Investigation of sea-breeze convergence in Salento Peninsula (southeastern Italy)

Abstract

The frequency, the location and the characteristics of convective rainfall events induced by the convergence of different sea breeze systems on a Mediterranean peninsula (Salento, in southeastern Italy) are analyzed. Such events have been studied considering satellite/radar images and output fields from two Limited Area Models in the summer period of 2011–2013. A total of 20days have been detected in which the precipitation due to sea-breeze convergence was clearly observed in satellite and radar images. The synoptic conditions associated with these events have been identified considering the averages of some relevant meteorological parameters in the selected days and the anomaly with respect to the climate. The presence of a cold trough in the central Mediterranean basin appears as a fundamental ingredient for the occurrence of sea breeze convergence and associated precipitation. High-resolution simulations with two state-of-art numerical models have revealed that both of them are generally able to simulate a convergence pattern correctly, apart from a couple of cases for each model. The higher rainfall amounts occur with weak synoptic wind, and weak-to-moderate values of Convective Available Potential Energy (CAPE). When the synoptic wind is of moderate intensity, the region of convergence moves toward the Adriatic coast for a prevailing southerly component, and toward the Ionian coast for a prevailing northerly component. On the opposite, the skin sea surface temperature is relatively uniform and the difference between the Ionian and the Adriatic Seas, surrounding the peninsula on the east and west side, is generally smaller than 1K, having only a marginal effect on the sea breeze patterns. Similarly, the value of CAPE before the occurrence of rainfall has low prognostic value. The results shows that limited area models with a grid spacing of few km appear as appropriate tools for the simulation for such relatively small scale phenomena.