Evaluating the evolution of cyclone IDAI using the physically based PASM air-sea flux model

Earth System Models (ESM) and Numerical Weather Prediction (NWP) systems often have large biases in their representation of surface-atmosphere fluxes when compared to observations. Over sea, these biases are more pronounced due to dynamic non-linear interactions between atmosphere and sea surface waves. This non-linearity is not accurately represented by traditional semi-emiprical models like COARE. To this end, the PASM (Physically derived Air-Sea Momentum flux) model, developed by us, is the first attempt to represent air-sea exchanges by considering the two-way interaction between the ocean-waves and the atmospheric flow. It can simulate (i) the main turbulent eddies of the air-flow, and (ii) the wind-wave interactions including wave growth, transport and breaking. This model has been previously demonstrated to better predict the air-sea fluxes under 10m high wind speeds greater than 20m/s, where traditional approaches like COARE fail. In this study, we evaluate for the first time, the evolution of cyclone IDAI off the coast of Madagascar, using PASM and COARE approaches, to demonstrate the efficiency of our physically based model in better simulating the evolution and trajectory of cyclones, and thus its usefulness in ESM and NWP models.