A study of the growth and decay of eddy available potential energy and eddy kinetic energy based on temporal correlations

Abstract

Abstract The growth and decay of vertically integrated eddy kinetic energy (KE) and eddy available potential energy (APE) are studied in terms of zonal wavenumber over a three‐year period for the Northern and the Southern Hemispheres by correlating the energies and their tendencies with terms in the energy budget equations. In the KE budget, the term that is the most highly correlated with the KE tendency is the transfer of KE from other waves by non‐linear interactions, indicating that this process is important in the growth and decay of wave KE. The APE‐to‐KE conversion term is weakly correlated with the KE tendency but strongly correlated with the KE suggesting that although this term is not important in producing growth and decay of KE, it does appear to maintain waves against dissipation. The transfer of energy to the zonal flow is slightly out of phase with the KE, with the maximum transfer to the zonal flow occurring shortly after the waves achieve their maximum KE. A similar result is obtained for the APE budget. The transfer of APE from other waves by non‐linear interactions is the term that is most strongly correlated with the APE tendency. The conversion of APE to KE, the transfer from the zonal flow to the wave and the APE of the wave are strongly correlated indicating that the transfer of APE from the zonal flow to a wave and then to KE in the wave is governed by the amplitude of the wave APE.