...
Identifier code: Météo-France System 9
First operational forecast run: April 2025
...
| Model | ARPEGE v6.5 SURFEX v8.0 |
|---|---|
| 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 |
...
NEMO: Madec et al. (2022). NEMO ocean engine reference manual. Zenodo. https://doi.org/10.5281/zenodo.6334656
SI3: Vancoppenolle et al. (2023). NEMO Sea Ice Engine (SI3). Zenodo. https://doi.org/10.5281/zenodo.7534900
...
| Hindcast | Forecast | |
|---|---|---|
| Ocean initialization | GLORYS12V1 | GLO12 |
| Ocean IC perturbations | None | None |
| Unperturbed control forecast? | NA | NA |
...
Météo-France System 9 is built on the CNRM-CM coupled climate model which embeds an output manager called the XIOS server (Meurdesoif et al, 2018). XIOS is an input/output parallel server software enabling to perform online field operations in the course of the model integration and writing the final result on NetCDF files. All For atmosphere and land surface data, all operations such as time sampling, time averaging, horizontal regridding or vertical interpolation are specified through xml files and performed by XIOS such that no or little post-processing is needed: the only output files written on disk are the files featuring the requested C3S 1°x1° horizontal grid and pressure levels. For ocean and sea-ice data, the output files are written by XIOS on the native NEMO grid and remapped on the C3S 1°x1° horizontal grid throug post-processing, using the cdo "remapbil" function.
Horizontal Interpolation
The ARPEGE atmospheric model is a spectral model, and horizontal fields such as temperature or geopotential are originally computed as spherical harmonic coefficients, but can be converted into grid point data on the corresponding reduced Gaussian grid (e.g 0.5° reduced Gaussian grid for Tl359 spectral resolution) using an internal function of the model. The XIOS server can perform online interpolation of this grid point data on any user specified grid such as the rectilinear C3S 1°x1° grid. The interpolation of atmospheric data by XIOS is a first-order conservative remapping. As for the oceanic fields from NEMO, they are internally defined as grid point data and can directly be interpolated by XIOS onto the 1°x1° grid. For both atmospheric and oceanic data, the interpolation method is a first order conservative remappingfirst output on the native model grid, and remapped using a bilinear interpolation.
Vertical interpolation
ARPEGE uses sigma coordinates in the vertical, meaning that near-surface model levels follow the orography. Transformation into data on pressure levels is done directly on request by ARPEGE through a linear interpolation, or linear extrapolation for data below the surface.
...