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Abstract:

The atmospheric circulation of Jupiter is shaped by a complex interplay between deep internal processes and cloud-level dynamics. Numerical simulations and observational analyses have suggested that Jupiter’s mid-latitude jets are strongly influenced by baroclinic instability [1], which is governed by the planet’s atmospheric thermal structure. Jupiter emits a substantial intrinsic heat flux originating from its interior. Past modelling efforts [2, 3] have demonstrated that this internal energy plays a key role in shaping large-scale atmospheric dynamics.Our previous work [4] showed that latitudinal variations in interior heat flux can significantly impact the structure and behaviour of Jupiter’s mid-latitude jets in a General Circulation Model (GCM).  Such an impact is best illustrated by the relative vorticity snapshots from two simulations with the lowest and highest latitudinal flux gradient (see Figure 1). In this study, we present a more detailed analysis linking these jet modifications to changes in the atmospheric thermal structure and, consequently, to the strength and distribution of baroclinic eddy activity. In particular, we use the Lorenz energy cycle framework to diagnose how variations in deep thermal forcing influence baroclinic energy conversion and eddy-mean flow interactions. We further examine the implications for meridional transport and the water cycle within Jupiter’s weather layer.Additionally, we present a control simulation in which the potential temperature at the model’s lower boundary is forced toward a fixed value (a deep adiabat setup). We compute the equivalent upward heat flux associated with this forcing to place it in the context of previous models that impose constant or latitudinally varying interior heat flux. This allows a direct comparison of how different representations of deep thermal forcing affect upper-atmospheric dynamics.Finally, we discuss the broader implications of these findings for future weather-layer models of Jupiter and other gas giant planets, especially on the effect of bottom boundary conditions in representing the coupling between deep and observable atmospheric dynamics. Figure 1: Mollweide projection of the relative vorticity at 1 bar at the end of two simulations.Reference:[1] Read, P. L. (2023). The dynamics of Jupiter’s and Saturn’s weather layers: a synthesis after Cassini and Juno. Annual Review of Fluid Mechanics, 56(1), 271–293. https://doi.org/10.1146/annurev-fluid-121021-040058[2] Liu, J., & Schneider, T. (2011). Convective Generation of Equatorial Superrotation in Planetary Atmospheres. Journal of the Atmospheric Sciences, 68(11), 2742-2756. https://doi.org/10.1175/JAS-D-10-05013.1[3] Young, R. M. B., Read, P. L., & Wang, Y. (2018). Simulating Jupiter’s weather layer. Part I: Jet spin-up in a dry atmosphere. Icarus, 326, 225–252. https://doi.org/10.1016/j.icarus.2018.12.005[‌4] Hu, X. and Read, P.: Latitudinal Variation in Internal Heat Flux in Jupiter's Atmosphere: Effect on Weather Layer Dynamics, Europlanet Science Congress 2024, EPSC2024-669, https://doi.org/10.5194/epsc2024-669, 2024.

Abstract:

Hypotheses involving energetic constraints and the down-gradient diffusion of heat in eddy parameterization theories are tested by estimating baroclinic eddy transports in rotating annulus laboratory experiments. Particle Imaging Velocimetry measurements are supplemented by numerical simulations to estimate variables not measured directly. The results with a topographic beta effect broadly 91̽�� Fick's first law, and are consistent with the GEOMETRIC framework in which eddy buoyancy flux is constrained by total eddy energy. With the topographic beta effect, a relatively simple relation is observed between the eddy buoyancy flux and the total eddy energy, with the ratio quantifying the eddy transport efficiency. This efficiency decreases in more complex flow regimes with larger rotation rates, associated with the changing energy partition between eddy available potential energy and eddy kinetic energy. In the absence of a topographic beta effect, more complicated dependencies are found, suggesting roles for other variables.

Abstract:

Barotropic instability represents a class of instabilities, usually of parallel shear flows, for which gravity and buoyancy play a negligible role, at least in their energetics. It is not restricted to purely barotropic fluids (for which ρ = ρ(p), where ρ is density and p is pressure) but can also apply to flows which are stratified and exhibit vertical shear, often leading to instabilities with mixed barotropic and baroclinic characteristics. The primary attribute of barotropic instability is usually taken to be the dominance of energy exchanges in which the kinetic energy of a perturbation grows principally at the expense of the kinetic energy of the basic state. Here we present an introduction to the basic mechanisms involved and the factors that determine the necessary and/or sufficient conditions for instability. Several examples are presented and the occurrence and subsequent nonlinear evolution of the instability is illustrated with reference to both laboratory experiments and observations in the atmospheres and oceans of the Earth and other planets in the Solar System.