Influence of mesoscale sea-surface temperature structures on the Mediterranean cyclone Ianos in convection-permitting simulations: Contributions of surface warming and cold wakes

This study examined the influence of mesoscale sea-surface temperature (SST) structures and warming on the tropical-like cyclone Ianos. The controlling mechanisms were investigated using a set of sensitivity experiments with the non-hydrostatic weather research and forecasting model. A simulation forced by a high-resolution SST field from the mesoscale eddy-resolving HYCOM reanalysis (CTRLH) performed better than a simulation forced by a coarse-resolution SST field from Optimum Interpolation Sea Surface Temperature (OISST) in terms of precipitation, wind intensity, and landfall location. The suppression of mesoscale SST variability affected the cyclone's intensity, its path, and associated processes. This effect depends on the nature of the anomalies (cold/warm). The suppression of mesoscale SST forcing intensified wind and precipitation in the presence of cold anomalies, leading to a northwestward shift of the storm's path during its mature phase. The magnitude of these changes varied with the scale of smoothing (mesoscale SST). Compared to the CTRLH simulation, a simulation in which a 60-km smoothing filter was applied to the SST field resulted in a cyclone centered slightly to the west (or delayed by 3-6 hr), which was further shifted to the west (or delayed) when the smoothing filter was increased to 150 km. The intensification of wind and precipitation may be associated with the reduction in the storm's cold wake, which would lead to enhanced turbulent fluxes and increased atmospheric water vapor. These results highlight the role of small-scale air-sea interaction processes that could have a strong impact on Mediterranean cyclones' path and intensity. Schematic representation of the impact of a medicane (tropical-like cyclone in the Mediterranean)-induced cold wake on precipitation and the associated mechanism. The coloured surface symbolizes the sea interface, differentiating between warm (red) and cold (blue) sea-surface temperatures (SST). The transition from dark to light blue and red signifies the mitigation of the cold and warm anomalies. The medicane-induced cold wake (cold anomaly) decreases the upward transport of turbulent fluxes (latent and sensible heat), consequently reducing moisture fluxes and, hence, precipitation. Conversely, the smoothing of mesoscale SST structures and the suppression of the cold wake enhance the upward transport of turbulent fluxes (latent and sensible heat), increasing atmospheric moisture and, consequently, precipitation. image