Scaling of high-wavenumber energy spectra in the unit aspect-ratio rotating Boussinesq system (1005.5366v2)

Abstract: Phenomenological and numerical studies of the small scale spectra of energy are presented for high Reynolds number rotating Boussinesq flows in unit aspect-ratio domains. We introduce a non-dimensional parameter Gamma such that when the potential vorticity is nearly linear in the dynamical variables, we deduce that for Gamma much less than 1, the potential enstrophy suppresses the transfer of horizontal kinetic energy into wavemodes with large horizontal component k_h while forcing it to become independent of vertical wavevector component k_z, scaling as k_h^{-5}. When Gamma much greater than 1, the potential enstrophy suppresses the transfer of potential energy into the wavemodes with large vertical component k_z while forcing it to become independent of k_h, scaling as k_z^{-5) power. Spectra computed from high-resolution simulations of the Boussinesq equations with isotropic low-wavenumber forcing are used to explore such anisotropic constraints on the energy and provide a posteriori justification for the joint flux ansatz used to obtain the (-5) scaling exponent. In all cases the empirical evidence points to both energy and potential enstrophy being jointly transferred downscale with the spectral scaling of the the former constrained by the latter.