Introduction

The -ijsmall_grib option writes the grid values to a grib2 file with the same grid spacing but a smaller domain. It is similar to the -small_grib option except it uses i,j values rather than lat-lon values. The grid point locations are unchanged. This option is used to make a regional subset and only works for certain grids such as the lat-lon, rotated lat-lon, Mercator and Lambert conformal.

Limitations

1. rotated lat-lon grid: must use WMO grid template and not the NCEP locally defined grid template
2. staggered grids are not supported

Usage

-ijsmall_grib ix0:ix1 iy0:iy1 file_name

Where, 1 <= ix0 < ix1 < nx
Where, 1 <= iy0 < iy1 < ny
By default, (i,j) is the South-West corner

File_name is the output grib2 file 

Example

$ wgrib2 fcst.grb2 -ijsmall_grib 10:20 20:30 small.grb
1:0:d=2007032600:HGT:1000 mb:anl:

$ wgrib2 small.grb -grid
1:0:grid_template=0:
        lat-lon grid:(11 x 11) units 1e-06 input WE:SN output WE:SN res 48
        lat -80.500000 to -75.500000 by 0.500000
        lon 4.500000 to 9.500000 by 0.500000 #points=121

See also: -undefine, -small_grib