Unveiling the Influence of the Daily Oceanic (Sub)Mesoscale Thermal Feedback to the Atmosphere

Abstract Oceanic mesoscale [ O (100) km] thermal feedback (TFB) can modify the marine atmospheric boundary layer through two main mechanisms: downward momentum mixing (DMM) and pressure adjustment (PA). In this study, we use ERA5 reanalysis, with the finest spatial resolution available (roughly 25 km globally), and a set of coupled ocean–atmosphere model experiments to investigate the extent to which the spatial resolution of oceanic fine-scale structures [ O (10)–(100) km] influences the TFB mechanisms on a daily time scale in the northwestern tropical Atlantic. We show that the low-level wind magnitude response to sea surface temperature anomalies is controlled by large oceanic mesoscale structures (>100 km), whereas finer structures play a minor role. However, the TFB mechanisms vary considerably depending on whether the mesoscale structures are fully represented or not. The DMM and PA mechanisms are diminished by about 36% and 85%, respectively, when the full range of mesoscale structures in the ocean is resolved. This reduction is associated with both a stronger atmospheric frontogenesis mechanism induced by submesoscale [ O (10) km] oceanic thermal structures and the divergence of submesoscale ocean currents, which is not the case at the large mesoscale. These processes have the potential to exert a destructive influence on the daily oceanic mesoscale TFB by inducing opposite low-level atmospheric vertical velocities, which is particularly enhanced in the case of the PA mechanism. Finally, our findings suggest that climate models must accurately represent fine-scale ocean thermal structures that directly influence TFB mechanisms and potentially affect cloud formation and precipitation patterns.