A composite diagnosis in sigma coordinates of the atmospheric energy balance during intense cyclonic activity

Abstract

Following the recent trend for composite analysis of the energetics of cyclonic systems, a rapidly deepening Saharan depression is studied within this framework. This case refers to a cyclone which was the prevailing feature in the synoptic analyses over the Mediterranean for several days in mid March 1981. This system was marked with a range of interesting phenomena over the central and eastern Mediterranean, such as very strong surface winds, rising and transportation of desert dust to large distances, and coloured precipitation. The synoptic dynamics of the evolution of the system is briefly presented and a reasoning for its unusually rapid deepening is provided. The forms of energy considered here are kinetic energy, and sensible and latent heats. The diagnostic analysis of the budgets of these forms of energy has been carried out using the sigma coordinate system. Bearing in mind the explosive nature of the cyclogenesis studied here, the analysis is separated into two parts: one associated with the deepening phase of the cyclone and the other with its filling phase. The results are presented and discussed as time-height cross-sections of the energy contents; as time-averaged vertical distributions of budget components; and as vertically averaged budgets. The analysis revealed contrasting differences in the energy budgets in each phase of the development of the system.