Limited area energy budget during a life cycle of Genoa cyclone (18-21 November 1999)

Abstract

A case of deep and rapid cyclogenesis over the Gulf of Genoa and its impact on a limited area energy budget are examined in this paper. Energy components, including boundary and generation terms, are calculated for the period 18-21 November 1999 over a limited region in which this disturbance is the major synoptic-scale feature. The energy contents and their changes through the studied atmospheric volume are discussed in the course of the cyclone's development. The combined boundary pressure work and dissipation terms of the zonal and eddy kinetic energies, as well as generation terms of zonal and eddy available energies, are computed as residuals. Data of ALADIN/LACE model are used as input fields for calculations. Formation of the cyclone under study initiated in the upper atmospheric levels. At the initial stage of its development, energy conversion C(K Z, K E) was intense. Thus, zonal flow acted as a source of eddy kinetic energy. The disturbance was induced by a very strong wind shear and the progress of the vortex toward the lower atmospheric layers was associated with downward eddy kinetic energy transport (from the jet stream level toward the surface). Simultaneously, the upward transport of both zonal and eddy available energies (from the lower and middle troposphere toward the upper levels) was present. The disturbance was a consequence of very strong wind shear and it was evident how it progressed toward the lower atmospheric layers. As the vortex reached the ground, energy conditions allowed its possible further growth there. In spite of that, the surface cyclone lifetime was very short due to dynamical conditions that attenuated cyclone development.