1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
|
C Copyright 1981-2007 ECMWF
C
C Licensed under the GNU Lesser General Public License which
C incorporates the terms and conditions of version 3 of the GNU
C General Public License.
C See LICENSE and gpl-3.0.txt for details.
C
SUBROUTINE NGVALUE(NEWFLD, NEXT, INROW, RLAT, RLON,
X POLELAT, POLELON, NGAUSS, TYPE, FIELD,
X GLATS, NGPTS)
C
C---->
C**** NGVALUE
C
C PURPOSE
C _______
C
C Rotates one line of latitude in a gaussian grid.
C
C INTERFACE
C _________
C
C CALL NGVALUE(NEWFLD, NEXT, INROW, RLAT, RLON,
C X POLELAT,POLELON,NGAUSS,TYPE,FIELD,GLATS,NGPTS)
C
C
C Input parameters
C ________________
C
C NEWFLD - The field of values being created
C NEXT - Start offset of the latitude row being created
C INROW - The number of points in the latitude row
C RLAT - Target point latitude in the rotated grid
C RLON - Target point longitude in the rotated grid
C POLELAT - Latitude of the rotated South Pole
C POLELON - Longitude of the rotated South Pole
C NGAUSS - Original unrotated gaussian field number
C TYPE - Original unrotated gaussian field type
C = 'F' for full (regular) gaussian field
C = 'R' for reduced (quasi) gaussian field
C FIELD - Original unrotated gaussian field values
C GLATS - Gaussian latitudes for original field
C NGPTS - Number of points along original field latitudes
C
C Output parameters
C ________________
C
C NEWFLD(NEXT) to NEWFLD(NEXT+INROW-1) contains the latitude row
C values.
C
C
C METHOD
C ______
C
C Rotates the lat/long positions of points along a latitude row in
C a rotated gaussian grid back to positions in the unrotated grid
C and then interpolates values from the original grid.
C
C
C EXTERNALS
C _________
C
C LL2XYZ - Converts a latitude/longitude position to (x,y,z)
C wrt axes through the centre of the globe. The z-axis
C runs from the south to north pole. The x- and y-axes
C are in the plane of the equator with the x-axis
C pointing out through lat/long (0,0).
C YROTATE - Rotates the globe about the new y-axis.
C XYZ2LL - Converts an (x,y,z) position to a latitude/longitude.
C NGINTRP - Interpolates a value from an existing grid.
C
C
C REFERENCE
C _________
C
C None
C
C
C COMMENTS
C ________
C
C The input field is assumed to be global in extent, and a known
C definition, either N160 or N80 (reduced or regular).
C
C
C AUTHOR
C ______
C
C J.D.Chambers ECMWF April 1996
C
C
C MODIFICATIONS
C _____________
C
C None.
C
C----<
C _______________________________________________________
C
C* Section 0. Definition of variables.
C _______________________________________________________
C
IMPLICIT NONE
C
C Parameters
C
INTEGER JPMAXGG
PARAMETER( JPMAXGG = 1280 )
C
C Function arguments
C
REAL RLAT, POLELAT, POLELON
REAL NEWFLD(*), RLON(*), FIELD(*), GLATS(*)
INTEGER NEXT, INROW, NGAUSS, NGPTS(*)
CHARACTER*1 TYPE
C
C Local variables
C
REAL X(JPMAXGG), Y(JPMAXGG), Z(JPMAXGG)
REAL RX(JPMAXGG),RY(JPMAXGG),RZ(JPMAXGG)
REAL OLAT(JPMAXGG),OLON(JPMAXGG)
INTEGER LOOP
C
C Convert the rotated row points lat/longs to (x,y,z) coordinates
C
CALL LL2XYZ(RLAT,RLON,X,Y,Z,INROW)
C
C Rotate the rotated row points back through the original latitude
C rotation
C
CALL YROTATE(-(90.0+POLELAT),X,Y,Z,RX,RY,RZ,INROW)
C
C Convert the rotated row points adjusted (x,y,z) coordinates to
C lat/long in the original grid (after longitude rotation)
C
CALL XYZ2LL(RX,RY,RZ,OLAT,OLON,INROW)
C
C Adjust the rotated line longitudes to remove the longitude
C rotation
C
DO LOOP = 1, INROW
OLON(LOOP) = OLON(LOOP) + POLELON
IF( OLON(LOOP).LT.0.0 ) OLON(LOOP) = OLON(LOOP) + 360.0
IF( OLON(LOOP).GE.360.0 ) OLON(LOOP) = OLON(LOOP) - 360.0
ENDDO
C
C Interpolate the original unrotated grid to the points in the
C rotated line
C
CALL NGINTRP(NEWFLD,NEXT,INROW,OLAT,OLON,NGAUSS,TYPE,FIELD,
X GLATS,NGPTS)
C
RETURN
END
|
