Variability of Jovian Meteorology from Ground-Based Mid-Infrared Observations

This thesis uses ground-based mid-infrared imaging data from the VISIR instrument at the Very Large Telescope in Chile to study the temperature, composition and aerosol distribution in Jupiter’s atmosphere. The mid-infrared region of the jovian spectrum probes upper-tropospheric and stratospheric dynamics and chemistry that give a three-dimensional view of the atmosphere. The work in this thesis is part of a wider ground-support campaign for the NASA Juno mission. Due to the lack of comparable mid-infrared sensors on the spacecraft, VISIR provides much-needed spatial, temporal and spectral coverage of Jupiter concurrent with each spacecraft orbit.

The two datasets considered in this thesis are intended to assess the temporal variability of Jupiter’s atmosphere before and during the Juno mission. These are 15/16 February 2016 (before Juno orbital insertion) and 24-27 May 2018 (concurrent with the thirteenth passage of the spacecraft). Global multi-spectral maps are obtained on each date that enable the atmospheric retrieval of the zonal mean properties of Jupiter.

In this work we develop a new method that exploits the centre-to-limb effects of the atmosphere to extract more information from the imaging data, to increase vertical sensitivity and break the degeneracies that arise from the low spectral resolution associated with imaging. The atmospheric profiles derived from this method are used to investigate discrete features and other meteorological phenomena in 2016 via spatially-resolved retrievals of temperature, composition and aerosols. Finally, the centre-to-limb method is extended to the polar latitudes in 2018, concurrent with Juno polar observations, to estimate the zonal mean structure of temperature and composition across the polar vortex boundary to investigate the role of aerosols in radiative balance at the poles.