degrib

Welcome to the NDFD Degrib program.

The main web site for this project is currently at: https://vlab.noaa.gov/web/mdl/degrib

Introduction

The NDFD (National Digital Forecast Database) will shortly be putting the national digital forecasts for the conus (continuous U.S.) on an anonymous ftp site. Those files will be in GRIB2 (Gridded Binary Edition 2) format, which is outlined in the WMO (World Meteorological Organization) document: The WMO GRIB2 Document FM92-X11 GRIB

In order to take advantage of this data, MDL (Meteorological Development Laboratory) created and maintains the official GRIB2 Decoder library. The GRIB2 Decoder library does a very good job of unpacking GRIB2 messages, but in order to understand how to use it, and what is returned, one needs a working knowledge of "The WMO GRIB2 Document FM92-X11 GRIB".

MDL felt that in order to make it easier for people to use NDFD data, a "driver" for the library should be provided. The main purposes for the driver are:

1.Provide an example of how to call the Decoder library. 2.Provide software to convert from GRIB2 to a simpler file format. 3.Provide a means to view the "meta" data without needing to reference "The WMO GRIB2 Document FM92-X11 GRIB" document.

Thus the creation of the degrib (and tkdegrib) programs, which convert a grid in a GRIB2 message to a ".flt" file (ESRI Spatial Analyst file), or a .shp file (ESRI ArcView file).

Installation

Please see: http://www.nws.noaa.gov/mdl/NDFD_GRIB2Decoder/howto.htm

Directory structure

• bin: Contains the programs (degrib, tkdegrib)
• docs: Contains project documentation
• lib: Contains extra libraries needed by tkdegrib
• output: Is the default output directory for tkdegrib
• tclsrc: Contains extra scripts neede by tkdegrib
• src: Contains the source code for the following:
  • grib2unpacker: Contains the current distribution of grib2unpacker Created by: Dr. Bob Glahn (MDL/OST/NWS/NOAA))
  • cmapf-c: Contains the current distribution of cmapf Created by: Dr. Albion Taylor (Air Resources Lab/NOAA))
  • degrib: Contains the source code for degrib and tkdegrib which uses the libraries: cmapf and grib2unpacker.

The following are for testing, and are part of the test "suites":

• ans: Contains sample answers
• data: Contains sample grib2 files
• test: Contains test scripts, which should generate in ./test the files that are in ./ans

The following are the "man" pages for the two programs:

• docs/degrib.txt
• docs/tkdegrib.txt

There are several other files in the docs directory which give information about the GRIB2 file format, as well as the Esri Shapefile formats. See docs/readme.txt.