Impact of using simulated wave field for tropical cyclone forecasting in the southwest Indian Ocean basin

While cyclonic trajectory forecasts have improved considerably over the last twenty years, intensity forecasts remain less reliable and are strongly modulated by ocean-atmosphere interactions, the study of which remains one of the main avenues for improvement.

In tropical cyclone wind conditions, a significant part of the wave field is produced by the cyclonic wind. This wind generates waves that modulate the roughness of the ocean surface and strongly influence the exchange of momentum between the atmosphere and the ocean. In turn, by modifying surface roughness, waves have a strong impact on the low-level wind. This feedback between wind and waves illustrates the complex but central role of ocean waves in the interaction between ocean and atmosphere within tropical cyclones.

One approach to understanding the impact of waves on tropical cyclone intensity is to perform coupled wave-atmosphere simulations, using air-sea exchange parameterizations. Here, we choose two different parameterizations that represent the saturation of the drag coefficient at the ocean surface for very strong low-level winds: the Exchange Coefficients from Unified Multi-campaigns Estimates (ECUME) (Belamari, 2005) and the Wave-Age-dependent Stress Parameterization (WASP) (Bouin et al., 2023).

In this study, we carry out atmospheric simulations using Météo France's operational forecasting model (AROME) and for six tropical cyclones in the Indian Ocean basin, we compare three numerical configurations: the AROME model coupled to the Wave Watch 3 (WW3) wave model with WASP parameterization, AROME in operational version with WASP or with ECUME.

In this study, we carry out atmospheric simulations using Météo France's operational forecasting model (AROME) and for six tropical cyclones in the Indian Ocean basin, we compare three numerical configurations: the AROME model coupled to the Wave Watch 3 (WW3) wave model with WASP parameterization, AROME in operational version with WASP or with ECUME.