On the Dynamics of Mediterranean Explosive Cyclogenesis

Abstract

In this study, a first attempt is made to examine the mechanisms contributing to the explosive cyclogenesis in the Mediterranean basin during the cold period of the year. Surface explosive cyclones and their vertical characteristics were defined with the aid of the University of Melbourne Cyclone Tracking and Vertical Tracing Software, using the 6-hourly ERA-40 datasets at the resolution of 1° × 1° for a 40-year period (1962–2001), separately for the western (WM), central (CM) and eastern Mediterranean (EM). Composite anomalies of various thermodynamic parameters verified the strong baroclinic character of the phenomenon and the decisive role of the upper level dynamics during the time of explosive cyclogenesis. Moreover, an interesting differentiation characterizes the low level thermodynamic structure of the WM and mainly CM cases in relation to the EM ones, since explosive cyclogenesis in the former areas seem to occur as cold low – level air warms from below, penetrating the Mediterranean from NW, while in the EM cold and high – PV upper level air moves over areas of warm and moist low level environment. Nevertheless, a synergy of the lower and the upper levels is implied for all parts of the Mediterranean basin with different relative importance.