Jupiter’s overturning circulation: Breaking waves take the place of solid boundaries

Cloud-tracked wind observations document the role of eddies in putting momentum into the zonal jets. Chemical tracers, lightning, clouds, and temperature anomalies document the rising and sinking in the belts and zones, but questions remain about what drives the flow between the belts and zones. We suggest an additional role for the eddies, which is to generate waves that propagate both up and down from the cloud layer. When the waves break they deposit momentum and thereby replace the friction forces at solid boundaries that enable overturning circulations on terrestrial planets. By depositing momentum of one sign within the cloud layer and momentum of the opposite sign above and below the clouds, the eddies maintain all components of the circulation, including the stacked, oppositely rotating cells between each belt-zone pair, and the zonal jets themselves.Plain Language SummaryThe dark belts and bright zones that circle the planet at constant latitude, along with the jet streams on the belt-zone boundaries, are the iconic dynamical features of Jupiter's atmosphere. But the circulation cells with rising, sinking, and cross-latitude motion are just as important because they maintain the storms and turbulent eddies. Voyager and Cassini have shown that the turbulent eddies put energy into the jet streams. We argue that the eddies also put energy into the circulation cells. They do this by generating waves that break as they propagate above and below the clouds. The breaking waves provide the essential forces that replace those that occur on planets with solid boundaries.</div

Super-adiabatic temperature gradient at Jupiter's equatorial zone and implications for the water abundance

The temperature structure of a giant planet was traditionally thought to be an adiabat assuming convective mixing homogenizes entropy. The only in-situ measurement made by the Galileo Probe detected a near-adiabatic temperature structure within one of Jupiter's 5μm hot spots with small but definite local departures from adiabaticity. We analyze Juno's microwave observations near Jupiter's equator (0– 5 oN) and find that the equatorial temperature structure is best characterized by a stable super-adiabatic temperature profile rather than an adiabatic one. Water is the only substance with sufficient abundance to alter the atmosphere's mean molecular weight and prevent dynamic instability if a super-adiabatic temperature gradient exists. Thus, from the super-adiabaticity, our results indicate a water concentration (or the oxygen to hydrogen ratio) of about 4.9 times solar with a possible range of 1.5– 8.3 times solar in Jupiter's equatorial region