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.