GRIB2 conversion and its usage at NCEP Dr. KRISHNA KUMAR & STEPHEN A GILBERT NOAA/NWS/NCEP/Central Operations. -g12 converts GRIB1 to GRIB2. GRIB edition 1 to 2 conversion. Conversely the conversion from grib2 to grib1 is not always lossless because the edition 2 format. '2 metre temperature' =.
Climate Prediction Center - wgrib2: converting MERRA HDF file to grib2 Search CPC Search About Us Contact Us >>>>wgrib2 - example converting MERRA HDF to grib2 wgrib2: Converting MERRA HDF file to GRIB-2 Introduction MERRA is a NASA reanalysis project that has created reanalyses in HDF format. For some people, grib is a more convenient format.
Here is our first attempt to convert a MERRA HDF file into grib-2. Surveying the situation we see that Lats or the simpler to use Lats4d can convert HDF into grib-1. Grib-1 can be converted into grib-2 by the cnvgrib utility except that lats creates a custom grib table. Therefore a program would have to be written that converts the grib-1 file with the custom grib table into a grib table using the standard NCEP table. Doable but the program wouldn't be very generic.
In addition the process would take 3 steps (convert to grib1, translate grib1, convert to grib2). Can we do better? Looking at the programs that can read HDF, we see a familiar face, GrADS.
GrADS can read the HDF and write it out as a binary file. Wgrib2 can then read the binary file, a grib-2 template and metadata and then create a grib-2 file. 1: The template Grib-2 files include much metadata that is constant such as grid, center that created the data, the process that created the data, etc. Making a template takes some knowledge and we'll assume it has already been done. For the MERRA template, I used copygb/cnvgrib to create a grib2 file with the proper grid definition and then used wgrib2 to fill in some of the metadata (center). Probably should have filled in more of the metadata but I didn't.
2: Writing the binary and meta data The script g2write takes three arguements, the GrADS variable/expression, the output file and some metadata (variable:level:forecast/analysis). The script then creates the binary and metadata for one or more grids depending whether t is varying.
These two files along with the template can be used to make a grib2 file. 3: All together • Start gradshdf. • open the HDF file, sdfopen hdf-file • run the script, merra2grb2.gs 4: What does merra2grb2 do? • set the grid. Grads often uses an extra column.
A GUIDE TO THE CODE FORM FM 92-IX Ext. GRIB Edition 1 (Technical Report No.17, Geneva, May 1994 (WMO TD-No.611) TABLE OF CONTENTS The World Meteorological Organization (WMO) Commission for Basic Systems (CBS) Extraordinary Meeting Number VIII (1985) approved a general purpose, bit-oriented data exchange format, designated FM 92-VIII Ext. GRIB (GRIdded Binary).
It is an efficient vehicle for transmitting large volumes of gridded data to automated centers over high-speed telecommunication lines using modern protocols. By packing information into the GRIB code, messages (or records - the terms are synonymous in this context) can be made more compact than character oriented bulletins, which will produce faster computer-to-computer transmissions. GRIB can equally well serve as a data storage format, generating the same efficiencies relative to information storage and retrieval devices.
Changes and extensions to GRIB were approved at the regular meeting of the WMO/CBS in February 1988; additional changes were introduced at the CBS/WGDM/Sub-Group on Data Representation (SGDR) meetings in May 1989 and in October 1990. The 1990 changes were of such structural magnitude as to require a new Edition of GRIB, Edition 1, which this document describes. The Sub-Group made further augmentations and interpretations on Data Representation and Codes (SGDRC) in September 1993, with approval by the WGDM in February 1994. These changes did not result in a new Edition to GRIB, but did change some of the Tables, resulting a new Version number for them.
This brings us now to Table Version 2. The changes from Version 1 were mainly additions of new parameters or more precise definition of existing ones. It is not anticipated that there will be any large-scale structural changes to GRIB for at least four to five years, or more.
The SGDRC is undertaking a thorough review of the present and future requirements that GRIB is supposed to satisfy. The plan is to design a major revision of GRIB capable of accommodating these requirements and more, without 'straining' the structure of the data representation form. Some things are getting a little strained even now. Note: the Edition number is placed in the same location, relative to the start of the GRIB message, for all Editions. Thus, decoding programs can detect which Edition was used to construct a particular GRIB message and behave accordingly. Breezes Of Confirmation Pdf Reader here. This is useful for archives of messages encoded in earlier Editions or during transition periods.