Louna Louis (Meteo France, France); Annabelle Ollivier (CLS, France); Alice Dalphinet (Meteo France, France); Adrien Nigou (CLS, France)

Wave forecasting models are increasingly better resolved in terms of grid size (2.5 km), and consequently this needs accounting more precisely along track change in wave height induced by wave-current interactions. The development of 5 hz processing opens up major perspectives for improving coastal wave forecasting, and also for better description of small scale physical processes at the ocean surface. This work aims to assess the impact of the assimilation of 5 Hz Significant Wave Height from altimetry multi-missions (Saral, CFOSAT, Jason-3 and HY2B) on sea state forecasting by the regional wave model MFWAM. The model configuration concerns the Iberian-Biscay-Ireland (IBI) domain of the Copernicus marine service, with a grid resolution of 5 km. The model runs are driven by IFS-ECMWF wind forcing and boundary conditions provided by the global MFWAM model for the Copernicus Marine Service. We implemented several assimilation runs of SWH at 5 Hz with the MFWAM-IBI model from January to March 2021. The results have been validated by comparison with independent wave data from buoys and altimetry missions.
The results show a significant improvement (roughly ~15%) of the scatter index of SWH when using multi-missions 5Hz wave data. The SWH bias is also reduced by roughly ~40% compared with the model run without assimilation. It is clearly shown that the impact for SWH below 2 m is better than with SWH assimilation at 1 hz. The impact of assimilation is effectively propagated near the coast for instance in the channel where the impact of tidal currents is strong. The results also indicate a strong reduction in SWH bias for long swells with peak period greater than 14 seconds during the winter season.
Further conclusions and comments will be presented during the final presentation.