Relationships between available potential energy, kinetic energy, and extratropical cyclone activity within East Coast cyclogenetic regions

Abstract

Interrelationships between the available potential energy and kinetic energy associated with extratropical cyclones are examined for portions of the First GARP Global Experiment (FGGE) year. The study is confined to the cyclogenetically active regions encompassing the eastern coasts of Asia and North America. Calculations of vertically integrated available potential energy (APE) and kinetic energy (KE) are done for an active winter storm period (February 14–28, 1979) and a relatively inactive summer period (July 1–15, 1979) using gridded isentropic data produced from the FGGE Level IIIa set of global analyses. During both the winter and summer study periods, good agreement is indicated between cyclone tracks and the spatial distributions of time mean and standard deviations of vertically integrated APE and KE. Energy distributions composited for rapidly strengthening and weakening storms show the patterns of available potential energy and kinetic energy which are associated with cyclones in these stages of development. The rapidly intensifying storms are accompanied by strong gradients in APE equatorward of the surface cyclone with maximum KE to the south and southwest of the storm center. Smaller values of kinetic energy and weaker gradients of available potential energy accompany the rapidly decaying storms. An examination of twice daily distributions of APE and KE for 29 individual cyclones reveals that a similar temporal evolution of vertically integrated energy patterns accompanies storms in these east coast regions. An example of this evolution is presented in conjunction with a case analysis of the February 1979 Presidents' Day cyclone along the east coast of North America.