Role of SST patterns on surface wind modulation of a heavy midlatitude precipitation event

The mechanisms controlling the influence of the sea surface temperature (SST) structure on the surface winds are studied by means of numerical simulations run with a nonhydrostatic fully compressible state-of-the-art numerical model in a realistic midlatitudes setup, leading to the 9 October 2014 Genoa heavy rainfall event. Starting from a simulation with high-resolution submesoscale eddy-permitting SST field, the surface temperature boundary conditions are changed to enhance, reduce, or smooth the SST gradient. It is found that the marine atmospheric boundary layer responds to the submesoscale SST forcing structures over time scales of the order of hours. In particular, through the downward momentum mixing mechanism, the presence of SST horizontal gradients impacts the spatial structure of the surface wind convergence, which can displace the convective heavy rain bands that develop over the sea.