Meridional Circulation with Latitude Bands of Long-Lived Cyclones in Jupiter’s Convective Atmosphere

Hans G Mayr,Kwing L Chan

doi:10.4236/ijaa.2021.113018

Abstract

Mayr et al. [1] proposed that the vertical velocities in the global scale meridional circulation can produce distinct latitude bands where Jovian vortices like the white and brown are observed, and we present here a brief review of the mechanism. The observed life times of the ovals are much longer than the estimated spin-down times, which indicates that the vortices must be sustained through the release of internal energy. Like Jupiter’s Great Red Spot (GRS), the white/brown ovals are treated like terrestrial hurricanes or cyclones, which are generated by convection. The planetary energy Jupiter emits is transferred by convection, and under this condition the upward motions in the meridional circulation, around the equator for example, release energy from below and decrease the convective instability to suppress the formation of cyclones. But the downward motions in the circulation, near 20° latitude for example, carry energy down so that the convective instability is amplified to produce a dynamical environment that is favorable for the development of cyclones like the GRS and white/brown ovals. This picture is supported by an analysis of results from a numerical model of Jupiter’s alternating jets (Chan and Mayr [2]). Generated by alternating vertical winds in the meridional circulation, the vertical temperature variations reveal distinct latitude bands with enhanced convective instability, most prominent at high latitudes where long-lived circumpolar cyclones are observed from the Juno spacecraft.

Highlights

A gaseous planet, Jupiter emits more than twice as much energy as it receives from the Sun
Like Jupiter’s Great Red Spot (GRS), the white/brown ovals are treated like terrestrial hurricanes or cyclones, which are generated by convection
The white and brown ovals have live times exceeding the spin-down times, which suggests that they originate well below the clouds. These long-lived vortices are observed organized along latitude bands, and Mayr et al [1] propose that the downward motions in the global-scale meridional circulation can produce regions with amplified convective instability, varying with latitude, where the dynamical conditions are favorable for generating and sustaining the Jovian vortices

Summary

Introduction

Considering that the observed horizontal dimension of the planetary vortex can reach as an upper limit the Rossby diameter of deformation (Holton [26]), the depths, h, and spin-down times, τ, can be estimated (Holton [27]) to produce h = 400 km and 200 km, and τ = 1.6 years and 4 months for the GRS and the white/brown ovals, respectively (Mayr et al [1]). The white and brown ovals have live times exceeding the spin-down times, which suggests that they originate well below the clouds These long-lived vortices are observed organized along latitude bands, and Mayr et al [1] propose that the downward motions in the global-scale meridional circulation can produce regions with amplified convective instability, varying with latitude, where the dynamical conditions are favorable for generating and sustaining the Jovian vortices

Vortex Generations

Latitudinal Vortex Stratification

Model Generated Latitude Bands of Instability

Findings

Conclusions