Cycles of Variability in Jupiter's Atmosphere from Ground-Based Mid-Infrared Observations

1. Overview

Jupiter's banded structure undergoes remarkable global-scale disturbances that can completely change its appearance from the deep troposphere below the cloud deck (2-7 bar) to the stratosphere (~1 mbar). These events can alter Jupiter's cloud structure, aerosols, and temperature field through mechanisms that are not well understood, and provide relevant insights into Jupiter’s time-variable atmospheric dynamics. Characterizing Jupiter's atmospheric changes in the long-term is crucial to better understand the origin and nature of the planetary scale disturbances, distinguishing between seasonal or mechanical forcing, and enables further investigation of the coupling of Jupiter's belts and zones that could explain the presence of 'Global Upheavals' (Rogers, 1995). In this study, we will describe how Jupiter's temperatures and aerosols vary over long spans of time, from the top NH₃ clouds to the stable mid-stratosphere, and we will show that although Jupiter's troposphere and stratosphere exhibit a large number dynamical phenomena, there exists quasi-periodic patterns that may aid in future predictions of planetary-scale changes to the banded structure.

2. Ground-Based Observations

Continued monitoring of Jupiter from ground-based observatories from the past 40 years has provided an unprecedented resource for understanding the cyclic/non-cyclic environmental changes  in temperature, aerosols, and composition governing Jupiter’s dynamic atmosphere. More recently, ground-based observations have provided essential temporal, spectral and spatial resolution to support observations from the Juno spacecraft. Our study uses ground-based mid-infrared observations captured between 1983 and 2019 at wavelengths between 7.9 µm and 24.5 µm by 7 different instruments: the BOLO-1 (1983-1993), AT-1 (1983-1993), MIRAC (1993-1999), MIRLIN (1996-2003) and MIRSI (2003-2011) instruments mounted at the 3-m NASA Infrared Telescope Facility (IRTF) in Hawai'i; the VISIR (2006-2011, 2016-2018) instrument mounted at the 8-m Very Large Telescope (VLT) in Chile; and the COMICS (2005-2019) instrument on the 8-m Subaru Telescope in Hawai'i. Examples of Jupiter images at different wavelengths are given in Figure 1.

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