Eddies and waves in a rotating flow: an experimental study

The variation of the Coriolis parameter with the latitude, the so-called β effect, strongly affects the turbulent up-scale cascade in fact the energy is preferentially channeled into zonal modes. This effect may be significant in planetary atmospheric and oceanic circulations; in this case, nonlinear eddy/wave interactions induce the flow self-organization into zonal patterns, in which Rossby waves and westward propagating cyclonic and anticyclonic eddies coexist. To investigate the connections between eddies, jets, and waves we realized a laboratory experiment suitable to reproducing eastward/westward zonal flows by applying an electromagnetic small-scale forcing to a thin layer of a rotating fluid. We performed a wide series of runs varying the characteristics of the forcing as well as the main experimental parameters as fluid thickness and rotation rate of the system. Velocity field were measured using a technique based on image analysis. We deeply investigated the flow features onset and their time evolution, in particular we were able to estimate the speed propagation of the travelling structures and compare the measured and expected theoretical values.