da_xyll_latlon.inc

1 subroutine da_xyll_latlon(x, y, proj, lat, lon)
2 
3    !-----------------------------------------------------------------------
4    ! Purpose: Compute the lat/lon location of an x/y on a LATLON grid.
5    !-----------------------------------------------------------------------
6 
7    implicit none
8 
9    real, intent(in)             :: x
10    real, intent(in)             :: y
11    type(proj_info), intent(in)  :: proj
12    real, intent(out)            :: lat
13    real, intent(out)            :: lon
14 
15    real                         :: deltalat
16    real                         :: deltalon
17    real                         :: latinc
18    real                         :: loninc
19 
20    if (trace_use_frequent) call da_trace_entry("da_xyll_latlon")
21 
22    ! Extract the latitude and longitude increments for this grid
23    ! (e.g., 2.5 deg for NCEP reanalysis) from the proj structure, where
24    ! loninc is saved in the stdlon tag and latinc is saved in truelat1
25 
26    latinc = proj%truelat1
27    loninc = proj%stdlon
28 
29    ! Compute deltalat and deltalon 
30 
31    deltalat = (x-1.0)*latinc
32    deltalon = (y-1.0)*loninc
33    lat = proj%lat1 + deltalat
34    lon = proj%lon1 + deltalon
35 
36    if ((ABS(lat) > 90.0).OR.(ABS(deltalon) > 360.0)) then
37       ! Off the earth for this grid
38       lat = -999.0
39       lon = -999.0
40    else
41       lon = lon + 360.0
42       lon = MOD(lon,360.0)
43       if (lon > 180.0) lon = lon -360.0
44    end if
45 
46    if (trace_use_frequent) call da_trace_exit("da_xyll_latlon")
47 
48 end subroutine da_xyll_latlon
49 
50