Michaelides, Silas Chr. (Meteorological Service, Nicosia, Cyprus)
The energetics of the atmosphere have been a familiar subject that was studied by many investigators during the past three to four decades. Initially, a great effort has been made to identify and quantify the various forms of atmospheric energy and their transformations on the global scale. The extension of the energetics research to individual synoptic scale disturbanes was the natural consequence of the establishement of the energetics approach as a useful diagnostic tool on the global scale. Particular attention was given to synoptic scale cyclonic circulations, due to the intense weather conditions normally associated with them.
Following the trends on the global scale, the issue of the atmospheric energetics associated with the cyclonic disturbances has been addressed using various analytical procedures. The present article deals wth the different approaches which were adopted in a series of investigations on the energetics of several cyclonic disturbances that were evolved in the Meditrranean basin. All of these systems were selected for study on the basis of their common intense weather that they produced during their life-cycle: very strong to gale force winds, intense and widespread preciptation and high seas. (Michaelidis and Angouridakis, 1980; Michaelides, 1983; Michaelides 1987; Prezerakos and Michaelides, 1989; Michaelides, 1992; Michaelides,S.C.,Prezerakos,N.G.
and Flocas E. 1996). Six case-studies are documented in the present article.
The first case-study refers to a case of cyclogenesis initiated over the Western Mediterranean and covers the period from 10 to 14 February, 1980. A very simple energetics approach was adopted in which the energy contents during the evolution of a winter Mediterranean depression were studied (Michaelidis and Angouridakis, 1980). The forms of energy considered are the kinetic energy and available potential energy.
The second case is one of eastern Mediterranean cyclogenesis and which was investigated from the point of view of the generation of kinetic energy at the expense of available potential energy and vice versa (Michaelides, 1983).
This case-study refers to the period from 9 to 11 December, 1980. The ageostrophic conversion between these two forms of energy is decomposed into zonal and meridional parts. The spatial and temporal distribution of these terms are presented.
In the complete Lorenz energy cycle, each of the available potential and kinetic energies is decomposed into zonal and eddy parts. This decomposition of energies leads to four energy conversions, namely from zonal a.p.e. into eddy a.p.e., from zonal a.p.e. into zonal k.e., from zonal k.e. into eddy k.e. and from eddy a.p.e.
into eddy k.e. Also, the diabatic generation and frictional dissipation are also partitioned into zonal and eddy components. Calculations on the basis of the above energy cycle have been performed in the third case study which is a typical Genoa depression and during its development in the period from 15 to 17 January, 1981 (Michaelides 1987). The respective temporal distribution of all the terms in the energy-cycle are presented.
The energy cycle outlined above formed the basis for the fourth case-study too. This approach is adopted in the study of a central Mediterranean depression developed during the period from 7 to 9 November, 1981 (Michaelides, 1992). The respective temporal distribution of all the terms in the energy-cycle are presented.
Also, the horizontal and vertical distributions of the conversion terms are discussed.
In the fifth case-study, the budgets of kinetic energy, sensible heat and latent heat have been considered simultaneously using the sigma coordinate system. In this study a depression that affected the Mediterranean from 17 to 20 March, 1981 was investigated (Prezerakos and Michaelides, 1989). The time evolution of the energy contents and tranformations are considered.
The sixth case-study of Mediterranean cyclone energetics refers to a wintertime frontal depression which formed in the central Mediterranean in the period from 6 to 9 December 1991 (Prezerakos, Flocas and Michaelides, 1996; Michaelides ,Prezerakos. and Flocas, 1996). In this case-study a novel quasi-Lagrangian framework was adopted. In this approach, the computational area consists of an area surounding the depression at each stage of its development and moving along with it. The Lorenz's zonal and eddy energy contents and their tranformations are discussed from the point of view of their temporal evolution.
Related literature
Michaelides,S.C., and V.E.Angouridakis, 1980 : Diagnostic study of a winter Mediterranean depression. Sci.
Annals, Fac.Phys. & Mathem., Univ. of Thessaloniki, 20a, 53-76.
Michaelides,S.C., 1983 : Components of large-scale kinetic energy generation during an eastern Mediterranean cyclogenesis. Arch. for Meteor., Geophys., and Bioclimat., Series A, 32, 247-256.
Michaelides,S.C., 1987 : Limited area energetics of Genoa cyclogenesis. Mon. Wea. Rev., 115, 13-26.
Prezerakos,N.G., and S.C.Michaelides, 1989 : A composite diagnosis in sigma coordinates of the atmospheric energy balance during intense cyclonic activity. Quart. J. Roy.Meteor. Soc., 115, 463-486.
Michaelides,S.C. 1992 : A spatial and temporal energetics analysis of a baroclinic disturbance in the Mediterranean. Mon.Wea.Rev.,120,1224-1243.
Michaelides,S.C.,Prezerakos,N.G. and Flocas E. 1996 : Lagrangian energetics of a Mediterranean depression.
(Accepted for publication in the Proceedings of the 3rd Pan-Hellenic Conference on Meteorology, Climatology and Atmospheric Physics - Athens Greece 25-27 September, 1996).
Michaelides,S.C.,Prezerakos,N.G. and Flocas E. 1996 : Quasi-Lagrangian energetics analysis of an intense Mediterranean cyclone (In preparation)
Prezerakos,N.G., Flocas E. and Michaelides S.C., 1996 : Relative-absolute vorticity and potential vorticity of the free troposphere as a synthetic tool for the diagnosis and forecasting of cyclogenesis. Atmosphere-Ocean (In Press).