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source: palm/trunk/SOURCE/init_grid.f90 @ 2522

Last change on this file since 2522 was 2478, checked in by suehring, 7 years ago
Bugfixes concerning top fluxes and TKE production
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File size: 85.6 KB

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1	!> @file init_grid.f90
2	!------------------------------------------------------------------------------!
3	! This file is part of PALM.
4	!
5	! PALM is free software: you can redistribute it and/or modify it under the
6	! terms of the GNU General Public License as published by the Free Software
7	! Foundation, either version 3 of the License, or (at your option) any later
8	! version.
9	!
10	! PALM is distributed in the hope that it will be useful, but WITHOUT ANY
11	! WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
12	! A PARTICULAR PURPOSE. See the GNU General Public License for more details.
13	!
14	! You should have received a copy of the GNU General Public License along with
15	! PALM. If not, see <http://www.gnu.org/licenses/>.
16	!
17	! Copyright 1997-2017 Leibniz Universitaet Hannover
18	!------------------------------------------------------------------------------!
19	!
20	! Current revisions:
21	! -----------------
22	!
23	!
24	! Former revisions:
25	! -----------------
26	! $Id: init_grid.f90 2478 2017-09-18 13:37:24Z schwenkel $
27	! Bugfix, correct flag for use_top
28	!
29	! 2365 2017-08-21 14:59:59Z kanani
30	! Vertical nesting implemented (SadiqHuq)
31	!
32	! 2319 2017-07-20 17:33:17Z suehring
33	! Remove print statements
34	!
35	! 2318 2017-07-20 17:27:44Z suehring
36	! Get topography top index via Function call
37	!
38	! 2317 2017-07-20 17:27:19Z suehring
39	! Bugfixes in reading 3D topography from file
40	!
41	! 2274 2017-06-09 13:27:48Z Giersch
42	! Changed error messages
43	!
44	! 2233 2017-05-30 18:08:54Z suehring
45	!
46	! 2232 2017-05-30 17:47:52Z suehring
47	! - Adjustments according to new topography representation
48	! - Bugfix: Move determination of nzb_max behind topography modification in
49	! cell-edge case
50	! - Get rid off global arrays required for topography output
51	! - Enable topography input via netcdf
52	! - Generic tunnel set-up added
53	!
54	! 2200 2017-04-11 11:37:51Z suehring
55	! monotonic_adjustment removed
56	!
57	! 2169 2017-03-06 18:16:35Z suehring
58	! Bugfix, move setting for topography grid convention to init_grid, else, if no
59	! value is set, the simulation may abort in case of restarts
60	!
61	! 2128 2017-01-23 15:00:03Z suehring
62	! Bugfix in setting topography from file in case of ocean simulations
63	!
64	! 2088 2016-12-19 16:30:25Z suehring
65	! Bugfix in generic topography in case of ocean simulations
66	!
67	! 2037 2016-10-26 11:15:40Z knoop
68	! Anelastic approximation implemented
69	!
70	! 2021 2016-10-07 14:08:57Z suehring
71	! Bugfix: setting Neumann boundary conditions for topography required for
72	! topography flags in multigrid_noopt solver
73	!
74	! 2000 2016-08-20 18:09:15Z knoop
75	! Forced header and separation lines into 80 columns
76	!
77	! 1994 2016-08-15 09:52:21Z suehring
78	! Bugfix in definition of generic topography
79	!
80	! 1982 2016-08-01 11:04:48Z suehring
81	! Bugfix concering consistency check for topography
82	!
83	! 1968 2016-07-18 12:01:49Z suehring
84	! Changed: PE-wise reading of topography file in order to avoid global definition
85	! of arrays nzb_local and nzb_tmp. Thereby, topography definition for single
86	! buildings and street canyons has changed, as well as flag setting for
87	! multigrid scheme.
88	!
89	! Bugfix in checking l_grid anisotropy.
90	! Simplify initial computation of lwall and vertical_influence, i.e. remove
91	! nzb_s_inner as it is still zero at this point.
92	!
93	! 1942 2016-06-14 12:18:18Z suehring
94	! Topography filter implemented to fill holes resolved by only one grid point.
95	! Initialization of flags for ws-scheme moved to advec_ws.
96	!
97	! 1931 2016-06-10 12:06:59Z suehring
98	! Rename multigrid into multigrid_noopt and multigrid_fast into multigrid
99	!
100	! 1910 2016-05-26 06:49:46Z raasch
101	! Bugfix: if topography is read from file, Neumann conditions are used for the
102	! nzb_local array (instead of cyclic conditions) in case that non-cyclic
103	! boundary conditions are switched on for the run
104	!
105	! 1902 2016-05-09 11:18:56Z suehring
106	! Set topography flags for multigrid solver only (not for multigrid_fast)
107	!
108	! 1886 2016-04-21 11:20:47Z suehring
109	! Bugfix: setting advection flags near walls
110	! reformulated index values for nzb_v_inner
111	! variable discriptions added in declaration block
112	!
113	! 1845 2016-04-08 08:29:13Z raasch
114	! nzb_2d removed
115	!
116	! 1804 2016-04-05 16:30:18Z maronga
117	! Removed code for parameter file check (__check)
118	!
119	! 1779 2016-03-03 08:01:28Z raasch
120	! coupling_char is trimmed at every place it occurs, because it can have
121	! different length now
122	!
123	! 1762 2016-02-25 12:31:13Z hellstea
124	! Introduction of nested domain feature
125	!
126	! 1743 2016-01-13 10:23:51Z raasch
127	! Bugfix for calculation of nzb_s_outer and nzb_u_outer at north boundary of
128	! total domain
129	!
130	! 1691 2015-10-26 16:17:44Z maronga
131	! Renamed prandtl_layer to constant_flux_layer.
132	!
133	! 1682 2015-10-07 23:56:08Z knoop
134	! Code annotations made doxygen readable
135	!
136	! 1677 2015-10-02 13:25:23Z boeske
137	! Bugfix: Ghost points are included in wall_flags_0 and wall_flags_00
138	!
139	! 1675 2015-10-02 08:28:59Z gronemeier
140	! Bugfix: Definition of topography grid levels
141	!
142	! 1660 2015-09-21 08:15:16Z gronemeier
143	! Bugfix: Definition of topography grid levels if vertical grid stretching
144	! starts below the maximum topography height.
145	!
146	! 1580 2015-04-10 13:43:49Z suehring
147	! Bugfix: setting flags for 5th order scheme near buildings
148	!
149	! 1575 2015-03-27 09:56:27Z raasch
150	! adjustments for psolver-queries
151	!
152	! 1557 2015-03-05 16:43:04Z suehring
153	! Adjustment for monotoinic limiter
154	!
155	! 1418 2014-06-06 13:05:08Z fricke
156	! Bugfix: Change if-condition for stretched grid in the ocean, with the old
157	! condition and a negative value for dz_stretch_level the condition
158	! was always true for the whole model domain
159	!
160	! 1409 2014-05-23 12:11:32Z suehring
161	! Bugfix: set wall_flags_0 at inflow and outflow boundary also for i <= nxlu
162	! j <= nysv
163	!
164	! 1353 2014-04-08 15:21:23Z heinze
165	! REAL constants provided with KIND-attribute
166	!
167	! 1322 2014-03-20 16:38:49Z raasch
168	! REAL constants defined as wp-kind
169	!
170	! 1320 2014-03-20 08:40:49Z raasch
171	! ONLY-attribute added to USE-statements,
172	! kind-parameters added to all INTEGER and REAL declaration statements,
173	! kinds are defined in new module kinds,
174	! revision history before 2012 removed,
175	! comment fields (!:) to be used for variable explanations added to
176	! all variable declaration statements
177	!
178	! 1221 2013-09-10 08:59:13Z raasch
179	! wall_flags_00 introduced to hold bits 32-63,
180	! additional 3D-flag arrays for replacing the 2D-index array nzb_s_inner in
181	! loops optimized for openACC (pres + flow_statistics)
182	!
183	! 1092 2013-02-02 11:24:22Z raasch
184	! unused variables removed
185	!
186	! 1069 2012-11-28 16:18:43Z maronga
187	! bugfix: added coupling_char to TOPOGRAPHY_DATA to allow topography in the
188	! ocean model in case of coupled runs
189	!
190	! 1036 2012-10-22 13:43:42Z raasch
191	! code put under GPL (PALM 3.9)
192	!
193	! 1015 2012-09-27 09:23:24Z raasch
194	! lower index for calculating wall_flags_0 set to nzb_w_inner instead of
195	! nzb_w_inner+1
196	!
197	! 996 2012-09-07 10:41:47Z raasch
198	! little reformatting
199	!
200	! 978 2012-08-09 08:28:32Z fricke
201	! Bugfix: nzb_max is set to nzt at non-cyclic lateral boundaries
202	! Bugfix: Set wall_flags_0 for inflow boundary
203	!
204	! 927 2012-06-06 19:15:04Z raasch
205	! Wall flags are not set for multigrid method in case of masking method
206	!
207	! 864 2012-03-27 15:10:33Z gryschka
208	! In case of ocean and Dirichlet bottom bc for u and v dzu_mg and ddzu_pres
209	! were not correctly defined for k=1.
210	!
211	! 861 2012-03-26 14:18:34Z suehring
212	! Set wall_flags_0. The array is needed for degradation in ws-scheme near walls,
213	! inflow and outflow boundaries as well as near the bottom and the top of the
214	! model domain.!
215	! Initialization of nzb_s_inner and nzb_w_inner.
216	! gls has to be at least nbgp to do not exceed the array bounds of nzb_local
217	! while setting wall_flags_0
218	!
219	! 843 2012-02-29 15:16:21Z gryschka
220	! In case of ocean and dirichlet bc for u and v at the bottom
221	! the first u-level ist defined at same height as the first w-level
222	!
223	! 818 2012-02-08 16:11:23Z maronga
224	! Bugfix: topo_height is only required if topography is used. It is thus now
225	! allocated in the topography branch
226	!
227	! 809 2012-01-30 13:32:58Z maronga
228	! Bugfix: replaced .AND. and .NOT. with && and ! in the preprocessor directives
229	!
230	! 807 2012-01-25 11:53:51Z maronga
231	! New cpp directive "__check" implemented which is used by check_namelist_files
232	!
233	! Revision 1.1 1997/08/11 06:17:45 raasch
234	! Initial revision (Testversion)
235	!
236	!
237	! Description:
238	! ------------
239	!> Creating grid depending constants
240	!> To Do: Setting topo flags only based on topo_3d array - flags for former
241	!> nzb_outer arrays are still not set properly.
242	!> To Do: Rearrange topo flag list
243	!------------------------------------------------------------------------------!
244	SUBROUTINE init_grid
245
246	USE advec_ws, &
247	ONLY: ws_init_flags
248
249	USE arrays_3d, &
250	ONLY: dd2zu, ddzu, ddzu_pres, ddzw, dzu, dzu_mg, dzw, dzw_mg, f1_mg, &
251	f2_mg, f3_mg, l_grid, l_wall, zu, zw
252
253	USE control_parameters, &
254	ONLY: bc_lr_cyc, bc_ns_cyc, building_height, building_length_x, &
255	building_length_y, building_wall_left, building_wall_south, &
256	canyon_height, canyon_wall_left, canyon_wall_south, &
257	canyon_width_x, canyon_width_y, constant_flux_layer, &
258	coupling_char, coupling_mode, &
259	dp_level_ind_b, dz, dz_max, dz_stretch_factor, &
260	dz_stretch_level, dz_stretch_level_index, grid_level, ibc_uv_b, &
261	io_blocks, io_group, inflow_l, inflow_n, inflow_r, inflow_s, &
262	lod, masking_method, maximum_grid_level, message_string, &
263	momentum_advec, nest_domain, nest_bound_l, nest_bound_n, &
264	nest_bound_r, nest_bound_s, ocean, outflow_l, outflow_n, &
265	outflow_r, outflow_s, psolver, scalar_advec, topography, &
266	topography_grid_convention, tunnel_height, tunnel_length, &
267	tunnel_width_x, tunnel_width_y, tunnel_wall_depth, &
268	use_surface_fluxes, use_top_fluxes, wall_adjustment_factor
269
270	USE grid_variables, &
271	ONLY: ddx, ddx2, ddy, ddy2, dx, dx2, dy, dy2, zu_s_inner, zw_w_inner
272
273	USE indices, &
274	ONLY: advc_flags_1, advc_flags_2, flags, nbgp, nx, nxl, nxlg, nxl_mg, &
275	nxr, nxrg, nxr_mg, ny, nyn, nyng, nyn_mg, nys, nys_mg, nysg, nz,&
276	nzb, nzb_diff, nzb_diff_s_inner, nzb_diff_s_outer, &
277	nzb_max, nzb_s_inner, nzb_s_outer, nzb_u_inner, &
278	nzb_u_outer, nzb_v_inner, nzb_v_outer, nzb_w_inner, &
279	nzb_w_outer, nzt, nzt_mg, wall_flags_0, wall_flags_1, &
280	wall_flags_10, wall_flags_2, wall_flags_3, wall_flags_4, &
281	wall_flags_5, wall_flags_6, wall_flags_7, wall_flags_8, &
282	wall_flags_9
283
284	USE kinds
285	#if defined ( __netcdf )
286	USE netcdf_interface, &
287	ONLY: netcdf_close_file, netcdf_open_read_file, netcdf_get_attribute, &
288	netcdf_get_variable
289	#endif
290	USE pegrid
291
292	USE surface_mod, &
293	ONLY: get_topography_top_index, init_bc
294
295	USE vertical_nesting_mod, &
296	ONLY: vnested, vnest_init_grid
297
298	IMPLICIT NONE
299
300	INTEGER(iwp) :: bh !< temporary vertical index of building height
301	INTEGER(iwp) :: blx !< grid point number of building size along x
302	INTEGER(iwp) :: bly !< grid point number of building size along y
303	INTEGER(iwp) :: bxl !< index for left building wall
304	INTEGER(iwp) :: bxr !< index for right building wall
305	INTEGER(iwp) :: byn !< index for north building wall
306	INTEGER(iwp) :: bys !< index for south building wall
307	INTEGER(iwp) :: ch !< temporary vertical index for canyon height
308	INTEGER(iwp) :: cwx !< grid point number of canyon size along x
309	INTEGER(iwp) :: cwy !< grid point number of canyon size along y
310	INTEGER(iwp) :: cxl !< index for left canyon wall
311	INTEGER(iwp) :: cxr !< index for right canyon wall
312	INTEGER(iwp) :: cyn !< index for north canyon wall
313	INTEGER(iwp) :: cys !< index for south canyon wall
314	INTEGER(iwp) :: i !< index variable along x
315	INTEGER(iwp) :: id_topo !< NetCDF id of topograhy input file
316	INTEGER(iwp) :: ii !< loop variable for reading topography file
317	INTEGER(iwp) :: inc !< incremental parameter for coarsening grid level
318	INTEGER(iwp) :: j !< index variable along y
319	INTEGER(iwp) :: k !< index variable along z
320	INTEGER(iwp) :: k_top !< topography top index on local PE
321	INTEGER(iwp) :: l !< loop variable
322	INTEGER(iwp) :: nxl_l !< index of left PE boundary for multigrid level
323	INTEGER(iwp) :: nxr_l !< index of right PE boundary for multigrid level
324	INTEGER(iwp) :: nyn_l !< index of north PE boundary for multigrid level
325	INTEGER(iwp) :: nys_l !< index of south PE boundary for multigrid level
326	INTEGER(iwp) :: nzb_local_max !< vertical grid index of maximum topography height
327	INTEGER(iwp) :: nzb_local_min !< vertical grid index of minimum topography height
328	INTEGER(iwp) :: nzt_l !< index of top PE boundary for multigrid level
329	INTEGER(iwp) :: num_hole !< number of holes (in topography) resolved by only one grid point
330	INTEGER(iwp) :: num_hole_l !< number of holes (in topography) resolved by only one grid point on local PE
331	INTEGER(iwp) :: num_wall !< number of surrounding vertical walls for a single grid point
332	INTEGER(iwp) :: skip_n_rows !< counting variable to skip rows while reading topography file
333	INTEGER(iwp) :: hv_in !< heavyside function to model inner tunnel surface
334	INTEGER(iwp) :: hv_out !< heavyside function to model outer tunnel surface
335	INTEGER(iwp) :: txe_out !< end position of outer tunnel wall in x
336	INTEGER(iwp) :: txs_out !< start position of outer tunnel wall in x
337	INTEGER(iwp) :: tye_out !< end position of outer tunnel wall in y
338	INTEGER(iwp) :: tys_out !< start position of outer tunnel wall in y
339	INTEGER(iwp) :: txe_in !< end position of inner tunnel wall in x
340	INTEGER(iwp) :: txs_in !< start position of inner tunnel wall in x
341	INTEGER(iwp) :: tye_in !< end position of inner tunnel wall in y
342	INTEGER(iwp) :: tys_in !< start position of inner tunnel wall in y
343	INTEGER(iwp) :: td !< tunnel wall depth
344	INTEGER(iwp) :: th !< height of outer tunnel wall
345
346	INTEGER(iwp), DIMENSION(:,:), ALLOCATABLE :: nzb_local !< index for topography top at cell-center
347	INTEGER(iwp), DIMENSION(:,:), ALLOCATABLE :: nzb_tmp !< dummy to calculate topography indices on u- and v-grid
348
349	INTEGER(iwp), DIMENSION(:,:,:), ALLOCATABLE :: topo_3d !< input array for 3D topography and dummy array for setting "outer"-flags
350
351	LOGICAL :: netcdf_extend = .FALSE. !< Flag indicating wether netcdf topography input file or not
352
353	REAL(wp) :: dum !< dummy variable to skip columns while reading topography file
354	REAL(wp) :: dz_stretched !< stretched vertical grid spacing
355
356	REAL(wp), DIMENSION(:,:), ALLOCATABLE :: oro_height !< input variable for terrain height
357	REAL(wp), DIMENSION(:,:), ALLOCATABLE :: topo_height !< input variable for topography height
358
359	INTEGER( KIND=1 ), DIMENSION(:,:,:), ALLOCATABLE :: topo_3d_read !< input variable for 3D topography
360
361	!
362	!-- Calculation of horizontal array bounds including ghost layers
363	nxlg = nxl - nbgp
364	nxrg = nxr + nbgp
365	nysg = nys - nbgp
366	nyng = nyn + nbgp
367
368	!
369	!-- Allocate grid arrays
370	ALLOCATE( ddzu(1:nzt+1), ddzw(1:nzt+1), dd2zu(1:nzt), dzu(1:nzt+1), &
371	dzw(1:nzt+1), l_grid(1:nzt), zu(nzb:nzt+1), zw(nzb:nzt+1) )
372
373	!
374	!-- Compute height of u-levels from constant grid length and dz stretch factors
375	IF ( dz == -1.0_wp ) THEN
376	message_string = 'missing dz'
377	CALL message( 'init_grid', 'PA0200', 1, 2, 0, 6, 0 )
378	ELSEIF ( dz <= 0.0_wp ) THEN
379	WRITE( message_string, * ) 'dz=',dz,' <= 0.0'
380	CALL message( 'init_grid', 'PA0201', 1, 2, 0, 6, 0 )
381	ENDIF
382
383	!
384	!-- Define the vertical grid levels
385	IF ( .NOT. ocean ) THEN
386	!
387	!-- Grid for atmosphere with surface at z=0 (k=0, w-grid).
388	!-- The second u-level (k=1) corresponds to the top of the
389	!-- Prandtl-layer.
390
391	IF ( ibc_uv_b == 0 .OR. ibc_uv_b == 2 ) THEN
392	zu(0) = 0.0_wp
393	! zu(0) = - dz * 0.5_wp
394	ELSE
395	zu(0) = - dz * 0.5_wp
396	ENDIF
397	zu(1) = dz * 0.5_wp
398
399	dz_stretch_level_index = nzt+1
400	dz_stretched = dz
401	DO k = 2, nzt+1
402	IF ( dz_stretch_level <= zu(k-1) .AND. dz_stretched < dz_max ) THEN
403	dz_stretched = dz_stretched * dz_stretch_factor
404	dz_stretched = MIN( dz_stretched, dz_max )
405	IF ( dz_stretch_level_index == nzt+1 ) dz_stretch_level_index = k-1
406	ENDIF
407	zu(k) = zu(k-1) + dz_stretched
408	ENDDO
409
410	!
411	!-- Compute the w-levels. They are always staggered half-way between the
412	!-- corresponding u-levels. In case of dirichlet bc for u and v at the
413	!-- ground the first u- and w-level (k=0) are defined at same height (z=0).
414	!-- The top w-level is extrapolated linearly.
415	zw(0) = 0.0_wp
416	DO k = 1, nzt
417	zw(k) = ( zu(k) + zu(k+1) ) * 0.5_wp
418	ENDDO
419	zw(nzt+1) = zw(nzt) + 2.0_wp * ( zu(nzt+1) - zw(nzt) )
420
421	ELSE
422	!
423	!-- Grid for ocean with free water surface is at k=nzt (w-grid).
424	!-- In case of neumann bc at the ground the first first u-level (k=0) lies
425	!-- below the first w-level (k=0). In case of dirichlet bc the first u- and
426	!-- w-level are defined at same height, but staggered from the second level.
427	!-- The second u-level (k=1) corresponds to the top of the Prandtl-layer.
428	zu(nzt+1) = dz * 0.5_wp
429	zu(nzt) = - dz * 0.5_wp
430
431	dz_stretch_level_index = 0
432	dz_stretched = dz
433	DO k = nzt-1, 0, -1
434	!
435	!-- The default value of dz_stretch_level is positive, thus the first
436	!-- condition is always true. Hence, the second condition is necessary.
437	IF ( dz_stretch_level >= zu(k+1) .AND. dz_stretch_level <= 0.0 &
438	.AND. dz_stretched < dz_max ) THEN
439	dz_stretched = dz_stretched * dz_stretch_factor
440	dz_stretched = MIN( dz_stretched, dz_max )
441	IF ( dz_stretch_level_index == 0 ) dz_stretch_level_index = k+1
442	ENDIF
443	zu(k) = zu(k+1) - dz_stretched
444	ENDDO
445
446	!
447	!-- Compute the w-levels. They are always staggered half-way between the
448	!-- corresponding u-levels, except in case of dirichlet bc for u and v
449	!-- at the ground. In this case the first u- and w-level are defined at
450	!-- same height. The top w-level (nzt+1) is not used but set for
451	!-- consistency, since w and all scalar variables are defined up tp nzt+1.
452	zw(nzt+1) = dz
453	zw(nzt) = 0.0_wp
454	DO k = 0, nzt
455	zw(k) = ( zu(k) + zu(k+1) ) * 0.5_wp
456	ENDDO
457
458	!
459	!-- In case of dirichlet bc for u and v the first u- and w-level are defined
460	!-- at same height.
461	IF ( ibc_uv_b == 0 ) THEN
462	zu(0) = zw(0)
463	ENDIF
464
465	ENDIF
466
467	!
468	!-- Compute grid lengths.
469	DO k = 1, nzt+1
470	dzu(k) = zu(k) - zu(k-1)
471	ddzu(k) = 1.0_wp / dzu(k)
472	dzw(k) = zw(k) - zw(k-1)
473	ddzw(k) = 1.0_wp / dzw(k)
474	ENDDO
475
476	DO k = 1, nzt
477	dd2zu(k) = 1.0_wp / ( dzu(k) + dzu(k+1) )
478	ENDDO
479
480	!
481	!-- The FFT- SOR-pressure solvers assume grid spacings of a staggered grid
482	!-- everywhere. For the actual grid, the grid spacing at the lowest level
483	!-- is only dz/2, but should be dz. Therefore, an additional array
484	!-- containing with appropriate grid information is created for these
485	!-- solvers.
486	IF ( psolver(1:9) /= 'multigrid' ) THEN
487	ALLOCATE( ddzu_pres(1:nzt+1) )
488	ddzu_pres = ddzu
489	ddzu_pres(1) = ddzu_pres(2) ! change for lowest level
490	ENDIF
491
492	!
493	!-- Compute the reciprocal values of the horizontal grid lengths.
494	ddx = 1.0_wp / dx
495	ddy = 1.0_wp / dy
496	dx2 = dx * dx
497	dy2 = dy * dy
498	ddx2 = 1.0_wp / dx2
499	ddy2 = 1.0_wp / dy2
500
501	!
502	!-- Compute the grid-dependent mixing length.
503	DO k = 1, nzt
504	l_grid(k) = ( dx * dy * dzw(k) )**0.33333333333333_wp
505	ENDDO
506
507	!
508	!-- Allocate outer and inner index arrays for topography and set
509	!-- defaults.
510	ALLOCATE( nzb_s_inner(nysg:nyng,nxlg:nxrg), &
511	nzb_s_outer(nysg:nyng,nxlg:nxrg), &
512	nzb_u_inner(nysg:nyng,nxlg:nxrg), &
513	nzb_u_outer(nysg:nyng,nxlg:nxrg), &
514	nzb_v_inner(nysg:nyng,nxlg:nxrg), &
515	nzb_v_outer(nysg:nyng,nxlg:nxrg), &
516	nzb_w_inner(nysg:nyng,nxlg:nxrg), &
517	nzb_w_outer(nysg:nyng,nxlg:nxrg), &
518	nzb_diff_s_inner(nysg:nyng,nxlg:nxrg), &
519	nzb_diff_s_outer(nysg:nyng,nxlg:nxrg), &
520	nzb_local(nysg:nyng,nxlg:nxrg), &
521	nzb_tmp(nysg:nyng,nxlg:nxrg), &
522	wall_flags_0(nzb:nzt+1,nysg:nyng,nxlg:nxrg) )
523
524	ALLOCATE( topo_3d(nzb:nzt+1,nysg:nyng,nxlg:nxrg) )
525	topo_3d = 0
526
527	ALLOCATE( l_wall(nzb:nzt+1,nysg:nyng,nxlg:nxrg) )
528
529	nzb_s_inner = nzb; nzb_s_outer = nzb
530	nzb_u_inner = nzb; nzb_u_outer = nzb
531	nzb_v_inner = nzb; nzb_v_outer = nzb
532	nzb_w_inner = nzb; nzb_w_outer = nzb
533
534	!
535	!-- Define vertical gridpoint from (or to) which on the usual finite difference
536	!-- form (which does not use surface fluxes) is applied
537	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
538	nzb_diff = nzb + 2
539	ELSE
540	nzb_diff = nzb + 1
541	ENDIF
542
543	nzb_diff_s_inner = nzb_diff; nzb_diff_s_outer = nzb_diff
544
545	!
546	!-- Initialize near-wall mixing length l_wall only in the vertical direction
547	!-- for the moment,
548	!-- multiplication with wall_adjustment_factor near the end of this routine
549	l_wall(nzb,:,:) = l_grid(1)
550	DO k = nzb+1, nzt
551	l_wall(k,:,:) = l_grid(k)
552	ENDDO
553	l_wall(nzt+1,:,:) = l_grid(nzt)
554
555	DO k = 1, nzt
556	IF ( l_grid(k) > 1.5_wp * dx * wall_adjustment_factor .OR. &
557	l_grid(k) > 1.5_wp * dy * wall_adjustment_factor ) THEN
558	WRITE( message_string, * ) 'grid anisotropy exceeds ', &
559	'threshold given by only local', &
560	' &horizontal reduction of near_wall ', &
561	'mixing length l_wall', &
562	' &starting from height level k = ', k, '.'
563	CALL message( 'init_grid', 'PA0202', 0, 1, 0, 6, 0 )
564	EXIT
565	ENDIF
566	ENDDO
567	!
568	!-- Set outer and inner index arrays for non-flat topography.
569	!-- Here consistency checks concerning domain size and periodicity are
570	!-- necessary.
571	!-- Within this SELECT CASE structure only nzb_local is initialized
572	!-- individually depending on the chosen topography type, all other index
573	!-- arrays are initialized further below.
574	SELECT CASE ( TRIM( topography ) )
575
576	CASE ( 'flat' )
577	!
578	!-- nzb_local is required for the multigrid solver
579	nzb_local = 0
580	!
581	!-- Initialilize 3D topography array, used later for initializing flags
582	topo_3d(nzb+1:nzt+1,:,:) = IBSET( topo_3d(nzb+1:nzt+1,:,:), 0 )
583	!
584	!-- level of detail is required for output routines
585	lod = 1
586
587	CASE ( 'single_building' )
588	!
589	!-- Single rectangular building, by default centered in the middle of the
590	!-- total domain
591	blx = NINT( building_length_x / dx )
592	bly = NINT( building_length_y / dy )
593	bh = MINLOC( ABS( zw - building_height ), 1 ) - 1
594	IF ( ABS( zw(bh) - building_height ) == &
595	ABS( zw(bh+1) - building_height ) ) bh = bh + 1
596
597	IF ( building_wall_left == 9999999.9_wp ) THEN
598	building_wall_left = ( nx + 1 - blx ) / 2 * dx
599	ENDIF
600	bxl = NINT( building_wall_left / dx )
601	bxr = bxl + blx
602
603	IF ( building_wall_south == 9999999.9_wp ) THEN
604	building_wall_south = ( ny + 1 - bly ) / 2 * dy
605	ENDIF
606	bys = NINT( building_wall_south / dy )
607	byn = bys + bly
608
609	!
610	!-- Building size has to meet some requirements
611	IF ( ( bxl < 1 ) .OR. ( bxr > nx-1 ) .OR. ( bxr < bxl+3 ) .OR. &
612	( bys < 1 ) .OR. ( byn > ny-1 ) .OR. ( byn < bys+3 ) ) THEN
613	WRITE( message_string, * ) 'inconsistent building parameters:', &
614	'& bxl=', bxl, 'bxr=', bxr, 'bys=', bys, &
615	'byn=', byn, 'nx=', nx, 'ny=', ny
616	CALL message( 'init_grid', 'PA0203', 1, 2, 0, 6, 0 )
617	ENDIF
618
619	!
620	!-- Define the building.
621	nzb_local = 0
622	IF ( bxl <= nxr .AND. bxr >= nxl .AND. &
623	bys <= nyn .AND. byn >= nys ) &
624	nzb_local(MAX(nys,bys):MIN(nyn,byn),MAX(nxl,bxl):MIN(nxr,bxr)) = bh
625
626	CALL exchange_horiz_2d_int( nzb_local, nys, nyn, nxl, nxr, nbgp )
627	!
628	!-- Set bit array to mask topography
629	DO i = nxlg, nxrg
630	DO j = nysg, nyng
631
632	topo_3d(nzb_local(j,i)+1:nzt+1,j,i) = &
633	IBSET( topo_3d(nzb_local(j,i)+1:nzt+1,j,i), 0 )
634	ENDDO
635	ENDDO
636	!
637	!-- level of detail is required for output routines. Here, 2D topography.
638	lod = 1
639
640	CALL exchange_horiz_int( topo_3d, nbgp )
641
642	CASE ( 'single_street_canyon' )
643	!
644	!-- Single quasi-2D street canyon of infinite length in x or y direction.
645	!-- The canyon is centered in the other direction by default.
646	IF ( canyon_width_x /= 9999999.9_wp ) THEN
647	!
648	!-- Street canyon in y direction
649	cwx = NINT( canyon_width_x / dx )
650	IF ( canyon_wall_left == 9999999.9_wp ) THEN
651	canyon_wall_left = ( nx + 1 - cwx ) / 2 * dx
652	ENDIF
653	cxl = NINT( canyon_wall_left / dx )
654	cxr = cxl + cwx
655
656	ELSEIF ( canyon_width_y /= 9999999.9_wp ) THEN
657	!
658	!-- Street canyon in x direction
659	cwy = NINT( canyon_width_y / dy )
660	IF ( canyon_wall_south == 9999999.9_wp ) THEN
661	canyon_wall_south = ( ny + 1 - cwy ) / 2 * dy
662	ENDIF
663	cys = NINT( canyon_wall_south / dy )
664	cyn = cys + cwy
665
666	ELSE
667
668	message_string = 'no street canyon width given'
669	CALL message( 'init_grid', 'PA0204', 1, 2, 0, 6, 0 )
670
671	ENDIF
672
673	ch = MINLOC( ABS( zw - canyon_height ), 1 ) - 1
674	IF ( ABS( zw(ch) - canyon_height ) == &
675	ABS( zw(ch+1) - canyon_height ) ) ch = ch + 1
676
677	dp_level_ind_b = ch
678	!
679	!-- Street canyon size has to meet some requirements
680	IF ( canyon_width_x /= 9999999.9_wp ) THEN
681	IF ( ( cxl < 1 ) .OR. ( cxr > nx-1 ) .OR. ( cwx < 3 ) .OR. &
682	( ch < 3 ) ) THEN
683	WRITE( message_string, * ) 'inconsistent canyon parameters:', &
684	'&cxl=', cxl, 'cxr=', cxr, &
685	'cwx=', cwx, &
686	'ch=', ch, 'nx=', nx, 'ny=', ny
687	CALL message( 'init_grid', 'PA0205', 1, 2, 0, 6, 0 )
688	ENDIF
689	ELSEIF ( canyon_width_y /= 9999999.9_wp ) THEN
690	IF ( ( cys < 1 ) .OR. ( cyn > ny-1 ) .OR. ( cwy < 3 ) .OR. &
691	( ch < 3 ) ) THEN
692	WRITE( message_string, * ) 'inconsistent canyon parameters:', &
693	'&cys=', cys, 'cyn=', cyn, &
694	'cwy=', cwy, &
695	'ch=', ch, 'nx=', nx, 'ny=', ny
696	CALL message( 'init_grid', 'PA0206', 1, 2, 0, 6, 0 )
697	ENDIF
698	ENDIF
699	IF ( canyon_width_x /= 9999999.9_wp .AND. &
700	canyon_width_y /= 9999999.9_wp ) THEN
701	message_string = 'inconsistent canyon parameters:' // &
702	'&street canyon can only be oriented' // &
703	'&either in x- or in y-direction'
704	CALL message( 'init_grid', 'PA0207', 1, 2, 0, 6, 0 )
705	ENDIF
706
707	nzb_local = ch
708	IF ( canyon_width_x /= 9999999.9_wp ) THEN
709	IF ( cxl <= nxr .AND. cxr >= nxl ) &
710	nzb_local(:,MAX(nxl,cxl+1):MIN(nxr,cxr-1)) = 0
711	ELSEIF ( canyon_width_y /= 9999999.9_wp ) THEN
712	IF ( cys <= nyn .AND. cyn >= nys ) &
713	nzb_local(MAX(nys,cys+1):MIN(nyn,cyn-1),:) = 0
714	ENDIF
715
716	CALL exchange_horiz_2d_int( nzb_local, nys, nyn, nxl, nxr, nbgp )
717	!
718	!-- Set bit array to mask topography
719	DO i = nxlg, nxrg
720	DO j = nysg, nyng
721	topo_3d(nzb_local(j,i)+1:nzt+1,j,i) = &
722	IBSET( topo_3d(nzb_local(j,i)+1:nzt+1,j,i), 0 )
723	ENDDO
724	ENDDO
725	!
726	!-- level of detail is required for output routines. Here, 2D topography.
727	lod = 1
728
729	CALL exchange_horiz_int( topo_3d, nbgp )
730
731	CASE ( 'tunnel' )
732
733	!
734	!-- Tunnel height
735	IF ( tunnel_height == 9999999.9_wp ) THEN
736	th = zw( INT( 0.2 * nz) )
737	ELSE
738	th = tunnel_height
739	ENDIF
740	!
741	!-- Tunnel-wall depth
742	IF ( tunnel_wall_depth == 9999999.9_wp ) THEN
743	td = MAX ( dx, dy, dz )
744	ELSE
745	td = tunnel_wall_depth
746	ENDIF
747	!
748	!-- Check for tunnel width
749	IF ( tunnel_width_x == 9999999.9_wp .AND. &
750	tunnel_width_y == 9999999.9_wp ) THEN
751	message_string = 'No tunnel width is given. '
752	CALL message( 'init_grid', 'PA0280', 1, 2, 0, 6, 0 )
753	ENDIF
754	IF ( tunnel_width_x /= 9999999.9_wp .AND. &
755	tunnel_width_y /= 9999999.9_wp ) THEN
756	message_string = 'Inconsistent tunnel parameters:' // &
757	'tunnel can only be oriented' // &
758	'either in x- or in y-direction.'
759	CALL message( 'init_grid', 'PA0281', 1, 2, 0, 6, 0 )
760	ENDIF
761	!
762	!-- Tunnel axis along y
763	IF ( tunnel_width_x /= 9999999.9_wp ) THEN
764	IF ( tunnel_width_x > ( nx + 1 ) * dx ) THEN
765	message_string = 'Tunnel width too large'
766	CALL message( 'init_grid', 'PA0282', 1, 2, 0, 6, 0 )
767	ENDIF
768
769	txs_out = INT( ( nx + 1 ) * 0.5_wp * dx - tunnel_width_x * 0.5_wp )
770	txe_out = INT( ( nx + 1 ) * 0.5_wp * dx + tunnel_width_x * 0.5_wp )
771	txs_in = INT( ( nx + 1 ) * 0.5_wp * dx - &
772	( tunnel_width_x * 0.5_wp - td ) )
773	txe_in = INT( ( nx + 1 ) * 0.5_wp * dx + &
774	( tunnel_width_x * 0.5_wp - td ) )
775
776	tys_out = INT( ( ny + 1 ) * 0.5_wp * dy - tunnel_length * 0.5_wp )
777	tye_out = INT( ( ny + 1 ) * 0.5_wp * dy + tunnel_length * 0.5_wp )
778	tys_in = tys_out
779	tye_in = tye_out
780	ENDIF
781	IF ( tunnel_width_x /= 9999999.9_wp .AND. &
782	tunnel_width_x - 2.0_wp * tunnel_wall_depth <= 2.0_wp * dx ) THEN
783	message_string = 'Tunnel width too small'
784	CALL message( 'init_grid', 'PA0175', 1, 2, 0, 6, 0 )
785	ENDIF
786	IF ( tunnel_width_y /= 9999999.9_wp .AND. &
787	tunnel_width_y - 2.0_wp * tunnel_wall_depth <= 2.0_wp * dy ) THEN
788	message_string = 'Tunnel width too small'
789	CALL message( 'init_grid', 'PA0455', 1, 2, 0, 6, 0 )
790	ENDIF
791	!
792	!-- Tunnel axis along x
793	IF ( tunnel_width_y /= 9999999.9_wp ) THEN
794	IF ( tunnel_width_y > ( ny + 1 ) * dy ) THEN
795	message_string = 'Tunnel width too large'
796	CALL message( 'init_grid', 'PA0456', 1, 2, 0, 6, 0 )
797	ENDIF
798
799	txs_out = INT( ( nx + 1 ) * 0.5_wp * dx - tunnel_length * 0.5_wp )
800	txe_out = INT( ( nx + 1 ) * 0.5_wp * dx + tunnel_length * 0.5_wp )
801	txs_in = txs_out
802	txe_in = txe_out
803
804	tys_out = INT( ( ny + 1 ) * 0.5_wp * dy - tunnel_width_y * 0.5_wp )
805	tye_out = INT( ( ny + 1 ) * 0.5_wp * dy + tunnel_width_y * 0.5_wp )
806	tys_in = INT( ( ny + 1 ) * 0.5_wp * dy - &
807	( tunnel_width_y * 0.5_wp - td ) )
808	tye_in = INT( ( ny + 1 ) * 0.5_wp * dy + &
809	( tunnel_width_y * 0.5_wp - td ) )
810	ENDIF
811
812	topo_3d = 0
813	DO i = nxl, nxr
814	DO j = nys, nyn
815	!
816	!-- Use heaviside function to model outer tunnel surface
817	hv_out = th * 0.5_wp * &
818	( ( SIGN( 1.0_wp, i * dx - txs_out ) + 1.0_wp ) &
819	- ( SIGN( 1.0_wp, i * dx - txe_out ) + 1.0_wp ) )
820
821	hv_out = hv_out * 0.5_wp * &
822	( ( SIGN( 1.0_wp, j * dy - tys_out ) + 1.0_wp ) &
823	- ( SIGN( 1.0_wp, j * dy - tye_out ) + 1.0_wp ) )
824	!
825	!-- Use heaviside function to model inner tunnel surface
826	hv_in = ( th - td ) * 0.5_wp * &
827	( ( SIGN( 1.0_wp, i * dx - txs_in ) + 1.0_wp ) &
828	- ( SIGN( 1.0_wp, i * dx - txe_in ) + 1.0_wp ) )
829
830	hv_in = hv_in * 0.5_wp * &
831	( ( SIGN( 1.0_wp, j * dy - tys_in ) + 1.0_wp ) &
832	- ( SIGN( 1.0_wp, j * dy - tye_in ) + 1.0_wp ) )
833	!
834	!-- Set flags at x-y-positions without any tunnel surface
835	IF ( hv_out - hv_in == 0.0_wp ) THEN
836	topo_3d(nzb+1:nzt+1,j,i) = IBSET( topo_3d(nzb+1:nzt+1,j,i), 0 )
837	!
838	!-- Set flags at x-y-positions with tunnel surfaces
839	ELSE
840	DO k = nzb + 1, nzt + 1
841	!
842	!-- Inner tunnel
843	IF ( hv_out - hv_in == th ) THEN
844	IF ( zw(k) <= hv_out ) THEN
845	topo_3d(k,j,i) = IBCLR( topo_3d(k,j,i), 0 )
846	ELSE
847	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 0 )
848	ENDIF
849	ENDIF
850	!
851	!-- Lateral tunnel walls
852	IF ( hv_out - hv_in == td ) THEN
853	IF ( zw(k) <= hv_in ) THEN
854	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 0 )
855	ELSEIF ( zw(k) > hv_in .AND. zw(k) <= hv_out ) THEN
856	topo_3d(k,j,i) = IBCLR( topo_3d(k,j,i), 0 )
857	ELSEIF ( zw(k) > hv_out ) THEN
858	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 0 )
859	ENDIF
860	ENDIF
861	ENDDO
862	ENDIF
863	ENDDO
864	ENDDO
865
866	nzb_local = 0
867	!
868	!-- level of detail is required for output routines. Here, 3D topography.
869	lod = 2
870
871	CALL exchange_horiz_int( topo_3d, nbgp )
872
873	CASE ( 'read_from_file' )
874
875	ALLOCATE ( oro_height(nys:nyn,nxl:nxr) )
876	ALLOCATE ( topo_height(nys:nyn,nxl:nxr) )
877	oro_height = 0.0_wp
878	topo_height = 0.0_wp
879
880	DO ii = 0, io_blocks-1
881	IF ( ii == io_group ) THEN
882
883	!
884	!-- Arbitrary irregular topography data in PALM format (exactly
885	!-- matching the grid size and total domain size).
886	!-- First, check if NetCDF file for topography exist or not.
887	!-- This case, read topography from NetCDF, else read it from
888	!-- ASCII file.
889	#if defined ( __netcdf )
890	INQUIRE( FILE='TOPOGRAPHY_DATA_NC'//TRIM( coupling_char ), &
891	EXIST=netcdf_extend )
892	!
893	!-- NetCDF branch
894	IF ( netcdf_extend ) THEN
895	!
896	!-- Open file in read-only mode
897	CALL netcdf_open_read_file( 'TOPOGRAPHY_DATA_NC', &
898	id_topo, 20 ) !Error number still need to be set properly
899
900	!
901	!-- Read terrain height. Reading is done PE-wise, i.e. each
902	!-- processor reads its own domain. Reading is realized
903	!-- via looping over x-dimension, i.e. calling
904	!-- netcdf_get_variable reads topography along y for given x.
905	!-- Orography is 2D.
906	DO i = nxl, nxr
907	CALL netcdf_get_variable( id_topo, 'orography_0', &
908	i, oro_height(:,i), 20 ) !Error number still need to be set properly
909	ENDDO
910	!
911	!-- Read attribute lod (level of detail), required for variable
912	!-- buildings_0
913	CALL netcdf_get_attribute( id_topo, "lod", lod, .FALSE., &
914	20, 'buildings_0' ) !Error number still need to be set properly
915	!
916	!-- Read building height
917	!-- 2D for lod = 1, 3D for lod = 2
918	IF ( lod == 1 ) THEN
919	DO i = nxl, nxr
920	CALL netcdf_get_variable( id_topo, 'buildings_0', &
921	i, topo_height(:,i), 20 ) !Error number still need to be set properly
922	ENDDO
923
924	ELSEIF ( lod == 2 ) THEN
925	!
926	!-- Allocate 1-byte integer dummy array to read 3D topography
927	ALLOCATE( topo_3d_read(nzb:nzt+1,nysg:nyng,nxlg:nxrg) )
928	!
929	!-- Read data PE-wise. Read yz-slices.
930	DO i = nxl, nxr
931	DO j = nys, nyn
932	CALL netcdf_get_variable( id_topo, 'buildings_0', &
933	i, j, topo_3d_read(:,j,i), 20 ) !Error number still need to be set properly
934	ENDDO
935	ENDDO
936	ELSE
937	message_string = 'NetCDF attribute lod ' // &
938	'(level of detail) is not set properly.'
939	CALL message( 'init_grid', 'PA0457', 1, 2, 0, 6, 0 )
940	ENDIF
941	!
942	!-- On file, 3D topography grid points is classified with 1,
943	!-- atmosphere is classified with 0, contrary to the internal
944	!-- treatment. Hence, conversion is required. Moreover, set
945	!-- topography array to zero at lowest grid level.
946	topo_3d = MERGE( 0, 1, topo_3d_read == 1 )
947	topo_3d(nzb,:,:) = 0
948	!
949	!-- Deallocate dummy array
950	DEALLOCATE( topo_3d_read )
951	!
952	!-- Close topography input file
953	CALL netcdf_close_file( id_topo, 20 )
954	#endif
955
956	!
957	!-- ASCII branch. Please note, reading of 3D topography is not
958	!-- supported in ASCII format. Further, no distinction is made
959	!-- between orography and buildings
960	ELSE
961
962	OPEN( 90, FILE='TOPOGRAPHY_DATA'//TRIM( coupling_char ), &
963	STATUS='OLD', FORM='FORMATTED', ERR=10 )
964	!
965	!-- Read topography PE-wise. Rows are read from nyn to nys, columns
966	!-- are read from nxl to nxr. At first, ny-nyn rows need to be skipped.
967	skip_n_rows = 0
968	DO WHILE ( skip_n_rows < ny - nyn )
969	READ( 90, * )
970	skip_n_rows = skip_n_rows + 1
971	ENDDO
972	!
973	!-- Read data from nyn to nys and nxl to nxr. Therefore, skip
974	!-- column until nxl-1 is reached
975	DO j = nyn, nys, -1
976	READ( 90, *, ERR=11, END=11 ) &
977	( dum, i = 0, nxl-1 ), &
978	( topo_height(j,i), i = nxl, nxr )
979	ENDDO
980
981	GOTO 12
982
983	10 message_string = 'file TOPOGRAPHY'//TRIM( coupling_char )// &
984	' does not exist'
985	CALL message( 'init_grid', 'PA0208', 1, 2, 0, 6, 0 )
986
987	11 message_string = 'errors in file TOPOGRAPHY_DATA'// &
988	TRIM( coupling_char )
989	CALL message( 'init_grid', 'PA0209', 1, 2, 0, 6, 0 )
990
991	12 CLOSE( 90 )
992
993	ENDIF
994
995	ENDIF
996	#if defined( __parallel )
997	CALL MPI_BARRIER( comm2d, ierr )
998	#endif
999	ENDDO
1000
1001	!
1002	!-- Calculate the index height of the topography
1003	nzb_local = 0
1004	DO i = nxl, nxr
1005	DO j = nys, nyn
1006	IF ( .NOT. ocean ) THEN
1007	nzb_local(j,i) = MINLOC( ABS( zw - topo_height(j,i) &
1008	- oro_height(j,i) ), 1 ) - 1
1009	IF ( ABS( zw(nzb_local(j,i) ) - topo_height(j,i) &
1010	- oro_height(j,i) ) == &
1011	ABS( zw(nzb_local(j,i)+1) - topo_height(j,i) &
1012	- oro_height(j,i) ) ) &
1013	nzb_local(j,i) = nzb_local(j,i) + 1
1014	ELSE
1015	nzb_local(j,i) = MINLOC( ABS( zw - zw(0) &
1016	- topo_height(j,i) &
1017	- oro_height(j,i) ), 1 ) - 1
1018	IF ( ABS( zw(nzb_local(j,i) ) - zw(0) &
1019	- topo_height(j,i) &
1020	- oro_height(j,i) ) == &
1021	ABS( zw(nzb_local(j,i)+1) - zw(0) &
1022	- topo_height(j,i) &
1023	- oro_height(j,i) ) ) &
1024	nzb_local(j,i) = nzb_local(j,i) + 1
1025	ENDIF
1026
1027	ENDDO
1028	ENDDO
1029
1030	DEALLOCATE ( oro_height )
1031	DEALLOCATE ( topo_height )
1032	!
1033	!-- Filter topography, i.e. fill holes resolved by only one grid point.
1034	!-- Such holes are suspected to lead to velocity blow-ups as continuity
1035	!-- equation on discrete grid cannot be fulfilled in such case.
1036	!-- For now, check only for holes and fill them to the lowest height level
1037	!-- of the directly adjoining grid points along x- and y- direction.
1038	!-- Before checking for holes, set lateral boundary conditions for
1039	!-- topography. After hole-filling, boundary conditions must be set again!
1040	CALL exchange_horiz_2d_int( nzb_local, nys, nyn, nxl, nxr, nbgp )
1041
1042	IF ( .NOT. bc_ns_cyc ) THEN
1043	IF ( nys == 0 ) nzb_local(-1,:) = nzb_local(0,:)
1044	IF ( nyn == ny ) nzb_local(ny+1,:) = nzb_local(ny,:)
1045	ENDIF
1046
1047	IF ( .NOT. bc_lr_cyc ) THEN
1048	IF ( nxl == 0 ) nzb_local(:,-1) = nzb_local(:,0)
1049	IF ( nxr == nx ) nzb_local(:,nx+1) = nzb_local(:,nx)
1050	ENDIF
1051
1052	num_hole_l = 0
1053	DO i = nxl, nxr
1054	DO j = nys, nyn
1055
1056	num_wall = 0
1057
1058	IF ( nzb_local(j-1,i) > nzb_local(j,i) ) &
1059	num_wall = num_wall + 1
1060	IF ( nzb_local(j+1,i) > nzb_local(j,i) ) &
1061	num_wall = num_wall + 1
1062	IF ( nzb_local(j,i-1) > nzb_local(j,i) ) &
1063	num_wall = num_wall + 1
1064	IF ( nzb_local(j,i+1) > nzb_local(j,i) ) &
1065	num_wall = num_wall + 1
1066
1067	IF ( num_wall == 4 ) THEN
1068	nzb_local(j,i) = MIN( nzb_local(j-1,i), nzb_local(j+1,i), &
1069	nzb_local(j,i-1), nzb_local(j,i+1) )
1070	num_hole_l = num_hole_l + 1
1071	ENDIF
1072	ENDDO
1073	ENDDO
1074	!
1075	!-- Count the total number of holes, required for informative message.
1076	#if defined( __parallel )
1077	CALL MPI_ALLREDUCE( num_hole_l, num_hole, 1, MPI_INTEGER, MPI_SUM, &
1078	comm2d, ierr )
1079	#else
1080	num_hole = num_hole_l
1081	#endif
1082	!
1083	!-- Create an informative message if any hole was removed.
1084	IF ( num_hole > 0 ) THEN
1085	WRITE( message_string, * ) num_hole, 'hole(s) resolved by only '//&
1086	'one grid point were filled'
1087	CALL message( 'init_grid', 'PA0430', 0, 0, 0, 6, 0 )
1088	ENDIF
1089
1090	!
1091	!-- Set bit array to mask topography. Only required for lod = 1
1092	IF ( lod == 1 ) THEN
1093	DO i = nxlg, nxrg
1094	DO j = nysg, nyng
1095	topo_3d(nzb_local(j,i)+1:nzt+1,j,i) = &
1096	IBSET( topo_3d(nzb_local(j,i)+1:nzt+1,j,i), 0 )
1097	ENDDO
1098	ENDDO
1099	ENDIF
1100	!
1101	!-- Exchange ghost-points, as well as add cyclic or Neumann boundary
1102	!-- conditions.
1103	CALL exchange_horiz_int( topo_3d, nbgp )
1104	CALL exchange_horiz_2d_int( nzb_local, nys, nyn, nxl, nxr, nbgp )
1105
1106	IF ( .NOT. bc_ns_cyc ) THEN
1107	IF ( nys == 0 ) topo_3d(:,-1,:) = topo_3d(:,0,:)
1108	IF ( nyn == ny ) topo_3d(:,ny+1,:) = topo_3d(:,ny,:)
1109
1110	IF ( nys == 0 ) nzb_local(-1,:) = nzb_local(0,:)
1111	IF ( nyn == ny ) nzb_local(ny+1,:) = nzb_local(ny,:)
1112	ENDIF
1113
1114	IF ( .NOT. bc_lr_cyc ) THEN
1115	IF ( nxl == 0 ) topo_3d(:,:,-1) = topo_3d(:,:,0)
1116	IF ( nxr == nx ) topo_3d(:,:,nx+1) = topo_3d(:,:,nx)
1117
1118	IF ( nxl == 0 ) nzb_local(:,-1) = nzb_local(:,0)
1119	IF ( nxr == nx ) nzb_local(:,nx+1) = nzb_local(:,nx)
1120	ENDIF
1121
1122
1123	CASE DEFAULT
1124	!
1125	!-- The DEFAULT case is reached either if the parameter topography
1126	!-- contains a wrong character string or if the user has defined a special
1127	!-- case in the user interface. There, the subroutine user_init_grid
1128	!-- checks which of these two conditions applies.
1129	CALL user_init_grid( topo_3d )
1130
1131	END SELECT
1132	!
1133	!-- Consistency checks and index array initialization are only required for
1134	!-- non-flat topography, also the initialization of topography height arrays
1135	!-- zu_s_inner and zw_w_inner
1136	IF ( TRIM( topography ) /= 'flat' ) THEN
1137	#if defined( __parallel )
1138	CALL MPI_ALLREDUCE( MAXVAL( nzb_local ), nzb_local_max, 1, MPI_INTEGER, &
1139	MPI_MAX, comm2d, ierr )
1140	CALL MPI_ALLREDUCE( MINVAL( nzb_local ), nzb_local_min, 1, MPI_INTEGER, &
1141	MPI_MIN, comm2d, ierr )
1142	#else
1143	nzb_local_max = MAXVAL( nzb_local )
1144	nzb_local_min = MINVAL( nzb_local )
1145	#endif
1146
1147	!
1148	!-- Consistency checks
1149	IF ( nzb_local_min < 0 .OR. nzb_local_max > nz + 1 ) THEN
1150	WRITE( message_string, * ) 'nzb_local values are outside the', &
1151	'model domain', &
1152	'&MINVAL( nzb_local ) = ', nzb_local_min, &
1153	'&MAXVAL( nzb_local ) = ', nzb_local_max
1154	CALL message( 'init_grid', 'PA0210', 1, 2, 0, 6, 0 )
1155	ENDIF
1156	!
1157	!-- In case of non-flat topography, check whether the convention how to
1158	!-- define the topography grid has been set correctly, or whether the default
1159	!-- is applicable. If this is not possible, abort.
1160	IF ( TRIM( topography_grid_convention ) == ' ' ) THEN
1161	IF ( TRIM( topography ) /= 'single_building' .AND. &
1162	TRIM( topography ) /= 'single_street_canyon' .AND. &
1163	TRIM( topography ) /= 'tunnel' .AND. &
1164	TRIM( topography ) /= 'read_from_file') THEN
1165	!-- The default value is not applicable here, because it is only valid
1166	!-- for the two standard cases 'single_building' and 'read_from_file'
1167	!-- defined in init_grid.
1168	WRITE( message_string, * ) &
1169	'The value for "topography_grid_convention" ', &
1170	'is not set. Its default value is & only valid for ', &
1171	'"topography" = ''single_building'', ', &
1172	'''single_street_canyon'' & or ''read_from_file''.', &
1173	' & Choose ''cell_edge'' or ''cell_center''.'
1174	CALL message( 'init_grid', 'PA0239', 1, 2, 0, 6, 0 )
1175	ELSE
1176	!-- The default value is applicable here.
1177	!-- Set convention according to topography.
1178	IF ( TRIM( topography ) == 'single_building' .OR. &
1179	TRIM( topography ) == 'single_street_canyon' ) THEN
1180	topography_grid_convention = 'cell_edge'
1181	ELSEIF ( TRIM( topography ) == 'read_from_file' .OR. &
1182	TRIM( topography ) == 'tunnel') THEN
1183	topography_grid_convention = 'cell_center'
1184	ENDIF
1185	ENDIF
1186	ELSEIF ( TRIM( topography_grid_convention ) /= 'cell_edge' .AND. &
1187	TRIM( topography_grid_convention ) /= 'cell_center' ) THEN
1188	WRITE( message_string, * ) &
1189	'The value for "topography_grid_convention" is ', &
1190	'not recognized. & Choose ''cell_edge'' or ''cell_center''.'
1191	CALL message( 'init_grid', 'PA0240', 1, 2, 0, 6, 0 )
1192	ENDIF
1193
1194	!
1195	!-- In case of non-flat topography, check whether the convention how to
1196	!-- define the topography grid has been set correctly, or whether the default
1197	!-- is applicable. If this is not possible, abort.
1198	IF ( TRIM( topography_grid_convention ) == ' ' ) THEN
1199	IF ( TRIM( topography ) /= 'single_building' .AND. &
1200	TRIM( topography ) /= 'single_street_canyon' .AND. &
1201	TRIM( topography ) /= 'read_from_file' ) THEN
1202	!-- The default value is not applicable here, because it is only valid
1203	!-- for the two standard cases 'single_building' and 'read_from_file'
1204	!-- defined in init_grid.
1205	WRITE( message_string, * ) &
1206	'The value for "topography_grid_convention" ', &
1207	'is not set. Its default value is & only valid for ', &
1208	'"topography" = ''single_building'', ', &
1209	'''single_street_canyon'' & or ''read_from_file''.', &
1210	' & Choose ''cell_edge'' or ''cell_center''.'
1211	CALL message( 'init_grid', 'PA0239', 1, 2, 0, 6, 0 )
1212	ELSE
1213	!-- The default value is applicable here.
1214	!-- Set convention according to topography.
1215	IF ( TRIM( topography ) == 'single_building' .OR. &
1216	TRIM( topography ) == 'single_street_canyon' ) THEN
1217	topography_grid_convention = 'cell_edge'
1218	ELSEIF ( TRIM( topography ) == 'read_from_file' ) THEN
1219	topography_grid_convention = 'cell_center'
1220	ENDIF
1221	ENDIF
1222	ELSEIF ( TRIM( topography_grid_convention ) /= 'cell_edge' .AND. &
1223	TRIM( topography_grid_convention ) /= 'cell_center' ) THEN
1224	WRITE( message_string, * ) &
1225	'The value for "topography_grid_convention" is ', &
1226	'not recognized. & Choose ''cell_edge'' or ''cell_center''.'
1227	CALL message( 'init_grid', 'PA0240', 1, 2, 0, 6, 0 )
1228	ENDIF
1229
1230	IF ( topography_grid_convention == 'cell_edge' ) THEN
1231	!
1232	!-- The array nzb_local as defined using the 'cell_edge' convention
1233	!-- describes the actual total size of topography which is defined at the
1234	!-- cell edges where u=0 on the topography walls in x-direction and v=0
1235	!-- on the topography walls in y-direction. However, PALM uses individual
1236	!-- arrays nzb_u\|v\|w\|s_inner\|outer that are based on nzb_s_inner.
1237	!-- Therefore, the extent of topography in nzb_local is now reduced by
1238	!-- 1dx at the E topography walls and by 1dy at the N topography walls
1239	!-- to form the basis for nzb_s_inner.
1240	!-- Note, the reverse memory access (i-j instead of j-i) is absolutely
1241	!-- required at this point.
1242	DO j = nys+1, nyn+1
1243	DO i = nxl-1, nxr
1244	nzb_local(j,i) = MIN( nzb_local(j,i), nzb_local(j,i+1) )
1245	ENDDO
1246	ENDDO
1247	!
1248	!-- Exchange ghost points
1249	CALL exchange_horiz_2d_int( nzb_local, nys, nyn, nxl, nxr, nbgp )
1250
1251	DO i = nxl, nxr+1
1252	DO j = nys-1, nyn
1253	nzb_local(j,i) = MIN( nzb_local(j,i), nzb_local(j+1,i) )
1254	ENDDO
1255	ENDDO
1256	!
1257	!-- Exchange ghost points
1258	CALL exchange_horiz_2d_int( nzb_local, nys, nyn, nxl, nxr, nbgp )
1259	!
1260	!-- Apply cell-edge convention also for 3D topo array. The former setting
1261	!-- of nzb_local will be removed later.
1262	DO j = nys+1, nyn+1
1263	DO i = nxl-1, nxr
1264	DO k = nzb, nzt+1
1265	IF ( BTEST( topo_3d(k,j,i), 0 ) .OR. &
1266	BTEST( topo_3d(k,j,i+1), 0 ) ) &
1267	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 0 )
1268	ENDDO
1269	ENDDO
1270	ENDDO
1271	CALL exchange_horiz_int( topo_3d, nbgp )
1272
1273	DO i = nxl, nxr+1
1274	DO j = nys-1, nyn
1275	DO k = nzb, nzt+1
1276	IF ( BTEST( topo_3d(k,j,i), 0 ) .OR. &
1277	BTEST( topo_3d(k,j+1,i), 0 ) ) &
1278	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 0 )
1279	ENDDO
1280	ENDDO
1281	ENDDO
1282	CALL exchange_horiz_int( topo_3d, nbgp )
1283
1284	ENDIF
1285
1286	!
1287	!-- Initialize index arrays nzb_s_inner and nzb_w_inner
1288
1289	nzb_s_inner = nzb_local
1290	nzb_w_inner = nzb_local
1291
1292	!
1293	!-- Initialize remaining index arrays:
1294	!-- first pre-initialize them with nzb_s_inner...
1295	nzb_u_inner = nzb_s_inner
1296	nzb_u_outer = nzb_s_inner
1297	nzb_v_inner = nzb_s_inner
1298	nzb_v_outer = nzb_s_inner
1299	nzb_w_outer = nzb_s_inner
1300	nzb_s_outer = nzb_s_inner
1301
1302	!
1303	!-- ...then extend pre-initialized arrays in their according directions
1304	!-- based on nzb_local using nzb_tmp as a temporary global index array
1305
1306	!
1307	!-- nzb_s_outer:
1308	!-- extend nzb_local east-/westwards first, then north-/southwards
1309	nzb_tmp = nzb_local
1310	DO j = nys, nyn
1311	DO i = nxl, nxr
1312	nzb_tmp(j,i) = MAX( nzb_local(j,i-1), nzb_local(j,i), &
1313	nzb_local(j,i+1) )
1314	ENDDO
1315	ENDDO
1316
1317	CALL exchange_horiz_2d_int( nzb_tmp, nys, nyn, nxl, nxr, nbgp )
1318
1319	DO i = nxl, nxr
1320	DO j = nys, nyn
1321	nzb_s_outer(j,i) = MAX( nzb_tmp(j-1,i), nzb_tmp(j,i), &
1322	nzb_tmp(j+1,i) )
1323	ENDDO
1324	!
1325	!-- non-cyclic boundary conditions (overwritten by call of
1326	!-- exchange_horiz_2d_int below in case of cyclic boundary conditions)
1327	IF ( nys == 0 ) THEN
1328	j = -1
1329	nzb_s_outer(j,i) = MAX( nzb_tmp(j+1,i), nzb_tmp(j,i) )
1330	ENDIF
1331	IF ( nyn == ny ) THEN
1332	j = ny + 1
1333	nzb_s_outer(j,i) = MAX( nzb_tmp(j-1,i), nzb_tmp(j,i) )
1334	ENDIF
1335	ENDDO
1336	!
1337	!-- nzb_w_outer:
1338	!-- identical to nzb_s_outer
1339	nzb_w_outer = nzb_s_outer
1340
1341	!
1342	!-- nzb_u_inner:
1343	!-- extend nzb_local rightwards only
1344	nzb_tmp = nzb_local
1345	DO j = nys, nyn
1346	DO i = nxl, nxr
1347	nzb_tmp(j,i) = MAX( nzb_local(j,i-1), nzb_local(j,i) )
1348	ENDDO
1349	ENDDO
1350
1351	CALL exchange_horiz_2d_int( nzb_tmp, nys, nyn, nxl, nxr, nbgp )
1352
1353	nzb_u_inner = nzb_tmp
1354	!
1355	!-- nzb_u_outer:
1356	!-- extend current nzb_tmp (nzb_u_inner) north-/southwards
1357	DO i = nxl, nxr
1358	DO j = nys, nyn
1359	nzb_u_outer(j,i) = MAX( nzb_tmp(j-1,i), nzb_tmp(j,i), &
1360	nzb_tmp(j+1,i) )
1361	ENDDO
1362	!
1363	!-- non-cyclic boundary conditions (overwritten by call of
1364	!-- exchange_horiz_2d_int below in case of cyclic boundary conditions)
1365	IF ( nys == 0 ) THEN
1366	j = -1
1367	nzb_u_outer(j,i) = MAX( nzb_tmp(j+1,i), nzb_tmp(j,i) )
1368	ENDIF
1369	IF ( nyn == ny ) THEN
1370	j = ny + 1
1371	nzb_u_outer(j,i) = MAX( nzb_tmp(j-1,i), nzb_tmp(j,i) )
1372	ENDIF
1373	ENDDO
1374
1375	!
1376	!-- nzb_v_inner:
1377	!-- extend nzb_local northwards only
1378	nzb_tmp = nzb_local
1379	DO i = nxl, nxr
1380	DO j = nys, nyn
1381	nzb_tmp(j,i) = MAX( nzb_local(j-1,i), nzb_local(j,i) )
1382	ENDDO
1383	ENDDO
1384
1385	CALL exchange_horiz_2d_int( nzb_tmp, nys, nyn, nxl, nxr, nbgp )
1386	nzb_v_inner = nzb_tmp
1387
1388	!
1389	!-- nzb_v_outer:
1390	!-- extend current nzb_tmp (nzb_v_inner) right-/leftwards
1391	DO j = nys, nyn
1392	DO i = nxl, nxr
1393	nzb_v_outer(j,i) = MAX( nzb_tmp(j,i-1), nzb_tmp(j,i), &
1394	nzb_tmp(j,i+1) )
1395	ENDDO
1396	!
1397	!-- non-cyclic boundary conditions (overwritten by call of
1398	!-- exchange_horiz_2d_int below in case of cyclic boundary conditions)
1399	IF ( nxl == 0 ) THEN
1400	i = -1
1401	nzb_v_outer(j,i) = MAX( nzb_tmp(j,i+1), nzb_tmp(j,i) )
1402	ENDIF
1403	IF ( nxr == nx ) THEN
1404	i = nx + 1
1405	nzb_v_outer(j,i) = MAX( nzb_tmp(j,i-1), nzb_tmp(j,i) )
1406	ENDIF
1407	ENDDO
1408
1409	!
1410	!-- Exchange of lateral boundary values (parallel computers) and cyclic
1411	!-- boundary conditions, if applicable.
1412	!-- Since nzb_s_inner and nzb_w_inner are derived directly from nzb_local
1413	!-- they do not require exchange and are not included here.
1414	CALL exchange_horiz_2d_int( nzb_u_inner, nys, nyn, nxl, nxr, nbgp )
1415	CALL exchange_horiz_2d_int( nzb_u_outer, nys, nyn, nxl, nxr, nbgp )
1416	CALL exchange_horiz_2d_int( nzb_v_inner, nys, nyn, nxl, nxr, nbgp )
1417	CALL exchange_horiz_2d_int( nzb_v_outer, nys, nyn, nxl, nxr, nbgp )
1418	CALL exchange_horiz_2d_int( nzb_w_outer, nys, nyn, nxl, nxr, nbgp )
1419	CALL exchange_horiz_2d_int( nzb_s_outer, nys, nyn, nxl, nxr, nbgp )
1420
1421	ENDIF
1422	!
1423	!-- Deallocate temporary array, as it might be reused for different
1424	!-- grid-levels further below.
1425	DEALLOCATE( nzb_tmp )
1426
1427	!
1428	!-- Determine the maximum level of topography. It is used for
1429	!-- steering the degradation of order of the applied advection scheme.
1430	!-- In case of non-cyclic lateral boundaries, the order of the advection
1431	!-- scheme has to be reduced up to nzt (required at the lateral boundaries).
1432	k_top = 0
1433	DO i = nxl, nxr
1434	DO j = nys, nyn
1435	DO k = nzb, nzt + 1
1436	k_top = MAX( k_top, MERGE( k, 0, &
1437	.NOT. BTEST( topo_3d(k,j,i), 0 ) ) )
1438	ENDDO
1439	ENDDO
1440	ENDDO
1441	#if defined( __parallel )
1442	CALL MPI_ALLREDUCE( k_top + 1, nzb_max, 1, MPI_INTEGER, & !is +1 really necessary here?
1443	MPI_MAX, comm2d, ierr )
1444	#else
1445	nzb_max = k_top + 1
1446	#endif
1447	IF ( inflow_l .OR. outflow_l .OR. inflow_r .OR. outflow_r .OR. &
1448	inflow_n .OR. outflow_n .OR. inflow_s .OR. outflow_s .OR. &
1449	nest_domain ) &
1450	THEN
1451	nzb_max = nzt
1452	ENDIF
1453	!
1454	!-- Finally, if topography extents up to the model top, limit nzb_max to nzt.
1455	nzb_max = MIN( nzb_max, nzt )
1456
1457	!
1458	!-- Set the individual index arrays which define the k index from which on
1459	!-- the usual finite difference form (which does not use surface fluxes) is
1460	!-- applied
1461	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
1462	nzb_diff_s_inner = nzb_s_inner + 2
1463	nzb_diff_s_outer = nzb_s_outer + 2
1464	ELSE
1465	nzb_diff_s_inner = nzb_s_inner + 1
1466	nzb_diff_s_outer = nzb_s_outer + 1
1467	ENDIF
1468
1469	!
1470	!-- Set-up topography flags. First, set flags only for s, u, v and w-grid.
1471	!-- Further special flags will be set in following loops.
1472	wall_flags_0 = 0
1473	DO j = nys, nyn
1474	DO i = nxl, nxr
1475	DO k = nzb, nzt+1
1476	!
1477	!-- scalar grid
1478	IF ( BTEST( topo_3d(k,j,i), 0 ) ) &
1479	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 0 )
1480	!
1481	!-- v grid
1482	IF ( BTEST( topo_3d(k,j,i), 0 ) .AND. &
1483	BTEST( topo_3d(k,j-1,i), 0 ) ) &
1484	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 2 )
1485	!
1486	!-- To do: set outer arrays on basis of topo_3d array, adjust for downward-facing walls
1487	!-- s grid outer array
1488	IF ( k >= nzb_s_outer(j,i) ) &
1489	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 24 )
1490	!
1491	!-- s grid outer array
1492	IF ( k >= nzb_u_outer(j,i) ) &
1493	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 26 )
1494	!
1495	!-- s grid outer array
1496	IF ( k >= nzb_v_outer(j,i) ) &
1497	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 27 )
1498	!
1499	!-- w grid outer array
1500	IF ( k >= nzb_w_outer(j,i) ) &
1501	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 28 )
1502	ENDDO
1503
1504	DO k = nzb, nzt
1505	!
1506	!-- w grid
1507	IF ( BTEST( topo_3d(k,j,i), 0 ) .AND. &
1508	BTEST( topo_3d(k+1,j,i), 0 ) ) &
1509	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 3 )
1510	ENDDO
1511	wall_flags_0(nzt+1,j,i) = IBSET( wall_flags_0(nzt+1,j,i), 3 )
1512
1513	ENDDO
1514	ENDDO
1515	!
1516	!-- u grid. Note, reverse
1517	!-- memory access is required for setting flag on u-grid
1518	DO j = nys, nyn
1519	DO i = nxl, nxr
1520	DO k = nzb, nzt+1
1521	IF ( BTEST( topo_3d(k,j,i), 0 ) .AND. &
1522	BTEST( topo_3d(k,j,i-1), 0 ) ) &
1523	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 1 )
1524	ENDDO
1525	ENDDO
1526	ENDDO
1527	!
1528	!-- Set further special flags
1529	DO i = nxl, nxr
1530	DO j = nys, nyn
1531	DO k = nzb, nzt+1
1532	!
1533	!-- scalar grid, former nzb_diff_s_inner.
1534	!-- Note, use this flag also to mask topography in diffusion_u and
1535	!-- diffusion_v along the vertical direction. In case of
1536	!-- use_surface_fluxes, fluxes are calculated via MOST, else, simple
1537	!-- gradient approach is applied. Please note, in case of u- and v-
1538	!-- diffuison, a small error is made at edges (on the east side for u,
1539	!-- at the north side for v), since topography on scalar grid point
1540	!-- is used instead of topography on u/v-grid. As number of topography grid
1541	!-- points on uv-grid is different than s-grid, different number of
1542	!-- surface elements would be required. In order to avoid this,
1543	!-- treat edges (u(k,j,i+1)) simply by a gradient approach, i.e. these
1544	!-- points are not masked within diffusion_u. Tests had shown that the
1545	!-- effect on the flow is negligible.
1546	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
1547	IF ( BTEST( wall_flags_0(k,j,i), 0 ) ) &
1548	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 8 )
1549	ELSE
1550	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 8 )
1551	ENDIF
1552
1553	ENDDO
1554	!
1555	!-- Special flag to control vertical diffusion at model top - former
1556	!-- nzt_diff
1557	wall_flags_0(:,j,i) = IBSET( wall_flags_0(:,j,i), 9 )
1558	IF ( use_top_fluxes ) &
1559	wall_flags_0(nzt+1,j,i) = IBCLR( wall_flags_0(nzt+1,j,i), 9 )
1560
1561	DO k = nzb+1, nzt
1562	!
1563	!-- Special flag on u grid, former nzb_u_inner + 1, required
1564	!-- for disturb_field and initialization. Do not disturb directly at
1565	!-- topography, as well as initialize u with zero one grid point outside
1566	!-- of topography.
1567	IF ( BTEST( wall_flags_0(k-1,j,i), 1 ) .AND. &
1568	BTEST( wall_flags_0(k,j,i), 1 ) .AND. &
1569	BTEST( wall_flags_0(k+1,j,i), 1 ) ) &
1570	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 20 )
1571	!
1572	!-- Special flag on v grid, former nzb_v_inner + 1, required
1573	!-- for disturb_field and initialization. Do not disturb directly at
1574	!-- topography, as well as initialize v with zero one grid point outside
1575	!-- of topography.
1576	IF ( BTEST( wall_flags_0(k-1,j,i), 2 ) .AND. &
1577	BTEST( wall_flags_0(k,j,i), 2 ) .AND. &
1578	BTEST( wall_flags_0(k+1,j,i), 2 ) ) &
1579	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 21 )
1580	!
1581	!-- Special flag on scalar grid, former nzb_s_inner+1. Used for
1582	!-- lpm_sgs_tke
1583	IF ( BTEST( wall_flags_0(k,j,i), 0 ) .AND. &
1584	BTEST( wall_flags_0(k-1,j,i), 0 ) .AND. &
1585	BTEST( wall_flags_0(k+1,j,i), 0 ) ) &
1586	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 25 )
1587	!
1588	!-- Special flag on scalar grid, nzb_diff_s_outer - 1, required in
1589	!-- in production_e
1590	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
1591	IF ( BTEST( wall_flags_0(k,j,i), 24 ) .AND. &
1592	BTEST( wall_flags_0(k-1,j,i), 24 ) .AND. &
1593	BTEST( wall_flags_0(k+1,j,i), 0 ) ) &
1594	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 29 )
1595	ELSE
1596	IF ( BTEST( wall_flags_0(k,j,i), 0 ) ) &
1597	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 29 )
1598	ENDIF
1599	!
1600	!-- Special flag on scalar grid, nzb_diff_s_outer - 1, required in
1601	!-- in production_e
1602	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
1603	IF ( BTEST( wall_flags_0(k,j,i), 0 ) .AND. &
1604	BTEST( wall_flags_0(k-1,j,i), 0 ) .AND. &
1605	BTEST( wall_flags_0(k+1,j,i), 0 ) ) &
1606	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 30 )
1607	ELSE
1608	IF ( BTEST( wall_flags_0(k,j,i), 0 ) ) &
1609	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 30 )
1610	ENDIF
1611	ENDDO
1612	!
1613	!-- Flags indicating downward facing walls
1614	DO k = nzb+1, nzt
1615	!
1616	!-- Scalar grid
1617	IF ( BTEST( wall_flags_0(k-1,j,i), 0 ) .AND. &
1618	.NOT. BTEST( wall_flags_0(k,j,i), 0 ) ) &
1619	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 13 )
1620	!
1621	!-- Downward facing wall on u grid
1622	IF ( BTEST( wall_flags_0(k-1,j,i), 1 ) .AND. &
1623	.NOT. BTEST( wall_flags_0(k,j,i), 1 ) ) &
1624	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 15 )
1625	!
1626	!-- Downward facing wall on v grid
1627	IF ( BTEST( wall_flags_0(k-1,j,i), 2 ) .AND. &
1628	.NOT. BTEST( wall_flags_0(k,j,i), 2 ) ) &
1629	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 17 )
1630	!
1631	!-- Downward facing wall on w grid
1632	IF ( BTEST( wall_flags_0(k-1,j,i), 3 ) .AND. &
1633	.NOT. BTEST( wall_flags_0(k,j,i), 3 ) ) &
1634	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 19 )
1635	ENDDO
1636	!
1637	!-- Flags indicating upward facing walls
1638	DO k = nzb, nzt
1639	!
1640	!-- Upward facing wall on scalar grid
1641	IF ( .NOT. BTEST( wall_flags_0(k,j,i), 0 ) .AND. &
1642	BTEST( wall_flags_0(k+1,j,i), 0 ) ) &
1643	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 12 )
1644	!
1645	!-- Upward facing wall on u grid
1646	IF ( .NOT. BTEST( wall_flags_0(k,j,i), 1 ) .AND. &
1647	BTEST( wall_flags_0(k+1,j,i), 1 ) ) &
1648	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 14 )
1649
1650	!
1651	!-- Upward facing wall on v grid
1652	IF ( .NOT. BTEST( wall_flags_0(k,j,i), 2 ) .AND. &
1653	BTEST( wall_flags_0(k+1,j,i), 2 ) ) &
1654	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 16 )
1655
1656	!
1657	!-- Upward facing wall on w grid
1658	IF ( .NOT. BTEST( wall_flags_0(k,j,i), 3 ) .AND. &
1659	BTEST( wall_flags_0(k+1,j,i), 3 ) ) &
1660	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 18 )
1661	!
1662	!-- Special flag on scalar grid, former nzb_s_inner
1663	IF ( BTEST( wall_flags_0(k,j,i), 0 ) .OR. &
1664	BTEST( wall_flags_0(k,j,i), 12 ) .OR. &
1665	BTEST( wall_flags_0(k,j,i), 13 ) ) &
1666	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 22 )
1667	!
1668	!-- Special flag on scalar grid, nzb_diff_s_inner - 1, required for
1669	!-- flow_statistics
1670	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
1671	IF ( BTEST( wall_flags_0(k,j,i), 0 ) .AND. &
1672	BTEST( wall_flags_0(k+1,j,i), 0 ) ) &
1673	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 23 )
1674	ELSE
1675	IF ( BTEST( wall_flags_0(k,j,i), 22 ) ) &
1676	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 23 )
1677	ENDIF
1678
1679
1680	ENDDO
1681	wall_flags_0(nzt+1,j,i) = IBSET( wall_flags_0(nzt+1,j,i), 22 )
1682	wall_flags_0(nzt+1,j,i) = IBSET( wall_flags_0(nzt+1,j,i), 23 )
1683	ENDDO
1684	ENDDO
1685	!
1686	!-- Exchange ghost points for wall flags
1687	CALL exchange_horiz_int( wall_flags_0, nbgp )
1688	!
1689	!-- Set boundary conditions also for flags. Can be interpreted as Neumann
1690	!-- boundary conditions for topography.
1691	IF ( .NOT. bc_ns_cyc ) THEN
1692	IF ( nys == 0 ) wall_flags_0(:,-1,:) = wall_flags_0(:,0,:)
1693	IF ( nyn == ny ) wall_flags_0(:,ny+1,:) = wall_flags_0(:,ny,:)
1694	ENDIF
1695	IF ( .NOT. bc_lr_cyc ) THEN
1696	IF ( nxl == 0 ) wall_flags_0(:,:,-1) = wall_flags_0(:,:,0)
1697	IF ( nxr == nx ) wall_flags_0(:,:,nx+1) = wall_flags_0(:,:,nx)
1698	ENDIF
1699
1700	!
1701	!-- Initialize boundary conditions via surface type
1702	CALL init_bc
1703	!
1704	!-- Allocate and set topography height arrays required for data output
1705	IF ( TRIM( topography ) /= 'flat' ) THEN
1706	!
1707	!-- Allocate and set the arrays containing the topography height
1708
1709	IF ( nxr == nx .AND. nyn /= ny ) THEN
1710	ALLOCATE( zu_s_inner(nxl:nxr+1,nys:nyn), &
1711	zw_w_inner(nxl:nxr+1,nys:nyn) )
1712	ELSEIF ( nxr /= nx .AND. nyn == ny ) THEN
1713	ALLOCATE( zu_s_inner(nxl:nxr,nys:nyn+1), &
1714	zw_w_inner(nxl:nxr,nys:nyn+1) )
1715	ELSEIF ( nxr == nx .AND. nyn == ny ) THEN
1716	ALLOCATE( zu_s_inner(nxl:nxr+1,nys:nyn+1), &
1717	zw_w_inner(nxl:nxr+1,nys:nyn+1) )
1718	ELSE
1719	ALLOCATE( zu_s_inner(nxl:nxr,nys:nyn), &
1720	zw_w_inner(nxl:nxr,nys:nyn) )
1721	ENDIF
1722
1723	zu_s_inner = 0.0_wp
1724	zw_w_inner = 0.0_wp
1725	!
1726	!-- Determine local topography height on scalar and w-grid. Note, setting
1727	!-- lateral boundary values is not necessary, realized via wall_flags_0
1728	!-- array. Further, please note that loop bounds are different from
1729	!-- nxl to nxr and nys to nyn on south and right model boundary, hence,
1730	!-- use intrinsic lbound and ubound functions to infer array bounds.
1731	DO i = LBOUND(zu_s_inner, 1), UBOUND(zu_s_inner, 1)
1732	DO j = LBOUND(zu_s_inner, 2), UBOUND(zu_s_inner, 2)
1733	!
1734	!-- Topography height on scalar grid. Therefore, determine index of
1735	!-- upward-facing surface element on scalar grid.
1736	zu_s_inner(i,j) = zu( get_topography_top_index( j, i, 's' ) )
1737	!
1738	!-- Topography height on w grid. Therefore, determine index of
1739	!-- upward-facing surface element on w grid.
1740	zw_w_inner(i,j) = zw( get_topography_top_index( j, i, 's' ) )
1741	ENDDO
1742	ENDDO
1743
1744	ENDIF
1745
1746	!
1747	!-- Calculate wall flag arrays for the multigrid method.
1748	!-- Please note, wall flags are only applied in the not cache-optimized
1749	!-- version.
1750	IF ( psolver == 'multigrid_noopt' ) THEN
1751
1752	!
1753	!-- Gridpoint increment of the current level.
1754	inc = 1
1755	DO l = maximum_grid_level, 1 , -1
1756	!
1757	!-- Set grid_level as it is required for exchange_horiz_2d_int
1758	grid_level = l
1759
1760	nxl_l = nxl_mg(l)
1761	nxr_l = nxr_mg(l)
1762	nys_l = nys_mg(l)
1763	nyn_l = nyn_mg(l)
1764	nzt_l = nzt_mg(l)
1765	!
1766	!-- Assign the flag level to be calculated
1767	SELECT CASE ( l )
1768	CASE ( 1 )
1769	flags => wall_flags_1
1770	CASE ( 2 )
1771	flags => wall_flags_2
1772	CASE ( 3 )
1773	flags => wall_flags_3
1774	CASE ( 4 )
1775	flags => wall_flags_4
1776	CASE ( 5 )
1777	flags => wall_flags_5
1778	CASE ( 6 )
1779	flags => wall_flags_6
1780	CASE ( 7 )
1781	flags => wall_flags_7
1782	CASE ( 8 )
1783	flags => wall_flags_8
1784	CASE ( 9 )
1785	flags => wall_flags_9
1786	CASE ( 10 )
1787	flags => wall_flags_10
1788	END SELECT
1789
1790	!
1791	!-- Depending on the grid level, set the respective bits in case of
1792	!-- neighbouring walls
1793	!-- Bit 0: wall to the bottom
1794	!-- Bit 1: wall to the top (not realized in remaining PALM code so far)
1795	!-- Bit 2: wall to the south
1796	!-- Bit 3: wall to the north
1797	!-- Bit 4: wall to the left
1798	!-- Bit 5: wall to the right
1799	!-- Bit 6: inside building
1800
1801	flags = 0
1802
1803	!
1804	!-- In case of masking method, flags are not set and multigrid method
1805	!-- works like FFT-solver
1806	IF ( .NOT. masking_method ) THEN
1807
1808	!
1809	!-- Allocate temporary array for topography heights on coarser grid
1810	!-- level. Please note, 2 ghoist points are required, in order to
1811	!-- calculate flags() on the interior ghost point.
1812	ALLOCATE( nzb_tmp(nys_l-2:nyn_l+2,nxl_l-2:nxr_l+2) )
1813	nzb_tmp = 0
1814
1815	DO i = nxl_l, nxr_l
1816	DO j = nys_l, nyn_l
1817	nzb_tmp(j,i) = nzb_local(jinc,iinc)
1818	ENDDO
1819	ENDDO
1820	!
1821	!-- Exchange ghost points on respective multigrid level. 2 ghost points
1822	!-- are required, in order to calculate flags on
1823	!-- nys_l-1 / nyn_l+1 / nxl_l-1 / nxr_l+1. The alternative would be to
1824	!-- exchange 3D-INTEGER array flags on the respective multigrid level.
1825	CALL exchange_horiz_2d_int( nzb_tmp, nys_l, nyn_l, nxl_l, nxr_l, 2 )
1826	!
1827	!-- Set non-cyclic boundary conditions on respective multigrid level
1828	IF ( .NOT. bc_ns_cyc ) THEN
1829	IF ( inflow_s .OR. outflow_s .OR. nest_bound_s ) THEN
1830	nzb_tmp(-2,:) = nzb_tmp(0,:)
1831	nzb_tmp(-1,:) = nzb_tmp(0,:)
1832	ENDIF
1833	IF ( inflow_n .OR. outflow_n .OR. nest_bound_n ) THEN
1834	nzb_tmp(nyn_l+2,:) = nzb_tmp(nyn_l,:)
1835	nzb_tmp(nyn_l+1,:) = nzb_tmp(nyn_l,:)
1836	ENDIF
1837	ENDIF
1838	IF ( .NOT. bc_lr_cyc ) THEN
1839	IF ( inflow_l .OR. outflow_l .OR. nest_bound_l ) THEN
1840	nzb_tmp(:,-2) = nzb_tmp(:,0)
1841	nzb_tmp(:,-1) = nzb_tmp(:,0)
1842	ENDIF
1843	IF ( inflow_r .OR. outflow_r .OR. nest_bound_r ) THEN
1844	nzb_tmp(:,nxr_l+1) = nzb_tmp(:,nxr_l)
1845	nzb_tmp(:,nxr_l+2) = nzb_tmp(:,nxr_l)
1846	ENDIF
1847	ENDIF
1848
1849	DO i = nxl_l-1, nxr_l+1
1850	DO j = nys_l-1, nyn_l+1
1851	DO k = nzb, nzt_l+1
1852	!
1853	!-- Inside/outside building (inside building does not need
1854	!-- further tests for walls)
1855	IF ( k*inc <= nzb_tmp(j,i) ) THEN
1856
1857	flags(k,j,i) = IBSET( flags(k,j,i), 6 )
1858
1859	ELSE
1860	!
1861	!-- Bottom wall
1862	IF ( (k-1)*inc <= nzb_tmp(j,i) ) THEN
1863	flags(k,j,i) = IBSET( flags(k,j,i), 0 )
1864	ENDIF
1865	!
1866	!-- South wall
1867	IF ( k*inc <= nzb_tmp(j-1,i) ) THEN
1868	flags(k,j,i) = IBSET( flags(k,j,i), 2 )
1869	ENDIF
1870	!
1871	!-- North wall
1872	IF ( k*inc <= nzb_tmp(j+1,i) ) THEN
1873	flags(k,j,i) = IBSET( flags(k,j,i), 3 )
1874	ENDIF
1875	!
1876	!-- Left wall
1877	IF ( k*inc <= nzb_tmp(j,i-1) ) THEN
1878	flags(k,j,i) = IBSET( flags(k,j,i), 4 )
1879	ENDIF
1880	!
1881	!-- Right wall
1882	IF ( k*inc <= nzb_tmp(j,i+1) ) THEN
1883	flags(k,j,i) = IBSET( flags(k,j,i), 5 )
1884	ENDIF
1885
1886	ENDIF
1887
1888	ENDDO
1889	ENDDO
1890	ENDDO
1891
1892	DEALLOCATE( nzb_tmp )
1893
1894	ENDIF
1895
1896	inc = inc * 2
1897
1898	ENDDO
1899	!
1900	!-- Reset grid_level to "normal" grid
1901	grid_level = 0
1902
1903	ENDIF
1904	!
1905	!-- Allocate flags needed for masking walls. Even though these flags are only
1906	!-- required in the ws-scheme, the arrays need to be allocated here as they are
1907	!-- used in OpenACC directives.
1908	ALLOCATE( advc_flags_1(nzb:nzt+1,nysg:nyng,nxlg:nxrg), &
1909	advc_flags_2(nzb:nzt+1,nysg:nyng,nxlg:nxrg) )
1910	advc_flags_1 = 0
1911	advc_flags_2 = 0
1912	!
1913	!-- Init flags for ws-scheme to degrade order of the numerics near walls, i.e.
1914	!-- to decrease the numerical stencil appropriately.
1915	IF ( momentum_advec == 'ws-scheme' .OR. scalar_advec == 'ws-scheme' &
1916	) THEN
1917	CALL ws_init_flags
1918	ENDIF
1919
1920	!
1921	!-- In case of topography: limit near-wall mixing length l_wall further:
1922	!-- Go through all points of the subdomain one by one and look for the closest
1923	!-- surface
1924	DO i = nxl, nxr
1925	DO j = nys, nyn
1926	DO k = nzb+1, nzt
1927	!
1928	!-- Check if current gridpoint belongs to the atmosphere
1929	IF ( BTEST( wall_flags_0(k,j,i), 0 ) ) THEN
1930	!
1931	!-- Check for neighbouring grid-points.
1932	!-- Vertical distance, down
1933	IF ( .NOT. BTEST( wall_flags_0(k-1,j,i), 0 ) ) &
1934	l_wall(k,j,i) = MIN( l_grid(k), zu(k) - zw(k-1) )
1935	!
1936	!-- Vertical distance, up
1937	IF ( .NOT. BTEST( wall_flags_0(k+1,j,i), 0 ) ) &
1938	l_wall(k,j,i) = MIN( l_grid(k), zw(k) - zu(k) )
1939	!
1940	!-- y-distance
1941	IF ( .NOT. BTEST( wall_flags_0(k,j-1,i), 0 ) .OR. &
1942	.NOT. BTEST( wall_flags_0(k,j+1,i), 0 ) ) &
1943	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), 0.5_wp * dy )
1944	!
1945	!-- x-distance
1946	IF ( .NOT. BTEST( wall_flags_0(k,j,i-1), 0 ) .OR. &
1947	.NOT. BTEST( wall_flags_0(k,j,i+1), 0 ) ) &
1948	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), 0.5_wp * dx )
1949	!
1950	!-- yz-distance (vertical edges, down)
1951	IF ( .NOT. BTEST( wall_flags_0(k-1,j-1,i), 0 ) .OR. &
1952	.NOT. BTEST( wall_flags_0(k-1,j+1,i), 0 ) ) &
1953	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), &
1954	SQRT( 0.25_wp * dy**2 + &
1955	( zu(k) - zw(k-1) )**2 ) )
1956	!
1957	!-- yz-distance (vertical edges, up)
1958	IF ( .NOT. BTEST( wall_flags_0(k+1,j-1,i), 0 ) .OR. &
1959	.NOT. BTEST( wall_flags_0(k+1,j+1,i), 0 ) ) &
1960	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), &
1961	SQRT( 0.25_wp * dy**2 + &
1962	( zw(k) - zu(k) )**2 ) )
1963	!
1964	!-- xz-distance (vertical edges, down)
1965	IF ( .NOT. BTEST( wall_flags_0(k-1,j,i-1), 0 ) .OR. &
1966	.NOT. BTEST( wall_flags_0(k-1,j,i+1), 0 ) ) &
1967	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), &
1968	SQRT( 0.25_wp * dx**2 + &
1969	( zu(k) - zw(k-1) )**2 ) )
1970	!
1971	!-- xz-distance (vertical edges, up)
1972	IF ( .NOT. BTEST( wall_flags_0(k+1,j,i-1), 0 ) .OR. &
1973	.NOT. BTEST( wall_flags_0(k+1,j,i+1), 0 ) ) &
1974	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), &
1975	SQRT( 0.25_wp * dx**2 + &
1976	( zw(k) - zu(k) )**2 ) )
1977	!
1978	!-- xy-distance (horizontal edges)
1979	IF ( .NOT. BTEST( wall_flags_0(k,j-1,i-1), 0 ) .OR. &
1980	.NOT. BTEST( wall_flags_0(k,j+1,i-1), 0 ) .OR. &
1981	.NOT. BTEST( wall_flags_0(k,j-1,i+1), 0 ) .OR. &
1982	.NOT. BTEST( wall_flags_0(k,j+1,i+1), 0 ) ) &
1983	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), &
1984	SQRT( 0.25_wp * ( dx2 + dy2 ) ) )
1985	!
1986	!-- xyz distance (vertical and horizontal edges, down)
1987	IF ( .NOT. BTEST( wall_flags_0(k-1,j-1,i-1), 0 ) .OR. &
1988	.NOT. BTEST( wall_flags_0(k-1,j+1,i-1), 0 ) .OR. &
1989	.NOT. BTEST( wall_flags_0(k-1,j-1,i+1), 0 ) .OR. &
1990	.NOT. BTEST( wall_flags_0(k-1,j+1,i+1), 0 ) ) &
1991	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), &
1992	SQRT( 0.25_wp * ( dx2 + dy2 ) &
1993	+ ( zu(k) - zw(k-1) )**2 ) )
1994	!
1995	!-- xyz distance (vertical and horizontal edges, up)
1996	IF ( .NOT. BTEST( wall_flags_0(k+1,j-1,i-1), 0 ) .OR. &
1997	.NOT. BTEST( wall_flags_0(k+1,j+1,i-1), 0 ) .OR. &
1998	.NOT. BTEST( wall_flags_0(k+1,j-1,i+1), 0 ) .OR. &
1999	.NOT. BTEST( wall_flags_0(k+1,j+1,i+1), 0 ) ) &
2000	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), &
2001	SQRT( 0.25_wp * ( dx2 + dy2 ) &
2002	+ ( zw(k) - zu(k) )**2 ) )
2003
2004	ENDIF
2005	ENDDO
2006	ENDDO
2007	ENDDO
2008	!
2009	!-- Set lateral boundary conditions for l_wall
2010	CALL exchange_horiz( l_wall, nbgp )
2011
2012	!
2013	!-- Vertical nesting: communicate vertical grid level arrays between fine and
2014	!-- coarse grid
2015	IF ( vnested ) CALL vnest_init_grid
2016
2017	END SUBROUTINE init_grid

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