Finding corners of grid cells

[gabriel_bromley]

Hello,

I would like to implement 1st order conservative remapping using the CDO utilities. They require the 4 corner lats and lons of each grid cell as referenced below. Is there any utility that exists that could get these corners? Any ideas?

Here is an example for the CDO description of a curvilinear grid. xvals/yvals describe the positions of the 6x5 quadrilateral grid cells. The first 4 values of xbounds/ybounds are the corners of the first grid cell.

gridtype  = curvilinear 
gridsize  = 30 
xsize     = 6 
ysize     = 5 
xvals     =  -21  -11    0   11   21   30  -25  -13    0   13 
              25   36  -31  -16    0   16   31   43  -38  -21 
               0   21   38   52  -51  -30    0   30   51   64 
xbounds   =  -23  -14  -17  -28       -14   -5   -6  -17        -5    5    6   -6 
               5   14   17    6        14   23   28   17        23   32   38   28 
             -28  -17  -21  -34       -17   -6   -7  -21        -6    6    7   -7 
               6   17   21    7        17   28   34   21        28   38   44   34 
             -34  -21  -27  -41       -21   -7   -9  -27        -7    7    9   -9 
               7   21   27    9        21   34   41   27        34   44   52   41 
             -41  -27  -35  -51       -27   -9  -13  -35        -9    9   13  -13 
               9   27   35   13        27   41   51   35        41   52   63   51 
             -51  -35  -51  -67       -35  -13  -21  -51       -13   13   21  -21 
              13   35   51   21        35   51   67   51        51   63   77   67 
yvals     =   29   32   32   32   29   26   39   42   42   42 
              39   35   48   51   52   51   48   43   57   61 
              62   61   57   51   65   70   72   70   65   58 
ybounds   =   23   26   36   32        26   27   37   36        27   27   37   37 
              27   26   36   37        26   23   32   36        23   19   28   32 
              32   36   45   41        36   37   47   45        37   37   47   47 
              37   36   45   47        36   32   41   45        32   28   36   41 
              41   45   55   50        45   47   57   55        47   47   57   57 
              47   45   55   57        45   41   50   55        41   36   44   50 
              50   55   64   58        55   57   67   64        57   57   67   67 
              57   55   64   67        55   50   58   64        50   44   51   58 
              58   64   72   64        64   67   77   72        67   67   77   77 
              67   64   72   77        64   58   64   72        58   51   56   64

 

[mgduda]

The XLAT_C and XLONG_C fields in the geogrid output files should provide you with the corner latitudes and longitudes:

	float XLAT_C(Time, south_north_stag, west_east_stag) ;
		XLAT_C:FieldType = 104 ;
		XLAT_C:MemoryOrder = "XY " ;
		XLAT_C:units = "degrees latitude" ;
		XLAT_C:description = "Latitude at grid cell corners" ;
		XLAT_C:stagger = "CORNER" ;
		XLAT_C:sr_x = 1 ;
		XLAT_C:sr_y = 1 ;
	float XLONG_C(Time, south_north_stag, west_east_stag) ;
		XLONG_C:FieldType = 104 ;
		XLONG_C:MemoryOrder = "XY " ;
		XLONG_C:units = "degrees longitude" ;
		XLONG_C:description = "Longitude at grid cell corners" ;
		XLONG_C:stagger = "CORNER" ;
		XLONG_C:sr_x = 1 ;
		XLONG_C:sr_y = 1 ;

 

[gabriel_bromley]

So the 4 corner longitudes of the first grid cell would be:

xlong_c[0][0]
xlong_c[0][1]
xlong_c[1][1]
xlong_c[1][0]

Am I interpreting this correctly?

Thanks,

Gabe

 

[mgduda]

Yes, that should work.