Numerical simulations demonstrating Eddy-driven jets and meridional circulation cells on gas giants

Jupiter's atmosphere consists of a number of dynamical regimes: the equatorial superrotation and its adjacent retrograde jets, the midlatitude, eddy-driven, alternating jet streams, and the associated meridional circulation cells and the turbulent polar region. While intensive research has been conducted in the past decades on each of these regimes, they all remain only partially understood and somewhat mysteries. Different models give a variety of possible explanations for each of these regions, and only a handful of models can even capture two areas at once. This study presents new numerical simulations, using a 3D anelastic GCM, that can reproduce the midlatitudinal pattern of the mostly barotropic, alternating eddy-driven jets and the meridional circulation cells accompanying them. As expected for a gas giant, we find that the vertical eddy momentum fluxes are just as important as the meridional eddy momentum fluxes, which drive the midlatitudinal circulation on Earth. The number of the jets/cells, their extent, strength, and location are directly related to the boundary conditions, the Ekman number, and the depth of the atmosphere. Studies have shown that the rotation rate, the forcing scheme, and the Rayleigh number are also responsible for the emergence of jets in simulations of gas giants, but we keep these constant in our simulations. Our simulations also capture the tilted convection columns in the tangent cylinder region, leading to the superrotation at the equator and the adjacent, subrotating jets. We show that tilted columns can also generate equatorial subrotation, possibly explaining the zonal wind pattern on the ice giants. We find that the location and strength of the adjacent jet can indicate the depth of the atmosphere, as they are well correlated in all the simulations and on Jupiter and Saturn, according to gravity measurements by Juno and Cassini, respectively. Our analysis provides another step towards understanding the deep atmospheres of gas giants.