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The Jovian Infrared Auroral Mapper (JIRAM, a payload element of the NASA Juno mission to Jupiter) includes an infrared spectrometer covering the 2.0–5.0 μm range. After reviewing the main results on the conditions of upper troposhere derived from the solar-dominated 2.0–3.2 μm spectral range and presented in Grassi et al. 2021, we focus our discussion on open modeling issues and recent attempts to study these altitudes from data in the thermal-dominated 4.0-5.0 μm spectral range. We present also the results of an automatic classification of data performed on the basis of the HDBSCAN algorithm (McInnes et al. 2017). We show that similar spatial patterns are obtained either considering the coefficents of a PCA performed directly on spectra or on the physical parameters (clouds altitude, haze thickness) retrieved by the algorithm adopted in Grassi et al. 2021. Grassi et al. 2021 doi:10.1093/mnras/stab740McInnes et al. 2017 doi:10.21105/joss.00205

A complex series of high-altitude clouds and hazes have been unveiled by images from the Juno mission’s JunoCam instrument. They appear to be ubiquitous at higher latitudes in both of Jupiter’s hemispheres but are particularly pronounced in the north. Juno’s polar orbit and JunoCam’s filter centered on the 889-nm absorption band of methane make JunoCam uniquely suited to observing high-altitude polar features. Among these are the North and South Polar Hoods, which JunoCam’s methane-band filter reveals in greater detail than from the Earth, together with bright and dark haze bands. These bright and dark bands commonly appear together in bundles, indicating vertical structure in widespread haze layers. Some bright hazes near the terminator exhibit an apparent color dispersion, appearing bluish on the side generally in the direction of illumination and reddish on the other, an effect that is consistent with more efficient scattering by shorter-wavelength light. The morphology of the observed haze bands appears to be quite different from the well-known zonal wind profile affecting the main cloud deck. On the other hand, some, including a semi-persistent long band of haze near the South Pole, are related to the locations of underlying cyclones and chaotic cyclonic features known as folded filamentary regions. Our high-resolution observations of Jupiter’s limb have revealed hazes, some continuous with the lower atmosphere and others that are singly and doubly detached. Toward high northern latitudes, these limb hazes become completely opaque.

JunoCam, the visible imager on the Juno mission’s payload that was designed primarily for public-outreach purposes, continues to produce images of Jupiter that provide unexpected scientific benefits. Juno’s polar orbits enable observing regions of the planet that have not previously been detected at such high resolution by any previous spacecraft. JunoCam has a single CCD detector with an integral color-strip filter that enables the instrument to image in four color bands—blue, green, red and an 889-nm methane band. JunoCam maps a field of view of 58° across the width of the detector, perpendicular to the spacecraft scan direction. We will describe characteristics and likely origins of bright white compact (~50 km) clouds, informally dubbed “pop-up” clouds by the JunoCam team. We used the length of shadows of these and other features to determine the relative heights of clouds and assigned a provisional chemical classification based on relative altitudes from equilibrium-chemistry predictions. We tracked the continued interactions of small anticyclonic ovals with Jupiter’s Great Red Spot (GRS) that drew off high-altitude reddish haze into strips (commonly called “flakes”) on its western edge. A lightning flash was detected in one of the compact circumpolar cyclones in late December. Observations of the south-polar circumpolar cyclones showed that the original unequally sided pentagon becoming a hexagon – with a cyclone filling in an open area, then a pentagon again over the course of 110 days. In a collaboration with amateur astronomer Clyde Foster (S. Africa), we observed the morphology of an unexpected upwelling in late May of 2020, now known as “Clyde’s Spot”, and tracked its evolution in concert with several ground-based observations. We also measured ~40-50 m/s winds around the sinuous jet bounding the South Polar Hood, an upper-level haze generated by auroral-related chemistry. Lightly processed and raw JunoCam data continue to be posted on the JunoCam webpage at https://missionjuno.swri.edu/junocam/processing. Citizen scientists download these images and upload their processed contributions.

Comparing JunoCam images with simulation runs of two-dimensional Euler fluids reveals similarities between the morphology of Jupiter's cloud tops and simulated vorticity maps. We present examples of these analogies. They are required to establish conjectures that state these similarities in a more formal way. Introduction and Context JunoCam [1] has been collecting images of Jupiter's cloud tops for almost four years at the time of the submission of this abstract. In examining these images, we realized that two-dimensional simulations of Euler fluids [2] revealed patterns in vorticity fields reminiscent of structures in Jupiter's cloud tops. We pursue this initial observation further. A small collection of analogies between real data and simulations is presented, which inspire formal conjectures describing a correlation between vorticity and cloud features. These initial conjectures result in algorithm candidates that translate cloud morphology into vorticity and can be assessed and further refined on the basis of fluid-dynamical simulations. In a larger-scale context, when two or more JunoCam images cover the same area of Jupiter with a time delay of several minutes, methods similar to stereo correspondence can be applied to retrieve velocity or vorticity field data. Displacements of corresponding areas of the surface between images can be used either to estimate a velocity field directly, or via the stream function component of a Helmholtz decomposition indirectly. Alternatively, measured rotations of surface areas can be used to estimate vorticities. Vorticity data inferred by any of these methods provide a low-resolution context and a reference for a refinement of the vorticity field on the basis of spatially higher-resolved morphological considerations. The presentation will focus on a small survey of JunoCam images together with simulation runs developing structures similar to those observed in the images. This collection of examples is required for the empirical definition of formal conjectures connecting morphology with vorticity. Example Figure 1 shows an excerpt of a map of Jupiter's north polar region during the PJ18 flyby that suggests a simplified model to initialize a simulation run. The initial model is simplified to consist of six Gauss vortices, representing four circumpolar cyclones (CPCs in yellow) and two anticyclonic white ovals (AWOs in blue). After a short simulation run, the vortices develop filamentary vorticity structures that are also apparent in the original JunoCam image, see detail in Fig. 2. Conjectures The above example suggests that the brightness of the cloud tops is correlated with the total amount of the relative vorticity. Intact vortices of similar size that touch each other are of opposite sign. They form a filamentary structure between them consisting of two parallel filaments of opposite vorticity. Two nearby cyclones are separated by a filament of anticyclonic vorticity. References [1] C.J. Hansen, M.A. Caplinger, A. Ingersoll, M.A. Ravine, E. Jensen, S. Bolton, G. Orton. Junocam: Juno’s Outreach Camera. Space Sci Rev 2013:475-506, 2017 [2] G. Eichstädt, C. Hansen, G. Orton. Fluid Dynamical 2D Simulations of Jupiter's South Polar Region Based On JunoCam Image Data. EGU2020-12025, https://doi.org/10.5194/egusphere-egu2020-12025

In the first 20 orbits of the Juno spacecraft around Jupiter, we have identified a variety of wave‐like features in images made by its public‐outreach camera, JunoCam. Because of Juno's unprecedented and repeated proximity to Jupiter's cloud tops during its close approaches, JunoCam has detected more wave structures than any previous surveys. Most of the waves appear in long wave packets, oriented east‐west and populated by narrow wave crests. Spacing between crests were measured as small as ~30 km, shorter than any previously measured. Some waves are associated with atmospheric features, but others are not ostensibly associated with any visible cloud phenomena and thus may be generated by dynamical forcing below the visible cloud tops. Some waves also appear to be converging, and others appear to be overlapping, possibly at different atmospheric levels. Another type of wave has a series of fronts that appear to be radiating outward from the center of a cyclone. Most of these waves appear within 5° of latitude from the equator, but we have detected waves covering planetocentric latitudes between 20°S and 45°N. The great majority of the waves appear in regions associated with prograde motions of the mean zonal flow. Juno was unable to measure the velocity of wave features to diagnose the wave types due to its close and rapid flybys. However, both by our own upper limits on wave motions and by analogy with previous measurements, we expect that the waves JunoCam detected near the equator are inertia‐gravity waves.

Within the first 26 orbits of the Juno spacecraft around Jupiter, we have identified a variety of wave-like features in images made by its public-outreach camera, JunoCam. Because of Juno’s unprecedented and repeated proximity to Jupiter’s cloud tops during its close approaches, JunoCam has detected more wave structures than any previous surveys. Most of the waves appear in long wave packets, oriented east-west and populated by narrow wave crests. Spacing between crests were measured as small as ~30 km, shorter than any previously measured. Some waves are associated with atmospheric features, but others are not ostensibly associated with any visible cloud phenomena and thus may be generated by dynamical forcing below the visible cloud tops. Some waves also appear to be converging and others appear to be overlapping, possibly at different atmospheric levels. Another type of wave has a series of fronts that appear to be radiating outward from the center of a cyclone. Although we have detected wave-like phenomena covering latitudes between 20°S and 45°N, most appear within 5° of latitude from the equator. Most waves appear in regions associated with prograde motions of the mean zonal winds. Although Juno was unable to measure the velocity of wave features to diagnose the wave types due to its close and rapid flybys, both by our own upper limits on wave motions and by analogy with previous measurements, we expect that the waves JunoCam detected near the equator are inertia-gravity waves.

We describe a huge planetary-scale disturbance in the highest-speed Jovian jet at latitude 23.5°N that was first observed in October 2016 during the Juno perijove-2 approach. An extraordinary outburst of four plumes was involved in the disturbance development. They were located in the range of planetographic latitudes from 22.2° to 23.0°N and moved faster than the jet peak with eastward velocities in the range 155 to 175 m s−1. In the wake of the plumes, a turbulent pattern of bright and dark spots (wave number 20–25) formed and progressed during October and November on both sides of the jet, moving with speeds in the range 100–125 m s−1 and leading to a new reddish and homogeneous belt when activity ceased in late November. Nonlinear numerical models reproduce the disturbance cloud patterns as a result of the interaction between local sources (the plumes) and the zonal eastward jet.