Introduction

wgrib2 is a swiss army knife for grib2 files. You can use it inventory or extract data. You can do basic database operations and other nifty things.

GRIB-2 has arrived and has begun replacing the the older standard GRIB (GRIB-1). Since GRIB-2 can reduce the file size by upto 80% (NAM, JPEG2000 compression), converting to the new standard may be faster than some expected.

Wgrib2 has been out in the wild since 9/16/2005 (alpha release). The original version was rough around the edges but the new design helped and now wgrib2 has much more functionality than the older wgrib.

News

2/2007: Manfred Schwarb went over the code last Christmas-New Years and sent in 31 patches. 31 patches sounds like a lot but he must have used a spell checker on the code. Anyways some of the patches were for the more unpolished code in the package which caused me to go over that code. Manfred also sent in a script that can read a grib2 table from the web documentation and create C code. Much better than typing by hand or any other script that I had in my tool box.

Some Good Stuff

• Almost trivial to add custom features!
• Customized inventories
• Table driven
• Code is reorganized
• Super easy integration of new and local options
• wgrib2 knows the lat-lon of the individual grid points for several grids
• Designed for multiple developers (hint, hint, hint)
• Works with the partial-http downloading aka "Fast Downloading of GRIB Files"

Bad Stuff

• Uses external libraries (png,jpeg,netcdf,compression,grib2 decode) which can make compiling and linking a real pain. At least all the external libraries are in C.
• interpolation to lat-lon values is done by nearest neighbor.
• wind rotation is not handled

Usage

• similar to wgrib but different
• type wgrib2 to see primary options
• inventory format is specified on command line by options
• if no "inv" options are specified, -s is used

Joining the development effort

• Source code: knowledge of C and grib-2
• Donated source code / non-trivial bug fixes must either be GNU or public domain.
• Prefer PD bug fixes for PD code and GNU bug fixes for GNU code.
• Bug reports are important
• Contact wesley.ebisuzaki@noaa.gov

Contributions by

• Wesley Ebisuzai: many modules
• Jaakko Hyvätti: gribtab
• Kristian Nilssen: netcdf module
• Karl Pfeiffer: georeference
• Manfred Schwarb: many modules
• Arlindo da Silva: openGrADS
• Niklas Sondell: mysql module
• Sergey Varlamov: netcdf module improvements, georeferencing updates
• thanks to the people who report the bugs and more who provide the fixes!

Documentation

• converting from wgrib to wgrib2 in scripts
• submessages
• writing a simple function
• selecting fields to decode
• option types: init inv out misc
• bin, ieee, text format
• usage questions
• compile questions
• some tricks

An incomplete list of the options

• -AAIG export arcinfo ascii grid
• -append set append mode flag
• -big_endian set ieee big0endian flag
• -bin write out file in binary format
• -bitmap
• -center
• -code_table
• -d
• -disc
• -end end/stop/bye/quit after 1 line of inventory
• -fix_ncep
• -ftime
• -GRIB write current grib message (potentially many fields)
• -grib write current grib submessage (one field)
• -grib_out
• -grid
• -help
• -i
• -ieee: data in IEEE format
• -if
• -ij
• -ijlat
• -lev
• -little_endian
• -lola
• -lon
• macros: -s -verf -V
• -match
• -match_inv
• -max
• -min
• -MM
• -not_if
• -npts
• -nxny
• -one_line
• -order
• -s
• -stats
• -tigge
• -var
• -undefine
• -verf
• -V

Exporting data to other programs

• -netcdf: write data in netcdf format
• -mysql: export data to a mysql datdabase
• -mysql_speed: export data to a mysql datdabase
• -spread: write data for spreadsheets
• -csv: write in column separated values, another one for spreadsheets
• -text: data in text format
• -bin: data native binary floating point
• -ieee: data in big endian IEEE format
• -AAIG: arcinfo ascii grid, GIS

Specialized options used by other programs

• -ctl_inv: print parameters needed by g2ctl
• -domain: print out the lat-lon domain
• -cyclic: needed by g2ctl
• -lev0: print level information needed by g2ctl
• -limit: web programs that need controls of cpu usage

Seeing the details of the grib file

• -code_table_I.J: to see contents of code table I.J
• -flag_table_I.J: to see contents of flag table I.J
• -SecI: see descriptions about section I, I = 0..6,
• -Sec_len: see length of each section
• -0xSec see hex dump of a section

Machines able to run wgrib2

• Redhat linux x86_32, Ubuntu: install gcc, libpng12-dev
• Mandriva linux, needs png library installed
• AIX, use makefile_all_libs, some fiddling is needed
• Solaris, needs gnu make and gcc (old report)
• HPUX, needs changes to makefiles
• XP, used cygwin and had to download many libraries modified makefiles use builtin-jasper library.
• Intel-based Mac

System dependencies: Windows and others

The same source code is used for windows, unix, linux, 32-bit, 64-bit, big endian and little endian executables. The main difference between the windows and linux versions is that windows treats binary and text files differently. Consequently you can send a grib or binary data to STDOUT in unix/linux with no problems. Under windows, the results are implementation dependent.

32-bit executables are limited to 2 GB files.

The maximum number of open files is system dependent.

The netcdf conversion is done in memory, so the speed is dependent on the amount of available physical memory.

Code: 32 and 64 bits

The code is designed to run on 32-bit and 64-bit computers. The advantages of compiling it for 64-bit (integers/pointers) is that that the code supports files that are larger than 2 GB. Note: NCEP runs the 64-bit version in operations.

• FTP directory
• README
• Changes
• compile questions
• wgrib2.tgz
• Windows XP

Status

The code is being developed on a linux x86_32 platform in standard C. Code is run on the AIX (64-bits) in NCEP operations.

Change logfile

Bugs

Please report then to wesley.ebisuzaki@noaa.gov. When you report bugs, try to make them reproduceable on a linux machine. Sample data file also help.

Distribution

The source code modules for wgrib2 are in the public domain or under the GNU licence depending on the authors of the various modules. Wgrib2 uses libraries that are in the public domain, under various GNU licences, the Image Power JPEG-2000 Public Licence, libpng licence, the zlib licence, the netcdf licence and perhaps others. How about one licence to rule them all?