The turbulent dynamics of Jupiter’s and Saturn’s weather layers: order out of chaos?

Abstract

The weather layers of the gas giant planets, Jupiter and Saturn, comprise the shallow atmospheric layers that are influenced energetically by a combination of incoming solar radiation and localised latent heating of condensates, as well as by upwelling heat from their planetary interiors. They are also the most accessible regions of those planets to direct observations. Recent analyses in Oxford of cloud-tracked winds on Jupiter have demonstrated that kinetic energy is injected into the weather layer at scales comparable to the Rossby radius of deformation and cascades both upscale, mostly into the extra-tropical zonal jets, and downscale to the smallest resolvable scales in Cassini images. The large-scale flow on both Jupiter and Saturn appears to equilibrate towards a state which is close to marginal instability according to Arnol’d’s 2nd stability theorem. This scenario is largely reproduced in a hierarchy of numerical models of giant planet weather layers, including relatively realistic models which seek to predict thermal and dynamical structures using a full set of parameterisations of radiative transfer, interior heat sources and even moist convection. Such models include (amongst others) the Jason GCM, developed in Oxford, which also represents the formation of (energetically passive) clouds of NH3, NH4SH and H2O condensates and the transport of condensable tracers. Recent results show some promise in comparison with observations from the Cassini and Juno missions, but some observed features (such as Jupiter’s Great Red Spot and other compact ovals) are not yet captured spontaneously by most weather layer models. We review recent work in this vein and discuss a number of open questions for future study.

Is Target-Based Drug Discovery Efficient? Discovery and “Off-Target” Mechanisms of All Drugs

“…” It can be said that coarse-graining and black-boxing increase cause-effect power and informativeness by capturing simpler higher-level attractor states of highly complex lower levels , and parameter space compression . References − present a few other examples of increased simplicity and informativeness at higher levels.…”

Stratospheric planetary flows from the perspective of the Euler equation on a rotating sphere

“…Rayleigh's criterion appears not to be sufficient for linear instability: it holds for the latitudinal profile of the persistent zonal jets on Jupiter and Saturn (see the data in [45]).…”

“…The condition that θ = 5π 12 with cos θ ≈ 1 4 is a critical point and the above two specific values of the function U 0 yield the linear system (4.18) has no roots, Theorem 6 yields that the zonal flow pattern of Neptune is also stable. Unfortunately this approach is not applicable to the likely stability of the zonal jets on Jupiter and Saturn to breaking up into meanders and vortex-like eddies, but both zonal jet patterns (see [45] for their detailed profiles) are not far off from entering the framework of Theorem 6. In contrast to this, the profiles of terrestrial stratospheric jets derived from observational data (see [41]) are well beyond condition (4.15), as is to be expected since the Earth's polar jet stream is known to be unstable.…”

Direct driving of simulated planetary jets by upscale energy transfer

“…Although deeply penetrating, the jets could still be driven by motions in a shallow weather layer (e.g., Showman 2007;Schneider & Liu 2009;Lian & Showman 2010;Read et al 2020;Cabanes et al 2020). Indeed, the dynamics of rotating systems predicts that the jets organize on geostrophic cylinders with minimal variation along the rotation axis, independent of where along the cylinders the flow is driven.…”