| 1 | SUBROUTINE timestep |
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| 2 | |
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| 3 | !--------------------------------------------------------------------------------! |
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| 4 | ! This file is part of PALM. |
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| 5 | ! |
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| 6 | ! PALM is free software: you can redistribute it and/or modify it under the terms |
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| 7 | ! of the GNU General Public License as published by the Free Software Foundation, |
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| 8 | ! either version 3 of the License, or (at your option) any later version. |
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| 9 | ! |
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| 10 | ! PALM is distributed in the hope that it will be useful, but WITHOUT ANY |
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| 11 | ! WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR |
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| 12 | ! A PARTICULAR PURPOSE. See the GNU General Public License for more details. |
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| 13 | ! |
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| 14 | ! You should have received a copy of the GNU General Public License along with |
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| 15 | ! PALM. If not, see <http://www.gnu.org/licenses/>. |
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| 16 | ! |
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| 17 | ! Copyright 1997-2014 Leibniz Universitaet Hannover |
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| 18 | !--------------------------------------------------------------------------------! |
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| 19 | ! |
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| 20 | ! Current revisions: |
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| 21 | ! ------------------ |
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| 22 | ! |
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| 23 | ! |
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| 24 | ! Former revisions: |
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| 25 | ! ----------------- |
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| 26 | ! $Id: timestep.f90 1343 2014-03-26 17:07:58Z boeske $ |
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| 27 | ! |
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| 28 | ! 1342 2014-03-26 17:04:47Z kanani |
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| 29 | ! REAL constants defined as wp-kind |
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| 30 | ! |
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| 31 | ! 1322 2014-03-20 16:38:49Z raasch |
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| 32 | ! REAL functions provided with KIND-attribute |
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| 33 | ! |
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| 34 | ! 1320 2014-03-20 08:40:49Z raasch |
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| 35 | ! ONLY-attribute added to USE-statements, |
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| 36 | ! kind-parameters added to all INTEGER and REAL declaration statements, |
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| 37 | ! kinds are defined in new module kinds, |
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| 38 | ! old module precision_kind is removed, |
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| 39 | ! revision history before 2012 removed, |
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| 40 | ! comment fields (!:) to be used for variable explanations added to |
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| 41 | ! all variable declaration statements |
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| 42 | ! |
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| 43 | ! 1257 2013-11-08 15:18:40Z raasch |
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| 44 | ! openacc porting |
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| 45 | ! bugfix for calculation of advective timestep in case of vertically stretched |
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| 46 | ! grids |
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| 47 | ! |
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| 48 | ! 1092 2013-02-02 11:24:22Z raasch |
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| 49 | ! unused variables removed |
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| 50 | ! |
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| 51 | ! 1053 2012-11-13 17:11:03Z hoffmann |
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| 52 | ! timestep is reduced in two-moment cloud scheme according to the maximum |
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| 53 | ! terminal velocity of rain drops |
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| 54 | ! |
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| 55 | ! 1036 2012-10-22 13:43:42Z raasch |
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| 56 | ! code put under GPL (PALM 3.9) |
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| 57 | ! |
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| 58 | ! 1001 2012-09-13 14:08:46Z raasch |
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| 59 | ! all actions concerning leapfrog scheme removed |
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| 60 | ! |
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| 61 | ! 978 2012-08-09 08:28:32Z fricke |
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| 62 | ! restriction of the outflow damping layer in the diffusion criterion removed |
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| 63 | ! |
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| 64 | ! 866 2012-03-28 06:44:41Z raasch |
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| 65 | ! bugfix for timestep calculation in case of Galilei transformation, |
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| 66 | ! special treatment in case of mirror velocity boundary condition removed |
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| 67 | ! |
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| 68 | ! Revision 1.1 1997/08/11 06:26:19 raasch |
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| 69 | ! Initial revision |
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| 70 | ! |
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| 71 | ! |
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| 72 | ! Description: |
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| 73 | ! ------------ |
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| 74 | ! Compute the time step under consideration of the FCL and diffusion criterion. |
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| 75 | !------------------------------------------------------------------------------! |
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| 76 | |
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| 77 | USE arrays_3d, & |
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| 78 | ONLY: cdc, dzu, dzw, kh, km, lad_u, lad_v, lad_w, u, v, w |
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| 79 | |
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| 80 | USE cloud_parameters, & |
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| 81 | ONLY: dt_precipitation |
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| 82 | |
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| 83 | USE control_parameters, & |
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| 84 | ONLY: cfl_factor, coupling_mode, dt_3d, dt_fixed, dt_max, & |
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| 85 | galilei_transformation, old_dt, plant_canopy, message_string, & |
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| 86 | stop_dt, terminate_coupled, terminate_coupled_remote, & |
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| 87 | timestep_reason, u_gtrans, use_ug_for_galilei_tr, v_gtrans |
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| 88 | |
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| 89 | USE cpulog, & |
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| 90 | ONLY: cpu_log, log_point |
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| 91 | |
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| 92 | USE grid_variables, & |
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| 93 | ONLY: dx, dx2, dy, dy2 |
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| 94 | |
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| 95 | USE indices, & |
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| 96 | ONLY: nxl, nxlg, nxr, nxrg, nyn, nyng, nys, nysg, nzb, nzt |
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| 97 | |
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| 98 | USE interfaces |
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| 99 | |
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| 100 | USE kinds |
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| 101 | |
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| 102 | USE pegrid |
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| 103 | |
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| 104 | USE statistics, & |
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| 105 | ONLY: flow_statistics_called, hom, u_max, u_max_ijk, v_max, v_max_ijk,& |
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| 106 | w_max, w_max_ijk |
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| 107 | |
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| 108 | IMPLICIT NONE |
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| 109 | |
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| 110 | INTEGER(iwp) :: i !: |
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| 111 | INTEGER(iwp) :: j !: |
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| 112 | INTEGER(iwp) :: k !: |
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| 113 | |
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| 114 | REAL(wp) :: div !: |
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| 115 | REAL(wp) :: dt_diff !: |
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| 116 | REAL(wp) :: dt_diff_l !: |
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| 117 | REAL(wp) :: dt_plant_canopy !: |
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| 118 | REAL(wp) :: dt_plant_canopy_l !: |
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| 119 | REAL(wp) :: dt_plant_canopy_u !: |
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| 120 | REAL(wp) :: dt_plant_canopy_v !: |
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| 121 | REAL(wp) :: dt_plant_canopy_w !: |
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| 122 | REAL(wp) :: dt_u !: |
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| 123 | REAL(wp) :: dt_u_l !: |
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| 124 | REAL(wp) :: dt_v !: |
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| 125 | REAL(wp) :: dt_v_l !: |
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| 126 | REAL(wp) :: dt_w !: |
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| 127 | REAL(wp) :: dt_w_l !: |
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| 128 | REAL(wp) :: u_gtrans_l !: |
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| 129 | REAL(wp) :: u_max_l !: |
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| 130 | REAL(wp) :: u_min_l !: |
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| 131 | REAL(wp) :: value !: |
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| 132 | REAL(wp) :: v_gtrans_l !: |
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| 133 | REAL(wp) :: v_max_l !: |
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| 134 | REAL(wp) :: v_min_l !: |
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| 135 | REAL(wp) :: w_max_l !: |
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| 136 | REAL(wp) :: w_min_l !: |
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| 137 | |
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| 138 | REAL(wp), DIMENSION(2) :: uv_gtrans !: |
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| 139 | REAL(wp), DIMENSION(2) :: uv_gtrans_l !: |
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| 140 | REAL(wp), DIMENSION(3) :: reduce !: |
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| 141 | REAL(wp), DIMENSION(3) :: reduce_l !: |
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| 142 | REAL(wp), DIMENSION(nzb+1:nzt) :: dxyz2_min !: |
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| 143 | |
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| 144 | |
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| 145 | |
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| 146 | CALL cpu_log( log_point(12), 'calculate_timestep', 'start' ) |
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| 147 | |
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| 148 | ! |
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| 149 | !-- In case of Galilei-transform not using the geostrophic wind as translation |
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| 150 | !-- velocity, compute the volume-averaged horizontal velocity components, which |
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| 151 | !-- will then be subtracted from the horizontal wind for the time step and |
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| 152 | !-- horizontal advection routines. |
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| 153 | IF ( galilei_transformation .AND. .NOT. use_ug_for_galilei_tr ) THEN |
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| 154 | IF ( flow_statistics_called ) THEN |
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| 155 | ! |
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| 156 | !-- Horizontal averages already existent, just need to average them |
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| 157 | !-- vertically. |
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| 158 | u_gtrans = 0.0_wp |
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| 159 | v_gtrans = 0.0_wp |
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| 160 | DO k = nzb+1, nzt |
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| 161 | u_gtrans = u_gtrans + hom(k,1,1,0) |
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| 162 | v_gtrans = v_gtrans + hom(k,1,2,0) |
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| 163 | ENDDO |
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| 164 | u_gtrans = u_gtrans / REAL( nzt - nzb, KIND=wp ) |
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| 165 | v_gtrans = v_gtrans / REAL( nzt - nzb, KIND=wp ) |
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| 166 | ELSE |
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| 167 | ! |
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| 168 | !-- Averaging over the entire model domain. |
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| 169 | u_gtrans_l = 0.0_wp |
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| 170 | v_gtrans_l = 0.0_wp |
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| 171 | !$acc parallel present( u, v ) |
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| 172 | DO i = nxl, nxr |
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| 173 | DO j = nys, nyn |
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| 174 | DO k = nzb+1, nzt |
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| 175 | u_gtrans_l = u_gtrans_l + u(k,j,i) |
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| 176 | v_gtrans_l = v_gtrans_l + v(k,j,i) |
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| 177 | ENDDO |
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| 178 | ENDDO |
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| 179 | ENDDO |
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| 180 | !$acc end parallel |
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| 181 | uv_gtrans_l(1) = u_gtrans_l / REAL( (nxr-nxl+1)*(nyn-nys+1)*(nzt-nzb), KIND=wp ) |
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| 182 | uv_gtrans_l(2) = v_gtrans_l / REAL( (nxr-nxl+1)*(nyn-nys+1)*(nzt-nzb), KIND=wp ) |
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| 183 | #if defined( __parallel ) |
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| 184 | IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr ) |
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| 185 | CALL MPI_ALLREDUCE( uv_gtrans_l, uv_gtrans, 2, MPI_REAL, MPI_SUM, & |
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| 186 | comm2d, ierr ) |
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| 187 | u_gtrans = uv_gtrans(1) / REAL( numprocs, KIND=wp ) |
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| 188 | v_gtrans = uv_gtrans(2) / REAL( numprocs, KIND=wp ) |
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| 189 | #else |
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| 190 | u_gtrans = uv_gtrans_l(1) |
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| 191 | v_gtrans = uv_gtrans_l(2) |
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| 192 | #endif |
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| 193 | ENDIF |
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| 194 | ENDIF |
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| 195 | |
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| 196 | ! |
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| 197 | !-- Determine the maxima of the velocity components, including their |
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| 198 | !-- grid index positions. |
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| 199 | #if defined( __openacc ) |
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| 200 | IF ( dt_fixed ) THEN ! otherwise do it further below for better cache usage |
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| 201 | u_max_l = -999999.9_wp |
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| 202 | u_min_l = 999999.9_wp |
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| 203 | v_max_l = -999999.9_wp |
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| 204 | v_min_l = 999999.9_wp |
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| 205 | w_max_l = -999999.9_wp |
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| 206 | w_min_l = 999999.9_wp |
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| 207 | !$acc parallel present( u, v, w ) |
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| 208 | DO i = nxl, nxr |
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| 209 | DO j = nys, nyn |
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| 210 | DO k = nzb+1, nzt |
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| 211 | u_max_l = MAX( u_max_l, u(k,j,i) ) |
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| 212 | u_min_l = MIN( u_min_l, u(k,j,i) ) |
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| 213 | v_max_l = MAX( v_max_l, v(k,j,i) ) |
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| 214 | v_min_l = MIN( v_min_l, v(k,j,i) ) |
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| 215 | w_max_l = MAX( w_max_l, w(k,j,i) ) |
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| 216 | w_min_l = MIN( w_min_l, w(k,j,i) ) |
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| 217 | ENDDO |
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| 218 | ENDDO |
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| 219 | ENDDO |
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| 220 | !$acc end parallel |
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| 221 | #if defined( __parallel ) |
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| 222 | reduce_l(1) = u_max_l |
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| 223 | reduce_l(2) = v_max_l |
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| 224 | reduce_l(3) = w_max_l |
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| 225 | IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr ) |
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| 226 | CALL MPI_ALLREDUCE( reduce_l, reduce, 3, MPI_REAL, MPI_MAX, comm2d, ierr ) |
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| 227 | u_max = reduce(1) |
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| 228 | v_max = reduce(2) |
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| 229 | w_max = reduce(3) |
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| 230 | reduce_l(1) = u_min_l |
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| 231 | reduce_l(2) = v_min_l |
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| 232 | reduce_l(3) = w_min_l |
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| 233 | IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr ) |
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| 234 | CALL MPI_ALLREDUCE( reduce_l, reduce, 3, MPI_REAL, MPI_MIN, comm2d, ierr ) |
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| 235 | IF ( ABS( reduce(1) ) > u_max ) u_max = reduce(1) |
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| 236 | IF ( ABS( reduce(2) ) > v_max ) v_max = reduce(2) |
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| 237 | IF ( ABS( reduce(3) ) > w_max ) w_max = reduce(3) |
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| 238 | #else |
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| 239 | IF ( ABS( u_min_l ) > u_max_l ) THEN |
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| 240 | u_max = u_min_l |
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| 241 | ELSE |
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| 242 | u_max = u_max_l |
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| 243 | ENDIF |
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| 244 | IF ( ABS( v_min_l ) > v_max_l ) THEN |
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| 245 | v_max = v_min_l |
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| 246 | ELSE |
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| 247 | v_max = v_max_l |
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| 248 | ENDIF |
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| 249 | IF ( ABS( w_min_l ) > w_max_l ) THEN |
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| 250 | w_max = w_min_l |
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| 251 | ELSE |
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| 252 | w_max = w_max_l |
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| 253 | ENDIF |
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| 254 | #endif |
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| 255 | ENDIF |
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| 256 | #else |
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| 257 | CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, u, 'abs', 0.0_wp, & |
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| 258 | u_max, u_max_ijk ) |
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| 259 | CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, v, 'abs', 0.0_wp, & |
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| 260 | v_max, v_max_ijk ) |
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| 261 | CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, w, 'abs', 0.0_wp, & |
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| 262 | w_max, w_max_ijk ) |
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| 263 | #endif |
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| 264 | |
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| 265 | IF ( .NOT. dt_fixed ) THEN |
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| 266 | #if defined( __openacc ) |
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| 267 | ! |
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| 268 | !-- Variable time step: |
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| 269 | !-- Calculate the maximum time step according to the CFL-criterion, |
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| 270 | !-- individually for each velocity component |
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| 271 | dt_u_l = 999999.9_wp |
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| 272 | dt_v_l = 999999.9_wp |
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| 273 | dt_w_l = 999999.9_wp |
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| 274 | u_max_l = -999999.9_wp |
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| 275 | u_min_l = 999999.9_wp |
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| 276 | v_max_l = -999999.9_wp |
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| 277 | v_min_l = 999999.9_wp |
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| 278 | w_max_l = -999999.9_wp |
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| 279 | w_min_l = 999999.9_wp |
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| 280 | !$acc parallel loop collapse(3) present( u, v, w ) |
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| 281 | DO i = nxl, nxr |
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| 282 | DO j = nys, nyn |
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| 283 | DO k = nzb+1, nzt |
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| 284 | dt_u_l = MIN( dt_u_l, ( dx / ( ABS( u(k,j,i) - u_gtrans ) + 1.0E-10_wp ) ) ) |
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| 285 | dt_v_l = MIN( dt_v_l, ( dy / ( ABS( v(k,j,i) - v_gtrans ) + 1.0E-10_wp ) ) ) |
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| 286 | dt_w_l = MIN( dt_w_l, ( dzu(k) / ( ABS( w(k,j,i) ) + 1.0E-10_wp ) ) ) |
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| 287 | u_max_l = MAX( u_max_l, u(k,j,i) ) |
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| 288 | u_min_l = MIN( u_min_l, u(k,j,i) ) |
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| 289 | v_max_l = MAX( v_max_l, v(k,j,i) ) |
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| 290 | v_min_l = MIN( v_min_l, v(k,j,i) ) |
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| 291 | w_max_l = MAX( w_max_l, w(k,j,i) ) |
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| 292 | w_min_l = MIN( w_min_l, w(k,j,i) ) |
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| 293 | ENDDO |
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| 294 | ENDDO |
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| 295 | ENDDO |
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| 296 | !$acc end parallel |
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| 297 | |
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| 298 | #if defined( __parallel ) |
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| 299 | reduce_l(1) = dt_u_l |
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| 300 | reduce_l(2) = dt_v_l |
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| 301 | reduce_l(3) = dt_w_l |
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| 302 | IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr ) |
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| 303 | CALL MPI_ALLREDUCE( reduce_l, reduce, 3, MPI_REAL, MPI_MIN, comm2d, ierr ) |
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| 304 | dt_u = reduce(1) |
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| 305 | dt_v = reduce(2) |
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| 306 | dt_w = reduce(3) |
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| 307 | |
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| 308 | reduce_l(1) = u_max_l |
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| 309 | reduce_l(2) = v_max_l |
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| 310 | reduce_l(3) = w_max_l |
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| 311 | IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr ) |
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| 312 | CALL MPI_ALLREDUCE( reduce_l, reduce, 3, MPI_REAL, MPI_MAX, comm2d, ierr ) |
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| 313 | u_max = reduce(1) |
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| 314 | v_max = reduce(2) |
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| 315 | w_max = reduce(3) |
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| 316 | reduce_l(1) = u_min_l |
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| 317 | reduce_l(2) = v_min_l |
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| 318 | reduce_l(3) = w_min_l |
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| 319 | IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr ) |
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| 320 | CALL MPI_ALLREDUCE( reduce_l, reduce, 3, MPI_REAL, MPI_MIN, comm2d, ierr ) |
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| 321 | IF ( ABS( reduce(1) ) > u_max ) u_max = reduce(1) |
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| 322 | IF ( ABS( reduce(2) ) > v_max ) v_max = reduce(2) |
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| 323 | IF ( ABS( reduce(3) ) > w_max ) w_max = reduce(3) |
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| 324 | #else |
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| 325 | dt_u = dt_u_l |
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| 326 | dt_v = dt_v_l |
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| 327 | dt_w = dt_w_l |
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| 328 | |
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| 329 | IF ( ABS( u_min_l ) > u_max_l ) THEN |
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| 330 | u_max = u_min_l |
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| 331 | ELSE |
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| 332 | u_max = u_max_l |
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| 333 | ENDIF |
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| 334 | IF ( ABS( v_min_l ) > v_max_l ) THEN |
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| 335 | v_max = v_min_l |
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| 336 | ELSE |
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| 337 | v_max = v_max_l |
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| 338 | ENDIF |
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| 339 | IF ( ABS( w_min_l ) > w_max_l ) THEN |
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| 340 | w_max = w_min_l |
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| 341 | ELSE |
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| 342 | w_max = w_max_l |
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| 343 | ENDIF |
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| 344 | #endif |
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| 345 | |
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| 346 | #else |
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| 347 | ! |
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| 348 | !-- Variable time step: |
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| 349 | !-- Calculate the maximum time step according to the CFL-criterion, |
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| 350 | !-- individually for each velocity component |
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| 351 | dt_u_l = 999999.9_wp |
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| 352 | dt_v_l = 999999.9_wp |
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| 353 | dt_w_l = 999999.9_wp |
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| 354 | DO i = nxl, nxr |
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| 355 | DO j = nys, nyn |
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| 356 | DO k = nzb+1, nzt |
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| 357 | dt_u_l = MIN( dt_u_l, ( dx / ( ABS( u(k,j,i) - u_gtrans ) + 1.0E-10_wp ) ) ) |
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| 358 | dt_v_l = MIN( dt_v_l, ( dy / ( ABS( v(k,j,i) - v_gtrans ) + 1.0E-10_wp ) ) ) |
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| 359 | dt_w_l = MIN( dt_w_l, ( dzu(k) / ( ABS( w(k,j,i) ) + 1.0E-10_wp ) ) ) |
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| 360 | ENDDO |
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| 361 | ENDDO |
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| 362 | ENDDO |
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| 363 | |
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| 364 | #if defined( __parallel ) |
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| 365 | reduce_l(1) = dt_u_l |
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| 366 | reduce_l(2) = dt_v_l |
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| 367 | reduce_l(3) = dt_w_l |
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| 368 | IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr ) |
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| 369 | CALL MPI_ALLREDUCE( reduce_l, reduce, 3, MPI_REAL, MPI_MIN, comm2d, ierr ) |
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| 370 | dt_u = reduce(1) |
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| 371 | dt_v = reduce(2) |
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| 372 | dt_w = reduce(3) |
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| 373 | #else |
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| 374 | dt_u = dt_u_l |
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| 375 | dt_v = dt_v_l |
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| 376 | dt_w = dt_w_l |
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| 377 | #endif |
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| 378 | |
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| 379 | #endif |
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| 380 | |
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| 381 | ! |
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| 382 | !-- Compute time step according to the diffusion criterion. |
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| 383 | !-- First calculate minimum grid spacing which only depends on index k |
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| 384 | !-- Note: also at k=nzb+1 a full grid length is being assumed, although |
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| 385 | !-- in the Prandtl-layer friction term only dz/2 is used. |
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| 386 | !-- Experience from the old model seems to justify this. |
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| 387 | dt_diff_l = 999999.0_wp |
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| 388 | |
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| 389 | DO k = nzb+1, nzt |
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| 390 | dxyz2_min(k) = MIN( dx2, dy2, dzw(k)*dzw(k) ) * 0.125_wp |
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| 391 | ENDDO |
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| 392 | |
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| 393 | !$OMP PARALLEL private(i,j,k,value) reduction(MIN: dt_diff_l) |
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| 394 | !$OMP DO |
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| 395 | !$acc parallel loop collapse(3) present( kh, km ) |
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| 396 | DO i = nxl, nxr |
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| 397 | DO j = nys, nyn |
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| 398 | DO k = nzb+1, nzt |
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| 399 | dt_diff_l = MIN( dt_diff_l, dxyz2_min(k) / & |
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| 400 | ( MAX( kh(k,j,i), km(k,j,i) ) + 1E-20_wp ) ) |
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| 401 | ENDDO |
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| 402 | ENDDO |
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| 403 | ENDDO |
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| 404 | !$acc end parallel |
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| 405 | !$OMP END PARALLEL |
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| 406 | #if defined( __parallel ) |
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| 407 | IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr ) |
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| 408 | CALL MPI_ALLREDUCE( dt_diff_l, dt_diff, 1, MPI_REAL, MPI_MIN, comm2d, & |
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| 409 | ierr ) |
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| 410 | #else |
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| 411 | dt_diff = dt_diff_l |
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| 412 | #endif |
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| 413 | |
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| 414 | ! |
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| 415 | !-- Additional timestep criterion with plant canopies: |
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| 416 | !-- it is not allowed to extract more than the available momentum |
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| 417 | IF ( plant_canopy ) THEN |
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| 418 | |
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| 419 | dt_plant_canopy_l = 0.0_wp |
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| 420 | DO i = nxl, nxr |
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| 421 | DO j = nys, nyn |
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| 422 | DO k = nzb+1, nzt |
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| 423 | dt_plant_canopy_u = cdc(k,j,i) * lad_u(k,j,i) * & |
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| 424 | SQRT( u(k,j,i)**2 + & |
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| 425 | ( ( v(k,j,i-1) + & |
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| 426 | v(k,j,i) + & |
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| 427 | v(k,j+1,i) + & |
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| 428 | v(k,j+1,i-1) ) & |
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| 429 | / 4.0_wp )**2 + & |
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| 430 | ( ( w(k-1,j,i-1) + & |
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| 431 | w(k-1,j,i) + & |
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| 432 | w(k,j,i-1) + & |
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| 433 | w(k,j,i) ) & |
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| 434 | / 4.0_wp )**2 ) |
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| 435 | IF ( dt_plant_canopy_u > dt_plant_canopy_l ) THEN |
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| 436 | dt_plant_canopy_l = dt_plant_canopy_u |
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| 437 | ENDIF |
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| 438 | dt_plant_canopy_v = cdc(k,j,i) * lad_v(k,j,i) * & |
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| 439 | SQRT( ( ( u(k,j-1,i) + & |
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| 440 | u(k,j-1,i+1) + & |
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| 441 | u(k,j,i) + & |
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| 442 | u(k,j,i+1) ) & |
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| 443 | / 4.0_wp )**2 + & |
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| 444 | v(k,j,i)**2 + & |
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| 445 | ( ( w(k-1,j-1,i) + & |
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| 446 | w(k-1,j,i) + & |
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| 447 | w(k,j-1,i) + & |
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| 448 | w(k,j,i) ) & |
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| 449 | / 4.0_wp )**2 ) |
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| 450 | IF ( dt_plant_canopy_v > dt_plant_canopy_l ) THEN |
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| 451 | dt_plant_canopy_l = dt_plant_canopy_v |
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| 452 | ENDIF |
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| 453 | dt_plant_canopy_w = cdc(k,j,i) * lad_w(k,j,i) * & |
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| 454 | SQRT( ( ( u(k,j,i) + & |
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| 455 | u(k,j,i+1) + & |
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| 456 | u(k+1,j,i) + & |
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| 457 | u(k+1,j,i+1) ) & |
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| 458 | / 4.0_wp )**2 + & |
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| 459 | ( ( v(k,j,i) + & |
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| 460 | v(k,j+1,i) + & |
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| 461 | v(k+1,j,i) + & |
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| 462 | v(k+1,j+1,i) ) & |
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| 463 | / 4.0_wp )**2 + & |
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| 464 | w(k,j,i)**2 ) |
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| 465 | IF ( dt_plant_canopy_w > dt_plant_canopy_l ) THEN |
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| 466 | dt_plant_canopy_l = dt_plant_canopy_w |
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| 467 | ENDIF |
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| 468 | ENDDO |
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| 469 | ENDDO |
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| 470 | ENDDO |
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| 471 | |
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| 472 | IF ( dt_plant_canopy_l > 0.0_wp ) THEN |
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| 473 | ! |
|---|
| 474 | !-- Invert dt_plant_canopy_l and apply a security timestep factor 0.1 |
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| 475 | dt_plant_canopy_l = 0.1_wp / dt_plant_canopy_l |
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| 476 | ELSE |
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| 477 | ! |
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| 478 | !-- In case of inhomogeneous plant canopy, some processors may have no |
|---|
| 479 | !-- canopy at all. Then use dt_max as dummy instead. |
|---|
| 480 | dt_plant_canopy_l = dt_max |
|---|
| 481 | ENDIF |
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| 482 | |
|---|
| 483 | ! |
|---|
| 484 | !-- Determine the global minumum |
|---|
| 485 | #if defined( __parallel ) |
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| 486 | IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr ) |
|---|
| 487 | CALL MPI_ALLREDUCE( dt_plant_canopy_l, dt_plant_canopy, 1, MPI_REAL, & |
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| 488 | MPI_MIN, comm2d, ierr ) |
|---|
| 489 | #else |
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| 490 | dt_plant_canopy = dt_plant_canopy_l |
|---|
| 491 | #endif |
|---|
| 492 | |
|---|
| 493 | ELSE |
|---|
| 494 | ! |
|---|
| 495 | !-- Use dt_diff as dummy value to avoid extra IF branches further below |
|---|
| 496 | dt_plant_canopy = dt_diff |
|---|
| 497 | |
|---|
| 498 | ENDIF |
|---|
| 499 | |
|---|
| 500 | ! |
|---|
| 501 | !-- The time step is the minimum of the 3-4 components and the diffusion time |
|---|
| 502 | !-- step minus a reduction (cfl_factor) to be on the safe side. |
|---|
| 503 | !-- The time step must not exceed the maximum allowed value. |
|---|
| 504 | dt_3d = cfl_factor * MIN( dt_diff, dt_plant_canopy, dt_u, dt_v, dt_w, & |
|---|
| 505 | dt_precipitation ) |
|---|
| 506 | dt_3d = MIN( dt_3d, dt_max ) |
|---|
| 507 | |
|---|
| 508 | ! |
|---|
| 509 | !-- Remember the restricting time step criterion for later output. |
|---|
| 510 | IF ( MIN( dt_u, dt_v, dt_w ) < MIN( dt_diff, dt_plant_canopy ) ) THEN |
|---|
| 511 | timestep_reason = 'A' |
|---|
| 512 | ELSEIF ( dt_plant_canopy < dt_diff ) THEN |
|---|
| 513 | timestep_reason = 'C' |
|---|
| 514 | ELSE |
|---|
| 515 | timestep_reason = 'D' |
|---|
| 516 | ENDIF |
|---|
| 517 | |
|---|
| 518 | ! |
|---|
| 519 | !-- Set flag if the time step becomes too small. |
|---|
| 520 | IF ( dt_3d < ( 0.00001_wp * dt_max ) ) THEN |
|---|
| 521 | stop_dt = .TRUE. |
|---|
| 522 | |
|---|
| 523 | WRITE( message_string, * ) 'Time step has reached minimum limit.', & |
|---|
| 524 | '&dt = ', dt_3d, ' s Simulation is terminated.', & |
|---|
| 525 | '&old_dt = ', old_dt, ' s', & |
|---|
| 526 | '&dt_u = ', dt_u, ' s', & |
|---|
| 527 | '&dt_v = ', dt_v, ' s', & |
|---|
| 528 | '&dt_w = ', dt_w, ' s', & |
|---|
| 529 | '&dt_diff = ', dt_diff, ' s', & |
|---|
| 530 | '&dt_plant_canopy = ', dt_plant_canopy, ' s', & |
|---|
| 531 | '&u_max = ', u_max, ' m/s k=', u_max_ijk(1), & |
|---|
| 532 | ' j=', u_max_ijk(2), ' i=', u_max_ijk(3), & |
|---|
| 533 | '&v_max = ', v_max, ' m/s k=', v_max_ijk(1), & |
|---|
| 534 | ' j=', v_max_ijk(2), ' i=', v_max_ijk(3), & |
|---|
| 535 | '&w_max = ', w_max, ' m/s k=', w_max_ijk(1), & |
|---|
| 536 | ' j=', w_max_ijk(2), ' i=', w_max_ijk(3) |
|---|
| 537 | CALL message( 'timestep', 'PA0312', 0, 1, 0, 6, 0 ) |
|---|
| 538 | ! |
|---|
| 539 | !-- In case of coupled runs inform the remote model of the termination |
|---|
| 540 | !-- and its reason, provided the remote model has not already been |
|---|
| 541 | !-- informed of another termination reason (terminate_coupled > 0) before. |
|---|
| 542 | #if defined( __parallel ) |
|---|
| 543 | IF ( coupling_mode /= 'uncoupled' .AND. terminate_coupled == 0 ) THEN |
|---|
| 544 | terminate_coupled = 2 |
|---|
| 545 | IF ( myid == 0 ) THEN |
|---|
| 546 | CALL MPI_SENDRECV( & |
|---|
| 547 | terminate_coupled, 1, MPI_INTEGER, target_id, 0, & |
|---|
| 548 | terminate_coupled_remote, 1, MPI_INTEGER, target_id, 0, & |
|---|
| 549 | comm_inter, status, ierr ) |
|---|
| 550 | ENDIF |
|---|
| 551 | CALL MPI_BCAST( terminate_coupled_remote, 1, MPI_INTEGER, 0, comm2d, ierr) |
|---|
| 552 | ENDIF |
|---|
| 553 | #endif |
|---|
| 554 | ENDIF |
|---|
| 555 | |
|---|
| 556 | ! |
|---|
| 557 | !-- Ensure a smooth value (two significant digits) of the timestep. |
|---|
| 558 | div = 1000.0_wp |
|---|
| 559 | DO WHILE ( dt_3d < div ) |
|---|
| 560 | div = div / 10.0_wp |
|---|
| 561 | ENDDO |
|---|
| 562 | dt_3d = NINT( dt_3d * 100.0_wp / div ) * div / 100.0_wp |
|---|
| 563 | |
|---|
| 564 | ! |
|---|
| 565 | !-- Adjust the time step |
|---|
| 566 | old_dt = dt_3d |
|---|
| 567 | |
|---|
| 568 | ENDIF |
|---|
| 569 | |
|---|
| 570 | CALL cpu_log( log_point(12), 'calculate_timestep', 'stop' ) |
|---|
| 571 | |
|---|
| 572 | END SUBROUTINE timestep |
|---|
