Strong Resemblance between Surface and Deep Zonal Winds inside Jupiter Revealed by High-degree Gravity Moments

Abstract

Jupiter’s atmosphere interior is a coupled fluid dynamical system strongly influenced by the rapid background rotation. While the visible atmosphere features east–west zonal winds on the order of ∼100 m s−1, zonal flows in the dynamo region are significantly slower, on the order of ∼cm s−1 or less, according to the latest magnetic secular variation analysis. The vertical profile of the zonal flows and the underlying mechanism remain elusive. The latest Juno radio tracking measurements afforded the derivation of Jupiter’s gravity field to spherical harmonic degree 40. Here, we use the latest gravity solution to reconstruct Jupiter’s deep zonal winds without a priori assumptions about their latitudinal profile. The pattern of our reconstructed deep zonal winds strongly resemble that of the surface wind within ±35° latitude from the equator, in particular the northern off-equatorial jet (NOEJ) and the southern off-equatorial jet. The reconstruction features larger uncertainties in the southern hemisphere due to the north–south asymmetric nature of Juno's trajectory. The amplitude of the reconstructed deep NOEJ matches that of the surface wind when the wind is truncated at a depth ∼2500 km, and becomes twice that of the surface wind if the truncation depth is reduced to ∼1500 km. Our analysis supports the physical picture in which a prominent part of the surface zonal winds extends into Jupiter’s interior significantly deeper than the water cloud layer.