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source: palm/trunk/SOURCE/init_grid.f90 @ 4572

Last change on this file since 4572 was 4564, checked in by raasch, 4 years ago
Vertical nesting method of Huq et al. (2019) removed
Property svn:keywords set to `Id`
File size: 118.1 KB

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1	!> @file init_grid.f90
2	!------------------------------------------------------------------------------!
3	! This file is part of the PALM model system.
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 1997-2020 Leibniz Universitaet Hannover
18	!------------------------------------------------------------------------------!
19	!
20	! Current revisions:
21	! -----------------
22	!
23	!
24	! Former revisions:
25	! -----------------
26	! $Id: init_grid.f90 4564 2020-06-12 14:03:36Z gronemeier $
27	! Vertical nesting method of Huq et al. (2019) removed
28	!
29	! 4543 2020-05-20 14:12:22Z gronemeier
30	! Remove non-required check for canyon height
31	!
32	! 4507 2020-04-22 18:21:45Z gronemeier
33	! update origin_z with shifting height of orography (oro_min)
34	!
35	! 4457 2020-03-11 14:20:43Z raasch
36	! use statement for exchange horiz added,
37	! bugfix for call of exchange horiz 2d
38	!
39	! 4444 2020-03-05 15:59:50Z raasch
40	! bugfix: cpp-directives for serial mode added
41	!
42	! 4414 2020-02-19 20:16:04Z suehring
43	! - Remove deprecated topography arrays nzb_s_inner, nzb_u_inner, etc.
44	! - Move initialization of boundary conditions and multigrid into an extra
45	! module interface.
46	!
47	! 4386 2020-01-27 15:07:30Z Giersch
48	! Allocation statements, comments, naming of variables revised and _wp added to
49	! real type values
50	!
51	! 4360 2020-01-07 11:25:50Z suehring
52	! Revise error messages for generic tunnel setup.
53	!
54	! 4346 2019-12-18 11:55:56Z motisi
55	! Introduction of wall_flags_total_0, which currently sets bits based on static
56	! topography information used in wall_flags_static_0
57	!
58	! 4340 2019-12-16 08:17:03Z Giersch
59	! Topography closed channel flow with symmetric boundaries implemented
60	!
61	! 4329 2019-12-10 15:46:36Z motisi
62	! Renamed wall_flags_0 to wall_flags_static_0
63	!
64	! 4328 2019-12-09 18:53:04Z suehring
65	! Minor change in nzb_max computation. Commentation added.
66	!
67	! 4314 2019-11-29 10:29:20Z suehring
68	! Set additional topography flag 4 to mark topography grid points emerged
69	! from the filtering process.
70	!
71	! 4294 2019-11-13 18:34:16Z suehring
72	! Bugfix, always set bit 5 and 6 of wall_flags, indicating terrain- and
73	! building surfaces in all cases, in order to enable terrain-following output
74	! also when no land- or urban-surface model is applied.
75	!
76	! 4265 2019-10-15 16:16:24Z suehring
77	! Bugfix for last commit, exchange oro_max variable only when it is allocated
78	! (not necessarily the case when topography is input from ASCII file).
79	!
80	! 4245 2019-09-30 08:40:37Z pavelkrc
81	! Store oro_max (building z-offset) in 2D for building surfaces
82	!
83	! 4189 2019-08-26 16:19:38Z suehring
84	! - Add check for proper setting of namelist parameter topography
85	! - Set flag to indicate land surfaces in case no topography is provided
86	!
87	! 4182 2019-08-22 15:20:23Z scharf
88	! Corrected "Former revisions" section
89	!
90	! 4168 2019-08-16 13:50:17Z suehring
91	! Pre-calculate topography top index and store it on an array (replaces former
92	! functions get_topography_top_index)
93	!
94	! 4159 2019-08-15 13:31:35Z suehring
95	! Revision of topography processing. This was not consistent between 2D and 3D
96	! buildings.
97	!
98	! 4144 2019-08-06 09:11:47Z raasch
99	! relational operators .EQ., .NE., etc. replaced by ==, /=, etc.
100	!
101	! 4115 2019-07-24 12:50:49Z suehring
102	! Bugfix in setting near-surface flag 24, inidicating wall-bounded grid points
103	!
104	! 4110 2019-07-22 17:05:21Z suehring
105	! - Separate initialization of advection flags for momentum and scalars.
106	! - Change subroutine interface for ws_init_flags_scalar to pass boundary flags
107	!
108	! 4109 2019-07-22 17:00:34Z suehring
109	! Fix bad commit
110	!
111	! 3926 2019-04-23 12:56:42Z suehring
112	! Minor bugfix in building mapping when all building IDs in the model domain
113	! are missing
114	!
115	! 3857 2019-04-03 13:00:16Z knoop
116	! In projection of non-building 3D objects onto numerical grid remove
117	! dependency on building_type
118	!
119	! 3763 2019-02-25 17:33:49Z suehring
120	! Replace work-around for ghost point exchange of 1-byte arrays with specific
121	! routine as already done in other routines
122	!
123	! 3761 2019-02-25 15:31:42Z raasch
124	! unused variables removed
125	!
126	! 3661 2019-01-08 18:22:50Z suehring
127	! Remove setting of nzb_max to nzt at non-cyclic boundary PEs, instead,
128	! order degradation of advection scheme is handeled directly in advec_ws
129	!
130	! 3655 2019-01-07 16:51:22Z knoop
131	! Comment added
132	!
133	! Revision 1.1 1997/08/11 06:17:45 raasch
134	! Initial revision (Testversion)
135	!
136	!
137	! Description:
138	! -----------------------------------------------------------------------------!
139	!> Creating grid depending constants
140	!> @todo: Rearrange topo flag list
141	!> @todo: reference 3D buildings on top of orography is not tested and may need
142	!> further improvement for steep slopes
143	!> @todo: Use more advanced setting of building type at filled holes
144	!------------------------------------------------------------------------------!
145	SUBROUTINE init_grid
146
147	USE arrays_3d, &
148	ONLY: dd2zu, ddzu, ddzu_pres, ddzw, dzu, dzw, x, xu, y, yv, zu, zw
149
150	USE control_parameters, &
151	ONLY: constant_flux_layer, dz, dz_max, dz_stretch_factor, &
152	dz_stretch_factor_array, dz_stretch_level, dz_stretch_level_end,&
153	dz_stretch_level_end_index, dz_stretch_level_start_index, &
154	dz_stretch_level_start, ibc_uv_b, message_string, &
155	number_stretch_level_end, &
156	number_stretch_level_start, &
157	ocean_mode, &
158	psolver, &
159	symmetry_flag, &
160	topography, &
161	use_surface_fluxes
162
163	USE grid_variables, &
164	ONLY: ddx, ddx2, ddy, ddy2, dx, dx2, dy, dy2, zu_s_inner, zw_w_inner
165
166	USE indices, &
167	ONLY: nbgp, &
168	nx, &
169	nxl, &
170	nxlg, &
171	nxr, &
172	nxrg, &
173	ny, &
174	nyn, &
175	nyng, &
176	nys, &
177	nysg, &
178	nz, &
179	nzb, &
180	nzb_diff, &
181	nzb_max, &
182	nzt, &
183	topo_top_ind, &
184	topo_min_level
185
186	USE kinds
187
188	USE pegrid
189
190	IMPLICIT NONE
191
192	INTEGER(iwp) :: i !< index variable along x
193	INTEGER(iwp) :: j !< index variable along y
194	INTEGER(iwp) :: k !< index variable along z
195	INTEGER(iwp) :: k_top !< topography top index on local PE
196	INTEGER(iwp) :: n !< loop variable for stretching
197	INTEGER(iwp) :: number_dz !< number of user-specified dz values
198	INTEGER(iwp) :: nzb_local_max !< vertical grid index of maximum topography height
199	INTEGER(iwp) :: nzb_local_min !< vertical grid index of minimum topography height
200
201	INTEGER(iwp), DIMENSION(:,:,:), ALLOCATABLE :: topo !< input array for 3D topography and dummy array for setting "outer"-flags
202
203	REAL(wp) :: dz_level_end !< distance between calculated height level for u/v-grid and user-specified end level for stretching
204	REAL(wp) :: dz_stretched !< stretched vertical grid spacing
205
206	REAL(wp), DIMENSION(:), ALLOCATABLE :: min_dz_stretch_level_end !< Array that contains all minimum heights where the stretching can end
207
208
209	!
210	!-- Calculation of horizontal array bounds including ghost layers
211	nxlg = nxl - nbgp
212	nxrg = nxr + nbgp
213	nysg = nys - nbgp
214	nyng = nyn + nbgp
215
216	!
217	!-- Allocate grid arrays
218	ALLOCATE( x(0:nx) )
219	ALLOCATE( xu(0:nx) )
220
221	DO i = 0, nx
222	xu(i) = i * dx
223	x(i) = i * dx + 0.5_wp * dx
224	ENDDO
225
226	ALLOCATE( y(0:ny) )
227	ALLOCATE( yv(0:ny) )
228
229	DO j = 0, ny
230	yv(j) = j * dy
231	y(j) = j * dy + 0.5_wp * dy
232	ENDDO
233
234	ALLOCATE( ddzu(1:nzt+1) )
235	ALLOCATE( ddzw(1:nzt+1) )
236	ALLOCATE( dd2zu(1:nzt) )
237	ALLOCATE( dzu(1:nzt+1) )
238	ALLOCATE( dzw(1:nzt+1) )
239	ALLOCATE( zu(nzb:nzt+1) )
240	ALLOCATE( zw(nzb:nzt+1) )
241
242	!
243	!-- For constructing an appropriate grid, the vertical grid spacing dz has to
244	!-- be specified with a non-negative value in the parameter file
245	IF ( dz(1) == -1.0_wp ) THEN
246	message_string = 'missing dz'
247	CALL message( 'init_grid', 'PA0200', 1, 2, 0, 6, 0 )
248	ELSEIF ( dz(1) <= 0.0_wp ) THEN
249	WRITE( message_string, * ) 'dz=',dz(1),' <= 0.0'
250	CALL message( 'init_grid', 'PA0201', 1, 2, 0, 6, 0 )
251	ENDIF
252
253	!
254	!-- Initialize dz_stretch_level_start with the value of dz_stretch_level
255	!-- if it was set by the user
256	IF ( dz_stretch_level /= -9999999.9_wp ) THEN
257	dz_stretch_level_start(1) = dz_stretch_level
258	ENDIF
259
260	!
261	!-- Determine number of dz values and stretching levels specified by the
262	!-- user to allow right controlling of the stretching mechanism and to
263	!-- perform error checks. The additional requirement that dz /= dz_max
264	!-- for counting number of user-specified dz values is necessary. Otherwise
265	!-- restarts would abort if the old stretching mechanism with dz_stretch_level
266	!-- is used (Attention: The user is not allowed to specify a dz value equal
267	!-- to the default of dz_max = 999.0).
268	number_dz = COUNT( dz /= -1.0_wp .AND. dz /= dz_max)
269	number_stretch_level_start = COUNT( dz_stretch_level_start /= &
270	-9999999.9_wp )
271	number_stretch_level_end = COUNT( dz_stretch_level_end /= &
272	9999999.9_wp )
273
274	!
275	!-- The number of specified end levels +1 has to be the same as the number
276	!-- of specified dz values
277	IF ( number_dz /= number_stretch_level_end + 1 ) THEN
278	WRITE( message_string, * ) 'The number of values for dz = ', &
279	number_dz, 'has to be the same as& ', &
280	'the number of values for ', &
281	'dz_stretch_level_end + 1 = ', &
282	number_stretch_level_end+1
283	CALL message( 'init_grid', 'PA0156', 1, 2, 0, 6, 0 )
284	ENDIF
285
286	!
287	!-- The number of specified start levels has to be the same or one less than
288	!-- the number of specified dz values
289	IF ( number_dz /= number_stretch_level_start + 1 .AND. &
290	number_dz /= number_stretch_level_start ) THEN
291	WRITE( message_string, * ) 'The number of values for dz = ', &
292	number_dz, 'has to be the same as or one ', &
293	'more than& the number of values for ', &
294	'dz_stretch_level_start = ', &
295	number_stretch_level_start
296	CALL message( 'init_grid', 'PA0211', 1, 2, 0, 6, 0 )
297	ENDIF
298
299	!-- The number of specified start levels has to be the same or one more than
300	!-- the number of specified end levels
301	IF ( number_stretch_level_start /= number_stretch_level_end + 1 .AND. &
302	number_stretch_level_start /= number_stretch_level_end ) THEN
303	WRITE( message_string, * ) 'The number of values for ', &
304	'dz_stretch_level_start = ', &
305	dz_stretch_level_start, 'has to be the ', &
306	'same or one more than& the number of ', &
307	'values for dz_stretch_level_end = ', &
308	number_stretch_level_end
309	CALL message( 'init_grid', 'PA0216', 1, 2, 0, 6, 0 )
310	ENDIF
311
312	!
313	!-- Initialize dz for the free atmosphere with the value of dz_max
314	IF ( dz(number_stretch_level_start+1) == -1.0_wp .AND. &
315	number_stretch_level_start /= 0 ) THEN
316	dz(number_stretch_level_start+1) = dz_max
317	ENDIF
318
319	!
320	!-- Initialize the stretching factor if (infinitely) stretching in the free
321	!-- atmosphere is desired (dz_stretch_level_end was not specified for the
322	!-- free atmosphere)
323	IF ( number_stretch_level_start == number_stretch_level_end + 1 ) THEN
324	dz_stretch_factor_array(number_stretch_level_start) = &
325	dz_stretch_factor
326	ENDIF
327
328	!
329	!-- Allocation of arrays for stretching
330	ALLOCATE( min_dz_stretch_level_end(number_stretch_level_start) )
331
332	!
333	!-- Define the vertical grid levels. Start with atmosphere branch
334	IF ( .NOT. ocean_mode ) THEN
335
336	!
337	!-- The stretching region has to be large enough to allow for a smooth
338	!-- transition between two different grid spacings. The number 4 is an
339	!-- empirical value
340	DO n = 1, number_stretch_level_start
341	min_dz_stretch_level_end(n) = dz_stretch_level_start(n) + &
342	4 * MAX( dz(n),dz(n+1) )
343	ENDDO
344
345	IF ( ANY( min_dz_stretch_level_end(1:number_stretch_level_start) > &
346	dz_stretch_level_end(1:number_stretch_level_start) ) ) THEN
347	message_string= 'Each dz_stretch_level_end has to be larger ' // &
348	'than its corresponding value for &' // &
349	'dz_stretch_level_start + 4*MAX(dz(n),dz(n+1)) '//&
350	'to allow for smooth grid stretching'
351	CALL message( 'init_grid', 'PA0224', 1, 2, 0, 6, 0 )
352	ENDIF
353
354	!
355	!-- Stretching must not be applied within the surface layer
356	!-- (first two grid points). For the default case dz_stretch_level_start
357	!-- is negative. Therefore the absolut value is checked here.
358	IF ( ANY( ABS( dz_stretch_level_start ) <= dz(1) * 1.5_wp ) ) THEN
359	WRITE( message_string, * ) 'Each dz_stretch_level_start has to be ',&
360	'larger than ', dz(1) * 1.5
361	CALL message( 'init_grid', 'PA0226', 1, 2, 0, 6, 0 )
362	ENDIF
363
364	!
365	!-- The stretching has to start and end on a grid level. Therefore
366	!-- user-specified values are mapped to the next lowest level. The
367	!-- calculation of the first level is realized differently just because of
368	!-- historical reasons (the advanced/new stretching mechanism was realized
369	!-- in a way that results don't change if the old parameters
370	!-- dz_stretch_level, dz_stretch_factor and dz_max are used)
371	IF ( number_stretch_level_start /= 0 ) THEN
372	dz_stretch_level_start(1) = INT( (dz_stretch_level_start(1) - &
373	dz(1)/2.0) / dz(1) ) &
374	* dz(1) + dz(1)/2.0
375	ENDIF
376
377	IF ( number_stretch_level_start > 1 ) THEN
378	DO n = 2, number_stretch_level_start
379	dz_stretch_level_start(n) = INT( dz_stretch_level_start(n) / &
380	dz(n) ) * dz(n)
381	ENDDO
382	ENDIF
383
384	IF ( number_stretch_level_end /= 0 ) THEN
385	DO n = 1, number_stretch_level_end
386	dz_stretch_level_end(n) = INT( dz_stretch_level_end(n) / &
387	dz(n+1) ) * dz(n+1)
388	ENDDO
389	ENDIF
390
391	!
392	!-- Determine stretching factor if necessary
393	IF ( number_stretch_level_end >= 1 ) THEN
394	CALL calculate_stretching_factor( number_stretch_level_end )
395	ENDIF
396
397	!
398	!-- Grid for atmosphere with surface at z=0 (k=0, w-grid).
399	!-- First compute the u- and v-levels. In case of dirichlet bc for u and v
400	!-- the first u/v- and w-level (k=0) are defined at same height (z=0).
401	!-- The second u-level (k=1) corresponds to the top of the
402	!-- surface layer. In case of symmetric boundaries (closed channel flow),
403	!-- the first grid point is always at z=0.
404	IF ( ibc_uv_b == 0 .OR. ibc_uv_b == 2 .OR. &
405	topography == 'closed_channel' ) THEN
406	zu(0) = 0.0_wp
407	ELSE
408	zu(0) = - dz(1) * 0.5_wp
409	ENDIF
410
411	zu(1) = dz(1) * 0.5_wp
412
413	!
414	!-- Determine u and v height levels considering the possibility of grid
415	!-- stretching in several heights.
416	n = 1
417	dz_stretch_level_start_index = nzt+1
418	dz_stretch_level_end_index = nzt+1
419	dz_stretched = dz(1)
420
421	!-- The default value of dz_stretch_level_start is negative, thus the first
422	!-- condition is true even if no stretching shall be applied. Hence, the
423	!-- second condition is also necessary.
424	DO k = 2, nzt+1-symmetry_flag
425	IF ( dz_stretch_level_start(n) <= zu(k-1) .AND. &
426	dz_stretch_level_start(n) /= -9999999.9_wp ) THEN
427	dz_stretched = dz_stretched * dz_stretch_factor_array(n)
428
429	IF ( dz(n) > dz(n+1) ) THEN
430	dz_stretched = MAX( dz_stretched, dz(n+1) ) !Restrict dz_stretched to the user-specified (higher) dz
431	ELSE
432	dz_stretched = MIN( dz_stretched, dz(n+1) ) !Restrict dz_stretched to the user-specified (lower) dz
433	ENDIF
434
435	IF ( dz_stretch_level_start_index(n) == nzt+1 ) &
436	dz_stretch_level_start_index(n) = k-1
437
438	ENDIF
439
440	zu(k) = zu(k-1) + dz_stretched
441
442	!
443	!-- Make sure that the stretching ends exactly at dz_stretch_level_end
444	dz_level_end = ABS( zu(k) - dz_stretch_level_end(n) )
445
446	IF ( dz_level_end < dz(n+1)/3.0 ) THEN
447	zu(k) = dz_stretch_level_end(n)
448	dz_stretched = dz(n+1)
449	dz_stretch_level_end_index(n) = k
450	n = n + 1
451	ENDIF
452	ENDDO
453
454	!
455	!-- If a closed channel flow is simulated, make sure that grid structure is
456	!-- the same for both bottom and top boundary. (Hint: Using a different dz
457	!-- at the bottom and at the top makes no sense due to symmetric boundaries
458	!-- where dz should be equal. Therefore, different dz at the bottom and top
459	!-- causes an abort (see check_parameters).)
460	IF ( topography == 'closed_channel' ) THEN
461	zu(nzt+1) = zu(nzt) + dz(1) * 0.5_wp
462	ENDIF
463
464	!
465	!-- Compute the w-levels. They are always staggered half-way between the
466	!-- corresponding u-levels. In case of dirichlet bc for u and v at the
467	!-- ground the first u- and w-level (k=0) are defined at same height (z=0).
468	!-- Per default, the top w-level is extrapolated linearly. In case of
469	!-- a closed channel flow, zu(nzt+1) and zw(nzt) must be set explicitely.
470	!-- (Hint: Using a different dz at the bottom and at the top makes no sense
471	!-- due to symmetric boundaries where dz should be equal. Therefore,
472	!-- different dz at the bottom and top causes an abort (see
473	!-- check_parameters).)
474	zw(0) = 0.0_wp
475	DO k = 1, nzt-symmetry_flag
476	zw(k) = ( zu(k) + zu(k+1) ) * 0.5_wp
477	ENDDO
478	IF ( topography == 'closed_channel' ) THEN
479	zw(nzt) = zw(nzt-1) + dz(1)
480	zw(nzt+1) = zw(nzt) + dz(1)
481	ELSE
482	zw(nzt+1) = zw(nzt) + 2.0_wp * ( zu(nzt+1) - zw(nzt) )
483	ENDIF
484
485	ELSE !ocean branch
486
487	!
488	!-- The stretching region has to be large enough to allow for a smooth
489	!-- transition between two different grid spacings. The number 4 is an
490	!-- empirical value
491	DO n = 1, number_stretch_level_start
492	min_dz_stretch_level_end(n) = dz_stretch_level_start(n) - &
493	4 * MAX( dz(n),dz(n+1) )
494	ENDDO
495
496	IF ( ANY( min_dz_stretch_level_end (1:number_stretch_level_start) < &
497	dz_stretch_level_end(1:number_stretch_level_start) ) ) THEN
498	message_string= 'Each dz_stretch_level_end has to be less ' // &
499	'than its corresponding value for &' // &
500	'dz_stretch_level_start - 4*MAX(dz(n),dz(n+1)) '//&
501	'to allow for smooth grid stretching'
502	CALL message( 'init_grid', 'PA0224', 1, 2, 0, 6, 0 )
503	ENDIF
504
505	!
506	!-- Stretching must not be applied close to the surface (last two grid
507	!-- points). For the default case dz_stretch_level_start is negative.
508	IF ( ANY( dz_stretch_level_start >= - dz(1) * 1.5_wp ) ) THEN
509	WRITE( message_string, * ) 'Each dz_stretch_level_start has to be ',&
510	'less than ', -dz(1) * 1.5
511	CALL message( 'init_grid', 'PA0226', 1, 2, 0, 6, 0 )
512	ENDIF
513
514	!
515	!-- The stretching has to start and end on a grid level. Therefore
516	!-- user-specified values are mapped to the next highest level. The
517	!-- calculation of the first level is realized differently just because of
518	!-- historical reasons (the advanced/new stretching mechanism was realized
519	!-- in a way that results don't change if the old parameters
520	!-- dz_stretch_level, dz_stretch_factor and dz_max are used)
521	IF ( number_stretch_level_start /= 0 ) THEN
522	dz_stretch_level_start(1) = INT( (dz_stretch_level_start(1) + &
523	dz(1)/2.0) / dz(1) ) &
524	* dz(1) - dz(1)/2.0
525	ENDIF
526
527	IF ( number_stretch_level_start > 1 ) THEN
528	DO n = 2, number_stretch_level_start
529	dz_stretch_level_start(n) = INT( dz_stretch_level_start(n) / &
530	dz(n) ) * dz(n)
531	ENDDO
532	ENDIF
533
534	IF ( number_stretch_level_end /= 0 ) THEN
535	DO n = 1, number_stretch_level_end
536	dz_stretch_level_end(n) = INT( dz_stretch_level_end(n) / &
537	dz(n+1) ) * dz(n+1)
538	ENDDO
539	ENDIF
540
541	!
542	!-- Determine stretching factor if necessary
543	IF ( number_stretch_level_end >= 1 ) THEN
544	CALL calculate_stretching_factor( number_stretch_level_end )
545	ENDIF
546
547	!
548	!-- Grid for ocean with free water surface is at k=nzt (w-grid).
549	!-- In case of neumann bc at the ground the first first u-level (k=0) lies
550	!-- below the first w-level (k=0). In case of dirichlet bc the first u- and
551	!-- w-level are defined at same height, but staggered from the second level.
552	!-- The second u-level (k=1) corresponds to the top of the surface layer.
553	!-- z values are negative starting from z=0 (surface)
554	zu(nzt+1) = dz(1) * 0.5_wp
555	zu(nzt) = - dz(1) * 0.5_wp
556
557	!
558	!-- Determine u and v height levels considering the possibility of grid
559	!-- stretching in several heights.
560	n = 1
561	dz_stretch_level_start_index = 0
562	dz_stretch_level_end_index = 0
563	dz_stretched = dz(1)
564
565	DO k = nzt-1, 0, -1
566
567	IF ( dz_stretch_level_start(n) >= zu(k+1) ) THEN
568	dz_stretched = dz_stretched * dz_stretch_factor_array(n)
569
570	IF ( dz(n) > dz(n+1) ) THEN
571	dz_stretched = MAX( dz_stretched, dz(n+1) ) !Restrict dz_stretched to the user-specified (higher) dz
572	ELSE
573	dz_stretched = MIN( dz_stretched, dz(n+1) ) !Restrict dz_stretched to the user-specified (lower) dz
574	ENDIF
575
576	IF ( dz_stretch_level_start_index(n) == 0 ) &
577	dz_stretch_level_start_index(n) = k+1
578
579	ENDIF
580
581	zu(k) = zu(k+1) - dz_stretched
582
583	!
584	!-- Make sure that the stretching ends exactly at dz_stretch_level_end
585	dz_level_end = ABS( zu(k) - dz_stretch_level_end(n) )
586
587	IF ( dz_level_end < dz(n+1)/3.0 ) THEN
588	zu(k) = dz_stretch_level_end(n)
589	dz_stretched = dz(n+1)
590	dz_stretch_level_end_index(n) = k
591	n = n + 1
592	ENDIF
593	ENDDO
594
595	!
596	!-- Compute the w-levels. They are always staggered half-way between the
597	!-- corresponding u-levels, except in case of dirichlet bc for u and v
598	!-- at the ground. In this case the first u- and w-level are defined at
599	!-- same height. The top w-level (nzt+1) is not used but set for
600	!-- consistency, since w and all scalar variables are defined up tp nzt+1.
601	zw(nzt+1) = dz(1)
602	zw(nzt) = 0.0_wp
603	DO k = 0, nzt
604	zw(k) = ( zu(k) + zu(k+1) ) * 0.5_wp
605	ENDDO
606
607	!
608	!-- In case of dirichlet bc for u and v the first u- and w-level are defined
609	!-- at same height.
610	IF ( ibc_uv_b == 0 ) THEN
611	zu(0) = zw(0)
612	ENDIF
613
614	ENDIF !End of defining the vertical grid levels
615
616	!
617	!-- Compute grid lengths.
618	DO k = 1, nzt+1
619	dzu(k) = zu(k) - zu(k-1)
620	ddzu(k) = 1.0_wp / dzu(k)
621	dzw(k) = zw(k) - zw(k-1)
622	ddzw(k) = 1.0_wp / dzw(k)
623	ENDDO
624
625	DO k = 1, nzt
626	dd2zu(k) = 1.0_wp / ( dzu(k) + dzu(k+1) )
627	ENDDO
628
629	!
630	!-- The FFT- SOR-pressure solvers assume grid spacings of a staggered grid
631	!-- everywhere. For the actual grid, the grid spacing at the lowest level
632	!-- is only dz/2, but should be dz. Therefore, an additional array
633	!-- containing with appropriate grid information is created for these
634	!-- solvers.
635	IF ( psolver(1:9) /= 'multigrid' ) THEN
636	ALLOCATE( ddzu_pres(1:nzt+1) )
637	ddzu_pres = ddzu
638	ddzu_pres(1) = ddzu_pres(2) ! change for lowest level
639	ENDIF
640
641	!
642	!-- Compute the reciprocal values of the horizontal grid lengths.
643	ddx = 1.0_wp / dx
644	ddy = 1.0_wp / dy
645	dx2 = dx * dx
646	dy2 = dy * dy
647	ddx2 = 1.0_wp / dx2
648	ddy2 = 1.0_wp / dy2
649
650	!
651	!-- Allocate 3D array to set topography
652	ALLOCATE( topo(nzb:nzt+1,nysg:nyng,nxlg:nxrg) )
653	topo = 0
654	!
655	!-- Initialize topography by generic topography or read topography from file.
656	CALL init_topo( topo )
657	!
658	!-- Set flags to mask topography on the grid.
659	CALL set_topo_flags( topo )
660
661	!
662	!-- Determine the maximum level of topography. It is used for
663	!-- steering the degradation of order of the applied advection scheme,
664	!-- as well in the lpm.
665	k_top = 0
666	DO i = nxl, nxr
667	DO j = nys, nyn
668	DO k = nzb, nzt + 1
669	k_top = MAX( k_top, MERGE( k, 0, .NOT. BTEST( topo(k,j,i), 0 ) ) )
670	ENDDO
671	ENDDO
672	ENDDO
673	#if defined( __parallel )
674	CALL MPI_ALLREDUCE( k_top, nzb_max, 1, MPI_INTEGER, &
675	MPI_MAX, comm2d, ierr )
676	#else
677	nzb_max = k_top
678	#endif
679	!
680	!-- Increment nzb_max by 1 in order to allow for proper diverengence correction.
681	!-- Further, in case topography extents up to the model top, limit to nzt.
682	nzb_max = MIN( nzb_max+1, nzt )
683	!
684	!-- Determine minimum index of topography. Usually, this will be nzb. In case
685	!-- there is elevated topography, however, the lowest topography will be higher.
686	!-- This index is e.g. used to calculate mean first-grid point atmosphere
687	!-- temperature, surface pressure and density, etc. .
688	topo_min_level = 0
689	#if defined( __parallel )
690	CALL MPI_ALLREDUCE( MINVAL( topo_top_ind(nys:nyn,nxl:nxr,0) ), &
691	topo_min_level, 1, MPI_INTEGER, MPI_MIN, comm2d, ierr )
692	#else
693	topo_min_level = MINVAL( topo_top_ind(nys:nyn,nxl:nxr,0) )
694	#endif
695
696	!
697	!-- Check topography for consistency with model domain. Therefore, use
698	!-- maximum and minium topography-top indices. Note, minimum topography top
699	!-- index is already calculated.
700	IF ( TRIM( topography ) /= 'flat' ) THEN
701	#if defined( __parallel )
702	CALL MPI_ALLREDUCE( MAXVAL( topo_top_ind(nys:nyn,nxl:nxr,0) ), &
703	nzb_local_max, 1, MPI_INTEGER, MPI_MAX, comm2d, ierr )
704	#else
705	nzb_local_max = MAXVAL( topo_top_ind(nys:nyn,nxl:nxr,0) )
706	#endif
707	nzb_local_min = topo_min_level
708	!
709	!-- Consistency checks
710	IF ( nzb_local_min < 0 .OR. nzb_local_max > nz + 1 ) THEN
711	WRITE( message_string, * ) 'nzb_local values are outside the', &
712	' model domain', &
713	'&MINVAL( nzb_local ) = ', nzb_local_min, &
714	'&MAXVAL( nzb_local ) = ', nzb_local_max
715	CALL message( 'init_grid', 'PA0210', 1, 2, 0, 6, 0 )
716	ENDIF
717	ENDIF
718	!
719	!-- Define vertical gridpoint from (or to) which on the usual finite difference
720	!-- form (which does not use surface fluxes) is applied
721	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
722	nzb_diff = nzb + 2
723	ELSE
724	nzb_diff = nzb + 1
725	ENDIF
726
727	IF ( TRIM( topography ) /= 'flat' ) THEN
728	!
729	!-- Allocate and set the arrays containing the topography height (for output
730	!-- reasons only).
731	IF ( nxr == nx .AND. nyn /= ny ) THEN
732	ALLOCATE( zu_s_inner(nxl:nxr+1,nys:nyn), &
733	zw_w_inner(nxl:nxr+1,nys:nyn) )
734	ELSEIF ( nxr /= nx .AND. nyn == ny ) THEN
735	ALLOCATE( zu_s_inner(nxl:nxr,nys:nyn+1), &
736	zw_w_inner(nxl:nxr,nys:nyn+1) )
737	ELSEIF ( nxr == nx .AND. nyn == ny ) THEN
738	ALLOCATE( zu_s_inner(nxl:nxr+1,nys:nyn+1), &
739	zw_w_inner(nxl:nxr+1,nys:nyn+1) )
740	ELSE
741	ALLOCATE( zu_s_inner(nxl:nxr,nys:nyn), &
742	zw_w_inner(nxl:nxr,nys:nyn) )
743	ENDIF
744
745	zu_s_inner = 0.0_wp
746	zw_w_inner = 0.0_wp
747	!
748	!-- Determine local topography height on scalar and w-grid. Note, setting
749	!-- lateral boundary values is not necessary, realized via wall_flags_static_0
750	!-- array. Further, please note that loop bounds are different from
751	!-- nxl to nxr and nys to nyn on south and right model boundary, hence,
752	!-- use intrinsic lbound and ubound functions to infer array bounds.
753	DO i = LBOUND(zu_s_inner, 1), UBOUND(zu_s_inner, 1)
754	DO j = LBOUND(zu_s_inner, 2), UBOUND(zu_s_inner, 2)
755	!
756	!-- Topography height on scalar grid. Therefore, determine index of
757	!-- upward-facing surface element on scalar grid.
758	zu_s_inner(i,j) = zu(topo_top_ind(j,i,0))
759	!
760	!-- Topography height on w grid. Therefore, determine index of
761	!-- upward-facing surface element on w grid.
762	zw_w_inner(i,j) = zw(topo_top_ind(j,i,3))
763	ENDDO
764	ENDDO
765	ENDIF
766
767	END SUBROUTINE init_grid
768
769
770	! Description:
771	! -----------------------------------------------------------------------------!
772	!> Calculation of the stretching factor through an iterative method. Ideas were
773	!> taken from the paper "Regional stretched grid generation and its application
774	!> to the NCAR RegCM (1999)". Normally, no analytic solution exists because the
775	!> system of equations has two variables (r,l) but four requirements
776	!> (l=integer, r=[0,88;1,2], Eq(6), Eq(5) starting from index j=1) which
777	!> results into an overdetermined system.
778	!------------------------------------------------------------------------------!
779	SUBROUTINE calculate_stretching_factor( number_end )
780
781	USE control_parameters, &
782	ONLY: dz, dz_stretch_factor_array, &
783	dz_stretch_level_end, dz_stretch_level_start, message_string
784
785	USE kinds
786
787	IMPLICIT NONE
788
789	INTEGER(iwp) :: iterations !< number of iterations until stretch_factor_lower/upper_limit is reached
790	INTEGER(iwp) :: l_rounded !< after l_rounded grid levels dz(n) is strechted to dz(n+1) with stretch_factor_2
791	INTEGER(iwp) :: n !< loop variable for stretching
792
793	INTEGER(iwp), INTENT(IN) :: number_end !< number of user-specified end levels for stretching
794
795	REAL(wp) :: delta_l !< absolute difference between l and l_rounded
796	REAL(wp) :: delta_stretch_factor !< absolute difference between stretch_factor_1 and stretch_factor_2
797	REAL(wp) :: delta_total_new !< sum of delta_l and delta_stretch_factor for the next iteration (should be as small as possible)
798	REAL(wp) :: delta_total_old !< sum of delta_l and delta_stretch_factor for the last iteration
799	REAL(wp) :: distance !< distance between dz_stretch_level_start and dz_stretch_level_end (stretching region)
800	REAL(wp) :: l !< value that fulfil Eq. (5) in the paper mentioned above together with stretch_factor_1 exactly
801	REAL(wp) :: numerator !< numerator of the quotient
802	REAL(wp) :: stretch_factor_1 !< stretching factor that fulfil Eq. (5) togehter with l exactly
803	REAL(wp) :: stretch_factor_2 !< stretching factor that fulfil Eq. (6) togehter with l_rounded exactly
804
805	REAL(wp) :: dz_stretch_factor_array_2(9) = 1.08_wp !< Array that contains all stretch_factor_2 that belongs to stretch_factor_1
806
807	REAL(wp), PARAMETER :: stretch_factor_interval = 1.0E-06_wp !< interval for sampling possible stretching factors
808	REAL(wp), PARAMETER :: stretch_factor_lower_limit = 0.88_wp !< lowest possible stretching factor
809	REAL(wp), PARAMETER :: stretch_factor_upper_limit = 1.12_wp !< highest possible stretching factor
810
811
812	l = 0
813	DO n = 1, number_end
814
815	iterations = 1
816	stretch_factor_1 = 1.0_wp
817	stretch_factor_2 = 1.0_wp
818	delta_total_old = 1.0_wp
819
820	!
821	!-- First branch for stretching from rough to fine
822	IF ( dz(n) > dz(n+1) ) THEN
823	DO WHILE ( stretch_factor_1 >= stretch_factor_lower_limit )
824
825	stretch_factor_1 = 1.0_wp - iterations * stretch_factor_interval
826	distance = ABS( dz_stretch_level_end(n) - &
827	dz_stretch_level_start(n) )
828	numerator = distance*stretch_factor_1/dz(n) + &
829	stretch_factor_1 - distance/dz(n)
830
831	IF ( numerator > 0.0_wp ) THEN
832	l = LOG( numerator ) / LOG( stretch_factor_1 ) - 1.0_wp
833	l_rounded = NINT( l )
834	delta_l = ABS( l_rounded - l ) / l
835	ENDIF
836
837	stretch_factor_2 = EXP( LOG( dz(n+1)/dz(n) ) / (l_rounded) )
838
839	delta_stretch_factor = ABS( stretch_factor_1 - &
840	stretch_factor_2 ) / &
841	stretch_factor_2
842
843	delta_total_new = delta_l + delta_stretch_factor
844
845	!
846	!-- stretch_factor_1 is taken to guarantee that the stretching
847	!-- procedure ends as close as possible to dz_stretch_level_end.
848	!-- stretch_factor_2 would guarantee that the stretched dz(n) is
849	!-- equal to dz(n+1) after l_rounded grid levels.
850	IF (delta_total_new < delta_total_old) THEN
851	dz_stretch_factor_array(n) = stretch_factor_1
852	dz_stretch_factor_array_2(n) = stretch_factor_2
853	delta_total_old = delta_total_new
854	ENDIF
855
856	iterations = iterations + 1
857
858	ENDDO
859
860	!
861	!-- Second branch for stretching from fine to rough
862	ELSEIF ( dz(n) < dz(n+1) ) THEN
863	DO WHILE ( stretch_factor_1 <= stretch_factor_upper_limit )
864
865	stretch_factor_1 = 1.0_wp + iterations * stretch_factor_interval
866	distance = ABS( dz_stretch_level_end(n) - &
867	dz_stretch_level_start(n) )
868	numerator = distance*stretch_factor_1/dz(n) + &
869	stretch_factor_1 - distance/dz(n)
870
871	l = LOG( numerator ) / LOG( stretch_factor_1 ) - 1.0_wp
872	l_rounded = NINT( l )
873	delta_l = ABS( l_rounded - l ) / l
874
875	stretch_factor_2 = EXP( LOG( dz(n+1)/dz(n) ) / (l_rounded) )
876
877	delta_stretch_factor = ABS( stretch_factor_1 - &
878	stretch_factor_2 ) / &
879	stretch_factor_2
880
881	delta_total_new = delta_l + delta_stretch_factor
882
883	!
884	!-- stretch_factor_1 is taken to guarantee that the stretching
885	!-- procedure ends as close as possible to dz_stretch_level_end.
886	!-- stretch_factor_2 would guarantee that the stretched dz(n) is
887	!-- equal to dz(n+1) after l_rounded grid levels.
888	IF (delta_total_new < delta_total_old) THEN
889	dz_stretch_factor_array(n) = stretch_factor_1
890	dz_stretch_factor_array_2(n) = stretch_factor_2
891	delta_total_old = delta_total_new
892	ENDIF
893
894	iterations = iterations + 1
895	ENDDO
896
897	ELSE
898	message_string= 'Two adjacent values of dz must be different'
899	CALL message( 'init_grid', 'PA0228', 1, 2, 0, 6, 0 )
900
901	ENDIF
902
903	!
904	!-- Check if also the second stretching factor fits into the allowed
905	!-- interval. If not, print a warning for the user.
906	IF ( dz_stretch_factor_array_2(n) < stretch_factor_lower_limit .OR. &
907	dz_stretch_factor_array_2(n) > stretch_factor_upper_limit ) THEN
908	WRITE( message_string, * ) 'stretch_factor_2 = ', &
909	dz_stretch_factor_array_2(n), ' which is',&
910	' responsible for exactly reaching& dz =',&
911	dz(n+1), 'after a specific amount of', &
912	' grid levels& exceeds the upper', &
913	' limit =', stretch_factor_upper_limit, &
914	' &or lower limit = ', &
915	stretch_factor_lower_limit
916	CALL message( 'init_grid', 'PA0499', 0, 1, 0, 6, 0 )
917
918	ENDIF
919	ENDDO
920
921	END SUBROUTINE calculate_stretching_factor
922
923
924	! Description:
925	! -----------------------------------------------------------------------------!
926	!> Set temporary topography flags and reference buildings on top of underlying
927	!> orography.
928	!------------------------------------------------------------------------------!
929	SUBROUTINE process_topography( topo_3d )
930
931	USE arrays_3d, &
932	ONLY: zu, zw
933
934	USE control_parameters, &
935	ONLY: bc_lr_cyc, bc_ns_cyc, ocean_mode
936
937	USE exchange_horiz_mod, &
938	ONLY: exchange_horiz_int, exchange_horiz_2d
939
940	USE indices, &
941	ONLY: nbgp, nx, nxl, nxlg, nxr, nxrg, ny, nyn, nyng, nys, nysg, nzb, &
942	nzt
943
944	USE netcdf_data_input_mod, &
945	ONLY: buildings_f, building_id_f, building_type_f, &
946	init_model, &
947	input_pids_static, &
948	terrain_height_f
949
950	USE kinds
951
952	USE pegrid
953
954	IMPLICIT NONE
955
956	INTEGER(iwp) :: i !< running index along x-direction
957	INTEGER(iwp) :: j !< running index along y-direction
958	INTEGER(iwp) :: k !< running index along z-direction with respect to numeric grid
959	INTEGER(iwp) :: k2 !< running index along z-direction with respect to netcdf grid
960	INTEGER(iwp) :: nr !< index variable indication maximum terrain height for respective building ID
961	INTEGER(iwp) :: num_build !< counter for number of buildings
962	INTEGER(iwp) :: topo_top_index !< orography top index, used to map 3D buildings onto terrain
963
964	#if defined( __parallel )
965	INTEGER(iwp), DIMENSION(:), ALLOCATABLE :: displace_dum !< displacements of start addresses, used for MPI_ALLGATHERV
966	#endif
967	INTEGER(iwp), DIMENSION(:), ALLOCATABLE :: build_ids !< building IDs on entire model domain
968	INTEGER(iwp), DIMENSION(:), ALLOCATABLE :: build_ids_final !< building IDs on entire model domain, multiple occurences are sorted out
969	INTEGER(iwp), DIMENSION(:), ALLOCATABLE :: build_ids_final_tmp !< temporary array used for resizing
970	INTEGER(iwp), DIMENSION(:), ALLOCATABLE :: build_ids_l !< building IDs on local subdomain
971	INTEGER(iwp), DIMENSION(:), ALLOCATABLE :: build_ids_l_tmp !< temporary array used to resize array of building IDs
972
973	INTEGER(iwp), DIMENSION(0:numprocs-1) :: num_buildings !< number of buildings with different ID on entire model domain
974	INTEGER(iwp), DIMENSION(0:numprocs-1) :: num_buildings_l !< number of buildings with different ID on local subdomain
975
976	INTEGER(iwp), DIMENSION(nzb:nzt+1,nysg:nyng,nxlg:nxrg) :: topo_3d !< input array for 3D topography and dummy array for setting "outer"-flags
977
978	REAL(wp) :: ocean_offset !< offset to consider inverse vertical coordinate at topography definition
979	REAL(wp) :: oro_min = 0.0_wp !< minimum terrain height in entire model domain, used to reference terrain to zero
980	REAL(wp), DIMENSION(:), ALLOCATABLE :: oro_max !< maximum terrain height occupied by an building with certain id
981	REAL(wp), DIMENSION(:), ALLOCATABLE :: oro_max_l !< maximum terrain height occupied by an building with certain id, on local subdomain
982
983	!
984	!-- Reference lowest terrain height to zero. This ensures that first,
985	!-- non-required gird levels (those which lie entirely below the minimum
986	!-- orography) are avoided, and second, that also negative orography can be used
987	!-- within the input file.
988	!-- Please note, in case of a nested run, the global minimum from all parent and
989	!-- childs need to be remove to avoid steep edges at the child-domain boundaries.
990	IF ( input_pids_static ) THEN
991
992	#if defined( __parallel )
993	CALL MPI_ALLREDUCE( MINVAL( terrain_height_f%var ), oro_min, 1, &
994	MPI_REAL, MPI_MIN, MPI_COMM_WORLD, ierr )
995	#else
996	oro_min = MINVAL( terrain_height_f%var )
997	#endif
998	terrain_height_f%var = terrain_height_f%var - oro_min
999	!
1000	!-- Update reference height used within output files
1001	init_model%origin_z = init_model%origin_z + oro_min
1002
1003	ENDIF
1004
1005	!
1006	!-- In the following, buildings and orography are further preprocessed
1007	!-- before they are mapped on the LES grid.
1008	!-- Buildings are mapped on top of the orography by maintaining the roof
1009	!-- shape of the building. This can be achieved by referencing building on
1010	!-- top of the maximum terrain height within the area occupied by the
1011	!-- respective building. As buildings and terrain height are defined PE-wise,
1012	!-- parallelization of this referencing is required (a building can be
1013	!-- distributed between different PEs).
1014	!-- In a first step, determine the number of buildings with different
1015	!-- building id on each PE. In a next step, all building ids are gathered
1016	!-- into one array which is present to all PEs. For each building ID,
1017	!-- the maximum terrain height occupied by the respective building is
1018	!-- computed and distributed to each PE.
1019	!-- Finally, for each building id and its respective reference orography,
1020	!-- builidings are mapped on top.
1021	!--
1022	!-- First, pre-set topography flags, bit 1 indicates orography, bit 2
1023	!-- buildings
1024	!-- classify the respective surfaces.
1025	topo_3d = IBSET( topo_3d, 0 )
1026	topo_3d(nzb,:,:) = IBCLR( topo_3d(nzb,:,:), 0 )
1027	!
1028	!-- In order to map topography on PALM grid also in case of ocean simulations,
1029	!-- pre-calculate an offset value.
1030	ocean_offset = MERGE( zw(0), 0.0_wp, ocean_mode )
1031	!
1032	!-- Reference buildings on top of orography. This is not necessary
1033	!-- if topography is read from ASCII file as no distinction between buildings
1034	!-- and terrain height can be made. Moreover, this is also not necessary if
1035	!-- urban-surface and land-surface model are used at the same time.
1036	IF ( input_pids_static ) THEN
1037
1038	IF ( buildings_f%from_file ) THEN
1039	num_buildings_l = 0
1040	num_buildings = 0
1041	!
1042	!-- Allocate at least one element for building ids and give it an inital
1043	!-- negative value that will be overwritten later. This, however, is
1044	!-- necessary in case there all IDs in the model domain are fill values.
1045	ALLOCATE( build_ids_l(1) )
1046	build_ids_l = -1
1047	DO i = nxl, nxr
1048	DO j = nys, nyn
1049	IF ( building_id_f%var(j,i) /= building_id_f%fill ) THEN
1050	IF ( num_buildings_l(myid) > 0 ) THEN
1051	IF ( ANY( building_id_f%var(j,i) == build_ids_l ) ) &
1052	THEN
1053	CYCLE
1054	ELSE
1055	num_buildings_l(myid) = num_buildings_l(myid) + 1
1056	!
1057	!-- Resize array with different local building ids
1058	ALLOCATE( build_ids_l_tmp(1:SIZE(build_ids_l)) )
1059	build_ids_l_tmp = build_ids_l
1060	DEALLOCATE( build_ids_l )
1061	ALLOCATE( build_ids_l(1:num_buildings_l(myid)) )
1062	build_ids_l(1:num_buildings_l(myid)-1) = &
1063	build_ids_l_tmp(1:num_buildings_l(myid)-1)
1064	build_ids_l(num_buildings_l(myid)) = building_id_f%var(j,i)
1065	DEALLOCATE( build_ids_l_tmp )
1066	ENDIF
1067	!
1068	!-- First occuring building id on PE
1069	ELSE
1070	num_buildings_l(myid) = num_buildings_l(myid) + 1
1071	build_ids_l(1) = building_id_f%var(j,i)
1072	ENDIF
1073	ENDIF
1074	ENDDO
1075	ENDDO
1076	!
1077	!-- Determine number of different building ids for the entire domain
1078	#if defined( __parallel )
1079	CALL MPI_ALLREDUCE( num_buildings_l, num_buildings, numprocs, &
1080	MPI_INTEGER, MPI_SUM, comm2d, ierr )
1081	#else
1082	num_buildings = num_buildings_l
1083	#endif
1084	!
1085	!-- Gather all buildings ids on each PEs.
1086	!-- First, allocate array encompassing all building ids in model domain.
1087	ALLOCATE( build_ids(1:SUM(num_buildings)) )
1088	#if defined( __parallel )
1089	!
1090	!-- Allocate array for displacements.
1091	!-- As each PE may has a different number of buildings, so that
1092	!-- the block sizes send by each PE may not be equal. Hence,
1093	!-- information about the respective displacement is required, indicating
1094	!-- the respective adress where each MPI-task writes into the receive
1095	!-- buffer array
1096	ALLOCATE( displace_dum(0:numprocs-1) )
1097	displace_dum(0) = 0
1098	DO i = 1, numprocs-1
1099	displace_dum(i) = displace_dum(i-1) + num_buildings(i-1)
1100	ENDDO
1101
1102	CALL MPI_ALLGATHERV( build_ids_l(1:num_buildings_l(myid)), &
1103	num_buildings(myid), &
1104	MPI_INTEGER, &
1105	build_ids, &
1106	num_buildings, &
1107	displace_dum, &
1108	MPI_INTEGER, &
1109	comm2d, ierr )
1110
1111	DEALLOCATE( displace_dum )
1112
1113	#else
1114	build_ids = build_ids_l
1115	#endif
1116
1117	!
1118	!-- Note, in parallel mode building ids can occure mutliple times, as
1119	!-- each PE has send its own ids. Therefore, sort out building ids which
1120	!-- appear more than one time.
1121	num_build = 0
1122	DO nr = 1, SIZE(build_ids)
1123
1124	IF ( ALLOCATED(build_ids_final) ) THEN
1125	IF ( ANY( build_ids(nr) == build_ids_final ) ) THEN
1126	CYCLE
1127	ELSE
1128	num_build = num_build + 1
1129	!
1130	!-- Resize
1131	ALLOCATE( build_ids_final_tmp(1:num_build) )
1132	build_ids_final_tmp(1:num_build-1) = build_ids_final(1:num_build-1)
1133	DEALLOCATE( build_ids_final )
1134	ALLOCATE( build_ids_final(1:num_build) )
1135	build_ids_final(1:num_build-1) = build_ids_final_tmp(1:num_build-1)
1136	build_ids_final(num_build) = build_ids(nr)
1137	DEALLOCATE( build_ids_final_tmp )
1138	ENDIF
1139	ELSE
1140	num_build = num_build + 1
1141	ALLOCATE( build_ids_final(1:num_build) )
1142	build_ids_final(num_build) = build_ids(nr)
1143	ENDIF
1144	ENDDO
1145
1146	!
1147	!-- Determine maximumum terrain height occupied by the respective
1148	!-- building and temporalily store on oro_max
1149	ALLOCATE( oro_max_l(1:SIZE(build_ids_final)) )
1150	ALLOCATE( oro_max(1:SIZE(build_ids_final)) )
1151	oro_max_l = 0.0_wp
1152
1153	DO nr = 1, SIZE(build_ids_final)
1154	oro_max_l(nr) = MAXVAL( &
1155	MERGE( terrain_height_f%var(nys:nyn,nxl:nxr), &
1156	0.0_wp, &
1157	building_id_f%var(nys:nyn,nxl:nxr) == &
1158	build_ids_final(nr) ) )
1159	ENDDO
1160
1161	#if defined( __parallel )
1162	IF ( SIZE(build_ids_final) >= 1 ) THEN
1163	CALL MPI_ALLREDUCE( oro_max_l, oro_max, SIZE( oro_max ), MPI_REAL,&
1164	MPI_MAX, comm2d, ierr )
1165	ENDIF
1166	#else
1167	oro_max = oro_max_l
1168	#endif
1169	!
1170	!-- Finally, determine discrete grid height of maximum orography occupied
1171	!-- by a building. Use all-or-nothing approach, i.e. if terrain
1172	!-- exceeds the scalar level the grid box is fully terrain and the
1173	!-- maximum terrain is set to the zw level.
1174	!-- terrain or
1175	oro_max_l = 0.0
1176	DO nr = 1, SIZE(build_ids_final)
1177	DO k = nzb, nzt
1178	IF ( zu(k) - ocean_offset <= oro_max(nr) ) &
1179	oro_max_l(nr) = zw(k) - ocean_offset
1180	ENDDO
1181	oro_max(nr) = oro_max_l(nr)
1182	ENDDO
1183	ENDIF
1184	!
1185	!-- Allocate array for storing terrain height under buildings
1186	IF ( buildings_f%from_file ) THEN
1187	ALLOCATE( buildings_f%oro_max(nysg:nyng,nxlg:nxrg) )
1188	buildings_f%oro_max = buildings_f%fill1
1189	END IF
1190	!
1191	!-- Map orography as well as buildings onto grid.
1192	DO i = nxl, nxr
1193	DO j = nys, nyn
1194	topo_top_index = 0
1195	!
1196	!-- Obtain index in global building_id array
1197	IF ( buildings_f%from_file ) THEN
1198	IF ( building_id_f%var(j,i) /= building_id_f%fill ) THEN
1199	!
1200	!-- Determine index where maximum terrain height occupied by
1201	!-- the respective building height is stored.
1202	nr = MINLOC( ABS( build_ids_final - &
1203	building_id_f%var(j,i) ), DIM = 1 )
1204	!
1205	!-- Save grid-indexed oro_max
1206	buildings_f%oro_max(j,i) = oro_max(nr)
1207	ENDIF
1208	ENDIF
1209	DO k = nzb, nzt
1210	!
1211	!-- In a first step, if grid point is below or equal the given
1212	!-- terrain height, grid point is flagged to be of type natural.
1213	!-- Please note, in case there is also a building which is lower
1214	!-- than the vertical grid spacing, initialization of surface
1215	!-- attributes will not be correct as given surface information
1216	!-- will not be in accordance to the classified grid points.
1217	!-- Hence, in this case, also a building flag.
1218	IF ( zu(k) - ocean_offset <= terrain_height_f%var(j,i) ) THEN
1219	topo_3d(k,j,i) = IBCLR( topo_3d(k,j,i), 0 )
1220	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 1 )
1221	topo_top_index = k ! topo_top_index + 1
1222	ENDIF
1223	!
1224	!-- Set building grid points. Here, only consider 2D buildings.
1225	!-- 3D buildings require separate treatment.
1226	IF ( buildings_f%from_file .AND. buildings_f%lod == 1 ) THEN
1227	!
1228	!-- Fill-up the terrain to the level of maximum orography
1229	!-- within the building-covered area.
1230	IF ( building_id_f%var(j,i) /= building_id_f%fill ) THEN
1231	!
1232	!-- Note, oro_max is always on zw level
1233	IF ( zu(k) - ocean_offset < oro_max(nr) ) THEN
1234	topo_3d(k,j,i) = IBCLR( topo_3d(k,j,i), 0 )
1235	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 1 )
1236	ELSEIF ( zu(k) - ocean_offset <= &
1237	oro_max(nr) + buildings_f%var_2d(j,i) ) THEN
1238	topo_3d(k,j,i) = IBCLR( topo_3d(k,j,i), 0 )
1239	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 2 )
1240	ENDIF
1241	ENDIF
1242	ENDIF
1243	ENDDO
1244	!
1245	!-- Special treatment for non grid-resolved buildings. This case,
1246	!-- the uppermost terrain grid point is flagged as building as well
1247	!-- well, even though no building exists at all. However, the
1248	!-- surface element will be identified as urban-surface and the
1249	!-- input data provided by the drivers is consistent to the surface
1250	!-- classification. Else, all non grid-resolved buildings would vanish
1251	!-- and identified as terrain grid points, which, however, won't be
1252	!-- consistent with the input data.
1253	IF ( buildings_f%from_file .AND. buildings_f%lod == 1 ) THEN
1254	IF ( building_id_f%var(j,i) /= building_id_f%fill ) THEN
1255	DO k = nzb, nzt
1256	IF( zw(k) - ocean_offset == oro_max(nr) ) THEN
1257	IF ( buildings_f%var_2d(j,i) <= zu(k+1) - zw(k) ) THEN
1258	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 2 )
1259	ENDIF
1260	ENDIF
1261	ENDDO
1262	ENDIF
1263	ENDIF
1264	!
1265	!-- Map 3D buildings onto terrain height.
1266	!-- In case of any slopes, map building on top of maximum terrain
1267	!-- height covered by the building. In other words, extend
1268	!-- building down to the respective local terrain-surface height.
1269	IF ( buildings_f%from_file .AND. buildings_f%lod == 2 ) THEN
1270	IF ( building_id_f%var(j,i) /= building_id_f%fill ) THEN
1271	!
1272	!-- Extend building down to the terrain surface, i.e. fill-up
1273	!-- surface irregularities below a building. Note, oro_max
1274	!-- is already a discrete height according to the all-or-nothing
1275	!-- approach, i.e. grid box is either topography or atmosphere,
1276	!-- terrain top is defined at upper bound of the grid box.
1277	!-- Hence, check for zw in this case.
1278	!-- Note, do this only for buildings which are surface mounted,
1279	!-- i.e. building types 1-6. Below bridges, which are represented
1280	!-- exclusively by building type 7, terrain shape should be
1281	!-- maintained.
1282	IF ( building_type_f%from_file ) THEN
1283	IF ( building_type_f%var(j,i) /= 7 ) THEN
1284	DO k = topo_top_index + 1, nzt + 1
1285	IF ( zu(k) - ocean_offset <= oro_max(nr) ) THEN
1286	topo_3d(k,j,i) = IBCLR( topo_3d(k,j,i), 0 )
1287	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 1 )
1288	ENDIF
1289	ENDDO
1290	!
1291	!-- After surface irregularities are smoothen, determine
1292	!-- lower start index where building starts.
1293	DO k = nzb, nzt
1294	IF ( zu(k) - ocean_offset <= oro_max(nr) ) &
1295	topo_top_index = k
1296	ENDDO
1297	ENDIF
1298	ENDIF
1299	!
1300	!-- Finally, map building on top.
1301	k2 = 0
1302	DO k = topo_top_index, nzt + 1
1303	IF ( k2 <= buildings_f%nz-1 ) THEN
1304	IF ( buildings_f%var_3d(k2,j,i) == 1 ) THEN
1305	topo_3d(k,j,i) = IBCLR( topo_3d(k,j,i), 0 )
1306	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 2 )
1307	ENDIF
1308	ENDIF
1309	k2 = k2 + 1
1310	ENDDO
1311	ENDIF
1312	ENDIF
1313	ENDDO
1314	ENDDO
1315	!
1316	!-- Horizontal exchange the oro_max array, which is required to for
1317	!-- initialization of building-surface properties.
1318	IF ( ALLOCATED( buildings_f%oro_max ) ) THEN
1319	CALL exchange_horiz_2d( buildings_f%oro_max(:,:) )
1320	ENDIF
1321	!
1322	!-- Deallocate temporary arrays required for processing and reading data
1323	IF ( ALLOCATED( oro_max ) ) DEALLOCATE( oro_max )
1324	IF ( ALLOCATED( oro_max_l ) ) DEALLOCATE( oro_max_l )
1325	IF ( ALLOCATED( build_ids_final ) ) DEALLOCATE( build_ids_final )
1326	!
1327	!-- Topography input via ASCII format.
1328	ELSE
1329	ocean_offset = MERGE( zw(0), 0.0_wp, ocean_mode )
1330	!
1331	!-- Initialize topography bit 0 (indicates obstacle) everywhere to zero
1332	!-- and clear all grid points at nzb, where alway a surface is defined.
1333	!-- Further, set also bit 1 (indicates terrain) at nzb, which is further
1334	!-- used for masked data output and further processing. Note, in the
1335	!-- ASCII case no distinction is made between buildings and terrain,
1336	!-- so that setting of bit 1 and 2 at the same time has no effect.
1337	topo_3d = IBSET( topo_3d, 0 )
1338	topo_3d(nzb,:,:) = IBCLR( topo_3d(nzb,:,:), 0 )
1339	topo_3d(nzb,:,:) = IBSET( topo_3d(nzb,:,:), 1 )
1340	DO i = nxl, nxr
1341	DO j = nys, nyn
1342	DO k = nzb, nzt
1343	!
1344	!-- Flag topography for all grid points which are below
1345	!-- the local topography height.
1346	!-- Note, each topography is flagged as building.
1347	IF ( zu(k) - ocean_offset <= buildings_f%var_2d(j,i) ) THEN
1348	topo_3d(k,j,i) = IBCLR( topo_3d(k,j,i), 0 )
1349	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 2 ) !indicates building
1350	ENDIF
1351	ENDDO
1352	ENDDO
1353	ENDDO
1354	ENDIF
1355
1356	CALL exchange_horiz_int( topo_3d, nys, nyn, nxl, nxr, nzt, nbgp )
1357
1358	IF ( .NOT. bc_ns_cyc ) THEN
1359	IF ( nys == 0 ) topo_3d(:,-1,:) = topo_3d(:,0,:)
1360	IF ( nyn == ny ) topo_3d(:,ny+1,:) = topo_3d(:,ny,:)
1361	ENDIF
1362
1363	IF ( .NOT. bc_lr_cyc ) THEN
1364	IF ( nxl == 0 ) topo_3d(:,:,-1) = topo_3d(:,:,0)
1365	IF ( nxr == nx ) topo_3d(:,:,nx+1) = topo_3d(:,:,nx)
1366	ENDIF
1367
1368	END SUBROUTINE process_topography
1369
1370
1371	! Description:
1372	! -----------------------------------------------------------------------------!
1373	!> Filter topography, i.e. fill holes resolved by only one grid point.
1374	!> Such holes are suspected to lead to velocity blow-ups as continuity
1375	!> equation on discrete grid cannot be fulfilled in such case.
1376	!------------------------------------------------------------------------------!
1377	SUBROUTINE filter_topography( topo_3d )
1378
1379	USE control_parameters, &
1380	ONLY: bc_lr_cyc, bc_ns_cyc, message_string
1381
1382	USE exchange_horiz_mod, &
1383	ONLY: exchange_horiz_int, exchange_horiz_2d_byte, exchange_horiz_2d_int
1384
1385	USE indices, &
1386	ONLY: nbgp, nx, nxl, nxlg, nxr, nxrg, ny, nyn, nyng, nys, nysg, nzb, nzt
1387
1388	USE netcdf_data_input_mod, &
1389	ONLY: building_id_f, building_type_f
1390
1391	USE pegrid
1392
1393	IMPLICIT NONE
1394
1395	LOGICAL :: filled = .FALSE. !< flag indicating if holes were filled
1396
1397	INTEGER(iwp) :: i !< running index along x-direction
1398	INTEGER(iwp) :: j !< running index along y-direction
1399	INTEGER(iwp) :: k !< running index along z-direction
1400	INTEGER(iwp) :: num_hole !< number of holes (in topography) resolved by only one grid point
1401	INTEGER(iwp) :: num_hole_l !< number of holes (in topography) resolved by only one grid point on local PE
1402	INTEGER(iwp) :: num_wall !< number of surrounding vertical walls for a single grid point
1403
1404	INTEGER(iwp), DIMENSION(:,:,:), ALLOCATABLE :: topo_tmp !< temporary 3D-topography used to fill holes
1405	INTEGER(iwp), DIMENSION(nzb:nzt+1,nysg:nyng,nxlg:nxrg) :: topo_3d !< 3D-topography array merging buildings and orography
1406	!
1407	!-- Before checking for holes, set lateral boundary conditions for
1408	!-- topography. After hole-filling, boundary conditions must be set again.
1409	!-- Several iterations are performed, in order to fill holes which might
1410	!-- emerge by the filling-algorithm itself.
1411	ALLOCATE( topo_tmp(nzb:nzt+1,nysg:nyng,nxlg:nxrg) )
1412	topo_tmp = 0
1413
1414	num_hole = 99999
1415	DO WHILE ( num_hole > 0 )
1416
1417	num_hole = 0
1418	CALL exchange_horiz_int( topo_3d, nys, nyn, nxl, nxr, nzt, nbgp )
1419	!
1420	!-- Exchange also building ID and type. Note, building_type is an one-byte
1421	!-- variable.
1422	IF ( building_id_f%from_file ) &
1423	CALL exchange_horiz_2d_int( building_id_f%var, nys, nyn, nxl, nxr, nbgp )
1424	IF ( building_type_f%from_file ) &
1425	CALL exchange_horiz_2d_byte( building_type_f%var, nys, nyn, nxl, nxr, nbgp )
1426
1427	topo_tmp = topo_3d
1428	!
1429	!-- In case of non-cyclic lateral boundaries, assume lateral boundary to be
1430	!-- a solid wall. Thus, intermediate spaces of one grid point between
1431	!-- boundary and some topographic structure will be filled.
1432	IF ( .NOT. bc_ns_cyc ) THEN
1433	IF ( nys == 0 ) topo_tmp(:,-1,:) = IBCLR( topo_tmp(:,0,:), 0 )
1434	IF ( nyn == ny ) topo_tmp(:,ny+1,:) = IBCLR( topo_tmp(:,ny,:), 0 )
1435	ENDIF
1436
1437	IF ( .NOT. bc_lr_cyc ) THEN
1438	IF ( nxl == 0 ) topo_tmp(:,:,-1) = IBCLR( topo_tmp(:,:,0), 0 )
1439	IF ( nxr == nx ) topo_tmp(:,:,nx+1) = IBCLR( topo_tmp(:,:,nx), 0 )
1440	ENDIF
1441
1442	num_hole_l = 0
1443	DO i = nxl, nxr
1444	DO j = nys, nyn
1445	DO k = nzb+1, nzt
1446	IF ( BTEST( topo_tmp(k,j,i), 0 ) ) THEN
1447	num_wall = 0
1448	IF ( .NOT. BTEST( topo_tmp(k,j-1,i), 0 ) ) &
1449	num_wall = num_wall + 1
1450	IF ( .NOT. BTEST( topo_tmp(k,j+1,i), 0 ) ) &
1451	num_wall = num_wall + 1
1452	IF ( .NOT. BTEST( topo_tmp(k,j,i-1), 0 ) ) &
1453	num_wall = num_wall + 1
1454	IF ( .NOT. BTEST( topo_tmp(k,j,i+1), 0 ) ) &
1455	num_wall = num_wall + 1
1456	IF ( .NOT. BTEST( topo_tmp(k-1,j,i), 0 ) ) &
1457	num_wall = num_wall + 1
1458	IF ( .NOT. BTEST( topo_tmp(k+1,j,i), 0 ) ) &
1459	num_wall = num_wall + 1
1460
1461	IF ( num_wall >= 4 ) THEN
1462	num_hole_l = num_hole_l + 1
1463	!
1464	!-- Clear flag 0 and set special flag ( bit 4) to indicate
1465	!-- that new topography point is a result of filtering process.
1466	topo_3d(k,j,i) = IBCLR( topo_3d(k,j,i), 0 )
1467	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 4 )
1468	!
1469	!-- If filled grid point is occupied by a building, classify
1470	!-- it as building grid point.
1471	IF ( building_type_f%from_file ) THEN
1472	IF ( building_type_f%var(j,i) /= &
1473	building_type_f%fill .OR. &
1474	building_type_f%var(j+1,i) /= &
1475	building_type_f%fill .OR. &
1476	building_type_f%var(j-1,i) /= &
1477	building_type_f%fill .OR. &
1478	building_type_f%var(j,i+1) /= &
1479	building_type_f%fill .OR. &
1480	building_type_f%var(j,i-1) /= &
1481	building_type_f%fill ) THEN
1482	!
1483	!-- Set flag indicating building surfaces
1484	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 2 )
1485	!
1486	!-- Set building_type and ID at this position if not
1487	!-- already set. This is required for proper
1488	!-- initialization of urban-surface energy balance
1489	!-- solver.
1490	IF ( building_type_f%var(j,i) == &
1491	building_type_f%fill ) THEN
1492
1493	IF ( building_type_f%var(j+1,i) /= &
1494	building_type_f%fill ) THEN
1495	building_type_f%var(j,i) = &
1496	building_type_f%var(j+1,i)
1497	building_id_f%var(j,i) = &
1498	building_id_f%var(j+1,i)
1499	ELSEIF ( building_type_f%var(j-1,i) /= &
1500	building_type_f%fill ) THEN
1501	building_type_f%var(j,i) = &
1502	building_type_f%var(j-1,i)
1503	building_id_f%var(j,i) = &
1504	building_id_f%var(j-1,i)
1505	ELSEIF ( building_type_f%var(j,i+1) /= &
1506	building_type_f%fill ) THEN
1507	building_type_f%var(j,i) = &
1508	building_type_f%var(j,i+1)
1509	building_id_f%var(j,i) = &
1510	building_id_f%var(j,i+1)
1511	ELSEIF ( building_type_f%var(j,i-1) /= &
1512	building_type_f%fill ) THEN
1513	building_type_f%var(j,i) = &
1514	building_type_f%var(j,i-1)
1515	building_id_f%var(j,i) = &
1516	building_id_f%var(j,i-1)
1517	ENDIF
1518	ENDIF
1519	ENDIF
1520	ENDIF
1521	!
1522	!-- If filled grid point is already classified as building
1523	!-- everything is fine, else classify this grid point as
1524	!-- natural type grid point. This case, values for the
1525	!-- surface type are already set.
1526	IF ( .NOT. BTEST( topo_3d(k,j,i), 2 ) ) THEN
1527	topo_3d(k,j,i) = IBSET( topo_3d(k,j,i), 1 )
1528	ENDIF
1529	ENDIF
1530	ENDIF
1531	ENDDO
1532	ENDDO
1533	ENDDO
1534	!
1535	!-- Count the total number of holes, required for informative message.
1536	#if defined( __parallel )
1537	CALL MPI_ALLREDUCE( num_hole_l, num_hole, 1, MPI_INTEGER, MPI_SUM, &
1538	comm2d, ierr )
1539	#else
1540	num_hole = num_hole_l
1541	#endif
1542	IF ( num_hole > 0 .AND. .NOT. filled ) filled = .TRUE.
1543
1544	ENDDO
1545	!
1546	!-- Create an informative message if any holes were filled.
1547	IF ( filled ) THEN
1548	WRITE( message_string, * ) 'Topography was filtered, i.e. holes ' // &
1549	'resolved by only one grid point ' // &
1550	'were filled during initialization.'
1551	CALL message( 'init_grid', 'PA0430', 0, 0, 0, 6, 0 )
1552	ENDIF
1553
1554	DEALLOCATE( topo_tmp )
1555	!
1556	!-- Finally, exchange topo_3d array again and if necessary set Neumann boundary
1557	!-- condition in case of non-cyclic lateral boundaries.
1558	CALL exchange_horiz_int( topo_3d, nys, nyn, nxl, nxr, nzt, nbgp )
1559
1560	IF ( .NOT. bc_ns_cyc ) THEN
1561	IF ( nys == 0 ) topo_3d(:,-1,:) = topo_3d(:,0,:)
1562	IF ( nyn == ny ) topo_3d(:,ny+1,:) = topo_3d(:,ny,:)
1563	ENDIF
1564
1565	IF ( .NOT. bc_lr_cyc ) THEN
1566	IF ( nxl == 0 ) topo_3d(:,:,-1) = topo_3d(:,:,0)
1567	IF ( nxr == nx ) topo_3d(:,:,nx+1) = topo_3d(:,:,nx)
1568	ENDIF
1569	!
1570	!-- Exchange building ID and type. Note, building_type is an one-byte variable.
1571	IF ( building_id_f%from_file ) &
1572	CALL exchange_horiz_2d_int( building_id_f%var, nys, nyn, nxl, nxr, nbgp )
1573	IF ( building_type_f%from_file ) &
1574	CALL exchange_horiz_2d_byte( building_type_f%var, nys, nyn, nxl, nxr, nbgp )
1575
1576	END SUBROUTINE filter_topography
1577
1578
1579	! Description:
1580	! -----------------------------------------------------------------------------!
1581	!> Reads topography information from file or sets generic topography. Moreover,
1582	!> all topography-relevant topography arrays are initialized, and grid flags
1583	!> are set.
1584	!------------------------------------------------------------------------------!
1585	SUBROUTINE init_topo( topo )
1586
1587	USE arrays_3d, &
1588	ONLY: zw
1589
1590	USE control_parameters, &
1591	ONLY: bc_lr_cyc, bc_ns_cyc, building_height, building_length_x, &
1592	building_length_y, building_wall_left, building_wall_south, &
1593	canyon_height, canyon_wall_left, canyon_wall_south, &
1594	canyon_width_x, canyon_width_y, dp_level_ind_b, dz, &
1595	message_string, topography, topography_grid_convention, &
1596	tunnel_height, tunnel_length, tunnel_width_x, tunnel_width_y, &
1597	tunnel_wall_depth
1598
1599	USE exchange_horiz_mod, &
1600	ONLY: exchange_horiz_int
1601
1602	USE grid_variables, &
1603	ONLY: dx, dy
1604
1605	USE indices, &
1606	ONLY: nbgp, nx, nxl, nxlg, nxr, nxrg, ny, nyn, nyng, nys, nysg, nz, &
1607	nzb, nzt
1608
1609	USE kinds
1610
1611	USE netcdf_data_input_mod, &
1612	ONLY: buildings_f, terrain_height_f
1613
1614	USE pegrid
1615
1616	IMPLICIT NONE
1617
1618	INTEGER(iwp) :: bh !< temporary vertical index of building height
1619	INTEGER(iwp) :: ngp_bx !< grid point number of building size along x
1620	INTEGER(iwp) :: ngp_by !< grid point number of building size along y
1621	INTEGER(iwp) :: index_left_bwall !< index for left building wall
1622	INTEGER(iwp) :: index_right_bwall !< index for right building wall
1623	INTEGER(iwp) :: index_north_bwall !< index for north building wall
1624	INTEGER(iwp) :: index_south_bwall !< index for south building wall
1625	INTEGER(iwp) :: ch !< temporary vertical index for canyon height
1626	INTEGER(iwp) :: ngp_cx !< grid point number of canyon size along x
1627	INTEGER(iwp) :: ngp_cy !< grid point number of canyon size along y
1628	INTEGER(iwp) :: index_left_cwall !< index for left canyon wall
1629	INTEGER(iwp) :: index_right_cwall !< index for right canyon wall
1630	INTEGER(iwp) :: index_north_cwall !< index for north canyon wall
1631	INTEGER(iwp) :: index_south_cwall !< index for south canyon wall
1632	INTEGER(iwp) :: i !< index variable along x
1633	INTEGER(iwp) :: j !< index variable along y
1634	INTEGER(iwp) :: k !< index variable along z
1635	INTEGER(iwp) :: hv_in !< heavyside function to model inner tunnel surface
1636	INTEGER(iwp) :: hv_out !< heavyside function to model outer tunnel surface
1637	INTEGER(iwp) :: txe_out !< end position of outer tunnel wall in x
1638	INTEGER(iwp) :: txs_out !< start position of outer tunnel wall in x
1639	INTEGER(iwp) :: tye_out !< end position of outer tunnel wall in y
1640	INTEGER(iwp) :: tys_out !< start position of outer tunnel wall in y
1641	INTEGER(iwp) :: txe_in !< end position of inner tunnel wall in x
1642	INTEGER(iwp) :: txs_in !< start position of inner tunnel wall in x
1643	INTEGER(iwp) :: tye_in !< end position of inner tunnel wall in y
1644	INTEGER(iwp) :: tys_in !< start position of inner tunnel wall in y
1645	INTEGER(iwp) :: td !< tunnel wall depth
1646	INTEGER(iwp) :: th !< height of outer tunnel wall
1647
1648	INTEGER(iwp), DIMENSION(:,:), ALLOCATABLE :: nzb_local !< index for topography top at cell-center
1649	INTEGER(iwp), DIMENSION(nzb:nzt+1,nysg:nyng,nxlg:nxrg) :: topo !< input array for 3D topography and dummy array for setting "outer"-flags
1650	!
1651	!-- Check for correct setting of the namelist parameter topography. If
1652	!-- topography information is read from file but topography = 'flat',
1653	!-- initialization does not work properly.
1654	IF ( ( buildings_f%from_file .OR. terrain_height_f%from_file ) .AND. &
1655	TRIM( topography ) /= 'read_from_file' ) THEN
1656	message_string = 'If topography information is provided (via ' // &
1657	'Netcdf or ASCII input) topography = ' // &
1658	'"read_from_file" is required.'
1659	CALL message( 'init_grid', 'PA0437', 1, 2, 0, 6, 0 )
1660	ENDIF
1661	!
1662	!-- Set outer and inner index arrays for non-flat topography.
1663	!-- Here consistency checks concerning domain size and periodicity are
1664	!-- necessary.
1665	!-- Within this SELECT CASE structure only nzb_local is initialized
1666	!-- individually depending on the chosen topography type, all other index
1667	!-- arrays are initialized further below.
1668	SELECT CASE ( TRIM( topography ) )
1669
1670	CASE ( 'flat' )
1671	!
1672	!-- Initialilize 3D topography array, used later for initializing flags
1673	topo(nzb+1:nzt+1,:,:) = IBSET( topo(nzb+1:nzt+1,:,:), 0 )
1674
1675	CASE ( 'closed_channel' )
1676	!
1677	!-- Initialilize 3D topography array, used later for initializing flags
1678	topo(nzb+1:nzt,:,:) = IBSET( topo(nzb+1:nzt,:,:), 0 )
1679
1680	CASE ( 'single_building' )
1681	!
1682	!-- Single rectangular building, by default centered in the middle of the
1683	!-- total domain
1684	ngp_bx = NINT( building_length_x / dx )
1685	ngp_by = NINT( building_length_y / dy )
1686	bh = MINLOC( ABS( zw - building_height ), 1 ) - 1
1687	IF ( ABS( zw(bh) - building_height ) == &
1688	ABS( zw(bh+1) - building_height ) ) bh = bh + 1
1689	IF ( building_wall_left == 9999999.9_wp ) THEN
1690	building_wall_left = ( nx + 1 - ngp_bx ) / 2 * dx
1691	ENDIF
1692	index_left_bwall = NINT( building_wall_left / dx )
1693	index_right_bwall = index_left_bwall + ngp_bx
1694
1695	IF ( building_wall_south == 9999999.9_wp ) THEN
1696	building_wall_south = ( ny + 1 - ngp_by ) / 2 * dy
1697	ENDIF
1698	index_south_bwall = NINT( building_wall_south / dy )
1699	index_north_bwall = index_south_bwall + ngp_by
1700
1701	!
1702	!-- Building size has to meet some requirements
1703	IF ( ( index_left_bwall < 1 ) .OR. ( index_right_bwall > nx-1 ) .OR. &
1704	( index_right_bwall < index_left_bwall+3 ) .OR. &
1705	( index_south_bwall < 1 ) .OR. ( index_north_bwall > ny-1 ) .OR.&
1706	( index_north_bwall < index_south_bwall+3 ) ) THEN
1707	WRITE( message_string, * ) 'inconsistent building parameters:', &
1708	'&index_left_bwall=', index_left_bwall, &
1709	'index_right_bwall=', index_right_bwall, &
1710	'index_south_bwall=', index_south_bwall, &
1711	'index_north_bwall=', index_north_bwall, &
1712	'nx=', nx, 'ny=', ny
1713	CALL message( 'init_grid', 'PA0203', 1, 2, 0, 6, 0 )
1714	ENDIF
1715
1716	ALLOCATE( nzb_local(nysg:nyng,nxlg:nxrg) )
1717	nzb_local = 0
1718	!
1719	!-- Define the building.
1720	IF ( index_left_bwall <= nxr .AND. index_right_bwall >= nxl .AND. &
1721	index_south_bwall <= nyn .AND. index_north_bwall >= nys ) &
1722	nzb_local(MAX(nys,index_south_bwall):MIN(nyn,index_north_bwall), &
1723	MAX(nxl,index_left_bwall):MIN(nxr,index_right_bwall)) = bh
1724	!
1725	!-- Set bit array on basis of nzb_local
1726	DO i = nxl, nxr
1727	DO j = nys, nyn
1728	topo(nzb_local(j,i)+1:nzt+1,j,i) = &
1729	IBSET( topo(nzb_local(j,i)+1:nzt+1,j,i), 0 )
1730	ENDDO
1731	ENDDO
1732
1733	DEALLOCATE( nzb_local )
1734
1735	CALL exchange_horiz_int( topo, nys, nyn, nxl, nxr, nzt, nbgp )
1736	!
1737	!-- Set boundary conditions also for flags. Can be interpreted as Neumann
1738	!-- boundary conditions for topography.
1739	IF ( .NOT. bc_ns_cyc ) THEN
1740	IF ( nys == 0 ) THEN
1741	DO i = 1, nbgp
1742	topo(:,nys-i,:) = topo(:,nys,:)
1743	ENDDO
1744	ENDIF
1745	IF ( nyn == ny ) THEN
1746	DO i = 1, nbgp
1747	topo(:,nyn+i,:) = topo(:,nyn,:)
1748	ENDDO
1749	ENDIF
1750	ENDIF
1751	IF ( .NOT. bc_lr_cyc ) THEN
1752	IF ( nxl == 0 ) THEN
1753	DO i = 1, nbgp
1754	topo(:,:,nxl-i) = topo(:,:,nxl)
1755	ENDDO
1756	ENDIF
1757	IF ( nxr == nx ) THEN
1758	DO i = 1, nbgp
1759	topo(:,:,nxr+i) = topo(:,:,nxr)
1760	ENDDO
1761	ENDIF
1762	ENDIF
1763
1764	CASE ( 'single_street_canyon' )
1765	!
1766	!-- Single quasi-2D street canyon of infinite length in x or y direction.
1767	!-- The canyon is centered in the other direction by default.
1768	IF ( canyon_width_x /= 9999999.9_wp ) THEN
1769	!
1770	!-- Street canyon in y direction
1771	ngp_cx = NINT( canyon_width_x / dx )
1772	IF ( canyon_wall_left == 9999999.9_wp ) THEN
1773	canyon_wall_left = ( nx + 1 - ngp_cx ) / 2 * dx
1774	ENDIF
1775	index_left_cwall= NINT( canyon_wall_left / dx )
1776	index_right_cwall= index_left_cwall+ ngp_cx
1777	ELSEIF ( canyon_width_y /= 9999999.9_wp ) THEN
1778	!
1779	!-- Street canyon in x direction
1780	ngp_cy = NINT( canyon_width_y / dy )
1781	IF ( canyon_wall_south == 9999999.9_wp ) THEN
1782	canyon_wall_south = ( ny + 1 - ngp_cy ) / 2 * dy
1783	ENDIF
1784	index_south_cwall = NINT( canyon_wall_south / dy )
1785	index_north_cwall = index_south_cwall + ngp_cy
1786
1787	ELSE
1788
1789	message_string = 'no street canyon width given'
1790	CALL message( 'init_grid', 'PA0204', 1, 2, 0, 6, 0 )
1791
1792	ENDIF
1793
1794	ch = MINLOC( ABS( zw - canyon_height ), 1 ) - 1
1795	IF ( ABS( zw(ch) - canyon_height ) == &
1796	ABS( zw(ch+1) - canyon_height ) ) ch = ch + 1
1797	dp_level_ind_b = ch
1798	!
1799	!-- Street canyon size has to meet some requirements
1800	IF ( canyon_width_x /= 9999999.9_wp ) THEN
1801	IF ( ( index_left_cwall< 1 ) .OR. ( index_right_cwall> nx-1 ) .OR.&
1802	( ngp_cx < 3 ) ) THEN
1803	WRITE( message_string, * ) 'inconsistent canyon parameters:', &
1804	'&index_left_cwall=', index_left_cwall, &
1805	' index_right_cwall=', index_right_cwall, &
1806	' ngp_cx=', ngp_cx, &
1807	' ch=', ch, ' nx=', nx, ' ny=', ny
1808	CALL message( 'init_grid', 'PA0205', 1, 2, 0, 6, 0 )
1809	ENDIF
1810	ELSEIF ( canyon_width_y /= 9999999.9_wp ) THEN
1811	IF ( ( index_south_cwall < 1 ) .OR. &
1812	( index_north_cwall > ny-1 ) .OR. ( ngp_cy < 3 ) ) THEN
1813	WRITE( message_string, * ) 'inconsistent canyon parameters:', &
1814	'&index_south_cwall=', index_south_cwall, &
1815	' index_north_cwall=', index_north_cwall, &
1816	' ngp_cy=', ngp_cy, &
1817	' ch=', ch, ' nx=', nx, ' ny=', ny
1818	CALL message( 'init_grid', 'PA0206', 1, 2, 0, 6, 0 )
1819	ENDIF
1820	ENDIF
1821	IF ( canyon_width_x /= 9999999.9_wp .AND. &
1822	canyon_width_y /= 9999999.9_wp ) THEN
1823	message_string = 'inconsistent canyon parameters:' // &
1824	'&street canyon can only be oriented' // &
1825	' either in x- or in y-direction'
1826	CALL message( 'init_grid', 'PA0207', 1, 2, 0, 6, 0 )
1827	ENDIF
1828
1829	ALLOCATE( nzb_local(nysg:nyng,nxlg:nxrg) )
1830	nzb_local = ch
1831	IF ( canyon_width_x /= 9999999.9_wp ) THEN
1832	IF ( index_left_cwall<= nxr .AND. index_right_cwall>= nxl ) &
1833	nzb_local(:,MAX(nxl,index_left_cwall+1):MIN(nxr,index_right_cwall-1)) = 0
1834	ELSEIF ( canyon_width_y /= 9999999.9_wp ) THEN
1835	IF ( index_south_cwall <= nyn .AND. index_north_cwall >= nys ) &
1836	nzb_local(MAX(nys,index_south_cwall+1):MIN(nyn,index_north_cwall-1),:) = 0
1837	ENDIF
1838	!
1839	!-- Set bit array on basis of nzb_local
1840	DO i = nxl, nxr
1841	DO j = nys, nyn
1842	topo(nzb_local(j,i)+1:nzt+1,j,i) = &
1843	IBSET( topo(nzb_local(j,i)+1:nzt+1,j,i), 0 )
1844	ENDDO
1845	ENDDO
1846	DEALLOCATE( nzb_local )
1847
1848	CALL exchange_horiz_int( topo, nys, nyn, nxl, nxr, nzt, nbgp )
1849	!
1850	!-- Set boundary conditions also for flags. Can be interpreted as Neumann
1851	!-- boundary conditions for topography.
1852	IF ( .NOT. bc_ns_cyc ) THEN
1853	IF ( nys == 0 ) THEN
1854	DO i = 1, nbgp
1855	topo(:,nys-i,:) = topo(:,nys,:)
1856	ENDDO
1857	ENDIF
1858	IF ( nyn == ny ) THEN
1859	DO i = 1, nbgp
1860	topo(:,nyn+i,:) = topo(:,nyn,:)
1861	ENDDO
1862	ENDIF
1863	ENDIF
1864	IF ( .NOT. bc_lr_cyc ) THEN
1865	IF ( nxl == 0 ) THEN
1866	DO i = 1, nbgp
1867	topo(:,:,nxl-i) = topo(:,:,nxl)
1868	ENDDO
1869	ENDIF
1870	IF ( nxr == nx ) THEN
1871	DO i = 1, nbgp
1872	topo(:,:,nxr+i) = topo(:,:,nxr)
1873	ENDDO
1874	ENDIF
1875	ENDIF
1876
1877	CASE ( 'tunnel' )
1878
1879	!
1880	!-- Tunnel height
1881	IF ( tunnel_height == 9999999.9_wp ) THEN
1882	th = zw( INT( 0.2 * nz) )
1883	ELSE
1884	th = tunnel_height
1885	ENDIF
1886	!
1887	!-- Tunnel-wall depth
1888	IF ( tunnel_wall_depth == 9999999.9_wp ) THEN
1889	td = MAX ( dx, dy, dz(1) )
1890	ELSE
1891	td = tunnel_wall_depth
1892	ENDIF
1893	!
1894	!-- Check for tunnel width
1895	IF ( tunnel_width_x == 9999999.9_wp .AND. &
1896	tunnel_width_y == 9999999.9_wp ) THEN
1897	message_string = 'No tunnel width is given. '
1898	CALL message( 'init_grid', 'PA0280', 1, 2, 0, 6, 0 )
1899	ENDIF
1900	IF ( tunnel_width_x /= 9999999.9_wp .AND. &
1901	tunnel_width_y /= 9999999.9_wp ) THEN
1902	message_string = 'Inconsistent tunnel parameters:' // &
1903	'tunnel can only be oriented' // &
1904	'either in x- or in y-direction.'
1905	CALL message( 'init_grid', 'PA0281', 1, 2, 0, 6, 0 )
1906	ENDIF
1907	!
1908	!-- Check for too small tunnel width in x- and y-direction
1909	IF ( tunnel_width_x /= 9999999.9_wp .AND. &
1910	tunnel_width_x - 2.0_wp * td <= 2.0_wp * dx ) THEN
1911	message_string = 'tunnel_width_x too small'
1912	CALL message( 'init_grid', 'PA0175', 1, 2, 0, 6, 0 )
1913	ENDIF
1914	IF ( tunnel_width_y /= 9999999.9_wp .AND. &
1915	tunnel_width_y - 2.0_wp * td <= 2.0_wp * dy ) THEN
1916	message_string = 'tunnel_width_y too small'
1917	CALL message( 'init_grid', 'PA0455', 1, 2, 0, 6, 0 )
1918	ENDIF
1919	!
1920	!-- Check for too large tunnel width.
1921	!-- Tunnel axis along y.
1922	IF ( tunnel_width_x /= 9999999.9_wp ) THEN
1923	IF ( tunnel_width_x > ( nx + 1 ) * dx ) THEN
1924	message_string = 'tunnel_width_x too large'
1925	CALL message( 'init_grid', 'PA0282', 1, 2, 0, 6, 0 )
1926	ENDIF
1927
1928	txs_out = INT( ( nx + 1 ) * 0.5_wp * dx - tunnel_width_x * 0.5_wp )
1929	txe_out = INT( ( nx + 1 ) * 0.5_wp * dx + tunnel_width_x * 0.5_wp )
1930	txs_in = INT( ( nx + 1 ) * 0.5_wp * dx - &
1931	( tunnel_width_x * 0.5_wp - td ) )
1932	txe_in = INT( ( nx + 1 ) * 0.5_wp * dx + &
1933	( tunnel_width_x * 0.5_wp - td ) )
1934
1935	tys_out = INT( ( ny + 1 ) * 0.5_wp * dy - tunnel_length * 0.5_wp )
1936	tye_out = INT( ( ny + 1 ) * 0.5_wp * dy + tunnel_length * 0.5_wp )
1937	tys_in = tys_out
1938	tye_in = tye_out
1939	ENDIF
1940	!
1941	!-- Tunnel axis along x.
1942	IF ( tunnel_width_y /= 9999999.9_wp ) THEN
1943	IF ( tunnel_width_y > ( ny + 1 ) * dy ) THEN
1944	message_string = 'tunnel_width_y too large'
1945	CALL message( 'init_grid', 'PA0456', 1, 2, 0, 6, 0 )
1946	ENDIF
1947
1948	txs_out = INT( ( nx + 1 ) * 0.5_wp * dx - tunnel_length * 0.5_wp )
1949	txe_out = INT( ( nx + 1 ) * 0.5_wp * dx + tunnel_length * 0.5_wp )
1950	txs_in = txs_out
1951	txe_in = txe_out
1952
1953	tys_out = INT( ( ny + 1 ) * 0.5_wp * dy - tunnel_width_y * 0.5_wp )
1954	tye_out = INT( ( ny + 1 ) * 0.5_wp * dy + tunnel_width_y * 0.5_wp )
1955	tys_in = INT( ( ny + 1 ) * 0.5_wp * dy - &
1956	( tunnel_width_y * 0.5_wp - td ) )
1957	tye_in = INT( ( ny + 1 ) * 0.5_wp * dy + &
1958	( tunnel_width_y * 0.5_wp - td ) )
1959	ENDIF
1960
1961	topo = 0
1962	DO i = nxl, nxr
1963	DO j = nys, nyn
1964	!
1965	!-- Use heaviside function to model outer tunnel surface
1966	hv_out = th * 0.5_wp * &
1967	( ( SIGN( 1.0_wp, i * dx - txs_out ) + 1.0_wp ) &
1968	- ( SIGN( 1.0_wp, i * dx - txe_out ) + 1.0_wp ) )
1969
1970	hv_out = hv_out * 0.5_wp * &
1971	( ( SIGN( 1.0_wp, j * dy - tys_out ) + 1.0_wp ) &
1972	- ( SIGN( 1.0_wp, j * dy - tye_out ) + 1.0_wp ) )
1973	!
1974	!-- Use heaviside function to model inner tunnel surface
1975	hv_in = ( th - td ) * 0.5_wp * &
1976	( ( SIGN( 1.0_wp, i * dx - txs_in ) + 1.0_wp ) &
1977	- ( SIGN( 1.0_wp, i * dx - txe_in ) + 1.0_wp ) )
1978
1979	hv_in = hv_in * 0.5_wp * &
1980	( ( SIGN( 1.0_wp, j * dy - tys_in ) + 1.0_wp ) &
1981	- ( SIGN( 1.0_wp, j * dy - tye_in ) + 1.0_wp ) )
1982	!
1983	!-- Set flags at x-y-positions without any tunnel surface
1984	IF ( hv_out - hv_in == 0.0_wp ) THEN
1985	topo(nzb+1:nzt+1,j,i) = IBSET( topo(nzb+1:nzt+1,j,i), 0 )
1986	!
1987	!-- Set flags at x-y-positions with tunnel surfaces
1988	ELSE
1989	DO k = nzb + 1, nzt + 1
1990	!
1991	!-- Inner tunnel
1992	IF ( hv_out - hv_in == th ) THEN
1993	IF ( zw(k) <= hv_out ) THEN
1994	topo(k,j,i) = IBCLR( topo(k,j,i), 0 )
1995	ELSE
1996	topo(k,j,i) = IBSET( topo(k,j,i), 0 )
1997	ENDIF
1998	ENDIF
1999	!
2000	!-- Lateral tunnel walls
2001	IF ( hv_out - hv_in == td ) THEN
2002	IF ( zw(k) <= hv_in ) THEN
2003	topo(k,j,i) = IBSET( topo(k,j,i), 0 )
2004	ELSEIF ( zw(k) > hv_in .AND. zw(k) <= hv_out ) THEN
2005	topo(k,j,i) = IBCLR( topo(k,j,i), 0 )
2006	ELSEIF ( zw(k) > hv_out ) THEN
2007	topo(k,j,i) = IBSET( topo(k,j,i), 0 )
2008	ENDIF
2009	ENDIF
2010	ENDDO
2011	ENDIF
2012	ENDDO
2013	ENDDO
2014
2015	CALL exchange_horiz_int( topo, nys, nyn, nxl, nxr, nzt, nbgp )
2016	!
2017	!-- Set boundary conditions also for flags. Can be interpreted as Neumann
2018	!-- boundary conditions for topography.
2019	IF ( .NOT. bc_ns_cyc ) THEN
2020	IF ( nys == 0 ) THEN
2021	DO i = 1, nbgp
2022	topo(:,nys-i,:) = topo(:,nys,:)
2023	ENDDO
2024	ENDIF
2025	IF ( nyn == ny ) THEN
2026	DO i = 1, nbgp
2027	topo(:,nyn+i,:) = topo(:,nyn,:)
2028	ENDDO
2029	ENDIF
2030	ENDIF
2031	IF ( .NOT. bc_lr_cyc ) THEN
2032	IF ( nxl == 0 ) THEN
2033	DO i = 1, nbgp
2034	topo(:,:,nxl-i) = topo(:,:,nxl)
2035	ENDDO
2036	ENDIF
2037	IF ( nxr == nx ) THEN
2038	DO i = 1, nbgp
2039	topo(:,:,nxr+i) = topo(:,:,nxr)
2040	ENDDO
2041	ENDIF
2042	ENDIF
2043
2044	CASE ( 'read_from_file' )
2045	!
2046	!-- Note, topography information have been already read.
2047	!-- If required, further process topography, i.e. reference buildings on
2048	!-- top of orography and set temporary 3D topography array, which is
2049	!-- used later to set grid flags. Calling of this rouinte is also
2050	!-- required in case of ASCII input, even though no distinction between
2051	!-- terrain- and building height is made in this case.
2052	CALL process_topography( topo )
2053	!
2054	!-- Filter holes resolved by only one grid-point
2055	CALL filter_topography( topo )
2056	!
2057	!-- Exchange ghost-points, as well as add cyclic or Neumann boundary
2058	!-- conditions.
2059	CALL exchange_horiz_int( topo, nys, nyn, nxl, nxr, nzt, nbgp )
2060	!
2061	!-- Set lateral boundary conditions for topography on all ghost layers
2062	IF ( .NOT. bc_ns_cyc ) THEN
2063	IF ( nys == 0 ) THEN
2064	DO i = 1, nbgp
2065	topo(:,nys-i,:) = topo(:,nys,:)
2066	ENDDO
2067	ENDIF
2068	IF ( nyn == ny ) THEN
2069	DO i = 1, nbgp
2070	topo(:,nyn+i,:) = topo(:,nyn,:)
2071	ENDDO
2072	ENDIF
2073	ENDIF
2074
2075	IF ( .NOT. bc_lr_cyc ) THEN
2076	IF ( nxl == 0 ) THEN
2077	DO i = 1, nbgp
2078	topo(:,:,nxl-i) = topo(:,:,nxl)
2079	ENDDO
2080	ENDIF
2081	IF ( nxr == nx ) THEN
2082	DO i = 1, nbgp
2083	topo(:,:,nxr+i) = topo(:,:,nxr)
2084	ENDDO
2085	ENDIF
2086	ENDIF
2087
2088
2089	CASE DEFAULT
2090	!
2091	!-- The DEFAULT case is reached either if the parameter topography
2092	!-- contains a wrong character string or if the user has defined a special
2093	!-- case in the user interface. There, the subroutine user_init_grid
2094	!-- checks which of these two conditions applies.
2095	CALL user_init_grid( topo )
2096	CALL filter_topography( topo )
2097
2098	END SELECT
2099	!
2100	!-- Consistency checks and index array initialization are only required for
2101	!-- non-flat topography.
2102	IF ( TRIM( topography ) /= 'flat' ) THEN
2103	!
2104	!-- In case of non-flat topography, check whether the convention how to
2105	!-- define the topography grid has been set correctly, or whether the default
2106	!-- is applicable. If this is not possible, abort.
2107	IF ( TRIM( topography_grid_convention ) == ' ' ) THEN
2108	IF ( TRIM( topography ) /= 'closed_channel' .AND. &
2109	TRIM( topography ) /= 'single_building' .AND. &
2110	TRIM( topography ) /= 'single_street_canyon' .AND. &
2111	TRIM( topography ) /= 'tunnel' .AND. &
2112	TRIM( topography ) /= 'read_from_file') THEN
2113	!-- The default value is not applicable here, because it is only valid
2114	!-- for the four standard cases 'single_building',
2115	!-- 'single_street_canyon', 'tunnel' and 'read_from_file'
2116	!-- defined in init_grid.
2117	WRITE( message_string, * ) &
2118	'The value for "topography_grid_convention" ', &
2119	'is not set. Its default value is & only valid for ', &
2120	'"topography" = ''single_building'', ''tunnel'' ', &
2121	'''single_street_canyon'', ''closed_channel'' & or ', &
2122	'''read_from_file''.', &
2123	'& Choose ''cell_edge'' or ''cell_center''.'
2124	CALL message( 'init_grid', 'PA0239', 1, 2, 0, 6, 0 )
2125	ELSE
2126	!-- The default value is applicable here.
2127	!-- Set convention according to topography.
2128	IF ( TRIM( topography ) == 'single_building' .OR. &
2129	TRIM( topography ) == 'single_street_canyon' ) THEN
2130	topography_grid_convention = 'cell_edge'
2131	ELSEIF ( TRIM( topography ) == 'read_from_file' .OR. &
2132	TRIM( topography ) == 'tunnel') THEN
2133	topography_grid_convention = 'cell_center'
2134	ENDIF
2135	ENDIF
2136	ELSEIF ( TRIM( topography_grid_convention ) /= 'cell_edge' .AND. &
2137	TRIM( topography_grid_convention ) /= 'cell_center' ) THEN
2138	WRITE( message_string, * ) &
2139	'The value for "topography_grid_convention" is ', &
2140	'not recognized.& Choose ''cell_edge'' or ''cell_center''.'
2141	CALL message( 'init_grid', 'PA0240', 1, 2, 0, 6, 0 )
2142	ENDIF
2143
2144
2145	IF ( topography_grid_convention == 'cell_edge' ) THEN
2146	!
2147	!-- The array nzb_local as defined using the 'cell_edge' convention
2148	!-- describes the actual total size of topography which is defined at the
2149	!-- cell edges where u=0 on the topography walls in x-direction and v=0
2150	!-- on the topography walls in y-direction. However, PALM uses individual
2151	!-- arrays nzb_u\|v\|w\|s_inner\|outer that are based on nzb_s_inner.
2152	!-- Therefore, the extent of topography in nzb_local is now reduced by
2153	!-- 1dx at the E topography walls and by 1dy at the N topography walls
2154	!-- to form the basis for nzb_s_inner.
2155	!-- Note, the reverse memory access (i-j instead of j-i) is absolutely
2156	!-- required at this point.
2157	DO j = nys+1, nyn+1
2158	DO i = nxl-1, nxr
2159	DO k = nzb, nzt+1
2160	IF ( BTEST( topo(k,j,i), 0 ) .OR. &
2161	BTEST( topo(k,j,i+1), 0 ) ) &
2162	topo(k,j,i) = IBSET( topo(k,j,i), 0 )
2163	ENDDO
2164	ENDDO
2165	ENDDO
2166	CALL exchange_horiz_int( topo, nys, nyn, nxl, nxr, nzt, nbgp )
2167
2168	DO i = nxl, nxr+1
2169	DO j = nys-1, nyn
2170	DO k = nzb, nzt+1
2171	IF ( BTEST( topo(k,j,i), 0 ) .OR. &
2172	BTEST( topo(k,j+1,i), 0 ) ) &
2173	topo(k,j,i) = IBSET( topo(k,j,i), 0 )
2174	ENDDO
2175	ENDDO
2176	ENDDO
2177	CALL exchange_horiz_int( topo, nys, nyn, nxl, nxr, nzt, nbgp )
2178
2179	ENDIF
2180	ENDIF
2181
2182
2183	END SUBROUTINE init_topo
2184
2185	SUBROUTINE set_topo_flags(topo)
2186
2187	USE control_parameters, &
2188	ONLY: bc_lr_cyc, bc_ns_cyc, constant_flux_layer, &
2189	scalar_advec, topography, use_surface_fluxes, use_top_fluxes
2190
2191	USE exchange_horiz_mod, &
2192	ONLY: exchange_horiz_int
2193
2194	USE indices, &
2195	ONLY: nbgp, nx, nxl, nxlg, nxr, nxrg, ny, nyn, nyng, nys, nysg, nzb, &
2196	nzt, topo_top_ind, wall_flags_static_0, wall_flags_total_0
2197
2198	USE kinds
2199
2200	IMPLICIT NONE
2201
2202	INTEGER(iwp) :: i !< index variable along x
2203	INTEGER(iwp) :: ibit !< integer bit position of topgraphy masking array
2204	INTEGER(iwp) :: j !< index variable along y
2205	INTEGER(iwp) :: k !< index variable along z
2206
2207	INTEGER(iwp), DIMENSION(nzb:nzt+1,nysg:nyng,nxlg:nxrg) :: topo !< input array for 3D topography and dummy array for setting "outer"-flags
2208
2209	ALLOCATE( wall_flags_static_0(nzb:nzt+1,nysg:nyng,nxlg:nxrg) )
2210	wall_flags_static_0 = 0
2211	!
2212	!-- Set-up topography flags. First, set flags only for s, u, v and w-grid.
2213	!-- Further special flags will be set in following loops.
2214	DO i = nxl, nxr
2215	DO j = nys, nyn
2216	DO k = nzb, nzt+1
2217	!
2218	!-- scalar grid
2219	IF ( BTEST( topo(k,j,i), 0 ) ) &
2220	wall_flags_static_0(k,j,i) = IBSET( wall_flags_static_0(k,j,i), 0 )
2221	!
2222	!-- u grid
2223	IF ( BTEST( topo(k,j,i), 0 ) .AND. &
2224	BTEST( topo(k,j,i-1), 0 ) ) &
2225	wall_flags_static_0(k,j,i) = IBSET( wall_flags_static_0(k,j,i), 1 )
2226	!
2227	!-- v grid
2228	IF ( BTEST( topo(k,j,i), 0 ) .AND. &
2229	BTEST( topo(k,j-1,i), 0 ) ) &
2230	wall_flags_static_0(k,j,i) = IBSET( wall_flags_static_0(k,j,i), 2 )
2231
2232	ENDDO
2233
2234	DO k = nzb, nzt
2235	!
2236	!-- w grid
2237	IF ( BTEST( topo(k,j,i), 0 ) .AND. &
2238	BTEST( topo(k+1,j,i), 0 ) ) &
2239	wall_flags_static_0(k,j,i) = IBSET( wall_flags_static_0(k,j,i), 3 )
2240	ENDDO
2241
2242	IF ( topography /= 'closed_channel' ) THEN
2243	wall_flags_static_0(nzt+1,j,i) = IBSET( wall_flags_static_0(nzt+1,j,i), 3 )
2244	ENDIF
2245
2246	ENDDO
2247	ENDDO
2248
2249	CALL exchange_horiz_int( wall_flags_static_0, nys, nyn, nxl, nxr, nzt, nbgp )
2250
2251	!
2252	!-- Set outer array for scalars to mask near-surface grid points. Note, on
2253	!-- basis of flag 24 futher flags will be derived which are used to control
2254	!-- production of subgrid TKE production near walls.
2255
2256	ALLOCATE( wall_flags_total_0(nzb:nzt+1,nysg:nyng,nxlg:nxrg) )
2257	wall_flags_total_0 = 0
2258
2259	DO i = nxl, nxr
2260	DO j = nys, nyn
2261	DO k = nzb, nzt+1
2262	wall_flags_total_0(k,j,i) = IOR( wall_flags_total_0(k,j,i), wall_flags_static_0(k,j,i) )
2263	ENDDO
2264	ENDDO
2265	ENDDO
2266
2267	CALL exchange_horiz_int( wall_flags_total_0, nys, nyn, nxl, nxr, nzt, nbgp )
2268
2269	DO i = nxl, nxr
2270	DO j = nys, nyn
2271	DO k = nzb, nzt+1
2272	IF ( BTEST( wall_flags_total_0(k,j-1,i), 0 ) .AND. &
2273	BTEST( wall_flags_total_0(k,j+1,i), 0 ) .AND. &
2274	BTEST( wall_flags_total_0(k,j,i-1), 0 ) .AND. &
2275	BTEST( wall_flags_total_0(k,j,i+1), 0 ) .AND. &
2276	BTEST( wall_flags_total_0(k,j-1,i-1), 0 ) .AND. &
2277	BTEST( wall_flags_total_0(k,j+1,i-1), 0 ) .AND. &
2278	BTEST( wall_flags_total_0(k,j-1,i+1), 0 ) .AND. &
2279	BTEST( wall_flags_total_0(k,j+1,i+1), 0 ) ) &
2280	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 24 )
2281	ENDDO
2282	ENDDO
2283	ENDDO
2284	!
2285	!-- Set further special flags
2286	DO i = nxl, nxr
2287	DO j = nys, nyn
2288	DO k = nzb, nzt+1
2289	!
2290	!-- scalar grid, former nzb_diff_s_inner.
2291	!-- Note, use this flag also to mask topography in diffusion_u and
2292	!-- diffusion_v along the vertical direction. In case of
2293	!-- use_surface_fluxes, fluxes are calculated via MOST, else, simple
2294	!-- gradient approach is applied. Please note, in case of u- and v-
2295	!-- diffuison, a small error is made at edges (on the east side for u,
2296	!-- at the north side for v), since topography on scalar grid point
2297	!-- is used instead of topography on u/v-grid. As number of topography grid
2298	!-- points on uv-grid is different than s-grid, different number of
2299	!-- surface elements would be required. In order to avoid this,
2300	!-- treat edges (u(k,j,i+1)) simply by a gradient approach, i.e. these
2301	!-- points are not masked within diffusion_u. Tests had shown that the
2302	!-- effect on the flow is negligible.
2303	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
2304	IF ( BTEST( wall_flags_total_0(k,j,i), 0 ) ) &
2305	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 8 )
2306	ELSE
2307	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 8 )
2308	ENDIF
2309
2310	ENDDO
2311	!
2312	!-- Special flag to control vertical diffusion at model top - former
2313	!-- nzt_diff
2314	wall_flags_total_0(:,j,i) = IBSET( wall_flags_total_0(:,j,i), 9 )
2315	IF ( use_top_fluxes ) &
2316	wall_flags_total_0(nzt+1,j,i) = IBCLR( wall_flags_total_0(nzt+1,j,i), 9 )
2317
2318
2319	DO k = nzb+1, nzt
2320	!
2321	!-- Special flag on u grid, former nzb_u_inner + 1, required
2322	!-- for disturb_field and initialization. Do not disturb directly at
2323	!-- topography, as well as initialize u with zero one grid point outside
2324	!-- of topography.
2325	IF ( BTEST( wall_flags_total_0(k-1,j,i), 1 ) .AND. &
2326	BTEST( wall_flags_total_0(k,j,i), 1 ) .AND. &
2327	BTEST( wall_flags_total_0(k+1,j,i), 1 ) ) &
2328	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 20 )
2329	!
2330	!-- Special flag on v grid, former nzb_v_inner + 1, required
2331	!-- for disturb_field and initialization. Do not disturb directly at
2332	!-- topography, as well as initialize v with zero one grid point outside
2333	!-- of topography.
2334	IF ( BTEST( wall_flags_total_0(k-1,j,i), 2 ) .AND. &
2335	BTEST( wall_flags_total_0(k,j,i), 2 ) .AND. &
2336	BTEST( wall_flags_total_0(k+1,j,i), 2 ) ) &
2337	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 21 )
2338	!
2339	!-- Special flag on scalar grid, former nzb_s_inner+1. Used for
2340	!-- lpm_sgs_tke
2341	IF ( BTEST( wall_flags_total_0(k,j,i), 0 ) .AND. &
2342	BTEST( wall_flags_total_0(k-1,j,i), 0 ) .AND. &
2343	BTEST( wall_flags_total_0(k+1,j,i), 0 ) ) &
2344	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 25 )
2345	!
2346	!-- Special flag on scalar grid, nzb_diff_s_outer - 1, required in
2347	!-- in production_e
2348	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
2349	IF ( BTEST( wall_flags_total_0(k,j,i), 24 ) .AND. &
2350	BTEST( wall_flags_total_0(k-1,j,i), 24 ) .AND. &
2351	BTEST( wall_flags_total_0(k+1,j,i), 0 ) ) &
2352	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 29 )
2353	ELSE
2354	IF ( BTEST( wall_flags_total_0(k,j,i), 0 ) ) &
2355	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 29 )
2356	ENDIF
2357	!
2358	!-- Special flag on scalar grid, nzb_diff_s_outer - 1, required in
2359	!-- in production_e
2360	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
2361	IF ( BTEST( wall_flags_total_0(k,j,i), 0 ) .AND. &
2362	BTEST( wall_flags_total_0(k-1,j,i), 0 ) .AND. &
2363	BTEST( wall_flags_total_0(k+1,j,i), 0 ) ) &
2364	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 30 )
2365	ELSE
2366	IF ( BTEST( wall_flags_total_0(k,j,i), 0 ) ) &
2367	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 30 )
2368	ENDIF
2369	ENDDO
2370	!
2371	!-- Flags indicating downward facing walls
2372	DO k = nzb+1, nzt+1
2373	!
2374	!-- Scalar grid
2375	IF ( BTEST( wall_flags_total_0(k-1,j,i), 0 ) .AND. &
2376	.NOT. BTEST( wall_flags_total_0(k,j,i), 0 ) ) &
2377	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 13 )
2378	!
2379	!-- Downward facing wall on u grid
2380	IF ( BTEST( wall_flags_total_0(k-1,j,i), 1 ) .AND. &
2381	.NOT. BTEST( wall_flags_total_0(k,j,i), 1 ) ) &
2382	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 15 )
2383	!
2384	!-- Downward facing wall on v grid
2385	IF ( BTEST( wall_flags_total_0(k-1,j,i), 2 ) .AND. &
2386	.NOT. BTEST( wall_flags_total_0(k,j,i), 2 ) ) &
2387	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 17 )
2388	!
2389	!-- Downward facing wall on w grid
2390	IF ( BTEST( wall_flags_total_0(k-1,j,i), 3 ) .AND. &
2391	.NOT. BTEST( wall_flags_total_0(k,j,i), 3 ) ) &
2392	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 19 )
2393	ENDDO
2394	!
2395	!-- Flags indicating upward facing walls
2396	DO k = nzb, nzt
2397	!
2398	!-- Upward facing wall on scalar grid
2399	IF ( .NOT. BTEST( wall_flags_total_0(k,j,i), 0 ) .AND. &
2400	BTEST( wall_flags_total_0(k+1,j,i), 0 ) ) &
2401	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 12 )
2402	!
2403	!-- Upward facing wall on u grid
2404	IF ( .NOT. BTEST( wall_flags_total_0(k,j,i), 1 ) .AND. &
2405	BTEST( wall_flags_total_0(k+1,j,i), 1 ) ) &
2406	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 14 )
2407
2408	!
2409	!-- Upward facing wall on v grid
2410	IF ( .NOT. BTEST( wall_flags_total_0(k,j,i), 2 ) .AND. &
2411	BTEST( wall_flags_total_0(k+1,j,i), 2 ) ) &
2412	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 16 )
2413
2414	!
2415	!-- Upward facing wall on w grid
2416	IF ( .NOT. BTEST( wall_flags_total_0(k,j,i), 3 ) .AND. &
2417	BTEST( wall_flags_total_0(k+1,j,i), 3 ) ) &
2418	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 18 )
2419	!
2420	!-- Special flag on scalar grid, former nzb_s_inner
2421	IF ( BTEST( wall_flags_total_0(k,j,i), 0 ) .OR. &
2422	BTEST( wall_flags_total_0(k,j,i), 12 ) .OR. &
2423	BTEST( wall_flags_total_0(k,j,i), 13 ) ) &
2424	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 22 )
2425	!
2426	!-- Special flag on scalar grid, nzb_diff_s_inner - 1, required for
2427	!-- flow_statistics
2428	IF ( constant_flux_layer .OR. use_surface_fluxes ) THEN
2429	IF ( BTEST( wall_flags_total_0(k,j,i), 0 ) .AND. &
2430	BTEST( wall_flags_total_0(k+1,j,i), 0 ) ) &
2431	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 23 )
2432	ELSE
2433	IF ( BTEST( wall_flags_total_0(k,j,i), 22 ) ) &
2434	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 23 )
2435	ENDIF
2436
2437
2438	ENDDO
2439	wall_flags_total_0(nzt+1,j,i) = IBSET( wall_flags_total_0(nzt+1,j,i), 22 )
2440	wall_flags_total_0(nzt+1,j,i) = IBSET( wall_flags_total_0(nzt+1,j,i), 23 )
2441	!
2442	!-- Set flags indicating that topography is close by in horizontal
2443	!-- direction, i.e. flags that infold the topography. These will be used
2444	!-- to set advection flags for passive scalars, where due to large
2445	!-- gradients near buildings stationary numerical oscillations can produce
2446	!-- unrealistically high concentrations. This is only necessary if
2447	!-- WS-scheme is applied for scalar advection. Note, these flags will be
2448	!-- only used for passive scalars such as chemical species or aerosols.
2449	IF ( scalar_advec == 'ws-scheme' ) THEN
2450	DO k = nzb, nzt
2451	IF ( BTEST( wall_flags_total_0(k,j,i), 0 ) .AND. ( &
2452	ANY( .NOT. BTEST( wall_flags_total_0(k,j-3:j+3,i-1), 0 ) ) .OR.&
2453	ANY( .NOT. BTEST( wall_flags_total_0(k,j-3:j+3,i-2), 0 ) ) .OR.&
2454	ANY( .NOT. BTEST( wall_flags_total_0(k,j-3:j+3,i-3), 0 ) ) .OR.&
2455	ANY( .NOT. BTEST( wall_flags_total_0(k,j-3:j+3,i+1), 0 ) ) .OR.&
2456	ANY( .NOT. BTEST( wall_flags_total_0(k,j-3:j+3,i+2), 0 ) ) .OR.&
2457	ANY( .NOT. BTEST( wall_flags_total_0(k,j-3:j+3,i+3), 0 ) ) .OR.&
2458	ANY( .NOT. BTEST( wall_flags_total_0(k,j-1,i-3:i+3), 0 ) ) .OR.&
2459	ANY( .NOT. BTEST( wall_flags_total_0(k,j-2,i-3:i+3), 0 ) ) .OR.&
2460	ANY( .NOT. BTEST( wall_flags_total_0(k,j-3,i-3:i+3), 0 ) ) .OR.&
2461	ANY( .NOT. BTEST( wall_flags_total_0(k,j+1,i-3:i+3), 0 ) ) .OR.&
2462	ANY( .NOT. BTEST( wall_flags_total_0(k,j+2,i-3:i+3), 0 ) ) .OR.&
2463	ANY( .NOT. BTEST( wall_flags_total_0(k,j+3,i-3:i+3), 0 ) ) &
2464	) ) &
2465	wall_flags_total_0(k,j,i) = IBSET( wall_flags_total_0(k,j,i), 31 )
2466
2467	ENDDO
2468	ENDIF
2469	ENDDO
2470	ENDDO
2471	!
2472	!-- Finally, set identification flags indicating natural terrain or buildings.
2473	!-- Natural terrain grid points. Information on the type of the surface is
2474	!-- stored in bit 1 of 3D Integer array topo. However, this bit is only set
2475	!-- when topography is read from file. In order to run the land-surface model
2476	!-- also without topography information, set bit 1 explicitely in this case.
2477	!--
2478	!-- Natural terrain grid points
2479	!-- If no topography is initialized, the land-surface is at k = nzb.
2480	IF ( TRIM( topography ) /= 'read_from_file' ) THEN
2481	wall_flags_static_0(nzb,:,:) = IBSET( wall_flags_static_0(nzb,:,:), 5 )
2482	ELSE
2483	DO i = nxl, nxr
2484	DO j = nys, nyn
2485	DO k = nzb, nzt+1
2486	!
2487	!-- Natural terrain grid point
2488	IF ( BTEST( topo(k,j,i), 1 ) ) &
2489	wall_flags_static_0(k,j,i) = IBSET( wall_flags_static_0(k,j,i), 5 )
2490	ENDDO
2491	ENDDO
2492	ENDDO
2493	ENDIF
2494	!
2495	!-- Building grid points.
2496	DO i = nxl, nxr
2497	DO j = nys, nyn
2498	DO k = nzb, nzt+1
2499	IF ( BTEST( topo(k,j,i), 2 ) ) &
2500	wall_flags_static_0(k,j,i) = IBSET( wall_flags_static_0(k,j,i), 6 )
2501	ENDDO
2502	ENDDO
2503	ENDDO
2504	!
2505	!-- Set flag 4, indicating new topography grid points due to filtering.
2506	DO i = nxl, nxr
2507	DO j = nys, nyn
2508	DO k = nzb, nzt+1
2509	IF ( BTEST( topo(k,j,i), 4 ) ) &
2510	wall_flags_static_0(k,j,i) = IBSET( wall_flags_static_0(k,j,i), 4 )
2511	ENDDO
2512	ENDDO
2513	ENDDO
2514
2515	CALL exchange_horiz_int( wall_flags_static_0, nys, nyn, nxl, nxr, nzt, nbgp )
2516
2517	DO i = nxl, nxr
2518	DO j = nys, nyn
2519	DO k = nzb, nzt+1
2520	wall_flags_total_0(k,j,i) = IOR( wall_flags_total_0(k,j,i), wall_flags_static_0(k,j,i) )
2521	ENDDO
2522	ENDDO
2523	ENDDO
2524	!
2525	!-- Exchange ghost points for wall flags
2526	CALL exchange_horiz_int( wall_flags_total_0, nys, nyn, nxl, nxr, nzt, nbgp )
2527	!
2528	!-- Set boundary conditions also for flags. Can be interpreted as Neumann
2529	!-- boundary conditions for topography.
2530	IF ( .NOT. bc_ns_cyc ) THEN
2531	IF ( nys == 0 ) THEN
2532	DO i = 1, nbgp
2533	wall_flags_total_0(:,nys-i,:) = wall_flags_total_0(:,nys,:)
2534	ENDDO
2535	ENDIF
2536	IF ( nyn == ny ) THEN
2537	DO i = 1, nbgp
2538	wall_flags_total_0(:,nyn+i,:) = wall_flags_total_0(:,nyn,:)
2539	ENDDO
2540	ENDIF
2541	ENDIF
2542	IF ( .NOT. bc_lr_cyc ) THEN
2543	IF ( nxl == 0 ) THEN
2544	DO i = 1, nbgp
2545	wall_flags_total_0(:,:,nxl-i) = wall_flags_total_0(:,:,nxl)
2546	ENDDO
2547	ENDIF
2548	IF ( nxr == nx ) THEN
2549	DO i = 1, nbgp
2550	wall_flags_total_0(:,:,nxr+i) = wall_flags_total_0(:,:,nxr)
2551	ENDDO
2552	ENDIF
2553	ENDIF
2554	!
2555	!-- Pre-calculate topography top indices (former get_topography_top_index
2556	!-- function)
2557	ALLOCATE( topo_top_ind(nysg:nyng,nxlg:nxrg,0:4) )
2558	!
2559	!-- Uppermost topography index on scalar grid
2560	ibit = 12
2561	topo_top_ind(:,:,0) = MAXLOC( &
2562	MERGE( 1, 0, &
2563	BTEST( wall_flags_total_0(:,:,:), ibit ) &
2564	), DIM = 1 &
2565	) - 1
2566	!
2567	!-- Uppermost topography index on u grid
2568	ibit = 14
2569	topo_top_ind(:,:,1) = MAXLOC( &
2570	MERGE( 1, 0, &
2571	BTEST( wall_flags_total_0(:,:,:), ibit ) &
2572	), DIM = 1 &
2573	) - 1
2574	!
2575	!-- Uppermost topography index on v grid
2576	ibit = 16
2577	topo_top_ind(:,:,2) = MAXLOC( &
2578	MERGE( 1, 0, &
2579	BTEST( wall_flags_total_0(:,:,:), ibit ) &
2580	), DIM = 1 &
2581	) - 1
2582	!
2583	!-- Uppermost topography index on w grid
2584	ibit = 18
2585	topo_top_ind(:,:,3) = MAXLOC( &
2586	MERGE( 1, 0, &
2587	BTEST( wall_flags_total_0(:,:,:), ibit ) &
2588	), DIM = 1 &
2589	) - 1
2590	!
2591	!-- Uppermost topography index on scalar outer grid
2592	ibit = 24
2593	topo_top_ind(:,:,4) = MAXLOC( &
2594	MERGE( 1, 0, &
2595	BTEST( wall_flags_total_0(:,:,:), ibit ) &
2596	), DIM = 1 &
2597	) - 1
2598
2599	END SUBROUTINE set_topo_flags

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