1. Forecast system version
Identifier code: SEAS5
First operational forecast run: 1 November 2017
2. Configuration of the forecast model
Is the model coupled to an ocean model? Yes
Coupling frequency: 1 hour
2.1 Atmosphere and land surface
| Model | IFS Cycle 43r1 |
|---|---|
| Horizontal resolution and grid | Dynamics:TCO319 cubic octahedral grid Physics: O320 Gaussian grid (36 km) |
| Atmosphere vertical resolution | L91 |
| Top of atmosphere | 0.01 hPa (approx. 80 km) |
| Soil levels (layers) | 4 Layer 1 : 0 - 7 cm |
| Time step | 20 minutes |
Detailed documentation: IFS cycle 43r1 documentation
2.2 Ocean and cryosphere
| Ocean model | NEMO v3.4 |
|---|---|
| Horizontal resolution | ORCA 0.25 |
| Vertical resolution | L75 |
| Time step | 1 hour |
| Sea ice model | LIM2 |
| Sea ice model resolution | ORCA 0.25 |
| Sea ice model levels | N/A |
| Wave model | ECMWF wave model |
| Wave model resolution | 0.5 degrees |
Detailed documentation: NEMO documentation and IFS cycle 43r1 documentation
3. Initialization and initial condition (IC) perturbations
3.1 Atmosphere and land
| Hindcast | Forecast | |
|---|---|---|
| Atmosphere initialization | ERA-Interim | ECMWF operations |
| Atmosphere IC perturbations | Ensemble data assimilation and leading singular vectors applied to upper air variables | Ensemble data assimilation and leading singular vectors applied to upper air variables |
Land Initialization | 43r1 land surface model driven by ERA-Interim (like ERA-Interim land) | ECMWF operations |
| Land IC perturbations | Ensemble data assimilation applied to some land fields | Ensemble data assimilation applied to some land fields |
| Soil moisture initialization | 43r1 land surface model driven by ERA-Interim (like ERA-Interim land) | ECMWF operations |
| Snow initialization | 43r1 land surface model driven by ERA-Interim (like ERA-Interim land) | ECMWF operations |
| Unperturbed control forecast? | Yes | Yes |
Data assimilation method for control analysis: 4D Var (atmosphere) and 3DVAR (ocean/sea-ice)
Horizontal and vertical resolution of perturbations: T42L91 SVs+ T399L137 EDA perturbations
Perturbations in +/- pairs: Yes
Detailed documentation: IFS cycle 43r1 documentation and SEAS5 user guide
3.2 Ocean and cryosphere
| Hindcast | Forecast | |
|---|---|---|
| Ocean initialization | ORAS5 | ORTA5 |
| Ocean IC perturbations | Yes - generated through perturbations to assimilated observations and surface forcing | Yes - generated through perturbations to assimilated observations and surface forcing |
| Unperturbed control forecast? | No | No |
Detailed documentation: ECMWF ocean reanalysis documentation and SEAS5 user guide
4. Model Uncertainties perturbations:
| Model dynamics perturbations | No |
|---|---|
| Model physics perturbations | 3-level SPPT and SPBS |
If there is a control forecast, is it perturbed? | Yes |
Detailed documentation: IFS cycle 43r1 documentation
5. Forecast system and hindcasts
Note, the ECMWF seasonal forecasts cover two time ranges: the long range (LR) forecasts out to 7 months and annual range (AR) forecasts out to 13 months (the latter not available from C3S). The model used for these forecasts is identical, but they have different numbers of forecast members.
| Forecast frequency | monthly (LR) quarterly (AR) |
|---|---|
| Forecast ensemble size | 51 (LR) 15 (AR) |
| Hindcast years | 36 (1981-2016) |
| Hindcast ensemble size | 25 (LR) 15 (AR) |
| On-the-fly or static hindcast set? | static |
6. Where to find more information
ECMWF seasonal forecast documentation page
