This page contains a rules on the TIGGE data encoding. A complete list of all parameters and sample GRIB2 encoding is given here.
Bitmaps should be used to indicate missing values (i.e. Soil moisture (sm) must be coded using a bitmap, because there is no model output over the sea)
Each partner will provide their eps data on the grid of their choice, although regular grids are favoured. Partners are encouraged to provide also their deterministic forecast (as additional control) projected on the same horizontal grid and resolution as the ensemble members.
Grids are defined in GRIB2 using an accuracy of 1/1000000 (one millionth) of a degree. If this accuracy is not sufficient to describe your grid (latitude/longitude of first and last points, as well as grid increments) without loss of information, you can use a GRIB2 feature that provides a way to describe any regular grid. See the page on encoding global latitude/longitude grid for more details.
The so called tigge_check tool is a part of ecCodes package. It should be used to validate all GRIB2 files prepared for TIGGE. The tool is checking all encoding details so that only fully compliant TIGGE files following exactly required definitions would pass. Find more information about the tool in the page Data encoding checking tools
Octet 20 of section 1 of a GRIB2 message contains the Production status of processed data. The WMO has added two values to table 1.3 Production status of data:
Control and perturbed forecasts are identified in section 1 and 4. The following tables explains how to code them in GRIB2:
| Section 1 | |||
|---|---|---|---|
| Octets | Example perturbed | Example control | |
| 21 | type of processed data | 4 | 3 |
| Ensemble (section 4, template 4.61) | |||
|---|---|---|---|
| Octets | Example perturbed | Example control | |
| 8-9 | product definition template number | 1/11* | 1/11* |
| 35 | type of ensemble forecast | 255 (missing) | 255 (missing) |
| 36 | perturbation number | 7 | 0 |
| 37 | number of forecasts in ensemble | 51 | 51 |
The input fields should be split by the output data type, level type and eps number as per below. All steps should be merged into the same file.
tigge_CCCC_YYYYMMDDHH_VVVV_TT_LL_NNN.grib2 ... for ensemble forecasts
tigge_CCCC_YYYYMMDDHH_VVVV_TT_LL.grib2 ... for high resolution forecasts