Keith Ngan, Peter Bartello and D.N. Straub
McGill University, Montreal, Quebec

Dissipation of synoptic-scale flow by small-scale turbulence

Critical avalanches of instabilities in sandpile models and bursty localized energy dissipation in high-Reynolds number fluids are paradigmatic examples of multiscale intermittency in nonlinear systems with spatially extended degrees of freedom.
In this work we examine the parameterisation problem in the context of rotating stratified turbulence, i.e., with a non-hydrostatic Boussinesq model. Using the normal modes as a first approximation to the balanced and unbalanced flow, we calculate the geostrophic-ageostrophic transfers and the growth of ageostrophic perturbations to the quasi-geostrophic base flow; the associated damping on the geostrophic base flow, the "wave drag" or "eddy viscosity", is highlighted. Connections with recent work on three-dimensionalization of decaying 2-D turbulence and spontaneous imbalance are discussed.