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Analysis of a Jovian Thunderstorm Mesoscale Convective Complex in the North Equatorial Belt.

Presentation #326.07 in the session Origin and Evolution of Giant Planet Systems II (Poster)

Published onOct 23, 2023
Analysis of a Jovian Thunderstorm Mesoscale Convective Complex in the North Equatorial Belt.

On November 29th, 2021, the Juno Spacecraft completed its 38th perijove as part of its Extended Mission. Three of the spacecraft’s instruments, JunoCam, JIRAM, and MWR, imaged a 3,430 km wide thunderstorm complex in the NEB at approximately 9oN planetocentric latitude. Ground-based observers tracked this storm over a period of two weeks, providing a planetary-scale perspective to Juno’s observations.

The morphology of the storm as shown in JunoCam, and from ground-based observers, is highly suggestive of a classic moist-convective thunderstorm mesoscale convective complex with clouds reaching the upper troposphere. Imaging also suggests a previous anvil top located to the west of the optically thick clouds, which may indicate a temporarily varying nature to the convection, which is consistent with ground-based observations showing upwelling at this location for several days before perijove and a rapid change in morphology shortly before perijove. JIRAM’s observations show a cold spot at 4.78 µm near the region of the thickest white clouds, which would be expected from optically thick clouds blocking heat transport to space.

The MWR instrument detected numerous lightning discharges at 0.6, 1.2 ,and 2.4 GHz, which are correlated with JunoCam and JIRAM’s observations of optically thick clouds, confirming the deep-moist convective nature of this feature. We find a lightning flash rate about 1/2 to 1/3 of previously estimated global flash rates conducted by the SRU instrument. MWR brightness temperatures also reveal that this feature appears to be wholly contained within the weather layer, i.e., tropopause down to the expected base of the water-cloud. MWR brightness temperatures, previous modeling results, and Earth-based observations suggest synoptic-to-mesoscale forcing mechanisms, perhaps from a dryline, were probably involved in sustaining this storm for its 2-week lifespan.

Given the close approach of the Juno spacecraft with three instruments observing the storm, this feature may be the most highly instrumented observation of a Jovian thunderstorm to date. The cloud morphology, size, thickness of its clouds, and lightning detections in this feature suggest that the storm is equivalent of a terrestrial mesoscale convective complex, possibly composed of multiple individual thunderstorms as is the case on Earth. The observations that we detail here may ultimately shed light on the mechanisms that form, sustain, and characterize moist convective storms in hydrogen-dominated atmospheres.

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