1. Forecast system version
Identifier code: Météo-France System 8
First operational forecast run: July 2021
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 | ARPEGE v6.4 SURFEX v8 |
|---|---|
| Horizontal resolution and grid | TL359; 0.5° reduced Gauss grid |
| Atmosphere vertical resolution | 137 layers |
| Top of atmosphere | top layer 1 Pa |
| Soil levels (layers) | 14 Layer 1 : 0 - 0.01 m |
| Time step | 10 min |
Detailed documentation:
ARPEGE: http://www.umr-cnrm.fr/IMG/pdf/arp62ca.july2017.pdf
SURFEX: http://www.umr-cnrm.fr/surfex//IMG/pdf/surfex_scidoc_v8.1.pdf
2.2 Ocean and cryosphere
| Ocean model | NEMO v3.6 |
|---|---|
| Horizontal resolution | 0.25° ORCA grid |
| Vertical resolution | 75 levels |
| Time step | 15 min |
| Sea ice model | GELATO v6 |
| Sea ice model resolution | 0.25° ORCA grid |
| Sea ice model levels | 5 |
| Wave model | None |
| Wave model resolution | NA |
Detailed documentation:
NEMO: NEMO documentation
GELATO: GELATO documentation
3. Initialization and initial condition (IC) perturbations
3.1 Atmosphere and land
| Hindcast | Forecast | |
|---|---|---|
| Atmosphere initialization | ERA5 | ERA5T |
| Atmosphere IC perturbations | None | None |
Land Initialization | ERA5 | ERA5T |
| Land IC perturbations | None | None |
| Soil moisture initialization | ERA5 | ERA5T |
| Snow initialization | ERA5 | ERA5T |
| Unperturbed control forecast? | NA | NA |
Detailed documentation: see ECMWF page
3.2 Ocean and cryosphere
| Hindcast | Forecast | |
|---|---|---|
| Ocean initialization | GLORYS12V1 MERCATOR-OCEAN | PSY4V3R1 MERCATOR-OCEAN |
| Ocean IC perturbations | None | None |
| Unperturbed control forecast? | NA | NA |
Detailed documentation: https://www.mercator-ocean.fr/solutions-expertises/produits-references-mercator-ocean/
GLORYS12V1: https://data.marine.copernicus.eu/product/GLOBAL_MULTIYEAR_PHY_001_030/description
PSY4V3R1: https://www.mercator-ocean.eu/wp-content/uploads/2017/02/SYSTEM-sheet-_PSY4V3R1_2017.pdf
4. Model Uncertainties perturbations:
| Model dynamics perturbations | Yes |
|---|---|
| Model physics perturbations | No |
If there is a control forecast, is it perturbed? | NA |
Detailed documentation: Batté, L. and Déqué, M., 2016: Randomly correcting model errors in the ARPEGE-Climate v6. 1 component of CNRM-CM: applications for seasonal forecasts, Geoscientific Model Development,9, 2055-2076, doi:10.5194/gmd-9-2055-2016
5. Forecast system and hindcasts
| Forecast frequency | month |
|---|---|
| Forecast ensemble size | 51 |
| Hindcast years | 1993-2018 |
| Hindcast ensemble size | 25 |
| On-the-fly or static hindcast set? | static |
| Calibration (bias correction) period | NA |
6. Other relevant information
The forecast uses three start dates:
- The penultimate Thursday of the previous month (25 members in the forecasts, 12 members in the hindcasts)
- The last Thursday of the previous month (25 members in the forecasts, 12 members in the hindcasts)
- the 1st of the month (1 member in the forecast/hindcast)
Data assimilation method for analysis : coupled initialization run nudged towards ERA5T (ERA5 in the hindcast) in the atmosphere and Mercator Ocean International analyses in the ocean. Sea ice initial conditions are provided by a separate NEMO-GELATO ORCA 0.25 forced run nudged towards the same ocean analyses.
7. Where to find more information
Technical implementation details can be found in http://www.umr-cnrm.fr/IMG/pdf/system8-technical.pdf
