NCEPLIBS-w3emc  2.9.3
w3fc08.f
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1 C> @file
2 C> @brief U-V Comps from Earth to north hem grid.
3 C> @author John Stackpole @date 1981-12-30
4 
5 C> Given the Earth-oriented wind components on a northern
6 C> hemisphere polar stereographic grid point, compute the grid-
7 C> oriented components at that point. Input wind components at the
8 C> north pole point are assumed to conform to
9 C> the 'WMO' standards for reporting winds at the north pole, with
10 C> the output components computed relative to the X-Y axes on the
11 C> grid. (see office note 241 for WMO definition.)
12 C>
13 C> Program history log:
14 C> - John Stackpole 1981-12-30
15 C> - P. Chase 1988-10-18 Let output variables overlay input.
16 C> - Ralph Jones 1991-03-06 Change to cray cft77 fortran.
17 C>
18 C> @param[in] FFID REAL I-displacement from point to north pole in
19 C> grid units.
20 C> @param[in] FFJD REAL J-displacement from point to north pole in
21 C> grid units.
22 C> @param[in] FU REAL Earth-oriented u-component, positive from west.
23 C> @param[in] FV REAL Earth-oriented v-component, positive from east.
24 C> @param[out] FGU REAL Grid-oriented u-component. May reference
25 C> same location as FU.
26 C> @param[out] FGV REAL Grid-oriented v-component. May reference
27 C> same location as FV.
28 C>
29 C> @note FFID and FFJD may be calculated as followS.....
30 C> FFID = real(ip - i)
31 C> FFJD = real(jp - j)
32 C> where (ip, jp) are the grid coordinates of the north pole and
33 C> (i,j) are the grid coordinates of the point.
34 C>
35 C> @author John Stackpole @date 1981-12-30
36  SUBROUTINE w3fc08(FFID, FFJD, FU, FV, FGU, FGV)
37 C
38  SAVE
39 C
40  DATA cos280/ 0.1736482 /
41  DATA sin280/ -0.9848078 /
42 C
43 C COS280 AND SIN280 ARE FOR WIND AT POLE
44 C (USED FOR CO-ORDINATE ROTATION TO GRID ORIENTATION)
45 C
46  dfp = sqrt(ffid * ffid + ffjd * ffjd)
47  IF (dfp .EQ. 0.) THEN
48  xfgu = -(fu * cos280 + fv * sin280)
49  fgv = -(fv * cos280 - fu * sin280)
50  ELSE
51  xfgu = (fu * ffjd + fv * ffid) / dfp
52  fgv = (fv * ffjd - fu * ffid) / dfp
53  ENDIF
54  fgu = xfgu
55  RETURN
56  END
w3fc08
subroutine w3fc08(FFID, FFJD, FU, FV, FGU, FGV)
Given the Earth-oriented wind components on a northern hemisphere polar stereographic grid point,...
Definition: w3fc08.f:37