A Spatial and Temporal Energetics Analysis of a Baroclinic Disturbance in the Mediterranen

Abstract

An analysis of the energetics of an extratropical baroclinic depression is performed. The approach is based on the computation of the components of an energy flow for an open atmospheric region in which this disturbance is the major synoptic-scale feature. The local fields of motion and man are partitioned into zonal and eddy terms, so that the resulting four energy forms are the zonal and eddy terms, so that the resulting four energy forms are the zonal and eddy components of the available potential and kinetic energies. The energy transformations, which can be considered to express well-defined physical process and which are stable from a computational point of view, the diabatic generation of available potential energy, and the frictional dissipation of kinetic energy all determine a composite energy flow over the region. Interactions with the surrounding atmospheric volume are also taken into amount in the form of energy transfers. Energies and their transformations and transfers are computed using the isobaric height, temperature, and wind analyses of the European Centre for Medium-Range Weather Forecasts. The generation of available potential energy is estimated as the residual required to maintain the energy balance. This case study refers to the evolution of a central Mediterranean depression formed during the period from 1200 UTC 7 November to 1200 UTC 9 November 1981. The cyclone formed on an incipient quasi-stationary front over the central Mediterranean. Although its life cycle lasted about 3 days, its rapid development was associated with severe weather conditions over the central and eastern Mediterranean region. The temporal and spatial variations of various components of the energy flow are presented in a detailed analysis. The energy contents and their changes in different atmospheric layers are discussed in the course of the cyclone?s development. From the analysis of the contribution of different layers to the energy conversions, it is shown that not only the intensity of the conversions but also their direction may vary greatly both in the horizontal and the vertical. The role of different layers in importing or exporting energy is also discussed. Integrating over the entire volume of the computational area, the complete energy flow of the cyclone is obtained and discussed within the framework of the available information on cyclone energetics.