Recommendations for the System 9 model

Météo-France is releasing the next generation of its seasonal forecasting system called System 9.This is the final product of more than three years of technical and scientific developments based onthe coupled climate model CNRM-CM (Voldoire et al, 2019). Part of these developments werefunded by the C3S2_370_MF contract within Work Package 3 (WP3) dedicated to the evolution ofthe seasonal forecasting system. The present deliverable is the conclusion of Task 3.1 from WP3,focusing on the evolution of the coupled model components. It describes the modeling choices forthe atmosphere, ocean, sea-ice and land surface component of CNRM-CM that were retained tomake seasonal forecasts with System 9. It also provides the scientific and technical reasons that ledto theses choices. The coupled model components of System 9 are the following:– Atmosphere: ARPEGE-Climat version 6.5, including PCMT convection scheme and ecRad radi-ation scheme;– Ocean: NEMO 4.2;– Sea-ice: SI3;– Land surface component: SURFEX v8.0 incorporating the ISBA land surface model and theCTRIP river routing model, without interactive vegetation.