High Vorticity Regions in Rotating Thermally Driven Flows

The regular and irregular non-axisymmetric flow regimes of thermal convection in a rotating fluid annulus subject to differential heating in the horizontal are characterized by the presence of upper level jet-streams, where intense concentrations of vorticity and high concomitant horizontal temperature gradients are found. The main features of the upper-level flow pattern can be interpreted by straightforward arguments based on general thermodynamic considerations and the requirement that the flow should be quasi—geostrophic nearly everywhere. Thus, when the distribution of applied heating and cooling is such that the corresponding gradient of the impressed radial temperature field has the same sign at all radii, the most conspicuous feature of the upper-level flow pattern in the regular non-axisymraetric regime is a single jet-stream meandering in a wavy pattern between the bounding cylinders. When, however, the impressed radial temperature gradient changes sign near mid-radius (as in the case when heat is introduced throughout the body of the fluid and withdrawn at both side-walls), the corresponding upper-level flow consists of several closed eddies, each circulating “anticyclonically” with the horizontal flow largely confined to a narrow jet-stream at the periphery of each eddy. In some respects these stable closed eddies are dynamically similar to long-lived anticyclonic eddies (including the Great Red Spot) seen in Jupiter’s atmosphere in the southern hemisphere. Previous work on stable baroclinic eddies is now being extended in various directions and supporting numerical work is also being carried out.