In progress. All details still to be updated..
General requirements
Encoding format
- WMO GRIB2 data format.
Missing values
- Bitmaps shall be used to indicate missing values.
Grid and resolution
- The fields have to be provided on...
- Grids are defined in GRIB2 using an accuracy of 1/1000000 (one millionth) of a degree.
GRIB2 encoding
All data must be encoded following the required rules described below to achieve fully compliant LC-GCR format from all centres.
Encoding software
ECMWF makes available a GRIB decoding library (ecCodes) for the benefit of the WMO community. ecCodes can be freely downloaded from here and the documentation can be found here.
For more general information about GRIB2 format please refer to WMO Manual on Codes .
Encoding details
General encoding (TBA)
Specific details which should be encoded in GRIB2 sections 1 and 4:
| Section 1 | |||
|---|---|---|---|
| Octets | Key name | Value | Description |
| 6-7 | centre | X | WMO Centre's code (table below) |
| 8-9 | subCentre | X | WMO Sub-Centre's code if needed (table below) |
| 10 | tablesVersion | X | The latest WMO table |
| 20 | productionStatusOfProcessedData | 14 | Production data |
| 15 | Test data | ||
| 21 | typeOfProcessedData | 0 | Analysis products |
| 1 | Forecast products | ||
| Section 4 | |||
|---|---|---|---|
| Octets | Key name | Value | Description |
| 8-9 | productDefinitionTemplateNumber | 0 | Analysis and Forecast products (instantaneous) (Analysis or forecast at a horizontal level or in a horizontal layer at a point in time (grib2/tables/17/4.0.table)) |
WMO Centre codes
The codes below are based on WMO Manual 306 - WMO Codes. Each organization must be uniquely identified by its WMO code. If necessary to distinguish between two organizations using the same WMO code the Sub-Centre one which differs must be provided.
| Organisation | Acronym | WMO Centre code | Centre acronym*1 |
|---|---|---|---|
China Meteorological Administration, China | CMA | babj | |
European Centre for Medium-Range Weather, UK | ECMWF | 98 | ecmf |
| Japan Meteorological Agency, Japan | JMA | 34 | rjtd |
| National Centres for Environmental Prediction, USA | NCEP | 7 | kwbc |
| National Aeronautics and Space Administration | NASA | nasa |
Remarks:
*1 in ECMWF's ecCodes package
Examples of the required GRIB2 files
parameter | Sample file | GRIB metadata dump*1 |
|---|---|---|
Time-mean 2 metre temperature | ecmf.202312.an.grib2 | ecmf.202312.an.dump |
Time-mean mean sea level pressure | ||
| Time-mean total precipitation | ecmf.202311.fc.grib2 | ecmf.202311.fc.dump |
*1 using "grib_dump -O" command from ecCodes package
Remarks
- content of the local GRIB section (SECTION_2 in metadata dump) used for archiving in MARS still to be updated
- exact encoding of time ranges might differ for different models depending on how its reanalysis is produced
- additional details will be specified, once full details are known for each model