   CALL pmci_interp_1sto_sn( nc, ncc, kcto, iflo, ifuo, kflo, kfuo, 'n', 's' )
                ENDIF

                IF ( bulk_cloud_model  .AND.  microphysics_seifert )  THEN
                   CALL pmci_interp_1sto_sn( qr, qrc, kcto, iflo, ifuo, kflo, kfuo, 'n', 's' )
                   CALL pmci_interp_1sto_sn( nr, nrc, kcto, iflo, ifuo, kflo, kfuo, 'n', 's' )
                ENDIF

             ENDIF

             IF ( passive_scalar )  THEN
                CALL pmci_interp_1sto_sn( s, sc, kcto, iflo, ifuo, kflo, kfuo, 'n', 's' )
             ENDIF

             IF ( air_chemistry  .AND.  nest_chemistry )  THEN
                DO  n = 1, nspec
                   CALL pmci_interp_1sto_sn( chem_species(n)%conc, chem_spec_c(:,:,:,n),            &
                        kcto, iflo, ifuo, kflo, kfuo, 'n', 's' )
                ENDDO
             ENDIF
          ENDIF

       ENDIF       ! IF ( nesting_mode /= 'vertical' )
!
!--    All PEs are top-border PEs
       CALL pmci_interp_1sto_t( w, wc, kctw, iflo, ifuo, jflo, jfuo, 'w' )
       CALL pmci_interp_1sto_t( u, uc, kcto, iflu, ifuu, jflo, jfuo, 'u' )
       CALL pmci_interp_1sto_t( v, vc, kcto, iflo, ifuo, jflv, jfuv, 'v' )

       IF ( (        rans_mode_parent  .AND.         rans_mode )  .OR.         &
            (  .NOT. rans_mode_parent  .AND.  .NOT.  rans_mode  .AND.          &
               .NOT. constant_diffusion ) )  THEN
!          CALL pmci_interp_1sto_t( e, ec, kcto, iflo, ifuo, jflo, jfuo, 'e' )
!
!--       Interpolation of e is replaced by the Neumann condition. 
          e(nzt+1,nys:nyn,nxl:nxr) = e(nzt,nys:nyn,nxl:nxr)
       ENDIF

       IF ( rans_mode_parent  .AND.  rans_mode  .AND.  rans_tke_e )  THEN
          CALL pmci_interp_1sto_t( diss, dissc, kcto, iflo, ifuo, jflo, jfuo, 's' )
       ENDIF

       IF ( .NOT. neutral )  THEN
          CALL pmci_interp_1sto_t( pt, ptc, kcto, iflo, ifuo, jflo, jfuo, 's' )
       ENDIF

       IF ( humidity )  THEN
          CALL pmci_interp_1sto_t( q, q_c, kcto, iflo, ifuo, jflo, jfuo, 's' )
          IF ( bulk_cloud_model  .AND.  microphysics_morrison )  THEN
             CALL pmci_interp_1sto_t( qc, qcc, kcto, iflo, ifuo, jflo, jfuo, 's' )
             CALL pmci_interp_1sto_t( nc, ncc, kcto, iflo, ifuo, jflo, jfuo, 's' )
          ENDIF
          IF ( bulk_cloud_model  .AND.  microphysics_seifert )  THEN
             CALL pmci_interp_1sto_t( qr, qrc, kcto, iflo, ifuo, jflo, jfuo, 's' )
             CALL pmci_interp_1sto_t( nr, nrc, kcto, iflo, ifuo, jflo, jfuo, 's' )
          ENDIF
       ENDIF

       IF ( passive_scalar )  THEN
          CALL pmci_interp_1sto_t( s, sc, kcto, iflo, ifuo, jflo, jfuo, 's' )
       ENDIF

       IF ( air_chemistry  .AND.  nest_chemistry )  THEN
          DO  n = 1, nspec
             CALL pmci_interp_1sto_t( chem_species(n)%conc, chem_spec_c(:,:,:,n),                   &
                                      kcto, iflo, ifuo, jflo, jfuo, 's' )
          ENDDO
       ENDIF

   END SUBROUTINE pmci_interpolation



   SUBROUTINE pmci_anterpolation

!
!--   A wrapper routine for all anterpolation actions.
!--   Note that TKE is not anterpolated.
      IMPLICIT NONE
      INTEGER(iwp) ::  n          !< running index for number of chemical species

      
      CALL pmci_anterp_tophat( u,  uc,  kcto, iflu, ifuu, jflo, jfuo, kflo, kfuo, ijkfc_u, 'u' )
      CALL pmci_anterp_tophat( v,  vc,  kcto, iflo, ifuo, jflv, jfuv, kflo, kfuo, ijkfc_v, 'v' )
      CALL pmci_anterp_tophat( w,  wc,  kctw, iflo, ifuo, jflo, jfuo, kflw, kfuw, ijkfc_w, 'w' )
!
!--   Anterpolation of TKE and dissipation rate if parent and child are in 
!--   RANS mode.
      IF ( rans_mode_parent  .AND.  rans_mode )  THEN
         CALL pmci_anterp_tophat( e, ec, kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, ijkfc_s, 'e' )
!
!--      Anterpolation of dissipation rate only if TKE-e closure is applied.
         IF ( rans_tke_e )  THEN
            CALL pmci_anterp_tophat( diss, dissc, kcto, iflo, ifuo, jflo, jfuo,&
                                     kflo, kfuo, ijkfc_s, 'diss' )
         ENDIF

      ENDIF

      IF ( .NOT. neutral )  THEN
         CALL pmci_anterp_tophat( pt, ptc, kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, ijkfc_s, 'pt' )
      ENDIF

      IF ( humidity )  THEN

         CALL pmci_anterp_tophat( q, q_c, kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, ijkfc_s, 'q' )

         IF ( bulk_cloud_model  .AND.  microphysics_morrison )  THEN

            CALL pmci_anterp_tophat( qc, qcc, kcto, iflo, ifuo, jflo, jfuo,                         &
                                     kflo, kfuo, ijkfc_s, 'qc' )
            
            CALL pmci_anterp_tophat( nc, ncc, kcto, iflo, ifuo, jflo, jfuo,                         &
                                     kflo, kfuo, ijkfc_s, 'nc' )

         ENDIF

         IF ( bulk_cloud_model  .AND.  microphysics_seifert )  THEN

            CALL pmci_anterp_tophat( qr, qrc, kcto, iflo, ifuo, jflo, jfuo,                         &
                                     kflo, kfuo, ijkfc_s, 'qr' )

            CALL pmci_anterp_tophat( nr, nrc, kcto, iflo, ifuo, jflo, jfuo,                         &
                                     kflo, kfuo, ijkfc_s, 'nr' )

         ENDIF

      ENDIF

      IF ( passive_scalar )  THEN
         CALL pmci_anterp_tophat( s, sc, kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, ijkfc_s, 's' )
      ENDIF

      IF ( air_chemistry  .AND.  nest_chemistry )  THEN
         DO  n = 1, nspec
            CALL pmci_anterp_tophat( chem_species(n)%conc, chem_spec_c(:,:,:,n),                    &
                                     kcto, iflo, ifuo, jflo, jfuo, kflo, kfuo, ijkfc_s, 's' )
         ENDDO
      ENDIF

   END SUBROUTINE pmci_anterpolation



   SUBROUTINE pmci_interp_1sto_lr( f, fc, kct, jfl, jfu, kfl, kfu, edge, var )
!
!--   Interpolation of ghost-node values used as the child-domain boundary
!--   conditions. This subroutine handles the left and right boundaries. 
      IMPLICIT NONE

      REAL(wp), DIMENSION(nzb:nzt+1,nysg:nyng,nxlg:nxrg), INTENT(INOUT) ::  f   !< Child-grid array
      REAL(wp), DIMENSION(0:cg%nz+1,jcs:jcn,icl:icr), INTENT(IN)        ::  fc  !< Parent-grid array
      INTEGER(iwp) :: kct                                     !< The parent-grid index in z-direction just below the boundary value node
      INTEGER(iwp), DIMENSION(jcsa:jcna), INTENT(IN) ::  jfl  !< Indicates start index of child cells belonging to certain parent cell - y direction
      INTEGER(iwp), DIMENSION(jcsa:jcna), INTENT(IN) ::  jfu  !< Indicates end index of child cells belonging to certain parent cell - y direction
      INTEGER(iwp), DIMENSION(0:cg%nz+1), INTENT(IN) ::  kfl  !< Indicates start index of child cells belonging to certain parent cell - z direction
      INTEGER(iwp), DIMENSION(0:cg%nz+1), INTENT(IN) ::  kfu  !< Indicates end index of child cells belonging to certain parent cell - z direction
      CHARACTER(LEN=1), INTENT(IN) ::  edge                   !< Edge symbol: 'l' or 'r'
      CHARACTER(LEN=1), INTENT(IN) ::  var                    !< Variable symbol: 'u', 'v', 'w' or 's'
!
!--   Local variables:
      INTEGER(iwp) ::  ib       !< Fixed i-index pointing to the node just behind the boundary-value node
      INTEGER(iwp) ::  ibc      !< Fixed i-index pointing to the boundary-value nodes (either i or iend)
      INTEGER(iwp) ::  ibgp     !< Index running over the redundant boundary ghost points in i-direction
      INTEGER(iwp) ::  ierr     !< MPI error code
      INTEGER(iwp) ::  j        !< Running index in the y-direction
      INTEGER(iwp) ::  k        !< Running index in the z-direction
      INTEGER(iwp) ::  lbeg     !< l-index pointing to the starting point of workarrc_lr in the l-direction 
      INTEGER(iwp) ::  lw       !< Reduced l-index for workarrc_lr pointing to the boundary ghost node
      INTEGER(iwp) ::  lwp      !< Reduced l-index for workarrc_lr pointing to the first prognostic node
      INTEGER(iwp) ::  m        !< Parent-grid running index in the y-direction
      INTEGER(iwp) ::  n        !< Parent-grid running index in the z-direction
      REAL(wp) ::  cb           !< Interpolation coefficient for the boundary ghost node  
      REAL(wp) ::  cp           !< Interpolation coefficient for the first prognostic node
      REAL(wp) ::  f_interp_1   !< Value interpolated in x direction from the parent-grid data
      REAL(wp) ::  f_interp_2   !< Auxiliary value interpolated in x direction from the parent-grid data

! 
!--   Check which edge is to be handled
      IF ( edge == 'l' )  THEN
!
!--      For u, nxl is a ghost node, but not for the other variables
         IF ( var == 'u' )  THEN
            ibc   = nxl    
            ib    = ibc - 1
            lw    = 2
            lwp   = lw        ! This is redundant when var == 'u' 
            lbeg  = icl
         ELSE
            ibc   = nxl - 1
            ib    = ibc - 1
            lw    = 1
            lwp   = 2
            lbeg  = icl
         ENDIF        
      ELSEIF ( edge == 'r' )  THEN
         IF ( var == 'u' )  THEN
            ibc   = nxr + 1 
            ib    = ibc + 1
            lw    = 1
            lwp   = lw        ! This is redundant when var == 'u'            
            lbeg  = icr - 2
         ELSE
            ibc   = nxr + 1
            ib    = ibc + 1
            lw    = 1
            lwp   = 0
            lbeg  = icr - 2
         ENDIF         
      ENDIF
!
!--   Interpolation coefficients
      IF  ( interpolation_scheme_lrsn == 1 )  THEN
         cb = 1.0_wp  ! 1st-order upwind 
      ELSE IF  ( interpolation_scheme_lrsn == 2 )  THEN
         cb = 0.5_wp  ! 2nd-order central
      ELSE
         cb = 0.5_wp  ! 2nd-order central (default)
      ENDIF         
      cp    = 1.0_wp - cb
!
!--   Substitute the necessary parent-grid data to the work array workarrc_lr. 
      workarrc_lr = 0.0_wp     
      IF  ( pdims(2) > 1 )  THEN
#if defined( __parallel )
         IF  ( bc_dirichlet_s )  THEN 
            workarrc_lr(0:cg%nz+1,jcsw:jcnw-1,0:2)                              &
                 = fc(0:cg%nz+1,jcsw:jcnw-1,lbeg:lbeg+2)
         ELSE IF  ( bc_dirichlet_n )  THEN
            workarrc_lr(0:cg%nz+1,jcsw+1:jcnw,0:2)                              &
                 = fc(0:cg%nz+1,jcsw+1:jcnw,lbeg:lbeg+2)
         ELSE
            workarrc_lr(0:cg%nz+1,jcsw+1:jcnw-1,0:2)                            &
                 = fc(0:cg%nz+1,jcsw+1:jcnw-1,lbeg:lbeg+2)
         ENDIF
!
!--      South-north exchange if more than one PE subdomain in the y-direction.
!--      Note that in case of 3-D nesting the south (psouth == MPI_PROC_NULL) 
!--      and north (pnorth == MPI_PROC_NULL) boundaries are not exchanged 
!--      because the nest domain is not cyclic.
!--      From south to north
         CALL MPI_SENDRECV( workarrc_lr(0,jcsw+1,0), 1,                         &
              workarrc_lr_exchange_type, psouth,  0,                            &
              workarrc_lr(0,jcnw,0), 1,                                         &
              workarrc_lr_exchange_type, pnorth,  0,                            &
              comm2d, status, ierr )                                      
!                                                                         
!--      From north to south                                              
         CALL MPI_SENDRECV( workarrc_lr(0,jcnw-1,0), 1,                         &
              workarrc_lr_exchange_type, pnorth,  1,                            &
              workarrc_lr(0,jcsw,0), 1,                                         &
              workarrc_lr_exchange_type, psouth,  1,                            &
              comm2d, status, ierr )                                      
#endif                                                                    
      ELSE                                                                
         workarrc_lr(0:cg%nz+1,jcsw:jcnw,0:2)                                   &
              = fc(0:cg%nz+1,jcsw:jcnw,lbeg:lbeg+2)            
      ENDIF

      IF  ( var == 'u' )  THEN

         DO  m = jcsw, jcnw
            DO n = 0, kct 
               
               DO  j = jfl(m), jfu(m)
                  DO  k = kfl(n), kfu(n)
                     f(k,j,ibc) = workarrc_lr(n,m,lw)
                  ENDDO
               ENDDO

            ENDDO
         ENDDO

      ELSE IF  ( var == 'v' )  THEN
         
         DO  m = jcsw, jcnw-1
            DO n = 0, kct 
!
!--            First interpolate to the flux point
               f_interp_1 = cb * workarrc_lr(n,m,lw)   + cp * workarrc_lr(n,m,lwp)
               f_interp_2 = cb * workarrc_lr(n,m+1,lw) + cp * workarrc_lr(n,m+1,lwp)
!
!--            Use averages of the neighbouring matching grid-line values
               DO  j = jfl(m), jfl(m+1)
                  f(kfl(n):kfu(n),j,ibc) = 0.5_wp * ( f_interp_1 + f_interp_2 )
               ENDDO
!
!--            Then set the values along the matching grid-lines  
               IF  ( MOD( jfl(m), jgsr ) == 0 )  THEN
                  f(kfl(n):kfu(n),jfl(m),ibc) = f_interp_1
               ENDIF
            ENDDO
         ENDDO
!
!--      Finally, set the values along the last matching grid-line  
         IF  ( MOD( jfl(jcnw), jgsr ) == 0 )  THEN
            DO  n = 0, kct
               f_interp_1 = cb * workarrc_lr(n,jcnw,lw) + cp * workarrc_lr(n,jcnw,lwp)
               f(kfl(n):kfu(n),jfl(jcnw),ibc) = f_interp_1
            ENDDO
         ENDIF
!
!--      A gap may still remain in some cases if the subdomain size is not 
!--      divisible by the grid-spacing ratio. In such a case, fill the 
!--      gap. Note however, this operation may produce some additional 
!--      momentum conservation error.
         IF  ( jfl(jcnw) < nyn )  THEN
            DO  n = 0, kct
               DO  j = jfl(jcnw)+1, nyn
                  f(kfl(n):kfu(n),j,ibc) = f(kfl(n):kfu(n),jfl(jcnw),ibc)
               ENDDO
            ENDDO
         ENDIF

      ELSE IF  ( var == 'w' )  THEN

         DO  m = jcsw, jcnw
            DO n = 0, kct + 1   ! It is important to go up to kct+1  
!
!--            Interpolate to the flux point
               f_interp_1 = cb * workarrc_lr(n,m,lw) + cp * workarrc_lr(n,m,lwp)
!
!--            First substitute only the matching-node values
               f(kfu(n),jfl(m):jfu(m),ibc) = f_interp_1
                  
            ENDDO
         ENDDO

         DO  m = jcsw, jcnw
            DO n = 1, kct + 1   ! It is important to go up to kct+1  
!
!--            Then fill up the nodes in between with the averages                  
               DO  k = kfu(n-1)+1, kfu(n)-1 
                  f(k,jfl(m):jfu(m),ibc) = 0.5_wp * ( f(kfu(n-1),jfl(m):jfu(m),ibc) &
                       + f(kfu(n),jfl(m):jfu(m),ibc) )
               ENDDO
                  
            ENDDO
         ENDDO

      ELSE   ! any scalar
         
         DO  m = jcsw, jcnw
            DO n = 0, kct 
!
!--            Interpolate to the flux point
               f_interp_1 = cb * workarrc_lr(n,m,lw) + cp * workarrc_lr(n,m,lwp)
               DO  j = jfl(m), jfu(m)
                  DO  k = kfl(n), kfu(n)
                     f(k,j,ibc) = f_interp_1
                  ENDDO
               ENDDO

            ENDDO
         ENDDO

      ENDIF  ! var
!
!--   Fill up also the redundant 2nd and 3rd ghost-node layers
      IF ( edge == 'l' )  THEN
         DO  ibgp = -nbgp, ib
            f(0:nzt+1,nysg:nyng,ibgp) = f(0:nzt+1,nysg:nyng,ibc)
         ENDDO
      ELSEIF ( edge == 'r' )  THEN
         DO  ibgp = ib, nx+nbgp
            f(0:nzt+1,nysg:nyng,ibgp) = f(0:nzt+1,nysg:nyng,ibc)
         ENDDO
      ENDIF

   END SUBROUTINE pmci_interp_1sto_lr



   SUBROUTINE pmci_interp_1sto_sn( f, fc, kct, ifl, ifu, kfl, kfu, edge, var )
!
!--   Interpolation of ghost-node values used as the child-domain boundary
!--   conditions. This subroutine handles the south and north boundaries. 
      IMPLICIT NONE

      REAL(wp), DIMENSION(nzb:nzt+1,nysg:nyng,nxlg:nxrg), INTENT(INOUT) ::  f   !< Child-grid array
      REAL(wp), DIMENSION(0:cg%nz+1,jcs:jcn,icl:icr), INTENT(IN)        ::  fc  !< Parent-grid array
      INTEGER(iwp) :: kct                                     !< The parent-grid index in z-direction just below the boundary value node
      INTEGER(iwp), DIMENSION(icla:icra), INTENT(IN) ::  ifl  !< Indicates start index of child cells belonging to certain parent cell - x direction
      INTEGER(iwp), DIMENSION(icla:icra), INTENT(IN) ::  ifu  !< Indicates end index of child cells belonging to certain parent cell - x direction
      INTEGER(iwp), DIMENSION(0:cg%nz+1), INTENT(IN) ::  kfl  !< Indicates start index of child cells belonging to certain parent cell - z direction
      INTEGER(iwp), DIMENSION(0:cg%nz+1), INTENT(IN) ::  kfu  !< Indicates end index of child cells belonging to certain parent cell - z direction
      CHARACTER(LEN=1), INTENT(IN) ::  edge   !< Edge symbol: 's' or 'n' 
      CHARACTER(LEN=1), INTENT(IN) ::  var    !< Variable symbol: 'u', 'v', 'w' or 's'
!
!--   Local variables:      
      INTEGER(iwp) ::  i        !< Running index in the x-direction
      INTEGER(iwp) ::  ierr     !< MPI error code
      INTEGER(iwp) ::  jb       !< Fixed j-index pointing to the node just behind the boundary-value node
      INTEGER(iwp) ::  jbc      !< Fixed j-index pointing to the boundary-value nodes (either j or jend)
      INTEGER(iwp) ::  jbgp     !< Index running over the redundant boundary ghost points in j-direction
      INTEGER(iwp) ::  k        !< Running index in the z-direction
      INTEGER(iwp) ::  l        !< Parent-grid running index in the x-direction
      INTEGER(iwp) ::  mbeg     !< m-index pointing to the starting point of workarrc_sn in the m-direction 
      INTEGER(iwp) ::  mw       !< Reduced m-index for workarrc_sn pointing to the boundary ghost node 
      INTEGER(iwp) ::  mwp      !< Reduced m-index for workarrc_sn pointing to the first prognostic node
      INTEGER(iwp) ::  n        !< Parent-grid running index in the z-direction
      REAL(wp) ::  cb           !< Interpolation coefficient for the boundary ghost node  
      REAL(wp) ::  cp           !< Interpolation coefficient for the first prognostic node
      REAL(wp) ::  f_interp_1   !< Value interpolated in y direction from the parent-grid data
      REAL(wp) ::  f_interp_2   !< Auxiliary value interpolated in y direction from the parent-grid data

!
!--   Check which edge is to be handled: south or north
      IF ( edge == 's' )  THEN
!
!--      For v, nys is a ghost node, but not for the other variables
         IF ( var == 'v' )  THEN
            jbc   = nys
            jb    = jbc - 1
            mw    = 2
            mwp   = 2         ! This is redundant when var == 'v'
            mbeg  = jcs
         ELSE
            jbc   = nys - 1
            jb    = jbc - 1
            mw    = 1
            mwp   = 2
            mbeg  = jcs
         ENDIF
      ELSEIF ( edge == 'n' )  THEN
         IF ( var == 'v' )  THEN
            jbc   = nyn + 1
            jb    = jbc + 1
            mw    = 1
            mwp   = 0         ! This is redundant when var == 'v'     
            mbeg  = jcn - 2
         ELSE
            jbc   = nyn + 1
            jb    = jbc + 1
            mw    = 1
            mwp   = 0
            mbeg  = jcn - 2
         ENDIF
      ENDIF
!
!--   Interpolation coefficients
      IF  ( interpolation_scheme_lrsn == 1 )  THEN
         cb = 1.0_wp  ! 1st-order upwind 
      ELSE IF  ( interpolation_scheme_lrsn == 2 )  THEN
         cb = 0.5_wp  ! 2nd-order central
      ELSE
         cb = 0.5_wp  ! 2nd-order central (default)
      ENDIF         
      cp    = 1.0_wp - cb
!
!--   Substitute the necessary parent-grid data to the work array workarrc_sn. 
      workarrc_sn = 0.0_wp     
      IF  ( pdims(1) > 1 )  THEN
#if defined( __parallel )
         IF  ( bc_dirichlet_l )  THEN
            workarrc_sn(0:cg%nz+1,0:2,iclw:icrw-1)                              &
                 = fc(0:cg%nz+1,mbeg:mbeg+2,iclw:icrw-1)
         ELSE IF  ( bc_dirichlet_r )  THEN
            workarrc_sn(0:cg%nz+1,0:2,iclw+1:icrw)                              &
                 = fc(0:cg%nz+1,mbeg:mbeg+2,iclw+1:icrw)
         ELSE
            workarrc_sn(0:cg%nz+1,0:2,iclw+1:icrw-1)                            &
                 = fc(0:cg%nz+1,mbeg:mbeg+2,iclw+1:icrw-1)
         ENDIF
!
!--      Left-right exchange if more than one PE subdomain in the x-direction.
!--      Note that in case of 3-D nesting the left (pleft == MPI_PROC_NULL) and 
!--      right (pright == MPI_PROC_NULL) boundaries are not exchanged because 
!--      the nest domain is not cyclic.
!--      From left to right
         CALL MPI_SENDRECV( workarrc_sn(0,0,iclw+1), 1,                         &
              workarrc_sn_exchange_type, pleft,   0,                            &
              workarrc_sn(0,0,icrw), 1,                                         &
              workarrc_sn_exchange_type, pright,  0,                            &
              comm2d, status, ierr ) 
!
!--      From right to left        
         CALL MPI_SENDRECV( workarrc_sn(0,0,icrw-1), 1,                         &
              workarrc_sn_exchange_type, pright,  1,                            &
              workarrc_sn(0,0,iclw), 1,                                         &
              workarrc_sn_exchange_type, pleft,   1,                            &
              comm2d, status, ierr )
#endif      
      ELSE
         workarrc_sn(0:cg%nz+1,0:2,iclw+1:icrw-1)                               &
              = fc(0:cg%nz+1,mbeg:mbeg+2,iclw+1:icrw-1)
      ENDIF

      IF  ( var == 'v' )  THEN

         DO  l = iclw, icrw
            DO n = 0, kct 
               
               DO  i = ifl(l), ifu(l)
                  DO  k = kfl(n), kfu(n)
                     f(k,jbc,i) = workarrc_sn(n,mw,l)
                  ENDDO
               ENDDO

            ENDDO
         ENDDO

      ELSE IF  ( var == 'u' )  THEN
         
         DO  l = iclw, icrw-1
            DO n = 0, kct
!
!--            First interpolate to the flux point
               f_interp_1 = cb * workarrc_sn(n,mw,l)   + cp * workarrc_sn(n,mwp,l)
               f_interp_2 = cb * workarrc_sn(n,mw,l+1) + cp * workarrc_sn(n,mwp,l+1)
!
!--            Use averages of the neighbouring matching grid-line values
               DO  i = ifl(l), ifl(l+1)
                  f(kfl(n):kfu(n),jbc,i) = 0.5_wp * ( f_interp_1 + f_interp_2 )
               ENDDO
!
!--            Then set the values along the matching grid-lines  
               IF  ( MOD( ifl(l), igsr ) == 0 )  THEN
                  f(kfl(n):kfu(n),jbc,ifl(l)) = f_interp_1
               ENDIF

            ENDDO
         ENDDO
!
!--      Finally, set the values along the last matching grid-line  
         IF  ( MOD( ifl(icrw), igsr ) == 0 )  THEN
            DO  n = 0, kct
               f_interp_1 = cb * workarrc_sn(n,mw,icrw) + cp * workarrc_sn(n,mwp,icrw)
               f(kfl(n):kfu(n),jbc,ifl(icrw)) = f_interp_1
            ENDDO
         ENDIF
!
!--      A gap may still remain in some cases if the subdomain size is not 
!--      divisible by the grid-spacing ratio. In such a case, fill the 
!--      gap. Note however, this operation may produce some additional 
!--      momentum conservation error.
         IF  ( ifl(icrw) < nxr )  THEN
            DO  n = 0, kct
               DO  i = ifl(icrw)+1, nxr
                  f(kfl(n):kfu(n),jbc,i) = f(kfl(n):kfu(n),jbc,ifl(icrw))
               ENDDO
            ENDDO
         ENDIF

      ELSE IF  ( var == 'w' )  THEN

         DO  l = iclw, icrw
            DO n = 0, kct + 1   ! It is important to go up to kct+1  
!
!--            Interpolate to the flux point
               f_interp_1 = cb * workarrc_sn(n,mw,l) + cp * workarrc_sn(n,mwp,l)
!                  
!--            First substitute only the matching-node values                 
               f(kfu(n),jbc,ifl(l):ifu(l)) = f_interp_1

            ENDDO
         ENDDO

         DO  l = iclw, icrw
            DO n = 1, kct + 1   ! It is important to go up to kct+1  
!
!--            Then fill up the nodes in between with the averages
               DO  k = kfu(n-1)+1, kfu(n)-1 
                  f(k,jbc,ifl(l):ifu(l)) = 0.5_wp * ( f(kfu(n-1),jbc,ifl(l):ifu(l)) &
                       + f(kfu(n),jbc,ifl(l):ifu(l)) )
               ENDDO

            ENDDO
         ENDDO

      ELSE   ! Any scalar
         
         DO  l = iclw, icrw
            DO n = 0, kct 
!
!--            Interpolate to the flux point
               f_interp_1 = cb * workarrc_sn(n,mw,l) + cp * workarrc_sn(n,mwp,l)
               DO  i = ifl(l), ifu(l)
                  DO  k = kfl(n), kfu(n)
                     f(k,jbc,i) = f_interp_1
                  ENDDO
               ENDDO

            ENDDO
         ENDDO

      ENDIF  ! var
!
!--   Fill up also the redundant 2nd and 3rd ghost-node layers
      IF ( edge == 's' )  THEN
         DO  jbgp = -nbgp, jb
            f(0:nzt+1,jbgp,nxlg:nxrg) = f(0:nzt+1,jbc,nxlg:nxrg)
         ENDDO
      ELSEIF ( edge == 'n' )  THEN
         DO  jbgp = jb, ny+nbgp
            f(0:nzt+1,jbgp,nxlg:nxrg) = f(0:nzt+1,jbc,nxlg:nxrg)
         ENDDO
      ENDIF

   END SUBROUTINE pmci_interp_1sto_sn



   SUBROUTINE pmci_interp_1sto_t( f, fc, kct, ifl, ifu, jfl, jfu, var )
!
!--   Interpolation of ghost-node values used as the child-domain boundary
!--   conditions. This subroutine handles the top boundary. 
      IMPLICIT NONE

      REAL(wp), DIMENSION(nzb:nzt+1,nysg:nyng,nxlg:nxrg), INTENT(INOUT) ::  f    !< Child-grid array
      REAL(wp), DIMENSION(0:cg%nz+1,jcs:jcn,icl:icr), INTENT(IN)        ::  fc   !< Parent-grid array
      INTEGER(iwp), DIMENSION(icla:icra), INTENT(IN)    ::  ifl  !< Indicates start index of child cells belonging to certain parent cell - x direction
      INTEGER(iwp), DIMENSION(icla:icra), INTENT(IN)    ::  ifu  !< Indicates end index of child cells belonging to certain parent cell - x direction
      INTEGER(iwp), DIMENSION(jcsa:jcna), INTENT(IN)    ::  jfl  !< Indicates start index of child cells belonging to certain parent cell - y direction
      INTEGER(iwp), DIMENSION(jcsa:jcna), INTENT(IN)    ::  jfu  !< Indicates end index of child cells belonging to certain parent cell - y direction
      INTEGER(iwp) :: kct                                        !< The parent-grid index in z-direction just below the boundary value node
      CHARACTER(LEN=1), INTENT(IN) :: var                        !< Variable symbol: 'u', 'v', 'w' or 's'
!
!--   Local variables:
      REAL(wp)     ::  c31         !< Interpolation coefficient for the 3rd-order WS scheme
      REAL(wp)     ::  c32         !< Interpolation coefficient for the 3rd-order WS scheme
      REAL(wp)     ::  c33         !< Interpolation coefficient for the 3rd-order WS scheme
      REAL(wp)     ::  f_interp_1  !< Value interpolated in z direction from the parent-grid data
      REAL(wp)     ::  f_interp_2  !< Auxiliary value interpolated in z direction from the parent-grid data
      INTEGER(iwp) ::  i           !< Child-grid index in x-direction
      INTEGER(iwp) ::  iclc        !< Lower i-index limit for copying fc-data to workarrc_t
      INTEGER(iwp) ::  icrc        !< Upper i-index limit for copying fc-data to workarrc_t
      INTEGER(iwp) ::  ierr        !< MPI error code
      INTEGER(iwp) ::  j           !< Child-grid index in y-direction
      INTEGER(iwp) ::  jcsc        !< Lower j-index limit for copying fc-data to workarrc_t
      INTEGER(iwp) ::  jcnc        !< Upper j-index limit for copying fc-data to workarrc_t
      INTEGER(iwp) ::  k           !< Vertical child-grid index fixed to the boundary-value level 
      INTEGER(iwp) ::  l           !< Parent-grid index in x-direction
      INTEGER(iwp) ::  m           !< Parent-grid index in y-direction
      INTEGER(iwp) ::  nw          !< Reduced n-index for workarrc_t pointing to the boundary ghost node 


      IF ( var == 'w' )  THEN
         k    = nzt
      ELSE
         k    = nzt + 1
      ENDIF
      nw = 1
!
!--   Interpolation coefficients
      IF  ( interpolation_scheme_t == 1 )  THEN
         c31 =  0.0_wp           ! 1st-order upwind
         c32 =  1.0_wp
         c33 =  0.0_wp
      ELSE IF  ( interpolation_scheme_t == 2 )  THEN
         c31 =  0.5_wp           ! 2nd-order central
         c32 =  0.5_wp
         c33 =  0.0_wp
      ELSE            
         c31 =  2.0_wp / 6.0_wp  ! 3rd-order WS upwind biased (default)
         c32 =  5.0_wp / 6.0_wp
         c33 = -1.0_wp / 6.0_wp         
      ENDIF         
!
!--   Substitute the necessary parent-grid data to the work array. 
!--   Note that the dimension of workarrc_t is (0:2,jcsw:jcnw,iclw:icrw),
!--   And the jc?w and ic?w-index bounds depend on the location of the PE-
!--   subdomain relative to the side boundaries. 
      iclc = iclw + 1
      icrc = icrw - 1      
      jcsc = jcsw + 1
      jcnc = jcnw - 1
      IF  ( bc_dirichlet_l )  THEN
         iclc = iclw
      ENDIF
      IF  ( bc_dirichlet_r )  THEN
         icrc = icrw
      ENDIF
      IF  ( bc_dirichlet_s )  THEN
         jcsc = jcsw
      ENDIF
      IF  ( bc_dirichlet_n )  THEN
         jcnc = jcnw
      ENDIF
      workarrc_t = 0.0_wp
      workarrc_t(-2:3,jcsc:jcnc,iclc:icrc) = fc(kct-2:kct+3,jcsc:jcnc,iclc:icrc)
!
!--   Left-right exchange if more than one PE subdomain in the x-direction.
!--   Note that in case of 3-D nesting the left and right boundaries are 
!--   not exchanged because the nest domain is not cyclic.
#if defined( __parallel )
      IF  ( pdims(1) > 1 )  THEN
!
!--      From left to right
         CALL MPI_SENDRECV( workarrc_t(0,jcsw,iclw+1), 1,                       &
              workarrc_t_exchange_type_y, pleft,  0,                            &
              workarrc_t(0,jcsw,icrw), 1,                                       &
              workarrc_t_exchange_type_y, pright, 0,                            &
              comm2d, status, ierr ) 
!
!--      From right to left        
         CALL MPI_SENDRECV( workarrc_t(0,jcsw,icrw-1), 1,                       &
              workarrc_t_exchange_type_y, pright, 1,                            &
              workarrc_t(0,jcsw,iclw), 1,                                       &
              workarrc_t_exchange_type_y, pleft,  1,                            &
              comm2d, status, ierr )
      ENDIF
!
!--   South-north exchange if more than one PE subdomain in the y-direction.
!--   Note that in case of 3-D nesting the south and north boundaries are 
!--   not exchanged because the nest domain is not cyclic.
      IF  ( pdims(2) > 1 )  THEN
!
!--      From south to north         
         CALL MPI_SENDRECV( workarrc_t(0,jcsw+1,iclw), 1,                       &
              workarrc_t_exchange_type_x, psouth, 2,                            &
              workarrc_t(0,jcnw,iclw), 1,                                       &
              workarrc_t_exchange_type_x, pnorth, 2,                            &
              comm2d, status, ierr ) 
!
!--      From north to south        
         CALL MPI_SENDRECV( workarrc_t(0,jcnw-1,iclw), 1,                       &
              workarrc_t_exchange_type_x, pnorth, 3,                            &
              workarrc_t(0,jcsw,iclw), 1,                                       &
              workarrc_t_exchange_type_x, psouth, 3,                            &
              comm2d, status, ierr )
      ENDIF
#endif      

      IF  ( var == 'w' )  THEN
         DO  l = iclw, icrw
            DO  m = jcsw, jcnw
 
               DO  i = ifl(l), ifu(l)
                  DO  j = jfl(m), jfu(m)
                     f(k,j,i) = workarrc_t(nw,m,l)
                  ENDDO
               ENDDO

            ENDDO
         ENDDO

      ELSE IF  ( var == 'u' )  THEN

         DO  l = iclw, icrw-1
            DO  m = jcsw, jcnw
!
!--            First interpolate to the flux point using the 3rd-order WS scheme
               f_interp_1 = c31 * workarrc_t(nw-1,m,l)   + c32 * workarrc_t(nw,m,l)   + c33 * workarrc_t(nw+1,m,l)
               f_interp_2 = c31 * workarrc_t(nw-1,m,l+1) + c32 * workarrc_t(nw,m,l+1) + c33 * workarrc_t(nw+1,m,l+1)
!
!--            Use averages of the neighbouring matching grid-line values
               DO  i = ifl(l), ifl(l+1)
!                  f(k,jfl(m):jfu(m),i) = 0.5_wp * ( workarrc_t(nw,m,l)   &
!                       + workarrc_t(nw,m,l+1) )
                  f(k,jfl(m):jfu(m),i) = 0.5_wp * ( f_interp_1 + f_interp_2 )
               ENDDO
!
!--            Then set the values along the matching grid-lines  
               IF  ( MOD( ifl(l), igsr ) == 0 )  THEN
!
!--            First interpolate to the flux point using the 3rd-order WS scheme
                  f_interp_1 = c31 * workarrc_t(nw-1,m,l) + c32 * workarrc_t(nw,m,l) + c33 * workarrc_t(nw+1,m,l)                  
!                  f(k,jfl(m):jfu(m),ifl(l)) = workarrc_t(nw,m,l)
                  f(k,jfl(m):jfu(m),ifl(l)) = f_interp_1
               ENDIF

            ENDDO
         ENDDO
!
!--      Finally, set the values along the last matching grid-line  
         IF  ( MOD( ifl(icrw), igsr ) == 0 )  THEN
            DO  m = jcsw, jcnw
!
!--            First interpolate to the flux point using the 3rd-order WS scheme
               f_interp_1 = c31 * workarrc_t(nw-1,m,icrw) + c32 * workarrc_t(nw,m,icrw) + c33 * workarrc_t(nw+1,m,icrw)
!               f(k,jfl(m):jfu(m),ifl(icrw)) = workarrc_t(nw,m,icrw)
               f(k,jfl(m):jfu(m),ifl(icrw)) = f_interp_1
            ENDDO
         ENDIF
!
!--      A gap may still remain in some cases if the subdomain size is not 
!--      divisible by the grid-spacing ratio. In such a case, fill the 
!--      gap. Note however, this operation may produce some additional 
!--      momentum conservation error.
         IF  ( ifl(icrw) < nxr )  THEN
            DO  m = jcsw, jcnw
               DO  i = ifl(icrw)+1, nxr
                  f(k,jfl(m):jfu(m),i) = f(k,jfl(m):jfu(m),ifl(icrw))
               ENDDO
            ENDDO
         ENDIF

      ELSE IF  ( var == 'v' )  THEN

         DO  l = iclw, icrw
            DO  m = jcsw, jcnw-1
!
!--            First interpolate to the flux point using the 3rd-order WS scheme
               f_interp_1 = c31 * workarrc_t(nw-1,m,l)   + c32 * workarrc_t(nw,m,l)   + c33 * workarrc_t(nw+1,m,l)
               f_interp_2 = c31 * workarrc_t(nw-1,m+1,l) + c32 * workarrc_t(nw,m+1,l) + c33 * workarrc_t(nw+1,m+1,l)
!
!--            Use averages of the neighbouring matching grid-line values
               DO  j = jfl(m), jfl(m+1)          
!                  f(k,j,ifl(l):ifu(l)) = 0.5_wp * ( workarrc_t(nw,m,l)   &
!                       + workarrc_t(nw,m+1,l) )
                  f(k,j,ifl(l):ifu(l)) = 0.5_wp * ( f_interp_1 + f_interp_2 )
               ENDDO
!
!--            Then set the values along the matching grid-lines  
               IF  ( MOD( jfl(m), jgsr ) == 0 )  THEN
                  f_interp_1 = c31 * workarrc_t(nw-1,m,l) + c32 * workarrc_t(nw,m,l) + c33 * workarrc_t(nw+1,m,l)
!                  f(k,jfl(m),ifl(l):ifu(l)) = workarrc_t(nw,m,l)
                  f(k,jfl(m),ifl(l):ifu(l)) = f_interp_1
               ENDIF
               
            ENDDO

         ENDDO
!
!--      Finally, set the values along the last matching grid-line
         IF  ( MOD( jfl(jcnw), jgsr ) == 0 )  THEN
            DO  l = iclw, icrw
!
!--            First interpolate to the flux point using the 3rd-order WS scheme
               f_interp_1 = c31 * workarrc_t(nw-1,jcnw,l) + c32 * workarrc_t(nw,jcnw,l) + c33 * workarrc_t(nw+1,jcnw,l)
!               f(k,jfl(jcnw),ifl(l):ifu(l)) = workarrc_t(nw,jcnw,l)
               f(k,jfl(jcnw),ifl(l):ifu(l)) = f_interp_1
            ENDDO
         ENDIF
!
!--      A gap may still remain in some cases if the subdomain size is not 
!--      divisible by the grid-spacing ratio. In such a case, fill the 
!--      gap. Note however, this operation may produce some additional 
!--      momentum conservation error.
         IF  ( jfl(jcnw) < nyn )  THEN
            DO  l = iclw, icrw
               DO  j = jfl(jcnw)+1, nyn
                  f(k,j,ifl(l):ifu(l)) = f(k,jfl(jcnw),ifl(l):ifu(l))
               ENDDO
            ENDDO
         ENDIF

      ELSE  ! any scalar variable

         DO  l = iclw, icrw
            DO  m = jcsw, jcnw
!
!--            First interpolate to the flux point using the 3rd-order WS scheme
               f_interp_1 = c31 * workarrc_t(nw-1,m,l) + c32 * workarrc_t(nw,m,l) + c33 * workarrc_t(nw+1,m,l)
               DO  i = ifl(l), ifu(l)
                  DO  j = jfl(m), jfu(m)
!                     f(k,j,i) = workarrc_t(nw,m,l)
                     f(k,j,i) = f_interp_1
                  ENDDO
               ENDDO

            ENDDO
         ENDDO

      ENDIF  ! var
!
!--   Just fill up the redundant second ghost-node layer in case of var == w.
      IF ( var == 'w' )  THEN
         f(nzt+1,:,:) = f(nzt,:,:)
      ENDIF

   END SUBROUTINE pmci_interp_1sto_t



   SUBROUTINE pmci_anterp_tophat( f, fc, kct, ifl, ifu, jfl, jfu, kfl, kfu, ijkfc, var )
!
!--   Anterpolation of internal-node values to be used as the parent-domain
!--   values. This subroutine is based on the first-order numerical
!--   integration of the child-grid values contained within the anterpolation
!--   cell.

      IMPLICIT NONE

      REAL(wp), DIMENSION(nzb:nzt+1,nysg:nyng,nxlg:nxrg), INTENT(IN) ::  f         !< Child-grid array
      REAL(wp), DIMENSION(0:cg%nz+1,jcs:jcn,icl:icr), INTENT(INOUT)  ::  fc        !< Parent-grid array
      INTEGER(iwp), DIMENSION(0:cg%nz+1,jcsa:jcna,icla:icra), INTENT(IN) :: ijkfc  !< number of child grid points contributing to a parent grid box
      INTEGER(iwp), INTENT(IN) ::  kct                                             !< Top boundary index for anterpolation along z
      INTEGER(iwp), DIMENSION(icla:icra), INTENT(IN) ::  ifl !< Indicates start index of child cells belonging to certain parent cell - x direction
      INTEGER(iwp), DIMENSION(icla:icra), INTENT(IN) ::  ifu !< Indicates end index of child cells belonging to certain parent cell - x direction
      INTEGER(iwp), DIMENSION(jcsa:jcna), INTENT(IN) ::  jfl !< Indicates start index of child cells belonging to certain parent cell - y direction
      INTEGER(iwp), DIMENSION(jcsa:jcna), INTENT(IN) ::  jfu !< Indicates end index of child cells belonging to certain parent cell - y direction
      INTEGER(iwp), DIMENSION(0:cg%nz+1), INTENT(IN) ::  kfl !< Indicates start index of child cells belonging to certain parent cell - z direction
      INTEGER(iwp), DIMENSION(0:cg%nz+1), INTENT(IN) ::  kfu !< Indicates end index of child cells belonging to certain parent cell - z direction
      CHARACTER(LEN=*), INTENT(IN) ::  var                   !< Variable symbol: 'u', 'v', 'w' or 's'
!
!--   Local variables:  
      REAL(wp) ::  cellsum       !< sum of respective child cells belonging to parent cell 
      INTEGER(iwp) ::  i         !< Running index x-direction - child grid
      INTEGER(iwp) ::  iclant    !< Left boundary index for anterpolation along x
      INTEGER(iwp) ::  icrant    !< Right boundary index for anterpolation along x
      INTEGER(iwp) ::  j         !< Running index y-direction - child grid
      INTEGER(iwp) ::  jcnant    !< North boundary index for anterpolation along y
      INTEGER(iwp) ::  jcsant    !< South boundary index for anterpolation along y
      INTEGER(iwp) ::  k         !< Running index z-direction - child grid     
      INTEGER(iwp) ::  kcb = 0   !< Bottom boundary index for anterpolation along z
      INTEGER(iwp) ::  kctant    !< Top boundary index for anterpolation along z
      INTEGER(iwp) ::  l         !< Running index x-direction - parent grid
      INTEGER(iwp) ::  m         !< Running index y-direction - parent grid
      INTEGER(iwp) ::  n         !< Running index z-direction - parent grid
      INTEGER(iwp) ::  var_flag  !< bit number used to flag topography on respective grid

!
!--   Define the index bounds iclant, icrant, jcsant and jcnant.
!--   Note that kcb is simply zero and kct enters here as a parameter and it is
!--   determined in pmci_define_index_mapping.
!--   Note that the grid points used also for interpolation (from parent to
!--   child) are excluded in anterpolation, e.g. anterpolation is only from 
!--   nzb:kct-1, as kct is used for interpolation. An additional buffer is
!--   also applied (default value for anterpolation_buffer_width = 2) in order
!--   to avoid unphysical accumulation of kinetic energy.
      iclant = icl
      icrant = icr
      jcsant = jcs
      jcnant = jcn
!      kctant = kct - 1
      kctant = kct - 1 - anterpolation_buffer_width
      kcb  = 0
      IF ( nesting_mode /= 'vertical' )  THEN
!         IF ( bc_dirichlet_l )  THEN
!!            iclant = icl + 3
!            iclant = icl + 3 + anterpolation_buffer_width
!         ENDIF
!         IF ( bc_dirichlet_r )  THEN
!!            icrant = icr - 3
!            icrant = icr - 3 - anterpolation_buffer_width
!         ENDIF
!
!         IF ( bc_dirichlet_s )  THEN
!!            jcsant = jcs + 3
!            jcsant = jcs + 3 + anterpolation_buffer_width
!         ENDIF
!         IF ( bc_dirichlet_n )  THEN
!!            jcnant = jcn - 3
!            jcnant = jcn - 3 - anterpolation_buffer_width
!         ENDIF

!
!--      New method: 
         iclant = MAX( icl, iplg + 3 + anterpolation_buffer_width )
         icrant = MIN( icr, iprg - 3 - anterpolation_buffer_width )
         jcsant = MAX( jcs, jpsg + 3 + anterpolation_buffer_width )
         jcnant = MIN( jcn, jpng - 3 - anterpolation_buffer_width )
         
      ENDIF
!
!--   Set masking bit for topography flags 
      IF ( var == 'u' )  THEN 
         var_flag = 1 
      ELSEIF ( var == 'v' )  THEN
         var_flag = 2 
      ELSEIF ( var == 'w' )  THEN
         var_flag = 3
      ELSE
         var_flag = 0
      ENDIF
!
!--   Note that l, m, and n are parent-grid indices and i,j, and k 
!--   are child-grid indices.
      DO  l = iclant, icrant
         DO  m = jcsant, jcnant
!
!--         For simplicity anterpolate within buildings and under elevated
!--         terrain too
            DO  n = kcb, kctant
               cellsum = 0.0_wp
               DO  i = ifl(l), ifu(l)
                  DO  j = jfl(m), jfu(m)
                     DO  k = kfl(n), kfu(n)
                        cellsum = cellsum + MERGE( f(k,j,i), 0.0_wp,          &
                             BTEST( wall_flags_0(k,j,i), var_flag ) )
                     ENDDO
                  ENDDO
               ENDDO
!
!--            In case all child grid points are inside topography, i.e. 
!--            ijkfc and cellsum are zero, also parent solution would have 
!--            zero values at that grid point, which may cause problems in 
!--            particular for the temperature. Therefore, in case cellsum is 
!--            zero, keep the parent solution at this point. 

               IF ( ijkfc(n,m,l) /= 0 )  THEN
                  fc(n,m,l) = cellsum / REAL( ijkfc(n,m,l), KIND=wp )
               ENDIF

            ENDDO
         ENDDO
      ENDDO

   END SUBROUTINE pmci_anterp_tophat

#endif

 END SUBROUTINE pmci_child_datatrans

! Description:
! ------------
!> Set boundary conditions for the prognostic quantities after interpolation 
!> and anterpolation at upward- and downward facing surfaces.  
!> @todo: add Dirichlet boundary conditions for pot. temperature, humdidity and
!> passive scalar.
!------------------------------------------------------------------------------!
 SUBROUTINE pmci_boundary_conds

    USE chem_modules,                                                          &
        ONLY:  ibc_cs_b

    USE control_parameters,                                                    &
        ONLY:  ibc_pt_b, ibc_q_b, ibc_s_b, ibc_uv_b

    USE surface_mod,                                                           &
        ONLY:  bc_h

    IMPLICIT NONE

    INTEGER(iwp) ::  i  !< Index along x-direction
    INTEGER(iwp) ::  j  !< Index along y-direction
    INTEGER(iwp) ::  k  !< Index along z-direction
    INTEGER(iwp) ::  m  !< Running index for surface type
    INTEGER(iwp) ::  n  !< running index for number of chemical species
    
!
!-- Set Dirichlet boundary conditions for horizontal velocity components
    IF ( ibc_uv_b == 0 )  THEN
!
!--    Upward-facing surfaces
       DO  m = 1, bc_h(0)%ns
          i = bc_h(0)%i(m)            
          j = bc_h(0)%j(m)
          k = bc_h(0)%k(m)
          u(k-1,j,i) = 0.0_wp
          v(k-1,j,i) = 0.0_wp
       ENDDO
!
!--    Downward-facing surfaces
       DO  m = 1, bc_h(1)%ns
          i = bc_h(1)%i(m)            
          j = bc_h(1)%j(m)
          k = bc_h(1)%k(m)
          u(k+1,j,i) = 0.0_wp
          v(k+1,j,i) = 0.0_wp
       ENDDO
    ENDIF
!
!-- Set Dirichlet boundary conditions for vertical velocity component
!-- Upward-facing surfaces
    DO  m = 1, bc_h(0)%ns
       i = bc_h(0)%i(m)            
       j = bc_h(0)%j(m)
       k = bc_h(0)%k(m)
       w(k-1,j,i) = 0.0_wp
    ENDDO
!
!-- Downward-facing surfaces
    DO  m = 1, bc_h(1)%ns
       i = bc_h(1)%i(m)            
       j = bc_h(1)%j(m)
       k = bc_h(1)%k(m)
       w(k+1,j,i) = 0.0_wp
    ENDDO
!
!-- Set Neumann boundary conditions for potential temperature
    IF ( .NOT. neutral )  THEN
       IF ( ibc_pt_b == 1 )  THEN
          DO  m = 1, bc_h(0)%ns
             i = bc_h(0)%i(m)            
             j = bc_h(0)%j(m)
             k = bc_h(0)%k(m)
             pt(k-1,j,i) = pt(k,j,i)
          ENDDO
          DO  m = 1, bc_h(1)%ns
             i = bc_h(1)%i(m)            
             j = bc_h(1)%j(m)
             k = bc_h(1)%k(m)
             pt(k+1,j,i) = pt(k,j,i)
          ENDDO   
       ENDIF
    ENDIF
!
!-- Set Neumann boundary conditions for humidity and cloud-physical quantities
    IF ( humidity )  THEN
       IF ( ibc_q_b == 1 )  THEN
          DO  m = 1, bc_h(0)%ns
             i = bc_h(0)%i(m)            
             j = bc_h(0)%j(m)
             k = bc_h(0)%k(m)
             q(k-1,j,i) = q(k,j,i)
          ENDDO  
          DO  m = 1, bc_h(1)%ns
             i = bc_h(1)%i(m)            
             j = bc_h(1)%j(m)
             k = bc_h(1)%k(m)
             q(k+1,j,i) = q(k,j,i)
          ENDDO  
       ENDIF
       IF ( bulk_cloud_model  .AND.  microphysics_morrison )  THEN
          DO  m = 1, bc_h(0)%ns
             i = bc_h(0)%i(m)            
             j = bc_h(0)%j(m)
             k = bc_h(0)%k(m)
             nc(k-1,j,i) = 0.0_wp
             qc(k-1,j,i) = 0.0_wp
          ENDDO  
          DO  m = 1, bc_h(1)%ns
             i = bc_h(1)%i(m)            
             j = bc_h(1)%j(m)
             k = bc_h(1)%k(m)

             nc(k+1,j,i) = 0.0_wp
             qc(k+1,j,i) = 0.0_wp
          ENDDO  
       ENDIF

       IF ( bulk_cloud_model  .AND.  microphysics_seifert )  THEN
          DO  m = 1, bc_h(0)%ns
             i = bc_h(0)%i(m)            
             j = bc_h(0)%j(m)
             k = bc_h(0)%k(m)
             nr(k-1,j,i) = 0.0_wp
             qr(k-1,j,i) = 0.0_wp
          ENDDO  
          DO  m = 1, bc_h(1)%ns
             i = bc_h(1)%i(m)            
             j = bc_h(1)%j(m)
             k = bc_h(1)%k(m)
             nr(k+1,j,i) = 0.0_wp
             qr(k+1,j,i) = 0.0_wp
          ENDDO  
       ENDIF

    ENDIF
!
!-- Set Neumann boundary conditions for passive scalar
    IF ( passive_scalar )  THEN
       IF ( ibc_s_b == 1 )  THEN
          DO  m = 1, bc_h(0)%ns
             i = bc_h(0)%i(m)            
             j = bc_h(0)%j(m)
             k = bc_h(0)%k(m)
             s(k-1,j,i) = s(k,j,i)
          ENDDO 
          DO  m = 1, bc_h(1)%ns
             i = bc_h(1)%i(m)            
             j = bc_h(1)%j(m)
             k = bc_h(1)%k(m)
             s(k+1,j,i) = s(k,j,i)
          ENDDO  
       ENDIF
    ENDIF
!
!-- Set Neumann boundary conditions for chemical species
    IF ( air_chemistry  .AND.  nest_chemistry )  THEN
       IF ( ibc_cs_b == 1 )  THEN
          DO  n = 1, nspec
             DO  m = 1, bc_h(0)%ns
                i = bc_h(0)%i(m)            
                j = bc_h(0)%j(m)
                k = bc_h(0)%k(m)
                chem_species(n)%conc(k-1,j,i) = chem_species(n)%conc(k,j,i)
             ENDDO 
             DO  m = 1, bc_h(1)%ns
                i = bc_h(1)%i(m)            
                j = bc_h(1)%j(m)
                k = bc_h(1)%k(m)
                chem_species(n)%conc(k+1,j,i) = chem_species(n)%conc(k,j,i)
             ENDDO
          ENDDO
       ENDIF
    ENDIF

 END SUBROUTINE pmci_boundary_conds


END MODULE pmc_interface