Transfer of energy to two-dimensional large scales in forced, rotating three-dimensional turbulence

Forced turbulence in a rotating frame is studied using numerical simulations in a triply periodic box. The random forcing is three dimensional and localized about an intermediate wavenumber k(f). The results show that energy is transferred to scales larger than the forcing scale when the rotation rate is large enough. The scaling of the energy spectrum approaches E(k) proportional to k(-3) for k < k(f). Almost all of the energy for k < k(f) lies in the two-dimensional (2D) plane perpendicular to the rotation z-axis, and thus the large-scale motions an quasi-2D with E(k) approximate to E(k(h), k(z) = 0), where k(h) and k(z) are, respectively, the horizontal and vertical components of the wavevector. The large scales consist of cyclonic vortices. Possible mechanisms responsible for the two-dimensionalization are discussed. The development of the 2D spectrum E(k(h), k(z) = 0) proportional to k(h)(-3) is analogous to the dynamics of beta-plane turbulence leading to the Rhines spectrum E(k(y), k(x) = 0) proportional to k(y)(-5). (C) 1999 American Institute of Physics. [S1070-6631(99)00706-0].