Investigating Barotropic Zonal Flow in Jupiter's Deep Atmosphere Using Juno Gravitational Data

Abstract

AbstractThe high‐precision Juno gravitational measurements allow us to infer the structure of Jupiter's deep atmospheric zonal flow. Since this inference is nonunique, it is important to explore the space of possible solutions. In this study, we consider a model in which Jupiter's deep atmospheric zonal flow is barotropic, or invariant along the direction of the rotation axis, until it is truncated at depth by some dynamical process (e.g., Reynolds stress, Lorentz or viscous force). We calculate the density perturbation produced by the z‐invariant part of the flow using the thermal wind equation and compare the associated odd zonal gravitational harmonics (J3, J5, J7, J9) to the Juno‐derived values. Most of the antisymmetric gravitational signal measured by Juno can be explained by extending observed winds between 20.9°S and 26.4°N to depths of km. Because the small‐scale features of the midlatitude/high‐latitude zonal flow may not persist to depth, we allow the zonal flow in this region to differ from the observed surface winds. We find that the Juno odd zonal gravitational harmonics can be fully explained by km deep barotropic zonal flows involving the observed winds between 20.9°S−26.4°N and a few broad midlatitude/high‐latitude jets.