What determines the strength and latitudinal extent of the equatorial zonal flows on Jupiter and Saturn? 

Abstract

Jupiter's equatorial zonal flows reach wind velocities of ∼ 100 m/s, while on Saturn they are three times as strong and extend about twice as wide in latitude, despite the two planets being overall dynamically similar. Recent gravity measurements obtained by the Juno and Cassini spacecraft uncover that the depth of zonal jets on Saturn is about three times greater than on Jupiter. Here we reveal, using high-resolution 3D simulations, that the atmospheric depth is the determining factor controlling both the strength and latitudinal extent of the equatorial zonal flows, consistent with the measurements for both planets. We show that the atmospheric depth is proportional to the convectively-driven eddy momentum flux, which controls the strength of the zonal flows. These insights provide a comprehensive explanation for the observed differences in the equatorial regions of Jupiter and Saturn and offer new understandings into the dynamics of gas giants.