Numerical high-resolution air-sea coupling over the Gulf of Lions during two tramontane/mistral events

The near-sea-surface meteorological conditions associated with strong wind events over the Mediterranean Sea constitute a strong forcing on the ocean mixed layer. The present study addresses the question of the sea surface scheme used in high-resolution and short-range atmospheric numerical modeling to represent the ocean mixed layer response under these severe mistral wind events in the Gulf of Lions area. Several slab ocean models have been used coupled with the Weather Research and Forecasting (WRF) model and applied on two mistral cases: (1) a slab model based on the transport divergence equation where the mixed layer evolution is only driven by the wind stress, (2) a slab model where the temperature is the only prognostic variable and evolves according to the net surface heat flux, and (3) a complete slab scheme from Price (1981). The coupled simulations are also compared to two basic simulations, one using a constant sea surface temperature (SST) field during all of the model integration and another using a 6-hourly update sea surface temperature reanalysis. In this study, we mainly focus on the slab model performances. We identify the processes involved in the ocean mixed layer response under strong wind situations, i.e., local and fast cooling and deepening. The feedbacks of an interactive ocean mixed layer on the atmospheric simulation are also investigated.