Generation of inertia-gravity waves in a baroclinically unstable fluid

A novel technique is used to visualize and measure the baroclinically unsta ble how in a two-layer, rotating annulus experiment with very high resoluti on in space and time. It is found that small-scale, high-frequency waves ar e generated in certain preferred locations within the flow by a baroclinic wave undergoing amplitude vacillation. These fast waves are investigated in terms of their dispersion relation, and are shown to be consistent with in ertia-gravity waves, generated in association with a source moving with the large-scale baroclinic wave. The occurrence of these waves is described an d discussed in the context of spontaneous adjustment radiation and the mete orological slow manifold. Phase-portrait analyses of the present experiment s indicate that, despite the apparent generation of inertia-gravity waves a s spontaneous adjustment radiation, the resulting vacillatory behaviour rem ains consistent with low-dimensional dynamics.