This page contains a few rules on the S2S parameters. A complete list of all the parameters and sample GRIB2 encoding is given here.
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General rules
Units
- All fields shall use units as defined in GRIB Edition 2
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- The Control Forecast must be number 0,
- The number of members is identical to the number of all EPS members plus the Control Forecast.
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GRIB2 encoding
ECMWF encoding/decoding Software
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You should use value 7 when testing (and set the vvvv part of the file naming convention to test), and 6 for operational data (in this case vvvvshould be set to prod).
S2S extension (Section 2)
It is proposed that the section 2 for S2S fields be the same for all partners. A GRIB2 decoder must decode the section 2 as a TIGGE extension based on the octet 36 of section 1 (Production status of processed data) being 6 or 7.
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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 | typeOfProcessedData | =4 | =3 | |
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| Ensemble (section 4, template 4.61) | |||
|---|---|---|---|
| Octets | Example perturbed | Example control | |
| 35 | type of ensemble forecast | = 255 (missing) | = 255 (missing) |
| 36 | perturbation number | = 7 | = 0 |
| 37 | number of forecasts in ensemble | = 51 | = 51 |
3) Time component and reforecasts
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reforecasts
4) Examples of GRIB2 files
| real-time | re-forecast | ||
| Daily average | Control Perturbed | Control Perturbed | |
| Accumulations | Control Perturbed | Control Perturbed | |
| Instantaneous | Control Perturbed | Control Perturbed | |
| Maximum over the last 6 hours | Control Perturbed | Control Perturbed | |
| Minimum over the last 6 hours | Control Perturbed | Control Perturbed |
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