MET Online Tutorial for METv3.0

COPYGB Tool: Lambert Conformal Grid

The COPYGB grid definition parameters for Lambert Conformal grids are listed below:

copygb -g"255 3 NX NY STARTLAT STARTLON 8 CENLON DX DY 0 64 TRUELAT1 TRUELAT2" -x in.grb out.grb

where  
  255 3 User-defined Lambert Conformal 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
  TRUELAT1 First true latitude * 1000
  TRUELAT2 Second true latitude * 1000

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 Lambert Conformal Grid

Rather than defining a Lambert Conformal manually, we'll use the output of wgrib to define the grid we'd like to use. Let's look again at the wgrib output for NCEP grid 212:

    wgrib -V data/sample_obs/ST2ml/ST2ml2005080712.Grb_G212

Here is the grid definition:

    Lambert Conf: Lat1 12.190000 Lon1 -133.459000 Lov -95.000000
    Latin1 25.000000 Latin2 25.000000 LatSP 0.000000 LonSP 0.000000
    North Pole (185 x 129) Dx 40.635000 Dy 40.635000 scan 64 mode 8

Translate this definition to the COPYGB grid specification as follows:

  • NX = 185
  • NY = 129
  • STARTLAT = 12190
  • STARTLON = -133459
  • CENLON = -95000
  • DX = 40635
  • DY = 40635
  • TRUELAT1 = 25000
  • TRUELAT2 = 25000

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

    copygb.exe \
    -xg"255 3 185 129 12190 -133459 8 -95000 40635 40635 0 64 25000 25000" \
    data/sample_fcst/2009123112/arw-fer-gep1/d01_2009123112_02400.grib \
    tutorial/out/copygb/d01_2009123112_02400.grib_lambert

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

    wgrib -V tutorial/out/copygb/d01_2009123112_02400.grib_lambert