Inertia-Gravity Waves Emitted from Balanced Flow: Observations, Properties, and Consequences

This paper describes laboratory observations of inertia-gravity waves emitted from balanced fluid flow. In a rotating two-layer annulus experiment, the wavelength of the inertia-gravity waves is very close to the deformation radius. Their amplitude varies linearly with Rossby number in the range 0.05-0.14, at constant Burger number (or rotational Froude number). This linear scaling challenges the notion, suggested by several dynamical theories, that inertia-gravity waves generated by balanced motion will be exponentially small. It is estimated that the balanced flow leaks roughly 1% of its energy each rotation period into the inertia-gravity waves at the peak of their generation. The findings of this study imply an inevitable emission of inertia-gravity waves at Rossby numbers similar to those of the large-scale atmospheric and oceanic flow. Extrapolation of the results suggests that inertia gravity waves might make a significant contribution to the energy budgets of the atmosphere and ocean. In particular, emission of inertia-gravity waves from mesoscale eddies may be an important source of energy for deep interior mixing in the ocean.