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

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Revision 1.14 - (show annotations) (download)
Sat Jan 14 20:47:43 2006 UTC (18 years, 5 months ago) by jmc
Branch: MAIN
CVS Tags: checkpoint58e_post, checkpoint58h_post, checkpoint58j_post, checkpoint58f_post, checkpoint58d_post, checkpoint58c_post, checkpoint58a_post, checkpoint58i_post, checkpoint58g_post, checkpoint58b_post
Changes since 1.13: +6 -12 lines
fix for different longitude origin in input field & model grid

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 for bilinear 2 for bicubic
56 C mythid = thread id
57 C
58
59 #include "SIZE.h"
60 #include "EEPARAMS.h"
61 #include "PARAMS.h"
62
63 C subroutine variables
64 character*(*) infile
65 integer filePrec, irecord, nx_in, ny_in
66 _RL arrayout(1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy)
67 _RS xG_in (1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy)
68 _RS yG (1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy)
69 _RL lon_0, lon_inc
70 _RL lat_0, lat_inc(ny_in-1)
71 integer method, mythid
72
73 C local variables
74 c real*8 ne_fac,nw_fac,se_fac,sw_fac
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 integer i, j, k, l, js, bi, bj, sp, interp_unit
83 _RS xG(1-OLx:sNx+OLx,1-OLy:sNy+OLy,nSx,nSy)
84 _RS threeSixtyRS
85 PARAMETER ( threeSixtyRS = 360. )
86
87 C put xG in interval [ lon_0 , lon_0+360 [
88 do bj=myByLo(myThid),myByHi(myThid)
89 do bi=myBxLo(myThid),myBxHi(myThid)
90 do j=1-OLy,sNy+OLy
91 do i=1-OLx,sNx+OLx
92 xG(i,j,bi,bj) = xG_in(i,j,bi,bj)-lon_0
93 & + threeSixtyRS*2.
94 xG(i,j,bi,bj) = lon_0+mod(xG(i,j,bi,bj),threeSixtyRS)
95 enddo
96 enddo
97 enddo
98 enddo
99
100 call exf_interp_read(
101 I infile,
102 I filePrec,
103 O arrayin,
104 I irecord, xG, yG,
105 I lon_0, lon_inc,
106 I lat_0, lat_inc,
107 I nx_in, ny_in, method, mythid)
108 _BARRIER
109
110 C _BEGIN_MASTER( myThid )
111
112 C setup input grid
113 do i=-1,nx_in+2
114 x_in(i) = lon_0 + (i-1)*lon_inc
115 enddo
116
117 y_in(0) = lat_0 - lat_inc(1)
118 y_in(-1)= lat_0 - 2.*lat_inc(1)
119 y_in(1) = lat_0
120 do j=2,ny_in
121 y_in(j) = y_in(j-1) + lat_inc(j-1)
122 enddo
123 y_in(ny_in+1) = y_in(ny_in) + lat_inc(ny_in-1)
124 y_in(ny_in+2) = y_in(ny_in) + 2.*lat_inc(ny_in-1)
125
126 C enlarge boundary
127 do j=1,ny_in
128 arrayin(0,j) = arrayin(nx_in,j)
129 arrayin(-1,j) = arrayin(nx_in-1,j)
130 arrayin(nx_in+1,j) = arrayin(1,j)
131 arrayin(nx_in+2,j) = arrayin(2,j)
132 enddo
133 do i=-1,nx_in+2
134 arrayin(i,0) = arrayin(i,1)
135 arrayin(i,-1) = arrayin(i,1)
136 arrayin(i,ny_in+1) = arrayin(i,ny_in)
137 arrayin(i,ny_in+2) = arrayin(i,ny_in)
138 enddo
139
140 C _END_MASTER( myThid )
141
142 do bj = mybylo(mythid), mybyhi(mythid)
143 do bi = mybxlo(mythid), mybxhi(mythid)
144
145 C check validity of input/output coordinates
146 #ifdef ALLOW_DEBUG
147 if ( debugLevel .ge. debLevB ) then
148 do i=1,snx
149 do j=1,sny
150 if ( xG(i,j,bi,bj) .lt. x_in(0) .or.
151 & xG(i,j,bi,bj) .ge. x_in(nx_in+1) .or.
152 & yG(i,j,bi,bj) .lt. y_in(0) .or.
153 & yG(i,j,bi,bj) .ge. y_in(ny_in+1) ) then
154 print*,'ERROR in S/R EXF_INTERP:'
155 print*,' input grid must encompass output grid.'
156 print*,'i,j,bi,bj' ,i,j,bi,bj
157 print*,'xG,yG' ,xG(i,j,bi,bj),yG(i,j,bi,bj)
158 print*,'nx_in,ny_in' ,nx_in ,ny_in
159 print*,'x_in(0,nx_in+1)',x_in(0) ,x_in(nx_in+1)
160 print*,'y_in(0,ny_in+1)',y_in(0) ,y_in(ny_in+1)
161 STOP ' ABNORMAL END: S/R EXF_INTERP'
162 endif
163 enddo
164 enddo
165 endif
166 #endif /* ALLOW_DEBUG */
167
168 C compute interpolation indices
169 do i=1,snx
170 do j=1,sny
171 if (xG(i,j,bi,bj)-x_in(1) .ge. 0.) then
172 w_ind(i,j) = int((xG(i,j,bi,bj)-x_in(1))/lon_inc) + 1
173 else
174 w_ind(i,j) = int((xG(i,j,bi,bj)-x_in(1))/lon_inc)
175 endif
176 e_ind(i,j) = w_ind(i,j) + 1
177 js = ny_in*.5
178 do while (yG(i,j,bi,bj) .lt. y_in(js))
179 js = (js - 1)*.5
180 enddo
181 do while (yG(i,j,bi,bj) .ge. y_in(js+1))
182 js = js + 1
183 enddo
184 s_ind(i,j) = js
185 n_ind(i,j) = js + 1
186 enddo
187 enddo
188
189 if (method .eq. 1) then
190
191 C bilinear interpolation
192 sp = 2
193 do j=1,sny
194 do i=1,snx
195 arrayout(i,j,bi,bj) = 0.
196 do l=0,1
197 px_ind(l+1) = x_in(w_ind(i,j)+l)
198 py_ind(l+1) = y_in(s_ind(i,j)+l)
199 enddo
200 do k=1,2
201 ew_val(k) = arrayin(w_ind(i,j),s_ind(i,j)+k-1)
202 & *lagran(1,xG(i,j,bi,bj),px_ind,sp)
203 & +arrayin(e_ind(i,j),s_ind(i,j)+k-1)
204 & *lagran(2,xG(i,j,bi,bj),px_ind,sp)
205 arrayout(i,j,bi,bj)=arrayout(i,j,bi,bj)
206 & +ew_val(k)*lagran(k,yG(i,j,bi,bj),py_ind,sp)
207 enddo
208 enddo
209 enddo
210 elseif (method .eq. 2) then
211
212 C bicubic interpolation
213 sp = 4
214 do j=1,sny
215 do i=1,snx
216 arrayout(i,j,bi,bj) = 0.
217 do l=-1,2
218 px_ind(l+2) = x_in(w_ind(i,j)+l)
219 py_ind(l+2) = y_in(s_ind(i,j)+l)
220 enddo
221 do k=1,4
222 ew_val(k) =
223 & arrayin(w_ind(i,j)-1,s_ind(i,j)+k-2)
224 & *lagran(1,xG(i,j,bi,bj),px_ind,sp)
225 & +arrayin(w_ind(i,j) ,s_ind(i,j)+k-2)
226 & *lagran(2,xG(i,j,bi,bj),px_ind,sp)
227 & +arrayin(e_ind(i,j) ,s_ind(i,j)+k-2)
228 & *lagran(3,xG(i,j,bi,bj),px_ind,sp)
229 & +arrayin(e_ind(i,j)+1,s_ind(i,j)+k-2)
230 & *lagran(4,xG(i,j,bi,bj),px_ind,sp)
231 arrayout(i,j,bi,bj)=arrayout(i,j,bi,bj)
232 & +ew_val(k)*lagran(k,yG(i,j,bi,bj),py_ind,sp)
233 enddo
234 enddo
235 enddo
236 else
237 stop 'stop in exf_interp.F: interpolation method not supported'
238 endif
239 enddo
240 enddo
241
242 END

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