The Effect of the Finite Rossby Radius on Two-Dimensional Isotropic

The effect of the finite outer Rossby radius on two-dimensional isotropic turbulence in a single-layered fluid is investigated using the modified cumulant expansion method. This type of turbulence may be considered as a model of geostrophic turbulence in the atmosphere. The beta effect is neglected in order to avoid extra complexity. It is found that turbulent motions with scale larger than the Rossby radius are strongly suppressed and consequently the inverse cascade of the energy is remarkably reduced. At large wavenumbers,the similarity law of the energy spectrum is identical to that of two-dimensional turbulence without rotation. The kinetic energy decreases in time, while the potential energy increases.