Planetary Climate Dynamics

Abstract:

Saturn's poles exhibit an unexpected symmetry in hot, cyclonic polar vortices, despite huge seasonal differences in solar flux. The cores of both vortices are depleted in phosphine gas, probably resulting from subsidence of air into the troposphere. The warm cores are present throughout the upper troposphere and stratosphere at both poles. The thermal structure associated with the marked hexagonal polar jet at 77 degrees N has been observed for the first time. Both the warm cyclonic belt at 79 degrees N and the cold anticyclonic zone at 75 degrees N exhibit the hexagonal structure.

Abstract:

Synchronization of periodic and chaotic oscillations between two coupled rotating baroclinic fluid systems will be presented. The numerical part of the study involves a pair of coupled two-layer quasigeostrophic models, and the experimental part comprises two thermally coupled baroclinic fluid annuli, rotating one above the other on the same turntable. Phase synchronization and imperfect synchronization (phase slips) have been found in both model and experiments, and model simulations also exhibit chaos-destroying synchronization. © 2008 IOP Publishing Ltd.

Abstract:

We report an analog laboratory study of planetary-scale turbulence and jet formation. A rotating annulus was cooled and heated at its inner and outer walls, respectively, causing baroclinic instability to develop in the fluid inside. At high rotation rates and low temperature differences, the flow became chaotic and ultimately fully turbulent. The inclusion of sloping top and bottom boundaries caused turbulent eddies to behave like planetary waves at large scales, and eddy interaction with the zonal flow then led to the formation of several alternating jets at mid-depth. The jets did not scale with the Rhines length, and spectral analysis of the flow indicated a distinct separation between jets and eddies in wavenumber space, with direct energy transfer occurring nonlocally between them. Our results suggest that the traditional "turbulent cascade" picture of zonal jet formation may be an inappropriate one in the geophysically important case of large-scale flows forced by differential solar heating.