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) propor. 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 are quasi-2D with E(k) approx= 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) propor. to k_h~(-3) is analogous to the dynamics of #beta#-plane turbulence leading to the Rhines spectrum E(k_y,k_x=0) propor. to k_y~(-5).
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