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

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Revision 1.18 - (show annotations) (download)
Sun Jul 2 13:02:22 2006 UTC (17 years, 11 months ago) by dimitri
Branch: MAIN
CVS Tags: checkpoint58l_post, checkpoint58u_post, checkpoint58w_post, checkpoint58r_post, checkpoint58n_post, checkpoint58x_post, checkpoint58t_post, checkpoint58q_post, checkpoint58o_post, checkpoint58y_post, checkpoint58k_post, checkpoint58v_post, checkpoint58s_post, checkpoint58p_post, checkpoint58m_post
Changes since 1.17: +36 -46 lines
for bicubic interpolation, identical consecutive
input grid latitudes are not allowed

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
83 PARAMETER ( ninety = 90. )
84 integer i, j, k, l, js, bi, bj, sp, interp_unit
85 _RS xG(1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy)
86 _RS threeSixtyRS, NorthValue
87 PARAMETER ( threeSixtyRS = 360. )
88
89 C put xG in interval [ lon_0 , lon_0+360 [
90 do bj=myByLo(myThid),myByHi(myThid)
91 do bi=myBxLo(myThid),myBxHi(myThid)
92 do j=1-OLy,sNy+OLy
93 do i=1-OLx,sNx+OLx
94 xG(i,j,bi,bj) = xG_in(i,j,bi,bj)-lon_0
95 & + threeSixtyRS*2.
96 xG(i,j,bi,bj) = lon_0+mod(xG(i,j,bi,bj),threeSixtyRS)
97 enddo
98 enddo
99 enddo
100 enddo
101
102 call exf_interp_read(
103 I infile, filePrec,
104 O arrayin,
105 I irecord, nx_in, ny_in, mythid)
106 _BARRIER
107
108 C _BEGIN_MASTER( myThid )
109
110 C setup input longitude grid
111 do i=-1,nx_in+2
112 x_in(i) = lon_0 + (i-1)*lon_inc
113 enddo
114
115 C setup input latitude grid
116 y_in(0) = lat_0 - lat_inc(1)
117 y_in(-1)= lat_0 - 2.*lat_inc(1)
118 y_in(1) = lat_0
119 do j=2,ny_in
120 y_in(j) = y_in(j-1) + lat_inc(j-1)
121 enddo
122 do j=ny_in+1,ny_in+2
123 if (y_in(j-1).eq.ninety) then
124 y_in(j) = 2 * ninety - y_in(j-2)
125 else
126 y_in(j) = min( y_in(j-1)+lat_inc(ny_in-1), ninety )
127 endif
128 enddo
129
130 C enlarge boundary
131 do j=1,ny_in
132 arrayin(0,j) = arrayin(nx_in,j)
133 arrayin(-1,j) = arrayin(nx_in-1,j)
134 arrayin(nx_in+1,j) = arrayin(1,j)
135 arrayin(nx_in+2,j) = arrayin(2,j)
136 enddo
137 do i=-1,nx_in+2
138 arrayin(i,0) = arrayin(i,1)
139 arrayin(i,-1) = arrayin(i,1)
140 arrayin(i,ny_in+1) = arrayin(i,ny_in)
141 arrayin(i,ny_in+2) = arrayin(i,ny_in)
142 enddo
143
144 C For tracer (method=1,2) set to northernmost zonal-mean value
145 C at 90N to avoid sharp zonal gradients near the Pole.
146 C For U (method=11,12) set to zero at 90N to minimize velocity
147 C gradient at North Pole
148 C For V (method=11,12) set to northernmost zonal value at 90N,
149 C as is already done above in order to allow cross-PoleArctic flow
150 do j=ny_in,ny_in+2
151 if (y_in(j).eq.ninety) then
152 if (method.eq.1 .or. method.eq.2) then
153 NorthValue = 0
154 do i=1,nx_in
155 NorthValue = NorthValue + arrayin(i,j)
156 enddo
157 NorthValue = NorthValue / nx_in
158 do i=-1,nx_in+2
159 arrayin(i,j) = NorthValue
160 enddo
161 elseif (method.eq.11 .or. method.eq.12) then
162 do i=-1,nx_in+2
163 arrayin(i,j) = 0
164 enddo
165 endif
166 endif
167 enddo
168
169 C _END_MASTER( myThid )
170
171 do bj = mybylo(mythid), mybyhi(mythid)
172 do bi = mybxlo(mythid), mybxhi(mythid)
173
174 C check validity of input/output coordinates
175 #ifdef ALLOW_DEBUG
176 if ( debugLevel .ge. debLevB ) then
177 do i=1,snx
178 do j=1,sny
179 if ( xG(i,j,bi,bj) .lt. x_in(0) .or.
180 & xG(i,j,bi,bj) .ge. x_in(nx_in+1) .or.
181 & yG(i,j,bi,bj) .lt. y_in(0) .or.
182 & yG(i,j,bi,bj) .ge. y_in(ny_in+1) ) then
183 print*,'ERROR in S/R EXF_INTERP:'
184 print*,' input grid must encompass output grid.'
185 print*,'i,j,bi,bj' ,i,j,bi,bj
186 print*,'xG,yG' ,xG(i,j,bi,bj),yG(i,j,bi,bj)
187 print*,'nx_in,ny_in' ,nx_in ,ny_in
188 print*,'x_in(0,nx_in+1)',x_in(0) ,x_in(nx_in+1)
189 print*,'y_in(0,ny_in+1)',y_in(0) ,y_in(ny_in+1)
190 STOP ' ABNORMAL END: S/R EXF_INTERP'
191 endif
192 enddo
193 enddo
194 endif
195 #endif /* ALLOW_DEBUG */
196
197 C compute interpolation indices
198 do i=1,snx
199 do j=1,sny
200 if (xG(i,j,bi,bj)-x_in(1) .ge. 0.) then
201 w_ind(i,j) = int((xG(i,j,bi,bj)-x_in(1))/lon_inc) + 1
202 else
203 w_ind(i,j) = int((xG(i,j,bi,bj)-x_in(1))/lon_inc)
204 endif
205 e_ind(i,j) = w_ind(i,j) + 1
206 js = ny_in*.5
207 do while (yG(i,j,bi,bj) .lt. y_in(js))
208 js = (js - 1)*.5
209 enddo
210 do while (yG(i,j,bi,bj) .ge. y_in(js+1))
211 js = js + 1
212 enddo
213 s_ind(i,j) = js
214 n_ind(i,j) = js + 1
215 enddo
216 enddo
217
218 if (method.eq.1 .or. method.eq.11 .or. method.eq.21) then
219
220 C bilinear interpolation
221 sp = 2
222 do j=1,sny
223 do i=1,snx
224 arrayout(i,j,bi,bj) = 0.
225 do l=0,1
226 px_ind(l+1) = x_in(w_ind(i,j)+l)
227 py_ind(l+1) = y_in(s_ind(i,j)+l)
228 enddo
229 do k=1,2
230 ew_val(k) = arrayin(w_ind(i,j),s_ind(i,j)+k-1)
231 & *lagran(1,xG(i,j,bi,bj),px_ind,sp)
232 & +arrayin(e_ind(i,j),s_ind(i,j)+k-1)
233 & *lagran(2,xG(i,j,bi,bj),px_ind,sp)
234 arrayout(i,j,bi,bj)=arrayout(i,j,bi,bj)
235 & +ew_val(k)*lagran(k,yG(i,j,bi,bj),py_ind,sp)
236 enddo
237 enddo
238 enddo
239 elseif (method .eq. 2 .or. method.eq.12 .or. method.eq.22) then
240
241 C bicubic interpolation
242 sp = 4
243 do j=1,sny
244 do i=1,snx
245 arrayout(i,j,bi,bj) = 0.
246 do l=-1,2
247 px_ind(l+2) = x_in(w_ind(i,j)+l)
248 py_ind(l+2) = y_in(s_ind(i,j)+l)
249 enddo
250 do k=1,4
251 ew_val(k) =
252 & arrayin(w_ind(i,j)-1,s_ind(i,j)+k-2)
253 & *lagran(1,xG(i,j,bi,bj),px_ind,sp)
254 & +arrayin(w_ind(i,j) ,s_ind(i,j)+k-2)
255 & *lagran(2,xG(i,j,bi,bj),px_ind,sp)
256 & +arrayin(e_ind(i,j) ,s_ind(i,j)+k-2)
257 & *lagran(3,xG(i,j,bi,bj),px_ind,sp)
258 & +arrayin(e_ind(i,j)+1,s_ind(i,j)+k-2)
259 & *lagran(4,xG(i,j,bi,bj),px_ind,sp)
260 arrayout(i,j,bi,bj)=arrayout(i,j,bi,bj)
261 & +ew_val(k)*lagran(k,yG(i,j,bi,bj),py_ind,sp)
262 enddo
263 enddo
264 enddo
265 else
266 stop 'stop in exf_interp.F: interpolation method not supported'
267 endif
268 enddo
269 enddo
270
271 END

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