[A-CG38] Dynamics of Oceanic and Atmospheric Waves, Vortices, and Circulations

[ACG38-13] Formulation and application of phase-independent energy conversion terms for quasi-geostrophic eddies on a zonally-varying basic flow

★Invited Papers

*Takaya Koutarou¹ (1.Kyoto Sangyo University)

Keywords:energy conversion, Rossby wave

A new formulation of energy conversion terms for quasi-geostrophic disturbances is proposed under an assumption that an eddy is almost a plane wave in the WKB sense. Estimating energy conversions could be valid to explore dynamics of low-frequent variability of the disturbances. A traditional form of the energy conversion terms contains quadratic terms in disturbance amplitudes, such as a momentum transport u’v’ and a heat transport v’T’. Therefore, it inherently includes an oscillatory component of one-half wavelength of the disturbances. For transient eddies, time-averaging longer than one wave period can be equivalent to eliminating the half-wavelength oscillatory components in the energy conversion terms, so that the traditional form of the terms may be available. However, for stationary waves, time-averaging is not equivalent to phase-averaging and therefore inappropriate. A new form of the energy conversion proposed in this study can be proved to be phase-independent of the eddies without any spatial- and time-averaging taken, and thus can represent a “snapshot” distribution of the energy conversion terms. Therefore, the new formulation can be applicable to estimating energy conversions for stationary eddies or snapshot features of transient eddies.

Actual applications of the new form of the energy conversions to some teleconnection patterns will also be given. Our analysis based on the new formulation suggests that energy extraction from the basic state and energy dispersion by group velocity can be essential for formation and/or maintenance mechanisms of the teleconnection patterns.