The COPYGB grid definition parameters for Polar Stereographic grids are listed below:
copygb -g"255 5 NX NY STARTLAT STARTLON 8 CENLON DX DY POLE 64" -x in.grb out.grb
| where | ||
| 255 5 | User-defined Polar Stereographic grid | |
| NX | Number of points on latitude circle | |
| NY | Number of points on longitude meridian | |
| STARTLAT | Southwest corner latitude * 1000 (lat = -90 ... 90) | |
| STARTLON | Southwest corner longitude * 1000 (lon = -180 ... 180) | |
| 8 | ||
| CENLON | Center longitude * 1000 | |
| DX | Longitudinal increment in meters | |
| DY | Latitudinal increment in meters | |
| POLE | Northern (0) or southern (128) hemisphere | |
| 64 |
Please note that all of the grid definition parameters must be integers. All latitude and longitude values are given in thousandths of a degree. The grid increments are given in meters.
User-Defined Polar Stereographic Grid
Again, let's look at the wgrib output for a Polar Stereographic grid and use it to define the grid definition arguments for COPYGB. Run wgrib on a Polar Stereographic dataset:
Here is the grid definition:
polar stereo: Lat1 7.838000 Long1 -141.028000 Orient -105.000000
north pole (65 x 43) Dx 190500 Dy 190500 scan 64 mode 9
Translate this definition to the COPYGB grid specification as follows:
- NX = 65
- NY = 43
- STARTLAT = 7838
- STARTLON = -141028
- CENLON = -105000
- DX = 190500
- DY = 190500
- POLE = 0
Plug these numbers into the grid specification and run COPYGB follows:
-xg"255 5 65 43 7838 -141028 8 -105000 190500 190500 0 64" \
$MET_TUTORIAL_DATA/input/sample_obs/ST2ml/ST2ml2005080712.Grb_G212 \
$MET_TUTORIAL_DATA/output/copygb/ST2ml2005080712.Grb_stereo
Lastly, run wgrib on the COPYGB output and make sure the grid matches the one listed above:
