A CONVECTIVE MODEL FOR THE ZONAL JETS IN THE ATMOSPHERES OF JUPITER AND SATURN

THE atmospheres of Jupiter and Saturn are stably stratified in a region extending from the tropopause down to the level of the cloud tops; the underlying region is dominated by convective overturning1,2. Horizontal velocities within the stable region decrease with altitude3, suggesting that they are driven by momentum transfer from the deeper flow. But the vertical structure within the convective region is still poorly understood1. Its visible component at cloud level consists of alternating east-west zonal jets, with the more pronounced eastward jets attaining velocities in excess of 100 m s-1 and widths of about 10(4) km (refs 2 and 3). Here we propose a mechanism whereby the zonal jets result from convection cells resembling atmospheric Hadley cells on the Earth4. We demonstrate this mechanism using a rotating axisymmetric bowl of fluid, uniformly cooled at the free surface; radially overturning convection cells are established, the surface manifestation of which are pronounced azimuthal jets. A simple linear theory reproduces the main characteristics of the laboratory flow and predicts a relatively shallow penetration depth for the convection cells on Jupiter and Saturn.