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Cyclonic circulation of Saturn’s atmosphere due to tilted convection


Saturn displays cyclonic vortices at its poles and the general atmospheric circulation at other latitudes is dominated by embedded zonal jets that display cyclonic circulation. The abundance of small-scale convective storms suggests that convection plays a role in producing and maintaining Saturn’s atmospheric circulation. However, the dynamical influence of small-scale convection on Saturn’s general circulation is not well understood. Here we present laboratory analogue experiments and propose that Saturn’s cyclonic circulation can be explained by tilted convection in which buoyancy forces do not align with the planet’s rotation axis. In our experiments—conducted with a cylindrical water tank that is heated at the bottom, cooled at the top and spun on a rotating table—warm rising plumes and cold sinking water generate small anticyclonic and cyclonic vortices that are qualitatively similar to Saturn’s convective storms. Numerical simulations complement the experiments and show that this small-scale convection leads to large-scale cyclonic flow at the surface and anticyclonic circulation at the base of the fluid layer, with a polar vortex forming from the merging of smaller cyclonic storms that are driven polewards.

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Fig. 1: Experimental set-up and observations.
Fig. 2: A schematic drawing of a convecting layer of water in a rotating tank.
Fig. 3: Temperature and surface elevation fields at the surface of the convecting fluid in the numerical simulations.
Fig. 4: Profiles of the azimuthal velocity.


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This research was supported by the Natural Sciences and Engineering Research Council of Canada.

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Y.D.A. designed the experiment, analysed data, developed the theory, performed numerical simulations and wrote the manuscript. Y.Z. performed the experiment, processed and analysed data and contributed to the manuscript.

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Correspondence to Y. D. Afanasyev.

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Afanasyev, Y.D., Zhang, Y. Cyclonic circulation of Saturn’s atmosphere due to tilted convection. Nature Geosci 11, 164–167 (2018).

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