MET Online Tutorial for METv3.0

MET Online Tutorial for METv3.0

COPYGB Tool: Polar Stereographic Grid

The COPYGB grid definition parameters for Polar Stereographic grids are listed below:

copygb -g"255 5 NX NY STARTLAT STARTLON 8 CENLON DX DY 0 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
  0 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:

    wgrib -V tutorial/out/copygb/ST2ml2005080712.Grb_G202

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

Plug these numbers into the grid specification and run COPYGB follows:

    copygb.exe \
    -xg"255 5 65 43 7838 -141028 8 -105000 190500 190500 0 64" \
    data/sample_obs/ST2ml/ST2ml2005080712.Grb_G212 \
    tutorial/out/copygb/ST2ml2005080712.Grb_stereo

Lastly, run wgrib on the COPYGB output and make sure the grid matches the one listed above:

    wgrib -V tutorial/out/copygb/ST2ml2005080712.Grb_stereo