grid_tools 1.14.0
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global_equiv_resol.f90
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1
4
16program global_equiv_resol
17
18 use netcdf
19
20 implicit none
21
22 integer, parameter :: dp = kind(1.0d0)
23 real(dp), parameter :: pi_geom = 4.0*atan(1.0), &
24 radius_earth = 6371200.0
25
26 character(len=256) :: grid_fn
27 integer :: ncid, nxsg_dimid, nysg_dimid, dasg_varid, num_args
28 integer :: nxsg, nysg, nx, ny, res_equiv
29 real(dp) :: avg_cell_size, min_cell_size, max_cell_size
30 real(dp), dimension(:,:), allocatable :: &
31 quarter_da_ll, quarter_da_lr, quarter_da_ur, quarter_da_ul, &
32 dasg, da, sqrt_da
33!
34!=======================================================================
35!
36! Read in the name of the file from the command line. The command-line
37! call to this program should have exactly one argument consisting of
38! the path to the NetCDF grid specification file to be read in. If this
39! is not the case, print out a usage message and exit.
40!
41!=======================================================================
42!
43 num_args = command_argument_count()
44 if (num_args == 1) then
45 call get_command_argument(1, grid_fn)
46 else
47 WRITE(*,500)
48 WRITE(*,500) "Exactly one argument must be specified to program global_equiv_resol."
49 WRITE(*,500) "Usage:"
50 WRITE(*,500)
51 WRITE(*,500) " global_equiv_resol path_to_grid_file"
52 WRITE(*,500)
53 WRITE(*,500) "where path_to_grid_file is the path to the NetCDF grid file. Actual "
54 WRITE(*,500) "number of specified command line arguments is:"
55 WRITE(*,510) " num_args = ", num_args
56 WRITE(*,500) "Stopping."
57500 FORMAT(a)
58510 FORMAT(a, i3)
59 stop
60 end if
61!
62!=======================================================================
63!
64! Open the grid file and read in the dimensions of the supergrid. The
65! supergrid is a grid that has twice the resolution of the actual/compu-
66! tational grid. In the file, the names of the supergrid dimensions are
67! nx and ny. Here, however, we reserve those names for the dimensions
68! of the actual grid (since in the FV3 code and in other data files, nx
69! and ny are used to denote the dimensions of the actual grid) and in-
70! stead use the variables nxSG and nySG to denote the dimensions of the
71! supergrid.
72!
73!=======================================================================
74!
75 WRITE(*,500)
76 WRITE(*,500) "Opening NetCDF grid file for reading/writing:"
77 WRITE(*,500) " grid_fn = " // trim(grid_fn)
78
79 call check( nf90_open(trim(grid_fn), nf90_write, ncid) )
80
81 call check( nf90_inq_dimid(ncid, "nx", nxsg_dimid) )
82 call check( nf90_inquire_dimension(ncid, nxsg_dimid, len=nxsg) )
83
84 call check( nf90_inq_dimid(ncid, "ny", nysg_dimid) )
85 call check( nf90_inquire_dimension(ncid, nysg_dimid, len=nysg) )
86
87 WRITE(*,500)
88 WRITE(*,500) "Dimensions of supergrid are:"
89 WRITE(*,520) " nxSG = ", nxsg
90 WRITE(*,520) " nySG = ", nysg
91520 FORMAT(a, i7)
92!
93!=======================================================================
94!
95! Read in the cell areas on the supergrid. Then add the areas of the
96! four supergrid cells that make up one grid cell to obtain the cell
97! areas on the actual grid.
98!
99!=======================================================================
100!
101 allocate(dasg(0:nxsg-1, 0:nysg-1))
102 call check( nf90_inq_varid(ncid, "area", dasg_varid) )
103 call check( nf90_get_var(ncid, dasg_varid, dasg) )
104
105 nx = nxsg/2
106 ny = nysg/2
107
108 WRITE(*,500)
109 WRITE(*,500) "Dimensions of (actual, i.e. computational) grid are:"
110 WRITE(*,520) " nx = ", nx
111 WRITE(*,520) " ny = ", ny
112
113 allocate(quarter_da_ll(0:nx-1, 0:ny-1))
114 allocate(quarter_da_lr(0:nx-1, 0:ny-1))
115 allocate(quarter_da_ul(0:nx-1, 0:ny-1))
116 allocate(quarter_da_ur(0:nx-1, 0:ny-1))
117
118 quarter_da_ll = dasg(0:nxsg-1:2, 0:nysg-1:2)
119 quarter_da_lr = dasg(0:nxsg-1:2, 1:nysg-1:2)
120 quarter_da_ur = dasg(1:nxsg-1:2, 1:nysg-1:2)
121 quarter_da_ul = dasg(1:nxsg-1:2, 0:nysg-1:2)
122
123 allocate(da(0:nx-1, 0:ny-1))
124 allocate(sqrt_da(0:nx-1, 0:ny-1))
125
126 da = quarter_da_ll + quarter_da_lr + quarter_da_ur + quarter_da_ul
127!
128!=======================================================================
129!
130! Calculate a typical/representative cell size for each cell by taking
131! the square root of the area of the cell. Then calculate the minimum,
132! maximum, and average cell sizes over the whole grid.
133!
134!=======================================================================
135!
136 sqrt_da = sqrt(da)
137 min_cell_size = minval(sqrt_da)
138 max_cell_size = maxval(sqrt_da)
139 avg_cell_size = sum(sqrt_da)/(nx*ny)
140
141 WRITE(*,500)
142 WRITE(*,500) "Minimum, maximum, and average cell sizes are (based on square"
143 WRITE(*,500) "root of cell area):"
144 WRITE(*,530) " min_cell_size = ", min_cell_size
145 WRITE(*,530) " max_cell_size = ", max_cell_size
146 WRITE(*,530) " avg_cell_size = ", avg_cell_size
147530 FORMAT(a, g11.4)
148!
149!=======================================================================
150!
151! Use the average cell size to calculate an equivalent global uniform
152! cubed-sphere resolution (in units of number of cells) for the regional
153! grid. This is the RES that a global uniform (i.e. stretch factor of
154! 1) cubed-sphere grid would need to have in order to have the same no-
155! minal cell size as the average cell size of the regional grid.
156!
157!=======================================================================
158!
159 res_equiv = nint( (2.0*pi_geom*radius_earth)/(4.0*avg_cell_size) )
160
161 WRITE(*,500)
162 WRITE(*,500) "Equivalent global uniform cubed-sphere resolution is:"
163 WRITE(*,*) " RES_equiv = ", res_equiv
164!
165!=======================================================================
166!
167! Write the average cell size and equivalent global resolution to the
168! grid file as a global attributes.
169!
170!=======================================================================
171!
172 WRITE(*,500)
173 WRITE(*,500) "Writing avg_cell_size and RES_equiv to the grid specification"
174 WRITE(*,500) "file as global attributes..."
175
176 call check( nf90_redef(ncid) )
177 call check( nf90_put_att(ncid, nf90_global, "avg_cell_size", avg_cell_size) )
178 call check( nf90_put_att(ncid, nf90_global, "RES_equiv", res_equiv) )
179 call check( nf90_enddef(ncid) )
180
181 call check( nf90_close(ncid) )
182
183 WRITE(*,500)
184 WRITE(*,500) "Done."
185
186end program global_equiv_resol
187
192subroutine check(status)
193 use netcdf
194 integer,intent(in) :: status
195!
196 if(status /= nf90_noerr) then
197 write(0,*) ' check netcdf status = ', status
198 write(0,'("error ", a)') trim(nf90_strerror(status))
199 stop "Stopped"
200 endif
201end subroutine check
check
subroutine check(status)
Check results of netCDF call.
Definition filter_topo.F90:1999
global_equiv_resol
program global_equiv_resol
Compute the global equivalent resolution for regional grids using the average model grid cell size in...
Definition global_equiv_resol.f90:16