Emergence of Circumpolar Vortex in Two Dimensional Turbulence on a Rotating Sphere

Abstract

Characteristics of the decaying non-divergent two dimensional turbulence on a rotating sphere is considered. The spontaneous appearance of circumpolar easterly vortices reported in the previous study (Yo-den and Yamada, 1993) is interpreted by the Rossby wave property from the framework of weak-nonlinear theory. The resolution of the numerical model utilized by Yoden and Yamada (1993) T85 is not high enough to represent the upward energy cascade of two dimensional turbulence. The initial energy spectral peak adapted there is located almost in the range of wave regime especially when the rotation rate is large, which justifies the explanation of angular momentum redistribution by Rossby waves. A series of new experiments with the higher resolution T341 and new sets of initial energy spectral distributions are performed to confirm that the circumpolar vortices appear even after the full nonlinear upward cascade of turbulent energy and that the band structure of angular momentum emerges even when the rotation rate of the system is large.