Links Between Sea Surface Temperature Structures, Clouds and Rainfall: Study Case of the Mediterranean Sea.

Using 25 years of ERA5 reanalysis data, this study shows that wind divergence is partially driven by small‐scale sea surface temperature (SST) patterns via their effect on the boundary layer stability. Moreover, strong warm‐to‐cold fronts (the upper quartile) are associated with a mean increase of cloud cover of 10% ± 5% and a mean increase in the probability of a rain event of 15% ± 6%, with respect to the average values. The cloud and rainfall dependence on SST fronts is more pronounced in Fall, probably due to the stronger SST gradients present at the end of the summer season. Plain Language Summary: Oceanic thermal structures impact surface winds, low‐level clouds, and rainfall. Using reanalysis data over the Mediterranean Sea, this paper shows that the reduced stability over warm patches increases the coupling of surface winds with winds aloft. This process affects the entire marine atmospheric boundary layer. This results in a cloud cover and rainfall response: when the wind blows from warm to cold (from cold to warm) water, a converging (diverging) cell is enhanced, increasing (decreasing) low‐cloud cover and favoring by about 15% a rain event. Key Points: Oceanic thermal feedback acts on the marine atmospheric boundary layer dynamics at daily time‐scaleThe downward momentum mixing mechanism imprints cloud cover and rainSST gradients partially drive cloud structures and rainfall over the Mediterranean Sea [ABSTRACT FROM AUTHOR]