ggrib--Extraction of geographic subdomains from GRIB files v2.0

• By v1.0 ggrib tackles global files and a subdomain that crosses the discontinuity (called the branch cut among math freaks, geophysicists place the discontinuity at 0 or 180^o longitude, whichever is more convenient). If lon1==lon2, ggrib will attempt to reproduce global grids where the discontinuity has been moved to lon1.
• The grid MUST be in geographic coordinates (lon,lat). The grid organization is arbitrary, but it is recommended that the ECMWF standard  be adhered to (first grid point in NW corner, adjacent grid points in east-west direction).
• By v1.0 the original binary representation together with bitmap section (if present) is retained.
• By v2.0 dots can be substituted for bounding coords, in which case the original grid boundaries will be used (see example 3).
• By v2.0 specifying bounding coords that go beyond the original grid boundaries will not produce an error but will quietly be adjusted to the original grid boundaries.

ggrib gribfile newgribfile westlon southlat eastlon northlat

Example:

ggrib world.grb smallworld.grb -10.0 45.0 35.0 70.0

Produces an excerpt from a global file with bounding coordinates (10W,45N) and (35E,70N).

Example 2:

ggrib world.grb smallworld.grb -170.0 45.0 -170.0 70.0

Produces a zonal "ribbon" from 45N to 70N that extends around the globe.

Example 3:

ggrib oldworld.grb bravenewworld.grb -20 . . 75

Prodcues a new grid which extends from 20W to the eastern rim of the old grid, takes the southern latitude of the old grid and goes to 75N.

Installation:

tar xvf ggrib.tar
cd ggrib
make -f ggrib.make

The TAR-file includes an SGI binary of ggrib, which makes compilation unnecessary for those fortunate owners of SGI's.

The library gribw must be compiled in advance using gribwlib.make. This software along with the other files listed in ggrib.make are all contained in the tape archive gribw.tar found at ftp://wesley.wwb.noaa.gov/pub/gribw.
 
 

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Oyvind Breivik, Norwegian Meteorological Institute, www.dnmi.no
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