Effects of ocean fronts on the atmospheric response in the Mediterranean

Sea surface temperature (SST) is known to affect the atmospheric boundary layer dynamics over various spatio-temporal scales. The direct effect of SST structures on the atmosphere at the daily time scale is generally masked by the large variability associated with the large scale atmospheric dynamics. It is hypothesised that over hourly and daily time scales the control by the SST is important for convective initiation, because SST fronts can generate convergence lines, that drive upward motion. In the literature, two mechanisms have been suggested to explain the SST control on the marine atmospheric boundary layer: the former ruled by the pressure adjustment of the air column to the forcing SST and the latter linked to the vertical redistribution of horizontal momentum due to changes in the stability of the air column. In the present work, analysis of 25 years of daily SST and surface wind vectors in the Mediterranean region show that wind convergence preferentially occurs along ocean thermal fronts. This work suggests that SST structures need to be properly represented in numerical weather prediction models.