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
(atmosphere)

SURFEX v8
(land surface)

Horizontal resolution and gridTL359; 0.5° reduced Gauss grid
Atmosphere vertical resolution137 layers
Top of atmospheretop layer 1 Pa
Soil levels (layers)14

Layer 1   : 0 - 0.01 m
Layer 2   : 0.01 - 0.04
Layer 3   : 0.04 – 0.1 m
Layer 4   : 0.1 – 0.2 m
Layer 5   : 0.2 – 0.4 m
Layer 6   : 0.4 – 0.6 m
Layer 7   : 0.6 – 0.8 m
Layer 8   : 0.8 – 1.0 m
Layer 9   : 1.0 – 1.5 m
Layer 10 : 1.5 – 2.0 m
Layer 11 : 2.0 – 3.0 m
Layer 12 : 3.0 – 5.0 m
Layer 13 : 5.0 – 8.0 m
Layer 14 : 8.0 – 12.0 m

Time step10 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 modelNEMO v3.6
Horizontal resolution0.25° ORCA grid
Vertical resolution75 levels
Time step15 min
Sea ice modelGELATO v6
Sea ice model resolution0.25° ORCA grid
Sea ice model levels5
Wave modelNone
Wave model resolutionNA

Detailed documentation:

NEMO: NEMO documentation

GELATO: GELATO documentation

3. Initialization and initial condition (IC) perturbations

3.1 Atmosphere and land


HindcastForecast
Atmosphere initialization
ERA5ERA5T
Atmosphere IC perturbationsNoneNone

Land Initialization

ERA5ERA5T
Land IC perturbationsNoneNone
Soil moisture initializationERA5ERA5T
Snow initializationERA5ERA5T
Unperturbed control forecast?NANA

Detailed documentation: see ECMWF page

3.2 Ocean and cryosphere


HindcastForecast
Ocean initialization

GLORYS12V1

MERCATOR-OCEAN

PSY4V3R1

MERCATOR-OCEAN

Ocean IC perturbationsNoneNone
Unperturbed control forecast?NANA

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 perturbationsYes
Model physics perturbationsNo

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 frequencymonth
Forecast ensemble size51
Hindcast years1993-2018
Hindcast ensemble size25
On-the-fly or static hindcast set?static
Calibration (bias correction) periodNA

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