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source: palm/trunk/SOURCE/init_grid.f90 @ 2397

Last change on this file since 2397 was 2365, checked in by kanani, 7 years ago
Vertical nesting implemented (SadiqHuq?)
Property svn:keywords set to `Id`
File size: 85.5 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 2365 2017-08-21 14:59:59Z suehring $
27	! Vertical nesting implemented (SadiqHuq)
28	!
29	! 2319 2017-07-20 17:33:17Z suehring
30	! Remove print statements
31	!
32	! 2318 2017-07-20 17:27:44Z suehring
33	! Get topography top index via Function call
34	!
35	! 2317 2017-07-20 17:27:19Z suehring
36	! Bugfixes in reading 3D topography from file
37	!
38	! 2274 2017-06-09 13:27:48Z Giersch
39	! Changed error messages
40	!
41	! 2233 2017-05-30 18:08:54Z suehring
42	!
43	! 2232 2017-05-30 17:47:52Z suehring
44	! - Adjustments according to new topography representation
45	! - Bugfix: Move determination of nzb_max behind topography modification in
46	! cell-edge case
47	! - Get rid off global arrays required for topography output
48	! - Enable topography input via netcdf
49	! - Generic tunnel set-up added
50	!
51	! 2200 2017-04-11 11:37:51Z suehring
52	! monotonic_adjustment removed
53	!
54	! 2169 2017-03-06 18:16:35Z suehring
55	! Bugfix, move setting for topography grid convention to init_grid, else, if no
56	! value is set, the simulation may abort in case of restarts
57	!
58	! 2128 2017-01-23 15:00:03Z suehring
59	! Bugfix in setting topography from file in case of ocean simulations
60	!
61	! 2088 2016-12-19 16:30:25Z suehring
62	! Bugfix in generic topography in case of ocean simulations
63	!
64	! 2037 2016-10-26 11:15:40Z knoop
65	! Anelastic approximation implemented
66	!
67	! 2021 2016-10-07 14:08:57Z suehring
68	! Bugfix: setting Neumann boundary conditions for topography required for
69	! topography flags in multigrid_noopt solver
70	!
71	! 2000 2016-08-20 18:09:15Z knoop
72	! Forced header and separation lines into 80 columns
73	!
74	! 1994 2016-08-15 09:52:21Z suehring
75	! Bugfix in definition of generic topography
76	!
77	! 1982 2016-08-01 11:04:48Z suehring
78	! Bugfix concering consistency check for topography
79	!
80	! 1968 2016-07-18 12:01:49Z suehring
81	! Changed: PE-wise reading of topography file in order to avoid global definition
82	! of arrays nzb_local and nzb_tmp. Thereby, topography definition for single
83	! buildings and street canyons has changed, as well as flag setting for
84	! multigrid scheme.
85	!
86	! Bugfix in checking l_grid anisotropy.
87	! Simplify initial computation of lwall and vertical_influence, i.e. remove
88	! nzb_s_inner as it is still zero at this point.
89	!
90	! 1942 2016-06-14 12:18:18Z suehring
91	! Topography filter implemented to fill holes resolved by only one grid point.
92	! Initialization of flags for ws-scheme moved to advec_ws.
93	!
94	! 1931 2016-06-10 12:06:59Z suehring
95	! Rename multigrid into multigrid_noopt and multigrid_fast into multigrid
96	!
97	! 1910 2016-05-26 06:49:46Z raasch
98	! Bugfix: if topography is read from file, Neumann conditions are used for the
99	! nzb_local array (instead of cyclic conditions) in case that non-cyclic
100	! boundary conditions are switched on for the run
101	!
102	! 1902 2016-05-09 11:18:56Z suehring
103	! Set topography flags for multigrid solver only (not for multigrid_fast)
104	!
105	! 1886 2016-04-21 11:20:47Z suehring
106	! Bugfix: setting advection flags near walls
107	! reformulated index values for nzb_v_inner
108	! variable discriptions added in declaration block
109	!
110	! 1845 2016-04-08 08:29:13Z raasch
111	! nzb_2d removed
112	!
113	! 1804 2016-04-05 16:30:18Z maronga
114	! Removed code for parameter file check (__check)
115	!
116	! 1779 2016-03-03 08:01:28Z raasch
117	! coupling_char is trimmed at every place it occurs, because it can have
118	! different length now
119	!
120	! 1762 2016-02-25 12:31:13Z hellstea
121	! Introduction of nested domain feature
122	!
123	! 1743 2016-01-13 10:23:51Z raasch
124	! Bugfix for calculation of nzb_s_outer and nzb_u_outer at north boundary of
125	! total domain
126	!
127	! 1691 2015-10-26 16:17:44Z maronga
128	! Renamed prandtl_layer to constant_flux_layer.
129	!
130	! 1682 2015-10-07 23:56:08Z knoop
131	! Code annotations made doxygen readable
132	!
133	! 1677 2015-10-02 13:25:23Z boeske
134	! Bugfix: Ghost points are included in wall_flags_0 and wall_flags_00
135	!
136	! 1675 2015-10-02 08:28:59Z gronemeier
137	! Bugfix: Definition of topography grid levels
138	!
139	! 1660 2015-09-21 08:15:16Z gronemeier
140	! Bugfix: Definition of topography grid levels if vertical grid stretching
141	! starts below the maximum topography height.
142	!
143	! 1580 2015-04-10 13:43:49Z suehring
144	! Bugfix: setting flags for 5th order scheme near buildings
145	!
146	! 1575 2015-03-27 09:56:27Z raasch
147	! adjustments for psolver-queries
148	!
149	! 1557 2015-03-05 16:43:04Z suehring
150	! Adjustment for monotoinic limiter
151	!
152	! 1418 2014-06-06 13:05:08Z fricke
153	! Bugfix: Change if-condition for stretched grid in the ocean, with the old
154	! condition and a negative value for dz_stretch_level the condition
155	! was always true for the whole model domain
156	!
157	! 1409 2014-05-23 12:11:32Z suehring
158	! Bugfix: set wall_flags_0 at inflow and outflow boundary also for i <= nxlu
159	! j <= nysv
160	!
161	! 1353 2014-04-08 15:21:23Z heinze
162	! REAL constants provided with KIND-attribute
163	!
164	! 1322 2014-03-20 16:38:49Z raasch
165	! REAL constants defined as wp-kind
166	!
167	! 1320 2014-03-20 08:40:49Z raasch
168	! ONLY-attribute added to USE-statements,
169	! kind-parameters added to all INTEGER and REAL declaration statements,
170	! kinds are defined in new module kinds,
171	! revision history before 2012 removed,
172	! comment fields (!:) to be used for variable explanations added to
173	! all variable declaration statements
174	!
175	! 1221 2013-09-10 08:59:13Z raasch
176	! wall_flags_00 introduced to hold bits 32-63,
177	! additional 3D-flag arrays for replacing the 2D-index array nzb_s_inner in
178	! loops optimized for openACC (pres + flow_statistics)
179	!
180	! 1092 2013-02-02 11:24:22Z raasch
181	! unused variables removed
182	!
183	! 1069 2012-11-28 16:18:43Z maronga
184	! bugfix: added coupling_char to TOPOGRAPHY_DATA to allow topography in the
185	! ocean model in case of coupled runs
186	!
187	! 1036 2012-10-22 13:43:42Z raasch
188	! code put under GPL (PALM 3.9)
189	!
190	! 1015 2012-09-27 09:23:24Z raasch
191	! lower index for calculating wall_flags_0 set to nzb_w_inner instead of
192	! nzb_w_inner+1
193	!
194	! 996 2012-09-07 10:41:47Z raasch
195	! little reformatting
196	!
197	! 978 2012-08-09 08:28:32Z fricke
198	! Bugfix: nzb_max is set to nzt at non-cyclic lateral boundaries
199	! Bugfix: Set wall_flags_0 for inflow boundary
200	!
201	! 927 2012-06-06 19:15:04Z raasch
202	! Wall flags are not set for multigrid method in case of masking method
203	!
204	! 864 2012-03-27 15:10:33Z gryschka
205	! In case of ocean and Dirichlet bottom bc for u and v dzu_mg and ddzu_pres
206	! were not correctly defined for k=1.
207	!
208	! 861 2012-03-26 14:18:34Z suehring
209	! Set wall_flags_0. The array is needed for degradation in ws-scheme near walls,
210	! inflow and outflow boundaries as well as near the bottom and the top of the
211	! model domain.!
212	! Initialization of nzb_s_inner and nzb_w_inner.
213	! gls has to be at least nbgp to do not exceed the array bounds of nzb_local
214	! while setting wall_flags_0
215	!
216	! 843 2012-02-29 15:16:21Z gryschka
217	! In case of ocean and dirichlet bc for u and v at the bottom
218	! the first u-level ist defined at same height as the first w-level
219	!
220	! 818 2012-02-08 16:11:23Z maronga
221	! Bugfix: topo_height is only required if topography is used. It is thus now
222	! allocated in the topography branch
223	!
224	! 809 2012-01-30 13:32:58Z maronga
225	! Bugfix: replaced .AND. and .NOT. with && and ! in the preprocessor directives
226	!
227	! 807 2012-01-25 11:53:51Z maronga
228	! New cpp directive "__check" implemented which is used by check_namelist_files
229	!
230	! Revision 1.1 1997/08/11 06:17:45 raasch
231	! Initial revision (Testversion)
232	!
233	!
234	! Description:
235	! ------------
236	!> Creating grid depending constants
237	!> To Do: Setting topo flags only based on topo_3d array - flags for former
238	!> nzb_outer arrays are still not set properly.
239	!> To Do: Rearrange topo flag list
240	!------------------------------------------------------------------------------!
241	SUBROUTINE init_grid
242
243	USE advec_ws, &
244	ONLY: ws_init_flags
245
246	USE arrays_3d, &
247	ONLY: dd2zu, ddzu, ddzu_pres, ddzw, dzu, dzu_mg, dzw, dzw_mg, f1_mg, &
248	f2_mg, f3_mg, l_grid, l_wall, zu, zw
249
250	USE control_parameters, &
251	ONLY: bc_lr_cyc, bc_ns_cyc, building_height, building_length_x, &
252	building_length_y, building_wall_left, building_wall_south, &
253	canyon_height, canyon_wall_left, canyon_wall_south, &
254	canyon_width_x, canyon_width_y, constant_flux_layer, &
255	coupling_char, coupling_mode, &
256	dp_level_ind_b, dz, dz_max, dz_stretch_factor, &
257	dz_stretch_level, dz_stretch_level_index, grid_level, ibc_uv_b, &
258	io_blocks, io_group, inflow_l, inflow_n, inflow_r, inflow_s, &
259	lod, masking_method, maximum_grid_level, message_string, &
260	momentum_advec, nest_domain, nest_bound_l, nest_bound_n, &
261	nest_bound_r, nest_bound_s, ocean, outflow_l, outflow_n, &
262	outflow_r, outflow_s, psolver, scalar_advec, topography, &
263	topography_grid_convention, tunnel_height, tunnel_length, &
264	tunnel_width_x, tunnel_width_y, tunnel_wall_depth, &
265	use_surface_fluxes, use_top_fluxes, wall_adjustment_factor
266
267	USE grid_variables, &
268	ONLY: ddx, ddx2, ddy, ddy2, dx, dx2, dy, dy2, zu_s_inner, zw_w_inner
269
270	USE indices, &
271	ONLY: advc_flags_1, advc_flags_2, flags, nbgp, nx, nxl, nxlg, nxl_mg, &
272	nxr, nxrg, nxr_mg, ny, nyn, nyng, nyn_mg, nys, nys_mg, nysg, nz,&
273	nzb, nzb_diff, nzb_diff_s_inner, nzb_diff_s_outer, &
274	nzb_max, nzb_s_inner, nzb_s_outer, nzb_u_inner, &
275	nzb_u_outer, nzb_v_inner, nzb_v_outer, nzb_w_inner, &
276	nzb_w_outer, nzt, nzt_mg, wall_flags_0, wall_flags_1, &
277	wall_flags_10, wall_flags_2, wall_flags_3, wall_flags_4, &
278	wall_flags_5, wall_flags_6, wall_flags_7, wall_flags_8, &
279	wall_flags_9
280
281	USE kinds
282	#if defined ( __netcdf )
283	USE netcdf_interface, &
284	ONLY: netcdf_close_file, netcdf_open_read_file, netcdf_get_attribute, &
285	netcdf_get_variable
286	#endif
287	USE pegrid
288
289	USE surface_mod, &
290	ONLY: get_topography_top_index, init_bc
291
292	USE vertical_nesting_mod, &
293	ONLY: vnested, vnest_init_grid
294
295	IMPLICIT NONE
296
297	INTEGER(iwp) :: bh !< temporary vertical index of building height
298	INTEGER(iwp) :: blx !< grid point number of building size along x
299	INTEGER(iwp) :: bly !< grid point number of building size along y
300	INTEGER(iwp) :: bxl !< index for left building wall
301	INTEGER(iwp) :: bxr !< index for right building wall
302	INTEGER(iwp) :: byn !< index for north building wall
303	INTEGER(iwp) :: bys !< index for south building wall
304	INTEGER(iwp) :: ch !< temporary vertical index for canyon height
305	INTEGER(iwp) :: cwx !< grid point number of canyon size along x
306	INTEGER(iwp) :: cwy !< grid point number of canyon size along y
307	INTEGER(iwp) :: cxl !< index for left canyon wall
308	INTEGER(iwp) :: cxr !< index for right canyon wall
309	INTEGER(iwp) :: cyn !< index for north canyon wall
310	INTEGER(iwp) :: cys !< index for south canyon wall
311	INTEGER(iwp) :: i !< index variable along x
312	INTEGER(iwp) :: id_topo !< NetCDF id of topograhy input file
313	INTEGER(iwp) :: ii !< loop variable for reading topography file
314	INTEGER(iwp) :: inc !< incremental parameter for coarsening grid level
315	INTEGER(iwp) :: j !< index variable along y
316	INTEGER(iwp) :: k !< index variable along z
317	INTEGER(iwp) :: k_top !< topography top index on local PE
318	INTEGER(iwp) :: l !< loop variable
319	INTEGER(iwp) :: nxl_l !< index of left PE boundary for multigrid level
320	INTEGER(iwp) :: nxr_l !< index of right PE boundary for multigrid level
321	INTEGER(iwp) :: nyn_l !< index of north PE boundary for multigrid level
322	INTEGER(iwp) :: nys_l !< index of south PE boundary for multigrid level
323	INTEGER(iwp) :: nzb_local_max !< vertical grid index of maximum topography height
324	INTEGER(iwp) :: nzb_local_min !< vertical grid index of minimum topography height
325	INTEGER(iwp) :: nzt_l !< index of top PE boundary for multigrid level
326	INTEGER(iwp) :: num_hole !< number of holes (in topography) resolved by only one grid point
327	INTEGER(iwp) :: num_hole_l !< number of holes (in topography) resolved by only one grid point on local PE
328	INTEGER(iwp) :: num_wall !< number of surrounding vertical walls for a single grid point
329	INTEGER(iwp) :: skip_n_rows !< counting variable to skip rows while reading topography file
330	INTEGER(iwp) :: hv_in !< heavyside function to model inner tunnel surface
331	INTEGER(iwp) :: hv_out !< heavyside function to model outer tunnel surface
332	INTEGER(iwp) :: txe_out !< end position of outer tunnel wall in x
333	INTEGER(iwp) :: txs_out !< start position of outer tunnel wall in x
334	INTEGER(iwp) :: tye_out !< end position of outer tunnel wall in y
335	INTEGER(iwp) :: tys_out !< start position of outer tunnel wall in y
336	INTEGER(iwp) :: txe_in !< end position of inner tunnel wall in x
337	INTEGER(iwp) :: txs_in !< start position of inner tunnel wall in x
338	INTEGER(iwp) :: tye_in !< end position of inner tunnel wall in y
339	INTEGER(iwp) :: tys_in !< start position of inner tunnel wall in y
340	INTEGER(iwp) :: td !< tunnel wall depth
341	INTEGER(iwp) :: th !< height of outer tunnel wall
342
343	INTEGER(iwp), DIMENSION(:,:), ALLOCATABLE :: nzb_local !< index for topography top at cell-center
344	INTEGER(iwp), DIMENSION(:,:), ALLOCATABLE :: nzb_tmp !< dummy to calculate topography indices on u- and v-grid
345
346	INTEGER(iwp), DIMENSION(:,:,:), ALLOCATABLE :: topo_3d !< input array for 3D topography and dummy array for setting "outer"-flags
347
348	LOGICAL :: netcdf_extend = .FALSE. !< Flag indicating wether netcdf topography input file or not
349
350	REAL(wp) :: dum !< dummy variable to skip columns while reading topography file
351	REAL(wp) :: dz_stretched !< stretched vertical grid spacing
352
353	REAL(wp), DIMENSION(:,:), ALLOCATABLE :: oro_height !< input variable for terrain height
354	REAL(wp), DIMENSION(:,:), ALLOCATABLE :: topo_height !< input variable for topography height
355
356	INTEGER( KIND=1 ), DIMENSION(:,:,:), ALLOCATABLE :: topo_3d_read !< input variable for 3D topography
357
358	!
359	!-- Calculation of horizontal array bounds including ghost layers
360	nxlg = nxl - nbgp
361	nxrg = nxr + nbgp
362	nysg = nys - nbgp
363	nyng = nyn + nbgp
364
365	!
366	!-- Allocate grid arrays
367	ALLOCATE( ddzu(1:nzt+1), ddzw(1:nzt+1), dd2zu(1:nzt), dzu(1:nzt+1), &
368	dzw(1:nzt+1), l_grid(1:nzt), zu(nzb:nzt+1), zw(nzb:nzt+1) )
369
370	!
371	!-- Compute height of u-levels from constant grid length and dz stretch factors
372	IF ( dz == -1.0_wp ) THEN
373	message_string = 'missing dz'
374	CALL message( 'init_grid', 'PA0200', 1, 2, 0, 6, 0 )
375	ELSEIF ( dz <= 0.0_wp ) THEN
376	WRITE( message_string, * ) 'dz=',dz,' <= 0.0'
377	CALL message( 'init_grid', 'PA0201', 1, 2, 0, 6, 0 )
378	ENDIF
379
380	!
381	!-- Define the vertical grid levels
382	IF ( .NOT. ocean ) THEN
383	!
384	!-- Grid for atmosphere with surface at z=0 (k=0, w-grid).
385	!-- The second u-level (k=1) corresponds to the top of the
386	!-- Prandtl-layer.
387
388	IF ( ibc_uv_b == 0 .OR. ibc_uv_b == 2 ) THEN
389	zu(0) = 0.0_wp
390	! zu(0) = - dz * 0.5_wp
391	ELSE
392	zu(0) = - dz * 0.5_wp
393	ENDIF
394	zu(1) = dz * 0.5_wp
395
396	dz_stretch_level_index = nzt+1
397	dz_stretched = dz
398	DO k = 2, nzt+1
399	IF ( dz_stretch_level <= zu(k-1) .AND. dz_stretched < dz_max ) THEN
400	dz_stretched = dz_stretched * dz_stretch_factor
401	dz_stretched = MIN( dz_stretched, dz_max )
402	IF ( dz_stretch_level_index == nzt+1 ) dz_stretch_level_index = k-1
403	ENDIF
404	zu(k) = zu(k-1) + dz_stretched
405	ENDDO
406
407	!
408	!-- Compute the w-levels. They are always staggered half-way between the
409	!-- corresponding u-levels. In case of dirichlet bc for u and v at the
410	!-- ground the first u- and w-level (k=0) are defined at same height (z=0).
411	!-- The top w-level is extrapolated linearly.
412	zw(0) = 0.0_wp
413	DO k = 1, nzt
414	zw(k) = ( zu(k) + zu(k+1) ) * 0.5_wp
415	ENDDO
416	zw(nzt+1) = zw(nzt) + 2.0_wp * ( zu(nzt+1) - zw(nzt) )
417
418	ELSE
419	!
420	!-- Grid for ocean with free water surface is at k=nzt (w-grid).
421	!-- In case of neumann bc at the ground the first first u-level (k=0) lies
422	!-- below the first w-level (k=0). In case of dirichlet bc the first u- and
423	!-- w-level are defined at same height, but staggered from the second level.
424	!-- The second u-level (k=1) corresponds to the top of the Prandtl-layer.
425	zu(nzt+1) = dz * 0.5_wp
426	zu(nzt) = - dz * 0.5_wp
427
428	dz_stretch_level_index = 0
429	dz_stretched = dz
430	DO k = nzt-1, 0, -1
431	!
432	!-- The default value of dz_stretch_level is positive, thus the first
433	!-- condition is always true. Hence, the second condition is necessary.
434	IF ( dz_stretch_level >= zu(k+1) .AND. dz_stretch_level <= 0.0 &
435	.AND. dz_stretched < dz_max ) THEN
436	dz_stretched = dz_stretched * dz_stretch_factor
437	dz_stretched = MIN( dz_stretched, dz_max )
438	IF ( dz_stretch_level_index == 0 ) dz_stretch_level_index = k+1
439	ENDIF
440	zu(k) = zu(k+1) - dz_stretched
441	ENDDO
442
443	!
444	!-- Compute the w-levels. They are always staggered half-way between the
445	!-- corresponding u-levels, except in case of dirichlet bc for u and v
446	!-- at the ground. In this case the first u- and w-level are defined at
447	!-- same height. The top w-level (nzt+1) is not used but set for
448	!-- consistency, since w and all scalar variables are defined up tp nzt+1.
449	zw(nzt+1) = dz
450	zw(nzt) = 0.0_wp
451	DO k = 0, nzt
452	zw(k) = ( zu(k) + zu(k+1) ) * 0.5_wp
453	ENDDO
454
455	!
456	!-- In case of dirichlet bc for u and v the first u- and w-level are defined
457	!-- at same height.
458	IF ( ibc_uv_b == 0 ) THEN
459	zu(0) = zw(0)
460	ENDIF
461
462	ENDIF
463
464	!
465	!-- Compute grid lengths.
466	DO k = 1, nzt+1
467	dzu(k) = zu(k) - zu(k-1)
468	ddzu(k) = 1.0_wp / dzu(k)
469	dzw(k) = zw(k) - zw(k-1)
470	ddzw(k) = 1.0_wp / dzw(k)
471	ENDDO
472
473	DO k = 1, nzt
474	dd2zu(k) = 1.0_wp / ( dzu(k) + dzu(k+1) )
475	ENDDO
476
477	!
478	!-- The FFT- SOR-pressure solvers assume grid spacings of a staggered grid
479	!-- everywhere. For the actual grid, the grid spacing at the lowest level
480	!-- is only dz/2, but should be dz. Therefore, an additional array
481	!-- containing with appropriate grid information is created for these
482	!-- solvers.
483	IF ( psolver(1:9) /= 'multigrid' ) THEN
484	ALLOCATE( ddzu_pres(1:nzt+1) )
485	ddzu_pres = ddzu
486	ddzu_pres(1) = ddzu_pres(2) ! change for lowest level
487	ENDIF
488
489	!
490	!-- Compute the reciprocal values of the horizontal grid lengths.
491	ddx = 1.0_wp / dx
492	ddy = 1.0_wp / dy
493	dx2 = dx * dx
494	dy2 = dy * dy
495	ddx2 = 1.0_wp / dx2
496	ddy2 = 1.0_wp / dy2
497
498	!
499	!-- Compute the grid-dependent mixing length.
500	DO k = 1, nzt
501	l_grid(k) = ( dx * dy * dzw(k) )**0.33333333333333_wp
502	ENDDO
503
504	!
505	!-- Allocate outer and inner index arrays for topography and set
506	!-- defaults.
507	ALLOCATE( nzb_s_inner(nysg:nyng,nxlg:nxrg), &
508	nzb_s_outer(nysg:nyng,nxlg:nxrg), &
509	nzb_u_inner(nysg:nyng,nxlg:nxrg), &
510	nzb_u_outer(nysg:nyng,nxlg:nxrg), &
511	nzb_v_inner(nysg:nyng,nxlg:nxrg), &
512	nzb_v_outer(nysg:nyng,nxlg:nxrg), &
513	nzb_w_inner(nysg:nyng,nxlg:nxrg), &
514	nzb_w_outer(nysg:nyng,nxlg:nxrg), &
515	nzb_diff_s_inner(nysg:nyng,nxlg:nxrg), &
516	nzb_diff_s_outer(nysg:nyng,nxlg:nxrg), &
517	nzb_local(nysg:nyng,nxlg:nxrg), &
518	nzb_tmp(nysg:nyng,nxlg:nxrg), &
519	wall_flags_0(nzb:nzt+1,nysg:nyng,nxlg:nxrg) )
520
521	ALLOCATE( topo_3d(nzb:nzt+1,nysg:nyng,nxlg:nxrg) )
522	topo_3d = 0
523
524	ALLOCATE( l_wall(nzb:nzt+1,nysg:nyng,nxlg:nxrg) )
525
526	nzb_s_inner = nzb; nzb_s_outer = nzb
527	nzb_u_inner = nzb; nzb_u_outer = nzb
528	nzb_v_inner = nzb; nzb_v_outer = nzb
529	nzb_w_inner = nzb; nzb_w_outer = nzb
530
531	!
532	!-- Define vertical gridpoint from (or to) which on the usual finite difference
533	!-- form (which does not use surface fluxes) is applied
534	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
535	nzb_diff = nzb + 2
536	ELSE
537	nzb_diff = nzb + 1
538	ENDIF
539
540	nzb_diff_s_inner = nzb_diff; nzb_diff_s_outer = nzb_diff
541
542	!
543	!-- Initialize near-wall mixing length l_wall only in the vertical direction
544	!-- for the moment,
545	!-- multiplication with wall_adjustment_factor near the end of this routine
546	l_wall(nzb,:,:) = l_grid(1)
547	DO k = nzb+1, nzt
548	l_wall(k,:,:) = l_grid(k)
549	ENDDO
550	l_wall(nzt+1,:,:) = l_grid(nzt)
551
552	DO k = 1, nzt
553	IF ( l_grid(k) > 1.5_wp * dx * wall_adjustment_factor .OR. &
554	l_grid(k) > 1.5_wp * dy * wall_adjustment_factor ) THEN
555	WRITE( message_string, * ) 'grid anisotropy exceeds ', &
556	'threshold given by only local', &
557	' &horizontal reduction of near_wall ', &
558	'mixing length l_wall', &
559	' &starting from height level k = ', k, '.'
560	CALL message( 'init_grid', 'PA0202', 0, 1, 0, 6, 0 )
561	EXIT
562	ENDIF
563	ENDDO
564	!
565	!-- Set outer and inner index arrays for non-flat topography.
566	!-- Here consistency checks concerning domain size and periodicity are
567	!-- necessary.
568	!-- Within this SELECT CASE structure only nzb_local is initialized
569	!-- individually depending on the chosen topography type, all other index
570	!-- arrays are initialized further below.
571	SELECT CASE ( TRIM( topography ) )
572
573	CASE ( 'flat' )
574	!
575	!-- nzb_local is required for the multigrid solver
576	nzb_local = 0
577	!
578	!-- Initialilize 3D topography array, used later for initializing flags
579	topo_3d(nzb+1:nzt+1,:,:) = IBSET( topo_3d(nzb+1:nzt+1,:,:), 0 )
580	!
581	!-- level of detail is required for output routines
582	lod = 1
583
584	CASE ( 'single_building' )
585	!
586	!-- Single rectangular building, by default centered in the middle of the
587	!-- total domain
588	blx = NINT( building_length_x / dx )
589	bly = NINT( building_length_y / dy )
590	bh = MINLOC( ABS( zw - building_height ), 1 ) - 1
591	IF ( ABS( zw(bh) - building_height ) == &
592	ABS( zw(bh+1) - building_height ) ) bh = bh + 1
593
594	IF ( building_wall_left == 9999999.9_wp ) THEN
595	building_wall_left = ( nx + 1 - blx ) / 2 * dx
596	ENDIF
597	bxl = NINT( building_wall_left / dx )
598	bxr = bxl + blx
599
600	IF ( building_wall_south == 9999999.9_wp ) THEN
601	building_wall_south = ( ny + 1 - bly ) / 2 * dy
602	ENDIF
603	bys = NINT( building_wall_south / dy )
604	byn = bys + bly
605
606	!
607	!-- Building size has to meet some requirements
608	IF ( ( bxl < 1 ) .OR. ( bxr > nx-1 ) .OR. ( bxr < bxl+3 ) .OR. &
609	( bys < 1 ) .OR. ( byn > ny-1 ) .OR. ( byn < bys+3 ) ) THEN
610	WRITE( message_string, * ) 'inconsistent building parameters:', &
611	'& bxl=', bxl, 'bxr=', bxr, 'bys=', bys, &
612	'byn=', byn, 'nx=', nx, 'ny=', ny
613	CALL message( 'init_grid', 'PA0203', 1, 2, 0, 6, 0 )
614	ENDIF
615
616	!
617	!-- Define the building.
618	nzb_local = 0
619	IF ( bxl <= nxr .AND. bxr >= nxl .AND. &
620	bys <= nyn .AND. byn >= nys ) &
621	nzb_local(MAX(nys,bys):MIN(nyn,byn),MAX(nxl,bxl):MIN(nxr,bxr)) = bh
622
623	CALL exchange_horiz_2d_int( nzb_local, nys, nyn, nxl, nxr, nbgp )
624	!
625	!-- Set bit array to mask topography
626	DO i = nxlg, nxrg
627	DO j = nysg, nyng
628
629	topo_3d(nzb_local(j,i)+1:nzt+1,j,i) = &
630	IBSET( topo_3d(nzb_local(j,i)+1:nzt+1,j,i), 0 )
631	ENDDO
632	ENDDO
633	!
634	!-- level of detail is required for output routines. Here, 2D topography.
635	lod = 1
636
637	CALL exchange_horiz_int( topo_3d, nbgp )
638
639	CASE ( 'single_street_canyon' )
640	!
641	!-- Single quasi-2D street canyon of infinite length in x or y direction.
642	!-- The canyon is centered in the other direction by default.
643	IF ( canyon_width_x /= 9999999.9_wp ) THEN
644	!
645	!-- Street canyon in y direction
646	cwx = NINT( canyon_width_x / dx )
647	IF ( canyon_wall_left == 9999999.9_wp ) THEN
648	canyon_wall_left = ( nx + 1 - cwx ) / 2 * dx
649	ENDIF
650	cxl = NINT( canyon_wall_left / dx )
651	cxr = cxl + cwx
652
653	ELSEIF ( canyon_width_y /= 9999999.9_wp ) THEN
654	!
655	!-- Street canyon in x direction
656	cwy = NINT( canyon_width_y / dy )
657	IF ( canyon_wall_south == 9999999.9_wp ) THEN
658	canyon_wall_south = ( ny + 1 - cwy ) / 2 * dy
659	ENDIF
660	cys = NINT( canyon_wall_south / dy )
661	cyn = cys + cwy
662
663	ELSE
664
665	message_string = 'no street canyon width given'
666	CALL message( 'init_grid', 'PA0204', 1, 2, 0, 6, 0 )
667
668	ENDIF
669
670	ch = MINLOC( ABS( zw - canyon_height ), 1 ) - 1
671	IF ( ABS( zw(ch) - canyon_height ) == &
672	ABS( zw(ch+1) - canyon_height ) ) ch = ch + 1
673
674	dp_level_ind_b = ch
675	!
676	!-- Street canyon size has to meet some requirements
677	IF ( canyon_width_x /= 9999999.9_wp ) THEN
678	IF ( ( cxl < 1 ) .OR. ( cxr > nx-1 ) .OR. ( cwx < 3 ) .OR. &
679	( ch < 3 ) ) THEN
680	WRITE( message_string, * ) 'inconsistent canyon parameters:', &
681	'&cxl=', cxl, 'cxr=', cxr, &
682	'cwx=', cwx, &
683	'ch=', ch, 'nx=', nx, 'ny=', ny
684	CALL message( 'init_grid', 'PA0205', 1, 2, 0, 6, 0 )
685	ENDIF
686	ELSEIF ( canyon_width_y /= 9999999.9_wp ) THEN
687	IF ( ( cys < 1 ) .OR. ( cyn > ny-1 ) .OR. ( cwy < 3 ) .OR. &
688	( ch < 3 ) ) THEN
689	WRITE( message_string, * ) 'inconsistent canyon parameters:', &
690	'&cys=', cys, 'cyn=', cyn, &
691	'cwy=', cwy, &
692	'ch=', ch, 'nx=', nx, 'ny=', ny
693	CALL message( 'init_grid', 'PA0206', 1, 2, 0, 6, 0 )
694	ENDIF
695	ENDIF
696	IF ( canyon_width_x /= 9999999.9_wp .AND. &
697	canyon_width_y /= 9999999.9_wp ) THEN
698	message_string = 'inconsistent canyon parameters:' // &
699	'&street canyon can only be oriented' // &
700	'&either in x- or in y-direction'
701	CALL message( 'init_grid', 'PA0207', 1, 2, 0, 6, 0 )
702	ENDIF
703
704	nzb_local = ch
705	IF ( canyon_width_x /= 9999999.9_wp ) THEN
706	IF ( cxl <= nxr .AND. cxr >= nxl ) &
707	nzb_local(:,MAX(nxl,cxl+1):MIN(nxr,cxr-1)) = 0
708	ELSEIF ( canyon_width_y /= 9999999.9_wp ) THEN
709	IF ( cys <= nyn .AND. cyn >= nys ) &
710	nzb_local(MAX(nys,cys+1):MIN(nyn,cyn-1),:) = 0
711	ENDIF
712
713	CALL exchange_horiz_2d_int( nzb_local, nys, nyn, nxl, nxr, nbgp )
714	!
715	!-- Set bit array to mask topography
716	DO i = nxlg, nxrg
717	DO j = nysg, nyng
718	topo_3d(nzb_local(j,i)+1:nzt+1,j,i) = &
719	IBSET( topo_3d(nzb_local(j,i)+1:nzt+1,j,i), 0 )
720	ENDDO
721	ENDDO
722	!
723	!-- level of detail is required for output routines. Here, 2D topography.
724	lod = 1
725
726	CALL exchange_horiz_int( topo_3d, nbgp )
727
728	CASE ( 'tunnel' )
729
730	!
731	!-- Tunnel height
732	IF ( tunnel_height == 9999999.9_wp ) THEN
733	th = zw( INT( 0.2 * nz) )
734	ELSE
735	th = tunnel_height
736	ENDIF
737	!
738	!-- Tunnel-wall depth
739	IF ( tunnel_wall_depth == 9999999.9_wp ) THEN
740	td = MAX ( dx, dy, dz )
741	ELSE
742	td = tunnel_wall_depth
743	ENDIF
744	!
745	!-- Check for tunnel width
746	IF ( tunnel_width_x == 9999999.9_wp .AND. &
747	tunnel_width_y == 9999999.9_wp ) THEN
748	message_string = 'No tunnel width is given. '
749	CALL message( 'init_grid', 'PA0280', 1, 2, 0, 6, 0 )
750	ENDIF
751	IF ( tunnel_width_x /= 9999999.9_wp .AND. &
752	tunnel_width_y /= 9999999.9_wp ) THEN
753	message_string = 'Inconsistent tunnel parameters:' // &
754	'tunnel can only be oriented' // &
755	'either in x- or in y-direction.'
756	CALL message( 'init_grid', 'PA0281', 1, 2, 0, 6, 0 )
757	ENDIF
758	!
759	!-- Tunnel axis along y
760	IF ( tunnel_width_x /= 9999999.9_wp ) THEN
761	IF ( tunnel_width_x > ( nx + 1 ) * dx ) THEN
762	message_string = 'Tunnel width too large'
763	CALL message( 'init_grid', 'PA0282', 1, 2, 0, 6, 0 )
764	ENDIF
765
766	txs_out = INT( ( nx + 1 ) * 0.5_wp * dx - tunnel_width_x * 0.5_wp )
767	txe_out = INT( ( nx + 1 ) * 0.5_wp * dx + tunnel_width_x * 0.5_wp )
768	txs_in = INT( ( nx + 1 ) * 0.5_wp * dx - &
769	( tunnel_width_x * 0.5_wp - td ) )
770	txe_in = INT( ( nx + 1 ) * 0.5_wp * dx + &
771	( tunnel_width_x * 0.5_wp - td ) )
772
773	tys_out = INT( ( ny + 1 ) * 0.5_wp * dy - tunnel_length * 0.5_wp )
774	tye_out = INT( ( ny + 1 ) * 0.5_wp * dy + tunnel_length * 0.5_wp )
775	tys_in = tys_out
776	tye_in = tye_out
777	ENDIF
778	IF ( tunnel_width_x /= 9999999.9_wp .AND. &
779	tunnel_width_x - 2.0_wp * tunnel_wall_depth <= 2.0_wp * dx ) THEN
780	message_string = 'Tunnel width too small'
781	CALL message( 'init_grid', 'PA0175', 1, 2, 0, 6, 0 )
782	ENDIF
783	IF ( tunnel_width_y /= 9999999.9_wp .AND. &
784	tunnel_width_y - 2.0_wp * tunnel_wall_depth <= 2.0_wp * dy ) THEN
785	message_string = 'Tunnel width too small'
786	CALL message( 'init_grid', 'PA0455', 1, 2, 0, 6, 0 )
787	ENDIF
788	!
789	!-- Tunnel axis along x
790	IF ( tunnel_width_y /= 9999999.9_wp ) THEN
791	IF ( tunnel_width_y > ( ny + 1 ) * dy ) THEN
792	message_string = 'Tunnel width too large'
793	CALL message( 'init_grid', 'PA0456', 1, 2, 0, 6, 0 )
794	ENDIF
795
796	txs_out = INT( ( nx + 1 ) * 0.5_wp * dx - tunnel_length * 0.5_wp )
797	txe_out = INT( ( nx + 1 ) * 0.5_wp * dx + tunnel_length * 0.5_wp )
798	txs_in = txs_out
799	txe_in = txe_out
800
801	tys_out = INT( ( ny + 1 ) * 0.5_wp * dy - tunnel_width_y * 0.5_wp )
802	tye_out = INT( ( ny + 1 ) * 0.5_wp * dy + tunnel_width_y * 0.5_wp )
803	tys_in = INT( ( ny + 1 ) * 0.5_wp * dy - &
804	( tunnel_width_y * 0.5_wp - td ) )
805	tye_in = INT( ( ny + 1 ) * 0.5_wp * dy + &
806	( tunnel_width_y * 0.5_wp - td ) )
807	ENDIF
808
809	topo_3d = 0
810	DO i = nxl, nxr
811	DO j = nys, nyn
812	!
813	!-- Use heaviside function to model outer tunnel surface
814	hv_out = th * 0.5_wp * &
815	( ( SIGN( 1.0_wp, i * dx - txs_out ) + 1.0_wp ) &
816	- ( SIGN( 1.0_wp, i * dx - txe_out ) + 1.0_wp ) )
817
818	hv_out = hv_out * 0.5_wp * &
819	( ( SIGN( 1.0_wp, j * dy - tys_out ) + 1.0_wp ) &
820	- ( SIGN( 1.0_wp, j * dy - tye_out ) + 1.0_wp ) )
821	!
822	!-- Use heaviside function to model inner tunnel surface
823	hv_in = ( th - td ) * 0.5_wp * &
824	( ( SIGN( 1.0_wp, i * dx - txs_in ) + 1.0_wp ) &
825	- ( SIGN( 1.0_wp, i * dx - txe_in ) + 1.0_wp ) )
826
827	hv_in = hv_in * 0.5_wp * &
828	( ( SIGN( 1.0_wp, j * dy - tys_in ) + 1.0_wp ) &
829	- ( SIGN( 1.0_wp, j * dy - tye_in ) + 1.0_wp ) )
830	!
831	!-- Set flags at x-y-positions without any tunnel surface
832	IF ( hv_out - hv_in == 0.0_wp ) THEN
833	topo_3d(nzb+1:nzt+1,j,i) = IBSET( topo_3d(nzb+1:nzt+1,j,i), 0 )
834	!
835	!-- Set flags at x-y-positions with tunnel surfaces
836	ELSE
837	DO k = nzb + 1, nzt + 1
838	!
839	!-- Inner tunnel
840	IF ( hv_out - hv_in == th ) THEN
841	IF ( zw(k) <= hv_out ) THEN
842	topo_3d(k,j,i) = IBCLR( topo_3d(k,j,i), 0 )
843	ELSE
844	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 0 )
845	ENDIF
846	ENDIF
847	!
848	!-- Lateral tunnel walls
849	IF ( hv_out - hv_in == td ) THEN
850	IF ( zw(k) <= hv_in ) THEN
851	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 0 )
852	ELSEIF ( zw(k) > hv_in .AND. zw(k) <= hv_out ) THEN
853	topo_3d(k,j,i) = IBCLR( topo_3d(k,j,i), 0 )
854	ELSEIF ( zw(k) > hv_out ) THEN
855	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 0 )
856	ENDIF
857	ENDIF
858	ENDDO
859	ENDIF
860	ENDDO
861	ENDDO
862
863	nzb_local = 0
864	!
865	!-- level of detail is required for output routines. Here, 3D topography.
866	lod = 2
867
868	CALL exchange_horiz_int( topo_3d, nbgp )
869
870	CASE ( 'read_from_file' )
871
872	ALLOCATE ( oro_height(nys:nyn,nxl:nxr) )
873	ALLOCATE ( topo_height(nys:nyn,nxl:nxr) )
874	oro_height = 0.0_wp
875	topo_height = 0.0_wp
876
877	DO ii = 0, io_blocks-1
878	IF ( ii == io_group ) THEN
879
880	!
881	!-- Arbitrary irregular topography data in PALM format (exactly
882	!-- matching the grid size and total domain size).
883	!-- First, check if NetCDF file for topography exist or not.
884	!-- This case, read topography from NetCDF, else read it from
885	!-- ASCII file.
886	#if defined ( __netcdf )
887	INQUIRE( FILE='TOPOGRAPHY_DATA_NC'//TRIM( coupling_char ), &
888	EXIST=netcdf_extend )
889	!
890	!-- NetCDF branch
891	IF ( netcdf_extend ) THEN
892	!
893	!-- Open file in read-only mode
894	CALL netcdf_open_read_file( 'TOPOGRAPHY_DATA_NC', &
895	id_topo, 20 ) !Error number still need to be set properly
896
897	!
898	!-- Read terrain height. Reading is done PE-wise, i.e. each
899	!-- processor reads its own domain. Reading is realized
900	!-- via looping over x-dimension, i.e. calling
901	!-- netcdf_get_variable reads topography along y for given x.
902	!-- Orography is 2D.
903	DO i = nxl, nxr
904	CALL netcdf_get_variable( id_topo, 'orography_0', &
905	i, oro_height(:,i), 20 ) !Error number still need to be set properly
906	ENDDO
907	!
908	!-- Read attribute lod (level of detail), required for variable
909	!-- buildings_0
910	CALL netcdf_get_attribute( id_topo, "lod", lod, .FALSE., &
911	20, 'buildings_0' ) !Error number still need to be set properly
912	!
913	!-- Read building height
914	!-- 2D for lod = 1, 3D for lod = 2
915	IF ( lod == 1 ) THEN
916	DO i = nxl, nxr
917	CALL netcdf_get_variable( id_topo, 'buildings_0', &
918	i, topo_height(:,i), 20 ) !Error number still need to be set properly
919	ENDDO
920
921	ELSEIF ( lod == 2 ) THEN
922	!
923	!-- Allocate 1-byte integer dummy array to read 3D topography
924	ALLOCATE( topo_3d_read(nzb:nzt+1,nysg:nyng,nxlg:nxrg) )
925	!
926	!-- Read data PE-wise. Read yz-slices.
927	DO i = nxl, nxr
928	DO j = nys, nyn
929	CALL netcdf_get_variable( id_topo, 'buildings_0', &
930	i, j, topo_3d_read(:,j,i), 20 ) !Error number still need to be set properly
931	ENDDO
932	ENDDO
933	ELSE
934	message_string = 'NetCDF attribute lod ' // &
935	'(level of detail) is not set properly.'
936	CALL message( 'init_grid', 'PA0457', 1, 2, 0, 6, 0 )
937	ENDIF
938	!
939	!-- On file, 3D topography grid points is classified with 1,
940	!-- atmosphere is classified with 0, contrary to the internal
941	!-- treatment. Hence, conversion is required. Moreover, set
942	!-- topography array to zero at lowest grid level.
943	topo_3d = MERGE( 0, 1, topo_3d_read == 1 )
944	topo_3d(nzb,:,:) = 0
945	!
946	!-- Deallocate dummy array
947	DEALLOCATE( topo_3d_read )
948	!
949	!-- Close topography input file
950	CALL netcdf_close_file( id_topo, 20 )
951	#endif
952
953	!
954	!-- ASCII branch. Please note, reading of 3D topography is not
955	!-- supported in ASCII format. Further, no distinction is made
956	!-- between orography and buildings
957	ELSE
958
959	OPEN( 90, FILE='TOPOGRAPHY_DATA'//TRIM( coupling_char ), &
960	STATUS='OLD', FORM='FORMATTED', ERR=10 )
961	!
962	!-- Read topography PE-wise. Rows are read from nyn to nys, columns
963	!-- are read from nxl to nxr. At first, ny-nyn rows need to be skipped.
964	skip_n_rows = 0
965	DO WHILE ( skip_n_rows < ny - nyn )
966	READ( 90, * )
967	skip_n_rows = skip_n_rows + 1
968	ENDDO
969	!
970	!-- Read data from nyn to nys and nxl to nxr. Therefore, skip
971	!-- column until nxl-1 is reached
972	DO j = nyn, nys, -1
973	READ( 90, *, ERR=11, END=11 ) &
974	( dum, i = 0, nxl-1 ), &
975	( topo_height(j,i), i = nxl, nxr )
976	ENDDO
977
978	GOTO 12
979
980	10 message_string = 'file TOPOGRAPHY'//TRIM( coupling_char )// &
981	' does not exist'
982	CALL message( 'init_grid', 'PA0208', 1, 2, 0, 6, 0 )
983
984	11 message_string = 'errors in file TOPOGRAPHY_DATA'// &
985	TRIM( coupling_char )
986	CALL message( 'init_grid', 'PA0209', 1, 2, 0, 6, 0 )
987
988	12 CLOSE( 90 )
989
990	ENDIF
991
992	ENDIF
993	#if defined( __parallel )
994	CALL MPI_BARRIER( comm2d, ierr )
995	#endif
996	ENDDO
997
998	!
999	!-- Calculate the index height of the topography
1000	nzb_local = 0
1001	DO i = nxl, nxr
1002	DO j = nys, nyn
1003	IF ( .NOT. ocean ) THEN
1004	nzb_local(j,i) = MINLOC( ABS( zw - topo_height(j,i) &
1005	- oro_height(j,i) ), 1 ) - 1
1006	IF ( ABS( zw(nzb_local(j,i) ) - topo_height(j,i) &
1007	- oro_height(j,i) ) == &
1008	ABS( zw(nzb_local(j,i)+1) - topo_height(j,i) &
1009	- oro_height(j,i) ) ) &
1010	nzb_local(j,i) = nzb_local(j,i) + 1
1011	ELSE
1012	nzb_local(j,i) = MINLOC( ABS( zw - zw(0) &
1013	- topo_height(j,i) &
1014	- oro_height(j,i) ), 1 ) - 1
1015	IF ( ABS( zw(nzb_local(j,i) ) - zw(0) &
1016	- topo_height(j,i) &
1017	- oro_height(j,i) ) == &
1018	ABS( zw(nzb_local(j,i)+1) - zw(0) &
1019	- topo_height(j,i) &
1020	- oro_height(j,i) ) ) &
1021	nzb_local(j,i) = nzb_local(j,i) + 1
1022	ENDIF
1023
1024	ENDDO
1025	ENDDO
1026
1027	DEALLOCATE ( oro_height )
1028	DEALLOCATE ( topo_height )
1029	!
1030	!-- Filter topography, i.e. fill holes resolved by only one grid point.
1031	!-- Such holes are suspected to lead to velocity blow-ups as continuity
1032	!-- equation on discrete grid cannot be fulfilled in such case.
1033	!-- For now, check only for holes and fill them to the lowest height level
1034	!-- of the directly adjoining grid points along x- and y- direction.
1035	!-- Before checking for holes, set lateral boundary conditions for
1036	!-- topography. After hole-filling, boundary conditions must be set again!
1037	CALL exchange_horiz_2d_int( nzb_local, nys, nyn, nxl, nxr, nbgp )
1038
1039	IF ( .NOT. bc_ns_cyc ) THEN
1040	IF ( nys == 0 ) nzb_local(-1,:) = nzb_local(0,:)
1041	IF ( nyn == ny ) nzb_local(ny+1,:) = nzb_local(ny,:)
1042	ENDIF
1043
1044	IF ( .NOT. bc_lr_cyc ) THEN
1045	IF ( nxl == 0 ) nzb_local(:,-1) = nzb_local(:,0)
1046	IF ( nxr == nx ) nzb_local(:,nx+1) = nzb_local(:,nx)
1047	ENDIF
1048
1049	num_hole_l = 0
1050	DO i = nxl, nxr
1051	DO j = nys, nyn
1052
1053	num_wall = 0
1054
1055	IF ( nzb_local(j-1,i) > nzb_local(j,i) ) &
1056	num_wall = num_wall + 1
1057	IF ( nzb_local(j+1,i) > nzb_local(j,i) ) &
1058	num_wall = num_wall + 1
1059	IF ( nzb_local(j,i-1) > nzb_local(j,i) ) &
1060	num_wall = num_wall + 1
1061	IF ( nzb_local(j,i+1) > nzb_local(j,i) ) &
1062	num_wall = num_wall + 1
1063
1064	IF ( num_wall == 4 ) THEN
1065	nzb_local(j,i) = MIN( nzb_local(j-1,i), nzb_local(j+1,i), &
1066	nzb_local(j,i-1), nzb_local(j,i+1) )
1067	num_hole_l = num_hole_l + 1
1068	ENDIF
1069	ENDDO
1070	ENDDO
1071	!
1072	!-- Count the total number of holes, required for informative message.
1073	#if defined( __parallel )
1074	CALL MPI_ALLREDUCE( num_hole_l, num_hole, 1, MPI_INTEGER, MPI_SUM, &
1075	comm2d, ierr )
1076	#else
1077	num_hole = num_hole_l
1078	#endif
1079	!
1080	!-- Create an informative message if any hole was removed.
1081	IF ( num_hole > 0 ) THEN
1082	WRITE( message_string, * ) num_hole, 'hole(s) resolved by only '//&
1083	'one grid point were filled'
1084	CALL message( 'init_grid', 'PA0430', 0, 0, 0, 6, 0 )
1085	ENDIF
1086
1087	!
1088	!-- Set bit array to mask topography. Only required for lod = 1
1089	IF ( lod == 1 ) THEN
1090	DO i = nxlg, nxrg
1091	DO j = nysg, nyng
1092	topo_3d(nzb_local(j,i)+1:nzt+1,j,i) = &
1093	IBSET( topo_3d(nzb_local(j,i)+1:nzt+1,j,i), 0 )
1094	ENDDO
1095	ENDDO
1096	ENDIF
1097	!
1098	!-- Exchange ghost-points, as well as add cyclic or Neumann boundary
1099	!-- conditions.
1100	CALL exchange_horiz_int( topo_3d, nbgp )
1101	CALL exchange_horiz_2d_int( nzb_local, nys, nyn, nxl, nxr, nbgp )
1102
1103	IF ( .NOT. bc_ns_cyc ) THEN
1104	IF ( nys == 0 ) topo_3d(:,-1,:) = topo_3d(:,0,:)
1105	IF ( nyn == ny ) topo_3d(:,ny+1,:) = topo_3d(:,ny,:)
1106
1107	IF ( nys == 0 ) nzb_local(-1,:) = nzb_local(0,:)
1108	IF ( nyn == ny ) nzb_local(ny+1,:) = nzb_local(ny,:)
1109	ENDIF
1110
1111	IF ( .NOT. bc_lr_cyc ) THEN
1112	IF ( nxl == 0 ) topo_3d(:,:,-1) = topo_3d(:,:,0)
1113	IF ( nxr == nx ) topo_3d(:,:,nx+1) = topo_3d(:,:,nx)
1114
1115	IF ( nxl == 0 ) nzb_local(:,-1) = nzb_local(:,0)
1116	IF ( nxr == nx ) nzb_local(:,nx+1) = nzb_local(:,nx)
1117	ENDIF
1118
1119
1120	CASE DEFAULT
1121	!
1122	!-- The DEFAULT case is reached either if the parameter topography
1123	!-- contains a wrong character string or if the user has defined a special
1124	!-- case in the user interface. There, the subroutine user_init_grid
1125	!-- checks which of these two conditions applies.
1126	CALL user_init_grid( topo_3d )
1127
1128	END SELECT
1129	!
1130	!-- Consistency checks and index array initialization are only required for
1131	!-- non-flat topography, also the initialization of topography height arrays
1132	!-- zu_s_inner and zw_w_inner
1133	IF ( TRIM( topography ) /= 'flat' ) THEN
1134	#if defined( __parallel )
1135	CALL MPI_ALLREDUCE( MAXVAL( nzb_local ), nzb_local_max, 1, MPI_INTEGER, &
1136	MPI_MAX, comm2d, ierr )
1137	CALL MPI_ALLREDUCE( MINVAL( nzb_local ), nzb_local_min, 1, MPI_INTEGER, &
1138	MPI_MIN, comm2d, ierr )
1139	#else
1140	nzb_local_max = MAXVAL( nzb_local )
1141	nzb_local_min = MINVAL( nzb_local )
1142	#endif
1143
1144	!
1145	!-- Consistency checks
1146	IF ( nzb_local_min < 0 .OR. nzb_local_max > nz + 1 ) THEN
1147	WRITE( message_string, * ) 'nzb_local values are outside the', &
1148	'model domain', &
1149	'&MINVAL( nzb_local ) = ', nzb_local_min, &
1150	'&MAXVAL( nzb_local ) = ', nzb_local_max
1151	CALL message( 'init_grid', 'PA0210', 1, 2, 0, 6, 0 )
1152	ENDIF
1153	!
1154	!-- In case of non-flat topography, check whether the convention how to
1155	!-- define the topography grid has been set correctly, or whether the default
1156	!-- is applicable. If this is not possible, abort.
1157	IF ( TRIM( topography_grid_convention ) == ' ' ) THEN
1158	IF ( TRIM( topography ) /= 'single_building' .AND. &
1159	TRIM( topography ) /= 'single_street_canyon' .AND. &
1160	TRIM( topography ) /= 'tunnel' .AND. &
1161	TRIM( topography ) /= 'read_from_file') THEN
1162	!-- The default value is not applicable here, because it is only valid
1163	!-- for the two standard cases 'single_building' and 'read_from_file'
1164	!-- defined in init_grid.
1165	WRITE( message_string, * ) &
1166	'The value for "topography_grid_convention" ', &
1167	'is not set. Its default value is & only valid for ', &
1168	'"topography" = ''single_building'', ', &
1169	'''single_street_canyon'' & or ''read_from_file''.', &
1170	' & Choose ''cell_edge'' or ''cell_center''.'
1171	CALL message( 'init_grid', 'PA0239', 1, 2, 0, 6, 0 )
1172	ELSE
1173	!-- The default value is applicable here.
1174	!-- Set convention according to topography.
1175	IF ( TRIM( topography ) == 'single_building' .OR. &
1176	TRIM( topography ) == 'single_street_canyon' ) THEN
1177	topography_grid_convention = 'cell_edge'
1178	ELSEIF ( TRIM( topography ) == 'read_from_file' .OR. &
1179	TRIM( topography ) == 'tunnel') THEN
1180	topography_grid_convention = 'cell_center'
1181	ENDIF
1182	ENDIF
1183	ELSEIF ( TRIM( topography_grid_convention ) /= 'cell_edge' .AND. &
1184	TRIM( topography_grid_convention ) /= 'cell_center' ) THEN
1185	WRITE( message_string, * ) &
1186	'The value for "topography_grid_convention" is ', &
1187	'not recognized. & Choose ''cell_edge'' or ''cell_center''.'
1188	CALL message( 'init_grid', 'PA0240', 1, 2, 0, 6, 0 )
1189	ENDIF
1190
1191	!
1192	!-- In case of non-flat topography, check whether the convention how to
1193	!-- define the topography grid has been set correctly, or whether the default
1194	!-- is applicable. If this is not possible, abort.
1195	IF ( TRIM( topography_grid_convention ) == ' ' ) THEN
1196	IF ( TRIM( topography ) /= 'single_building' .AND. &
1197	TRIM( topography ) /= 'single_street_canyon' .AND. &
1198	TRIM( topography ) /= 'read_from_file' ) THEN
1199	!-- The default value is not applicable here, because it is only valid
1200	!-- for the two standard cases 'single_building' and 'read_from_file'
1201	!-- defined in init_grid.
1202	WRITE( message_string, * ) &
1203	'The value for "topography_grid_convention" ', &
1204	'is not set. Its default value is & only valid for ', &
1205	'"topography" = ''single_building'', ', &
1206	'''single_street_canyon'' & or ''read_from_file''.', &
1207	' & Choose ''cell_edge'' or ''cell_center''.'
1208	CALL message( 'init_grid', 'PA0239', 1, 2, 0, 6, 0 )
1209	ELSE
1210	!-- The default value is applicable here.
1211	!-- Set convention according to topography.
1212	IF ( TRIM( topography ) == 'single_building' .OR. &
1213	TRIM( topography ) == 'single_street_canyon' ) THEN
1214	topography_grid_convention = 'cell_edge'
1215	ELSEIF ( TRIM( topography ) == 'read_from_file' ) THEN
1216	topography_grid_convention = 'cell_center'
1217	ENDIF
1218	ENDIF
1219	ELSEIF ( TRIM( topography_grid_convention ) /= 'cell_edge' .AND. &
1220	TRIM( topography_grid_convention ) /= 'cell_center' ) THEN
1221	WRITE( message_string, * ) &
1222	'The value for "topography_grid_convention" is ', &
1223	'not recognized. & Choose ''cell_edge'' or ''cell_center''.'
1224	CALL message( 'init_grid', 'PA0240', 1, 2, 0, 6, 0 )
1225	ENDIF
1226
1227	IF ( topography_grid_convention == 'cell_edge' ) THEN
1228	!
1229	!-- The array nzb_local as defined using the 'cell_edge' convention
1230	!-- describes the actual total size of topography which is defined at the
1231	!-- cell edges where u=0 on the topography walls in x-direction and v=0
1232	!-- on the topography walls in y-direction. However, PALM uses individual
1233	!-- arrays nzb_u\|v\|w\|s_inner\|outer that are based on nzb_s_inner.
1234	!-- Therefore, the extent of topography in nzb_local is now reduced by
1235	!-- 1dx at the E topography walls and by 1dy at the N topography walls
1236	!-- to form the basis for nzb_s_inner.
1237	!-- Note, the reverse memory access (i-j instead of j-i) is absolutely
1238	!-- required at this point.
1239	DO j = nys+1, nyn+1
1240	DO i = nxl-1, nxr
1241	nzb_local(j,i) = MIN( nzb_local(j,i), nzb_local(j,i+1) )
1242	ENDDO
1243	ENDDO
1244	!
1245	!-- Exchange ghost points
1246	CALL exchange_horiz_2d_int( nzb_local, nys, nyn, nxl, nxr, nbgp )
1247
1248	DO i = nxl, nxr+1
1249	DO j = nys-1, nyn
1250	nzb_local(j,i) = MIN( nzb_local(j,i), nzb_local(j+1,i) )
1251	ENDDO
1252	ENDDO
1253	!
1254	!-- Exchange ghost points
1255	CALL exchange_horiz_2d_int( nzb_local, nys, nyn, nxl, nxr, nbgp )
1256	!
1257	!-- Apply cell-edge convention also for 3D topo array. The former setting
1258	!-- of nzb_local will be removed later.
1259	DO j = nys+1, nyn+1
1260	DO i = nxl-1, nxr
1261	DO k = nzb, nzt+1
1262	IF ( BTEST( topo_3d(k,j,i), 0 ) .OR. &
1263	BTEST( topo_3d(k,j,i+1), 0 ) ) &
1264	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 0 )
1265	ENDDO
1266	ENDDO
1267	ENDDO
1268	CALL exchange_horiz_int( topo_3d, nbgp )
1269
1270	DO i = nxl, nxr+1
1271	DO j = nys-1, nyn
1272	DO k = nzb, nzt+1
1273	IF ( BTEST( topo_3d(k,j,i), 0 ) .OR. &
1274	BTEST( topo_3d(k,j+1,i), 0 ) ) &
1275	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 0 )
1276	ENDDO
1277	ENDDO
1278	ENDDO
1279	CALL exchange_horiz_int( topo_3d, nbgp )
1280
1281	ENDIF
1282
1283	!
1284	!-- Initialize index arrays nzb_s_inner and nzb_w_inner
1285
1286	nzb_s_inner = nzb_local
1287	nzb_w_inner = nzb_local
1288
1289	!
1290	!-- Initialize remaining index arrays:
1291	!-- first pre-initialize them with nzb_s_inner...
1292	nzb_u_inner = nzb_s_inner
1293	nzb_u_outer = nzb_s_inner
1294	nzb_v_inner = nzb_s_inner
1295	nzb_v_outer = nzb_s_inner
1296	nzb_w_outer = nzb_s_inner
1297	nzb_s_outer = nzb_s_inner
1298
1299	!
1300	!-- ...then extend pre-initialized arrays in their according directions
1301	!-- based on nzb_local using nzb_tmp as a temporary global index array
1302
1303	!
1304	!-- nzb_s_outer:
1305	!-- extend nzb_local east-/westwards first, then north-/southwards
1306	nzb_tmp = nzb_local
1307	DO j = nys, nyn
1308	DO i = nxl, nxr
1309	nzb_tmp(j,i) = MAX( nzb_local(j,i-1), nzb_local(j,i), &
1310	nzb_local(j,i+1) )
1311	ENDDO
1312	ENDDO
1313
1314	CALL exchange_horiz_2d_int( nzb_tmp, nys, nyn, nxl, nxr, nbgp )
1315
1316	DO i = nxl, nxr
1317	DO j = nys, nyn
1318	nzb_s_outer(j,i) = MAX( nzb_tmp(j-1,i), nzb_tmp(j,i), &
1319	nzb_tmp(j+1,i) )
1320	ENDDO
1321	!
1322	!-- non-cyclic boundary conditions (overwritten by call of
1323	!-- exchange_horiz_2d_int below in case of cyclic boundary conditions)
1324	IF ( nys == 0 ) THEN
1325	j = -1
1326	nzb_s_outer(j,i) = MAX( nzb_tmp(j+1,i), nzb_tmp(j,i) )
1327	ENDIF
1328	IF ( nyn == ny ) THEN
1329	j = ny + 1
1330	nzb_s_outer(j,i) = MAX( nzb_tmp(j-1,i), nzb_tmp(j,i) )
1331	ENDIF
1332	ENDDO
1333	!
1334	!-- nzb_w_outer:
1335	!-- identical to nzb_s_outer
1336	nzb_w_outer = nzb_s_outer
1337
1338	!
1339	!-- nzb_u_inner:
1340	!-- extend nzb_local rightwards only
1341	nzb_tmp = nzb_local
1342	DO j = nys, nyn
1343	DO i = nxl, nxr
1344	nzb_tmp(j,i) = MAX( nzb_local(j,i-1), nzb_local(j,i) )
1345	ENDDO
1346	ENDDO
1347
1348	CALL exchange_horiz_2d_int( nzb_tmp, nys, nyn, nxl, nxr, nbgp )
1349
1350	nzb_u_inner = nzb_tmp
1351	!
1352	!-- nzb_u_outer:
1353	!-- extend current nzb_tmp (nzb_u_inner) north-/southwards
1354	DO i = nxl, nxr
1355	DO j = nys, nyn
1356	nzb_u_outer(j,i) = MAX( nzb_tmp(j-1,i), nzb_tmp(j,i), &
1357	nzb_tmp(j+1,i) )
1358	ENDDO
1359	!
1360	!-- non-cyclic boundary conditions (overwritten by call of
1361	!-- exchange_horiz_2d_int below in case of cyclic boundary conditions)
1362	IF ( nys == 0 ) THEN
1363	j = -1
1364	nzb_u_outer(j,i) = MAX( nzb_tmp(j+1,i), nzb_tmp(j,i) )
1365	ENDIF
1366	IF ( nyn == ny ) THEN
1367	j = ny + 1
1368	nzb_u_outer(j,i) = MAX( nzb_tmp(j-1,i), nzb_tmp(j,i) )
1369	ENDIF
1370	ENDDO
1371
1372	!
1373	!-- nzb_v_inner:
1374	!-- extend nzb_local northwards only
1375	nzb_tmp = nzb_local
1376	DO i = nxl, nxr
1377	DO j = nys, nyn
1378	nzb_tmp(j,i) = MAX( nzb_local(j-1,i), nzb_local(j,i) )
1379	ENDDO
1380	ENDDO
1381
1382	CALL exchange_horiz_2d_int( nzb_tmp, nys, nyn, nxl, nxr, nbgp )
1383	nzb_v_inner = nzb_tmp
1384
1385	!
1386	!-- nzb_v_outer:
1387	!-- extend current nzb_tmp (nzb_v_inner) right-/leftwards
1388	DO j = nys, nyn
1389	DO i = nxl, nxr
1390	nzb_v_outer(j,i) = MAX( nzb_tmp(j,i-1), nzb_tmp(j,i), &
1391	nzb_tmp(j,i+1) )
1392	ENDDO
1393	!
1394	!-- non-cyclic boundary conditions (overwritten by call of
1395	!-- exchange_horiz_2d_int below in case of cyclic boundary conditions)
1396	IF ( nxl == 0 ) THEN
1397	i = -1
1398	nzb_v_outer(j,i) = MAX( nzb_tmp(j,i+1), nzb_tmp(j,i) )
1399	ENDIF
1400	IF ( nxr == nx ) THEN
1401	i = nx + 1
1402	nzb_v_outer(j,i) = MAX( nzb_tmp(j,i-1), nzb_tmp(j,i) )
1403	ENDIF
1404	ENDDO
1405
1406	!
1407	!-- Exchange of lateral boundary values (parallel computers) and cyclic
1408	!-- boundary conditions, if applicable.
1409	!-- Since nzb_s_inner and nzb_w_inner are derived directly from nzb_local
1410	!-- they do not require exchange and are not included here.
1411	CALL exchange_horiz_2d_int( nzb_u_inner, nys, nyn, nxl, nxr, nbgp )
1412	CALL exchange_horiz_2d_int( nzb_u_outer, nys, nyn, nxl, nxr, nbgp )
1413	CALL exchange_horiz_2d_int( nzb_v_inner, nys, nyn, nxl, nxr, nbgp )
1414	CALL exchange_horiz_2d_int( nzb_v_outer, nys, nyn, nxl, nxr, nbgp )
1415	CALL exchange_horiz_2d_int( nzb_w_outer, nys, nyn, nxl, nxr, nbgp )
1416	CALL exchange_horiz_2d_int( nzb_s_outer, nys, nyn, nxl, nxr, nbgp )
1417
1418	ENDIF
1419	!
1420	!-- Deallocate temporary array, as it might be reused for different
1421	!-- grid-levels further below.
1422	DEALLOCATE( nzb_tmp )
1423
1424	!
1425	!-- Determine the maximum level of topography. It is used for
1426	!-- steering the degradation of order of the applied advection scheme.
1427	!-- In case of non-cyclic lateral boundaries, the order of the advection
1428	!-- scheme has to be reduced up to nzt (required at the lateral boundaries).
1429	k_top = 0
1430	DO i = nxl, nxr
1431	DO j = nys, nyn
1432	DO k = nzb, nzt + 1
1433	k_top = MAX( k_top, MERGE( k, 0, &
1434	.NOT. BTEST( topo_3d(k,j,i), 0 ) ) )
1435	ENDDO
1436	ENDDO
1437	ENDDO
1438	#if defined( __parallel )
1439	CALL MPI_ALLREDUCE( k_top + 1, nzb_max, 1, MPI_INTEGER, & !is +1 really necessary here?
1440	MPI_MAX, comm2d, ierr )
1441	#else
1442	nzb_max = k_top + 1
1443	#endif
1444	IF ( inflow_l .OR. outflow_l .OR. inflow_r .OR. outflow_r .OR. &
1445	inflow_n .OR. outflow_n .OR. inflow_s .OR. outflow_s .OR. &
1446	nest_domain ) &
1447	THEN
1448	nzb_max = nzt
1449	ENDIF
1450	!
1451	!-- Finally, if topography extents up to the model top, limit nzb_max to nzt.
1452	nzb_max = MIN( nzb_max, nzt )
1453
1454	!
1455	!-- Set the individual index arrays which define the k index from which on
1456	!-- the usual finite difference form (which does not use surface fluxes) is
1457	!-- applied
1458	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
1459	nzb_diff_s_inner = nzb_s_inner + 2
1460	nzb_diff_s_outer = nzb_s_outer + 2
1461	ELSE
1462	nzb_diff_s_inner = nzb_s_inner + 1
1463	nzb_diff_s_outer = nzb_s_outer + 1
1464	ENDIF
1465
1466	!
1467	!-- Set-up topography flags. First, set flags only for s, u, v and w-grid.
1468	!-- Further special flags will be set in following loops.
1469	wall_flags_0 = 0
1470	DO j = nys, nyn
1471	DO i = nxl, nxr
1472	DO k = nzb, nzt+1
1473	!
1474	!-- scalar grid
1475	IF ( BTEST( topo_3d(k,j,i), 0 ) ) &
1476	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 0 )
1477	!
1478	!-- v grid
1479	IF ( BTEST( topo_3d(k,j,i), 0 ) .AND. &
1480	BTEST( topo_3d(k,j-1,i), 0 ) ) &
1481	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 2 )
1482	!
1483	!-- To do: set outer arrays on basis of topo_3d array, adjust for downward-facing walls
1484	!-- s grid outer array
1485	IF ( k >= nzb_s_outer(j,i) ) &
1486	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 24 )
1487	!
1488	!-- s grid outer array
1489	IF ( k >= nzb_u_outer(j,i) ) &
1490	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 26 )
1491	!
1492	!-- s grid outer array
1493	IF ( k >= nzb_v_outer(j,i) ) &
1494	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 27 )
1495	!
1496	!-- w grid outer array
1497	IF ( k >= nzb_w_outer(j,i) ) &
1498	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 28 )
1499	ENDDO
1500
1501	DO k = nzb, nzt
1502	!
1503	!-- w grid
1504	IF ( BTEST( topo_3d(k,j,i), 0 ) .AND. &
1505	BTEST( topo_3d(k+1,j,i), 0 ) ) &
1506	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 3 )
1507	ENDDO
1508	wall_flags_0(nzt+1,j,i) = IBSET( wall_flags_0(nzt+1,j,i), 3 )
1509
1510	ENDDO
1511	ENDDO
1512	!
1513	!-- u grid. Note, reverse
1514	!-- memory access is required for setting flag on u-grid
1515	DO j = nys, nyn
1516	DO i = nxl, nxr
1517	DO k = nzb, nzt+1
1518	IF ( BTEST( topo_3d(k,j,i), 0 ) .AND. &
1519	BTEST( topo_3d(k,j,i-1), 0 ) ) &
1520	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 1 )
1521	ENDDO
1522	ENDDO
1523	ENDDO
1524	!
1525	!-- Set further special flags
1526	DO i = nxl, nxr
1527	DO j = nys, nyn
1528	DO k = nzb, nzt+1
1529	!
1530	!-- scalar grid, former nzb_diff_s_inner.
1531	!-- Note, use this flag also to mask topography in diffusion_u and
1532	!-- diffusion_v along the vertical direction. In case of
1533	!-- use_surface_fluxes, fluxes are calculated via MOST, else, simple
1534	!-- gradient approach is applied. Please note, in case of u- and v-
1535	!-- diffuison, a small error is made at edges (on the east side for u,
1536	!-- at the north side for v), since topography on scalar grid point
1537	!-- is used instead of topography on u/v-grid. As number of topography grid
1538	!-- points on uv-grid is different than s-grid, different number of
1539	!-- surface elements would be required. In order to avoid this,
1540	!-- treat edges (u(k,j,i+1)) simply by a gradient approach, i.e. these
1541	!-- points are not masked within diffusion_u. Tests had shown that the
1542	!-- effect on the flow is negligible.
1543	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
1544	IF ( BTEST( wall_flags_0(k,j,i), 0 ) ) &
1545	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 8 )
1546	ELSE
1547	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 8 )
1548	ENDIF
1549
1550	ENDDO
1551	!
1552	!-- Special flag to control vertical diffusion at model top - former
1553	!-- nzt_diff
1554	wall_flags_0(:,j,i) = IBSET( wall_flags_0(:,j,i), 9 )
1555	IF ( use_top_fluxes ) &
1556	wall_flags_0(nzt:nzt+1,j,i) = IBCLR( wall_flags_0(nzt:nzt+1,j,i), 9 )
1557
1558	DO k = nzb+1, nzt
1559	!
1560	!-- Special flag on u grid, former nzb_u_inner + 1, required
1561	!-- for disturb_field and initialization. Do not disturb directly at
1562	!-- topography, as well as initialize u with zero one grid point outside
1563	!-- of topography.
1564	IF ( BTEST( wall_flags_0(k-1,j,i), 1 ) .AND. &
1565	BTEST( wall_flags_0(k,j,i), 1 ) .AND. &
1566	BTEST( wall_flags_0(k+1,j,i), 1 ) ) &
1567	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 20 )
1568	!
1569	!-- Special flag on v grid, former nzb_v_inner + 1, required
1570	!-- for disturb_field and initialization. Do not disturb directly at
1571	!-- topography, as well as initialize v with zero one grid point outside
1572	!-- of topography.
1573	IF ( BTEST( wall_flags_0(k-1,j,i), 2 ) .AND. &
1574	BTEST( wall_flags_0(k,j,i), 2 ) .AND. &
1575	BTEST( wall_flags_0(k+1,j,i), 2 ) ) &
1576	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 21 )
1577	!
1578	!-- Special flag on scalar grid, former nzb_s_inner+1. Used for
1579	!-- lpm_sgs_tke
1580	IF ( BTEST( wall_flags_0(k,j,i), 0 ) .AND. &
1581	BTEST( wall_flags_0(k-1,j,i), 0 ) .AND. &
1582	BTEST( wall_flags_0(k+1,j,i), 0 ) ) &
1583	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 25 )
1584	!
1585	!-- Special flag on scalar grid, nzb_diff_s_outer - 1, required in
1586	!-- in production_e
1587	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
1588	IF ( BTEST( wall_flags_0(k,j,i), 24 ) .AND. &
1589	BTEST( wall_flags_0(k-1,j,i), 24 ) .AND. &
1590	BTEST( wall_flags_0(k+1,j,i), 0 ) ) &
1591	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 29 )
1592	ELSE
1593	IF ( BTEST( wall_flags_0(k,j,i), 0 ) ) &
1594	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 29 )
1595	ENDIF
1596	!
1597	!-- Special flag on scalar grid, nzb_diff_s_outer - 1, required in
1598	!-- in production_e
1599	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
1600	IF ( BTEST( wall_flags_0(k,j,i), 0 ) .AND. &
1601	BTEST( wall_flags_0(k-1,j,i), 0 ) .AND. &
1602	BTEST( wall_flags_0(k+1,j,i), 0 ) ) &
1603	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 30 )
1604	ELSE
1605	IF ( BTEST( wall_flags_0(k,j,i), 0 ) ) &
1606	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 30 )
1607	ENDIF
1608	ENDDO
1609	!
1610	!-- Flags indicating downward facing walls
1611	DO k = nzb+1, nzt
1612	!
1613	!-- Scalar grid
1614	IF ( BTEST( wall_flags_0(k-1,j,i), 0 ) .AND. &
1615	.NOT. BTEST( wall_flags_0(k,j,i), 0 ) ) &
1616	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 13 )
1617	!
1618	!-- Downward facing wall on u grid
1619	IF ( BTEST( wall_flags_0(k-1,j,i), 1 ) .AND. &
1620	.NOT. BTEST( wall_flags_0(k,j,i), 1 ) ) &
1621	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 15 )
1622	!
1623	!-- Downward facing wall on v grid
1624	IF ( BTEST( wall_flags_0(k-1,j,i), 2 ) .AND. &
1625	.NOT. BTEST( wall_flags_0(k,j,i), 2 ) ) &
1626	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 17 )
1627	!
1628	!-- Downward facing wall on w grid
1629	IF ( BTEST( wall_flags_0(k-1,j,i), 3 ) .AND. &
1630	.NOT. BTEST( wall_flags_0(k,j,i), 3 ) ) &
1631	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 19 )
1632	ENDDO
1633	!
1634	!-- Flags indicating upward facing walls
1635	DO k = nzb, nzt
1636	!
1637	!-- Upward facing wall on scalar grid
1638	IF ( .NOT. BTEST( wall_flags_0(k,j,i), 0 ) .AND. &
1639	BTEST( wall_flags_0(k+1,j,i), 0 ) ) &
1640	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 12 )
1641	!
1642	!-- Upward facing wall on u grid
1643	IF ( .NOT. BTEST( wall_flags_0(k,j,i), 1 ) .AND. &
1644	BTEST( wall_flags_0(k+1,j,i), 1 ) ) &
1645	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 14 )
1646
1647	!
1648	!-- Upward facing wall on v grid
1649	IF ( .NOT. BTEST( wall_flags_0(k,j,i), 2 ) .AND. &
1650	BTEST( wall_flags_0(k+1,j,i), 2 ) ) &
1651	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 16 )
1652
1653	!
1654	!-- Upward facing wall on w grid
1655	IF ( .NOT. BTEST( wall_flags_0(k,j,i), 3 ) .AND. &
1656	BTEST( wall_flags_0(k+1,j,i), 3 ) ) &
1657	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 18 )
1658	!
1659	!-- Special flag on scalar grid, former nzb_s_inner
1660	IF ( BTEST( wall_flags_0(k,j,i), 0 ) .OR. &
1661	BTEST( wall_flags_0(k,j,i), 12 ) .OR. &
1662	BTEST( wall_flags_0(k,j,i), 13 ) ) &
1663	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 22 )
1664	!
1665	!-- Special flag on scalar grid, nzb_diff_s_inner - 1, required for
1666	!-- flow_statistics
1667	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
1668	IF ( BTEST( wall_flags_0(k,j,i), 0 ) .AND. &
1669	BTEST( wall_flags_0(k+1,j,i), 0 ) ) &
1670	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 23 )
1671	ELSE
1672	IF ( BTEST( wall_flags_0(k,j,i), 22 ) ) &
1673	wall_flags_0(k,j,i) = IBSET( wall_flags_0(k,j,i), 23 )
1674	ENDIF
1675
1676
1677	ENDDO
1678	wall_flags_0(nzt+1,j,i) = IBSET( wall_flags_0(nzt+1,j,i), 22 )
1679	wall_flags_0(nzt+1,j,i) = IBSET( wall_flags_0(nzt+1,j,i), 23 )
1680	ENDDO
1681	ENDDO
1682	!
1683	!-- Exchange ghost points for wall flags
1684	CALL exchange_horiz_int( wall_flags_0, nbgp )
1685	!
1686	!-- Set boundary conditions also for flags. Can be interpreted as Neumann
1687	!-- boundary conditions for topography.
1688	IF ( .NOT. bc_ns_cyc ) THEN
1689	IF ( nys == 0 ) wall_flags_0(:,-1,:) = wall_flags_0(:,0,:)
1690	IF ( nyn == ny ) wall_flags_0(:,ny+1,:) = wall_flags_0(:,ny,:)
1691	ENDIF
1692	IF ( .NOT. bc_lr_cyc ) THEN
1693	IF ( nxl == 0 ) wall_flags_0(:,:,-1) = wall_flags_0(:,:,0)
1694	IF ( nxr == nx ) wall_flags_0(:,:,nx+1) = wall_flags_0(:,:,nx)
1695	ENDIF
1696
1697	!
1698	!-- Initialize boundary conditions via surface type
1699	CALL init_bc
1700	!
1701	!-- Allocate and set topography height arrays required for data output
1702	IF ( TRIM( topography ) /= 'flat' ) THEN
1703	!
1704	!-- Allocate and set the arrays containing the topography height
1705
1706	IF ( nxr == nx .AND. nyn /= ny ) THEN
1707	ALLOCATE( zu_s_inner(nxl:nxr+1,nys:nyn), &
1708	zw_w_inner(nxl:nxr+1,nys:nyn) )
1709	ELSEIF ( nxr /= nx .AND. nyn == ny ) THEN
1710	ALLOCATE( zu_s_inner(nxl:nxr,nys:nyn+1), &
1711	zw_w_inner(nxl:nxr,nys:nyn+1) )
1712	ELSEIF ( nxr == nx .AND. nyn == ny ) THEN
1713	ALLOCATE( zu_s_inner(nxl:nxr+1,nys:nyn+1), &
1714	zw_w_inner(nxl:nxr+1,nys:nyn+1) )
1715	ELSE
1716	ALLOCATE( zu_s_inner(nxl:nxr,nys:nyn), &
1717	zw_w_inner(nxl:nxr,nys:nyn) )
1718	ENDIF
1719
1720	zu_s_inner = 0.0_wp
1721	zw_w_inner = 0.0_wp
1722	!
1723	!-- Determine local topography height on scalar and w-grid. Note, setting
1724	!-- lateral boundary values is not necessary, realized via wall_flags_0
1725	!-- array. Further, please note that loop bounds are different from
1726	!-- nxl to nxr and nys to nyn on south and right model boundary, hence,
1727	!-- use intrinsic lbound and ubound functions to infer array bounds.
1728	DO i = LBOUND(zu_s_inner, 1), UBOUND(zu_s_inner, 1)
1729	DO j = LBOUND(zu_s_inner, 2), UBOUND(zu_s_inner, 2)
1730	!
1731	!-- Topography height on scalar grid. Therefore, determine index of
1732	!-- upward-facing surface element on scalar grid.
1733	zu_s_inner(i,j) = zu( get_topography_top_index( j, i, 's' ) )
1734	!
1735	!-- Topography height on w grid. Therefore, determine index of
1736	!-- upward-facing surface element on w grid.
1737	zw_w_inner(i,j) = zw( get_topography_top_index( j, i, 's' ) )
1738	ENDDO
1739	ENDDO
1740
1741	ENDIF
1742
1743	!
1744	!-- Calculate wall flag arrays for the multigrid method.
1745	!-- Please note, wall flags are only applied in the not cache-optimized
1746	!-- version.
1747	IF ( psolver == 'multigrid_noopt' ) THEN
1748
1749	!
1750	!-- Gridpoint increment of the current level.
1751	inc = 1
1752	DO l = maximum_grid_level, 1 , -1
1753	!
1754	!-- Set grid_level as it is required for exchange_horiz_2d_int
1755	grid_level = l
1756
1757	nxl_l = nxl_mg(l)
1758	nxr_l = nxr_mg(l)
1759	nys_l = nys_mg(l)
1760	nyn_l = nyn_mg(l)
1761	nzt_l = nzt_mg(l)
1762	!
1763	!-- Assign the flag level to be calculated
1764	SELECT CASE ( l )
1765	CASE ( 1 )
1766	flags => wall_flags_1
1767	CASE ( 2 )
1768	flags => wall_flags_2
1769	CASE ( 3 )
1770	flags => wall_flags_3
1771	CASE ( 4 )
1772	flags => wall_flags_4
1773	CASE ( 5 )
1774	flags => wall_flags_5
1775	CASE ( 6 )
1776	flags => wall_flags_6
1777	CASE ( 7 )
1778	flags => wall_flags_7
1779	CASE ( 8 )
1780	flags => wall_flags_8
1781	CASE ( 9 )
1782	flags => wall_flags_9
1783	CASE ( 10 )
1784	flags => wall_flags_10
1785	END SELECT
1786
1787	!
1788	!-- Depending on the grid level, set the respective bits in case of
1789	!-- neighbouring walls
1790	!-- Bit 0: wall to the bottom
1791	!-- Bit 1: wall to the top (not realized in remaining PALM code so far)
1792	!-- Bit 2: wall to the south
1793	!-- Bit 3: wall to the north
1794	!-- Bit 4: wall to the left
1795	!-- Bit 5: wall to the right
1796	!-- Bit 6: inside building
1797
1798	flags = 0
1799
1800	!
1801	!-- In case of masking method, flags are not set and multigrid method
1802	!-- works like FFT-solver
1803	IF ( .NOT. masking_method ) THEN
1804
1805	!
1806	!-- Allocate temporary array for topography heights on coarser grid
1807	!-- level. Please note, 2 ghoist points are required, in order to
1808	!-- calculate flags() on the interior ghost point.
1809	ALLOCATE( nzb_tmp(nys_l-2:nyn_l+2,nxl_l-2:nxr_l+2) )
1810	nzb_tmp = 0
1811
1812	DO i = nxl_l, nxr_l
1813	DO j = nys_l, nyn_l
1814	nzb_tmp(j,i) = nzb_local(jinc,iinc)
1815	ENDDO
1816	ENDDO
1817	!
1818	!-- Exchange ghost points on respective multigrid level. 2 ghost points
1819	!-- are required, in order to calculate flags on
1820	!-- nys_l-1 / nyn_l+1 / nxl_l-1 / nxr_l+1. The alternative would be to
1821	!-- exchange 3D-INTEGER array flags on the respective multigrid level.
1822	CALL exchange_horiz_2d_int( nzb_tmp, nys_l, nyn_l, nxl_l, nxr_l, 2 )
1823	!
1824	!-- Set non-cyclic boundary conditions on respective multigrid level
1825	IF ( .NOT. bc_ns_cyc ) THEN
1826	IF ( inflow_s .OR. outflow_s .OR. nest_bound_s ) THEN
1827	nzb_tmp(-2,:) = nzb_tmp(0,:)
1828	nzb_tmp(-1,:) = nzb_tmp(0,:)
1829	ENDIF
1830	IF ( inflow_n .OR. outflow_n .OR. nest_bound_n ) THEN
1831	nzb_tmp(nyn_l+2,:) = nzb_tmp(nyn_l,:)
1832	nzb_tmp(nyn_l+1,:) = nzb_tmp(nyn_l,:)
1833	ENDIF
1834	ENDIF
1835	IF ( .NOT. bc_lr_cyc ) THEN
1836	IF ( inflow_l .OR. outflow_l .OR. nest_bound_l ) THEN
1837	nzb_tmp(:,-2) = nzb_tmp(:,0)
1838	nzb_tmp(:,-1) = nzb_tmp(:,0)
1839	ENDIF
1840	IF ( inflow_r .OR. outflow_r .OR. nest_bound_r ) THEN
1841	nzb_tmp(:,nxr_l+1) = nzb_tmp(:,nxr_l)
1842	nzb_tmp(:,nxr_l+2) = nzb_tmp(:,nxr_l)
1843	ENDIF
1844	ENDIF
1845
1846	DO i = nxl_l-1, nxr_l+1
1847	DO j = nys_l-1, nyn_l+1
1848	DO k = nzb, nzt_l+1
1849	!
1850	!-- Inside/outside building (inside building does not need
1851	!-- further tests for walls)
1852	IF ( k*inc <= nzb_tmp(j,i) ) THEN
1853
1854	flags(k,j,i) = IBSET( flags(k,j,i), 6 )
1855
1856	ELSE
1857	!
1858	!-- Bottom wall
1859	IF ( (k-1)*inc <= nzb_tmp(j,i) ) THEN
1860	flags(k,j,i) = IBSET( flags(k,j,i), 0 )
1861	ENDIF
1862	!
1863	!-- South wall
1864	IF ( k*inc <= nzb_tmp(j-1,i) ) THEN
1865	flags(k,j,i) = IBSET( flags(k,j,i), 2 )
1866	ENDIF
1867	!
1868	!-- North wall
1869	IF ( k*inc <= nzb_tmp(j+1,i) ) THEN
1870	flags(k,j,i) = IBSET( flags(k,j,i), 3 )
1871	ENDIF
1872	!
1873	!-- Left wall
1874	IF ( k*inc <= nzb_tmp(j,i-1) ) THEN
1875	flags(k,j,i) = IBSET( flags(k,j,i), 4 )
1876	ENDIF
1877	!
1878	!-- Right wall
1879	IF ( k*inc <= nzb_tmp(j,i+1) ) THEN
1880	flags(k,j,i) = IBSET( flags(k,j,i), 5 )
1881	ENDIF
1882
1883	ENDIF
1884
1885	ENDDO
1886	ENDDO
1887	ENDDO
1888
1889	DEALLOCATE( nzb_tmp )
1890
1891	ENDIF
1892
1893	inc = inc * 2
1894
1895	ENDDO
1896	!
1897	!-- Reset grid_level to "normal" grid
1898	grid_level = 0
1899
1900	ENDIF
1901	!
1902	!-- Allocate flags needed for masking walls. Even though these flags are only
1903	!-- required in the ws-scheme, the arrays need to be allocated here as they are
1904	!-- used in OpenACC directives.
1905	ALLOCATE( advc_flags_1(nzb:nzt+1,nysg:nyng,nxlg:nxrg), &
1906	advc_flags_2(nzb:nzt+1,nysg:nyng,nxlg:nxrg) )
1907	advc_flags_1 = 0
1908	advc_flags_2 = 0
1909	!
1910	!-- Init flags for ws-scheme to degrade order of the numerics near walls, i.e.
1911	!-- to decrease the numerical stencil appropriately.
1912	IF ( momentum_advec == 'ws-scheme' .OR. scalar_advec == 'ws-scheme' &
1913	) THEN
1914	CALL ws_init_flags
1915	ENDIF
1916
1917	!
1918	!-- In case of topography: limit near-wall mixing length l_wall further:
1919	!-- Go through all points of the subdomain one by one and look for the closest
1920	!-- surface
1921	DO i = nxl, nxr
1922	DO j = nys, nyn
1923	DO k = nzb+1, nzt
1924	!
1925	!-- Check if current gridpoint belongs to the atmosphere
1926	IF ( BTEST( wall_flags_0(k,j,i), 0 ) ) THEN
1927	!
1928	!-- Check for neighbouring grid-points.
1929	!-- Vertical distance, down
1930	IF ( .NOT. BTEST( wall_flags_0(k-1,j,i), 0 ) ) &
1931	l_wall(k,j,i) = MIN( l_grid(k), zu(k) - zw(k-1) )
1932	!
1933	!-- Vertical distance, up
1934	IF ( .NOT. BTEST( wall_flags_0(k+1,j,i), 0 ) ) &
1935	l_wall(k,j,i) = MIN( l_grid(k), zw(k) - zu(k) )
1936	!
1937	!-- y-distance
1938	IF ( .NOT. BTEST( wall_flags_0(k,j-1,i), 0 ) .OR. &
1939	.NOT. BTEST( wall_flags_0(k,j+1,i), 0 ) ) &
1940	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), 0.5_wp * dy )
1941	!
1942	!-- x-distance
1943	IF ( .NOT. BTEST( wall_flags_0(k,j,i-1), 0 ) .OR. &
1944	.NOT. BTEST( wall_flags_0(k,j,i+1), 0 ) ) &
1945	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), 0.5_wp * dx )
1946	!
1947	!-- yz-distance (vertical edges, down)
1948	IF ( .NOT. BTEST( wall_flags_0(k-1,j-1,i), 0 ) .OR. &
1949	.NOT. BTEST( wall_flags_0(k-1,j+1,i), 0 ) ) &
1950	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), &
1951	SQRT( 0.25_wp * dy**2 + &
1952	( zu(k) - zw(k-1) )**2 ) )
1953	!
1954	!-- yz-distance (vertical edges, up)
1955	IF ( .NOT. BTEST( wall_flags_0(k+1,j-1,i), 0 ) .OR. &
1956	.NOT. BTEST( wall_flags_0(k+1,j+1,i), 0 ) ) &
1957	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), &
1958	SQRT( 0.25_wp * dy**2 + &
1959	( zw(k) - zu(k) )**2 ) )
1960	!
1961	!-- xz-distance (vertical edges, down)
1962	IF ( .NOT. BTEST( wall_flags_0(k-1,j,i-1), 0 ) .OR. &
1963	.NOT. BTEST( wall_flags_0(k-1,j,i+1), 0 ) ) &
1964	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), &
1965	SQRT( 0.25_wp * dx**2 + &
1966	( zu(k) - zw(k-1) )**2 ) )
1967	!
1968	!-- xz-distance (vertical edges, up)
1969	IF ( .NOT. BTEST( wall_flags_0(k+1,j,i-1), 0 ) .OR. &
1970	.NOT. BTEST( wall_flags_0(k+1,j,i+1), 0 ) ) &
1971	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), &
1972	SQRT( 0.25_wp * dx**2 + &
1973	( zw(k) - zu(k) )**2 ) )
1974	!
1975	!-- xy-distance (horizontal edges)
1976	IF ( .NOT. BTEST( wall_flags_0(k,j-1,i-1), 0 ) .OR. &
1977	.NOT. BTEST( wall_flags_0(k,j+1,i-1), 0 ) .OR. &
1978	.NOT. BTEST( wall_flags_0(k,j-1,i+1), 0 ) .OR. &
1979	.NOT. BTEST( wall_flags_0(k,j+1,i+1), 0 ) ) &
1980	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), &
1981	SQRT( 0.25_wp * ( dx2 + dy2 ) ) )
1982	!
1983	!-- xyz distance (vertical and horizontal edges, down)
1984	IF ( .NOT. BTEST( wall_flags_0(k-1,j-1,i-1), 0 ) .OR. &
1985	.NOT. BTEST( wall_flags_0(k-1,j+1,i-1), 0 ) .OR. &
1986	.NOT. BTEST( wall_flags_0(k-1,j-1,i+1), 0 ) .OR. &
1987	.NOT. BTEST( wall_flags_0(k-1,j+1,i+1), 0 ) ) &
1988	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), &
1989	SQRT( 0.25_wp * ( dx2 + dy2 ) &
1990	+ ( zu(k) - zw(k-1) )**2 ) )
1991	!
1992	!-- xyz distance (vertical and horizontal edges, up)
1993	IF ( .NOT. BTEST( wall_flags_0(k+1,j-1,i-1), 0 ) .OR. &
1994	.NOT. BTEST( wall_flags_0(k+1,j+1,i-1), 0 ) .OR. &
1995	.NOT. BTEST( wall_flags_0(k+1,j-1,i+1), 0 ) .OR. &
1996	.NOT. BTEST( wall_flags_0(k+1,j+1,i+1), 0 ) ) &
1997	l_wall(k,j,i) = MIN( l_wall(k,j,i), l_grid(k), &
1998	SQRT( 0.25_wp * ( dx2 + dy2 ) &
1999	+ ( zw(k) - zu(k) )**2 ) )
2000
2001	ENDIF
2002	ENDDO
2003	ENDDO
2004	ENDDO
2005	!
2006	!-- Set lateral boundary conditions for l_wall
2007	CALL exchange_horiz( l_wall, nbgp )
2008
2009	!
2010	!-- Vertical nesting: communicate vertical grid level arrays between fine and
2011	!-- coarse grid
2012	IF ( vnested ) CALL vnest_init_grid
2013
2014	END SUBROUTINE init_grid

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