Instructions for Degribbing ROFS (Ver. 3.6) Files

Marine Modeling and Analysis Branch > Regional Ocean > ROFS Output > ROFS GRIB

1. What is GRIB?
2. Where to find software for de-GRIBbing on the internet?
3. What is 'wgrib'?
4. How to use wgrib?
5. How to decode from GRIB format to ASCII?
6. How successful has 'wgrib' been on different machines?
7. How about using 'wgrib' on PCs?
8. Where to look for more info on 'wgrib'?
9. Now, I know everything I need to know about 'wgrib', but where do I get the ocean model (ROFS) results from?
10. Finally, how to display GRIB data with GrADS graphical software directly?
11. Point of contact

1. What is GRIB?

The Regional Ocean Forecast System (ROFS) output is packed and archived in the World Meteorological Organization standard GRIB (GRIdded Binary) format. Specifically, it is an international standard for the identification, storage and transmission of large gridded data files in a binary format. It uses its own, hardwire-independent binary representation of floating-point data which allows for a more efficient storage.

2. Where to find software for de-GRIBbing on the internet?

1. Go to Wesley Ebisuzaki's Web Site and follow the instructions.

Back to ROFS main page | Back to top /

3. What is 'wgrib'?

WGRIB is a portable program to read grib files that were created by the NCEP/NCAR Reanalysis Project. This program is not meant to be a general purpose decoder. It was developed by Wesley Ebisuzaki (click here for more details).

Back to ROFS main page | Back to top /

4. How to use wgrib?

At the prompt do: wgrib -V gribfilename

Example: If you have a gribfile called 'current.igb' then do: wgrib -V current.igb

and this would give the complete description of the records in the file and a brief information of the fields that are packed in GRIB format. For more information on this and more on wgrib usage, click here

Back to ROFS main page | Back to top /

5. How to decode from GRIB format to ASCII?

At the prompt do:
wgrib gribfilename | grep ":FIELDNAME:" | wgrib -i -text gribfilename -o outputfilename

Example: For the gribfile 'current.igb' do
wgrib current.igb | grep ":SALTY:" | wgrib -i -text current.igb -o salinity

and you will get something like:

     1:0:d=97013100:DSLM:sfc:24hr fcst:NAve=0
     2:26602:d=97013100:UOGRD::24hr fcst:NAve=0
     3:50954:d=97013100:VOGRD::24hr fcst:NAve=0
     4:75226:d=97013100:WTMP::24hr fcst:NAve=0
     5:107886:d=97013100:SALTY::24hr fcst:NAve=0
     6:138526:d=97013100:TKE::24hr fcst:NAve=0

and so on.......

From the first line:

• 1 is the record number,

• 0 is the position in bytes

• d=97013100 is the date

• DSLM is the parameter name(in this case the deviation from mean sea-level)

• sfc:24hr fcst tells whether it is forecast or analysis and

• NAve=0 is for an average number of fields averaged together

Back to ROFS main page | Back to top /

6. How successful has 'wgrib' been on different machines?

The different versions of 'wgrib' (SGI, SUN,CRAY, MS-DOS etc.) have been tested on the corresponding machines successfully.

Back to ROFS main page | Back to top /

7. How about using 'wgrib' on PCs?

DOS version to decode from GRIB format can be found here.

Back to ROFS main page | Back to top /

8. Where to look for more info on 'wgrib'?

The comprehensive archive of "wgrib"-related information is here. Particularly check "some tricks" link.

Back to ROFS main page | Back to top /

9. Now, I know everything I need to know about 'wgrib', but where do I get the ocean model (ROFS) results from ?

Currently, we store only today ROFS results locally. The archive of digital fields is available by anonimous ftp from NOAA's National Oceanographic Data Center) in Silver Spring, MD. To access these fields, please contact Darrel Knoll (Darrel.Knoll@noaa.gov ).

Back to ROFS main page | Back to top /

10. Finally, how to display GRIB data with GrADS graphical software directly?

The Grid Analysis and Display System (GrADS) is an interactive desktop tool for the analysis and display of earth science data.

NOTE: The maps on our ROFS www site are created not by GrADS but by using Interactive Data Language (IDL).

Back to ROFS main page | Back to top /