The Role of Sea Surface Temperature in the Simulation Of

The Mediterranean basin is as a strongly cyclogenetic area. Most of the cyclonic events arise from the interplay between the thermal structure of the Mediterranean sea and the orographic structure surrounding it. In many cases, the dynamics of deeply convective cyclones are strongly determined by latent and sensible heat fluxes that, over the sea, are driven by the Sea Surface Temperature (SST). Nevertheless also in these cases other mechanisms, like baroclinic instability and lee cyclogenis, especially in the early stages, play an important role. In this work, we present numerical simulations of a flash flood event in southern Italy to assess the sensitivity of the forecast of these extreme events to the spatial and temporal evolution of MSG-based high resolution SST patterns. The meteorological model we used is the Weather Research and Forecasting (WRF-ARW) prediction system, with two nested grids (the coarse grid with 10 km horizontal resolution, the fine 3.3 km). Numerical simulations were run with SST fields obtained using both climatological SSTs and MSG-based SSTs at 0.04° horizontal resolution. These latter were computed through two different approaches: one using constant MSG-based SST data for the whole simulation, the other updating the MSG-based SST data every 6 hours. The differences in terms of the most relevant variables (e.g., surface pressure, heat fluxes, CAPE, etc.) are evaluated in order to assess the relevance of an accurate specification of SST fields, their temporal evolution and spatial variability.