/[MITgcm]/MITgcm/pkg/exf/exf_interp.F
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Contents of /MITgcm/pkg/exf/exf_interp.F

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Revision 1.16 - (show annotations) (download)
Sat Jul 1 03:20:33 2006 UTC (17 years, 11 months ago) by dimitri
Branch: MAIN
Changes since 1.15: +5 -4 lines
numeral 90 changed to parameter ninety as required by certain compilers

1 #include "EXF_OPTIONS.h"
2 CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
3 C Flux Coupler using C
4 C Bilinear interpolation of forcing fields C
5 C C
6 C B. Cheng (12/2002) C
7 C C
8 C added Bicubic (bnc 1/2003) C
9 C C
10 CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC
11
12 real*8 function lagran(i,x,a,sp)
13
14 INTEGER i,k,sp
15 _RS x
16 real*8 a(4)
17 real*8 numer,denom
18
19 numer = 1.D0
20 denom = 1.D0
21
22 do k=1,sp
23 if ( k .ne. i) then
24 denom = denom*(a(i) - a(k))
25 numer = numer*(x - a(k))
26 endif
27 enddo
28
29 lagran = numer/denom
30
31 return
32 end
33
34
35 SUBROUTINE exf_interp(
36 I infile,
37 I filePrec,
38 O arrayout,
39 I irecord, xG_in, yG,
40 I lon_0, lon_inc,
41 I lat_0, lat_inc,
42 I nx_in, ny_in, method, mythid)
43
44 implicit none
45
46 C infile = name of the input file (direct access binary)
47 C filePrec = file precicision (currently not used, assumes real*4)
48 C arrout = output arrays (different for each processor)
49 C irecord = record number in global file
50 C xG,yG = coordinates for output grid
51 C lon_0, lat_0 = lon and lat of sw corner of global input grid
52 C lon_inc = scalar x-grid increment
53 C lat_inc = vector y-grid increments
54 C nx_in, ny_in = input x-grid and y-grid size
55 C method = 1,11,21 for bilinear; 2,12,22 for bicubic
56 C 1,2 for tracer; 11,12 for U; 21,22 for V
57 C mythid = thread id
58 C
59
60 #include "SIZE.h"
61 #include "EEPARAMS.h"
62 #include "PARAMS.h"
63
64 C subroutine variables
65 character*(*) infile
66 integer filePrec, irecord, nx_in, ny_in
67 _RL arrayout(1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy)
68 _RS xG_in (1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy)
69 _RS yG (1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy)
70 _RL lon_0, lon_inc
71 _RL lat_0, lat_inc(ny_in-1)
72 integer method, mythid
73
74 C local variables
75 integer e_ind(snx,sny),w_ind(snx,sny)
76 integer n_ind(snx,sny),s_ind(snx,sny)
77 real*8 px_ind(4), py_ind(4), ew_val(4)
78 external lagran
79 real*8 lagran
80 real*4 arrayin(-1:nx_in+2 , -1:ny_in+2)
81 real*8 x_in (-1:nx_in+2), y_in(-1:ny_in+2)
82 real*8 ninety PARAMETER ( ninety = 90. )
83 integer i, j, k, l, js, bi, bj, sp, interp_unit
84 _RS xG(1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy)
85 _RS threeSixtyRS, NorthValue
86 PARAMETER ( threeSixtyRS = 360. )
87
88 C put xG in interval [ lon_0 , lon_0+360 [
89 do bj=myByLo(myThid),myByHi(myThid)
90 do bi=myBxLo(myThid),myBxHi(myThid)
91 do j=1-OLy,sNy+OLy
92 do i=1-OLx,sNx+OLx
93 xG(i,j,bi,bj) = xG_in(i,j,bi,bj)-lon_0
94 & + threeSixtyRS*2.
95 xG(i,j,bi,bj) = lon_0+mod(xG(i,j,bi,bj),threeSixtyRS)
96 enddo
97 enddo
98 enddo
99 enddo
100
101 call exf_interp_read(
102 I infile, filePrec,
103 O arrayin,
104 I irecord, nx_in, ny_in, mythid)
105 _BARRIER
106
107 C _BEGIN_MASTER( myThid )
108
109 C setup input grid
110 do i=-1,nx_in+2
111 x_in(i) = lon_0 + (i-1)*lon_inc
112 enddo
113
114 y_in(0) = lat_0 - lat_inc(1)
115 y_in(-1)= lat_0 - 2.*lat_inc(1)
116 y_in(1) = lat_0
117 do j=2,ny_in
118 y_in(j) = y_in(j-1) + lat_inc(j-1)
119 enddo
120 c y_in(ny_in+1) = y_in(ny_in) + lat_inc(ny_in-1)
121 c y_in(ny_in+2) = y_in(ny_in) + 2.*lat_inc(ny_in-1)
122 y_in(ny_in+1) = min( y_in(ny_in) + lat_inc(ny_in-1), ninety )
123 y_in(ny_in+2) = min( y_in(ny_in) + 2.*lat_inc(ny_in-1), ninety )
124
125 C enlarge boundary
126 do j=1,ny_in
127 arrayin(0,j) = arrayin(nx_in,j)
128 arrayin(-1,j) = arrayin(nx_in-1,j)
129 arrayin(nx_in+1,j) = arrayin(1,j)
130 arrayin(nx_in+2,j) = arrayin(2,j)
131 enddo
132 do i=-1,nx_in+2
133 arrayin(i,0) = arrayin(i,1)
134 arrayin(i,-1) = arrayin(i,1)
135 arrayin(i,ny_in+1) = arrayin(i,ny_in)
136 arrayin(i,ny_in+2) = arrayin(i,ny_in)
137 enddo
138
139 C For tracer (method=1,2) set to northernmost zonal-mean value
140 C at 90N to avoid sharp zonal gradients near the Pole.
141 C For U (method=11,12) set to zero at 90N to minimize velocity
142 C gradient at North Pole
143 C For V (method=11,12) set to northernmost zonal value at 90N,
144 C as is already done above in order to allow cross-PoleArctic flow
145 if (y_in(ny_in+1).eq.ninety) then
146 if (method.eq.1 .or. method.eq.2) then
147 NorthValue = 0
148 do i=1,nx_in
149 NorthValue = NorthValue + arrayin(i,ny_in)
150 enddo
151 NorthValue = NorthValue / nx_in
152 do i=-1,nx_in+2
153 arrayin(i,ny_in+1) = NorthValue
154 enddo
155 elseif (method.eq.11 .or. method.eq.12) then
156 do i=-1,nx_in+2
157 arrayin(i,ny_in+1) = 0
158 enddo
159 endif
160 endif
161 if (y_in(ny_in+2).eq.ninety) then
162 if (method.eq.1 .or. method.eq.2) then
163 NorthValue = 0
164 do i=1,nx_in
165 NorthValue = NorthValue + arrayin(i,ny_in)
166 enddo
167 NorthValue = NorthValue / nx_in
168 do i=-1,nx_in+2
169 arrayin(i,ny_in+2) = NorthValue
170 enddo
171 elseif (method.eq.11 .or. method.eq.12) then
172 do i=-1,nx_in+2
173 arrayin(i,ny_in+2) = 0
174 enddo
175 endif
176 endif
177
178 C _END_MASTER( myThid )
179
180 do bj = mybylo(mythid), mybyhi(mythid)
181 do bi = mybxlo(mythid), mybxhi(mythid)
182
183 C check validity of input/output coordinates
184 #ifdef ALLOW_DEBUG
185 if ( debugLevel .ge. debLevB ) then
186 do i=1,snx
187 do j=1,sny
188 if ( xG(i,j,bi,bj) .lt. x_in(0) .or.
189 & xG(i,j,bi,bj) .ge. x_in(nx_in+1) .or.
190 & yG(i,j,bi,bj) .lt. y_in(0) .or.
191 & yG(i,j,bi,bj) .ge. y_in(ny_in+1) ) then
192 print*,'ERROR in S/R EXF_INTERP:'
193 print*,' input grid must encompass output grid.'
194 print*,'i,j,bi,bj' ,i,j,bi,bj
195 print*,'xG,yG' ,xG(i,j,bi,bj),yG(i,j,bi,bj)
196 print*,'nx_in,ny_in' ,nx_in ,ny_in
197 print*,'x_in(0,nx_in+1)',x_in(0) ,x_in(nx_in+1)
198 print*,'y_in(0,ny_in+1)',y_in(0) ,y_in(ny_in+1)
199 STOP ' ABNORMAL END: S/R EXF_INTERP'
200 endif
201 enddo
202 enddo
203 endif
204 #endif /* ALLOW_DEBUG */
205
206 C compute interpolation indices
207 do i=1,snx
208 do j=1,sny
209 if (xG(i,j,bi,bj)-x_in(1) .ge. 0.) then
210 w_ind(i,j) = int((xG(i,j,bi,bj)-x_in(1))/lon_inc) + 1
211 else
212 w_ind(i,j) = int((xG(i,j,bi,bj)-x_in(1))/lon_inc)
213 endif
214 e_ind(i,j) = w_ind(i,j) + 1
215 js = ny_in*.5
216 do while (yG(i,j,bi,bj) .lt. y_in(js))
217 js = (js - 1)*.5
218 enddo
219 do while (yG(i,j,bi,bj) .ge. y_in(js+1))
220 js = js + 1
221 enddo
222 s_ind(i,j) = js
223 n_ind(i,j) = js + 1
224 enddo
225 enddo
226
227 if (method.eq.1 .or. method.eq.11 .or. method.eq.21) then
228
229 C bilinear interpolation
230 sp = 2
231 do j=1,sny
232 do i=1,snx
233 arrayout(i,j,bi,bj) = 0.
234 do l=0,1
235 px_ind(l+1) = x_in(w_ind(i,j)+l)
236 py_ind(l+1) = y_in(s_ind(i,j)+l)
237 enddo
238 do k=1,2
239 ew_val(k) = arrayin(w_ind(i,j),s_ind(i,j)+k-1)
240 & *lagran(1,xG(i,j,bi,bj),px_ind,sp)
241 & +arrayin(e_ind(i,j),s_ind(i,j)+k-1)
242 & *lagran(2,xG(i,j,bi,bj),px_ind,sp)
243 arrayout(i,j,bi,bj)=arrayout(i,j,bi,bj)
244 & +ew_val(k)*lagran(k,yG(i,j,bi,bj),py_ind,sp)
245 enddo
246 enddo
247 enddo
248 elseif (method .eq. 2 .or. method.eq.12 .or. method.eq.22) then
249
250 C bicubic interpolation
251 sp = 4
252 do j=1,sny
253 do i=1,snx
254 arrayout(i,j,bi,bj) = 0.
255 do l=-1,2
256 px_ind(l+2) = x_in(w_ind(i,j)+l)
257 py_ind(l+2) = y_in(s_ind(i,j)+l)
258 enddo
259 do k=1,4
260 ew_val(k) =
261 & arrayin(w_ind(i,j)-1,s_ind(i,j)+k-2)
262 & *lagran(1,xG(i,j,bi,bj),px_ind,sp)
263 & +arrayin(w_ind(i,j) ,s_ind(i,j)+k-2)
264 & *lagran(2,xG(i,j,bi,bj),px_ind,sp)
265 & +arrayin(e_ind(i,j) ,s_ind(i,j)+k-2)
266 & *lagran(3,xG(i,j,bi,bj),px_ind,sp)
267 & +arrayin(e_ind(i,j)+1,s_ind(i,j)+k-2)
268 & *lagran(4,xG(i,j,bi,bj),px_ind,sp)
269 arrayout(i,j,bi,bj)=arrayout(i,j,bi,bj)
270 & +ew_val(k)*lagran(k,yG(i,j,bi,bj),py_ind,sp)
271 enddo
272 enddo
273 enddo
274 else
275 stop 'stop in exf_interp.F: interpolation method not supported'
276 endif
277 enddo
278 enddo
279
280 END

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