Multi-instrument sounding of a Jovian thunderstorm from Juno

Thunderstorms play a significant role in transporting heat from the deep interior to space on giant planets. We present observations of a 3,400-km wide thunderstorm complex in Jupiter’s North Equatorial Belt (NEB) during the 38th periapse of the Juno spacecraft on 29 Nov. 2021. Data were acquired by the Microwave Radiometer (MWR), the visible light JunoCam instrument, the Jovian InfraRed Auroral Mapper (JIRAM), and from supporting Earth-based imaging. This was the first time Juno was able to observe a thunderstorm at suitably low emission angles with multiple instruments at close range ( ∼ 5,690 km), making it the most comprehensive close-up assessment of a Jovian thunderstorm to date. Lightning detection confirmed the Storm’s vigorous convective nature. MWR brightness temperatures indicate this Storm appears to be wholly contained within the weather layer, i.e., no deeper than the expected base of the H 2 O cloud, and not as a result of any detected deep-seated upwelling beneath the H 2 O cloud base. Earth-based observations tracked it over its ∼ 2-week lifespan, providing evidence that mesoscale-to-synoptic-scale forcing mechanisms were involved in sustaining it, including the intriguing possibility of a humidity front (’dryline’), a sharp gradient in the vapor abundance, promoting lift along a concentrated region. • Juno observed a ∼ 3,430 km-wide mesoscale convective complex. • Synoptic & mesoscale forcings were likely responsible for origin and long lifespan. • MWR data supports the hypothesis that a dryline (humidity front) was involved. • The Storm was shallow; i.e., at & above the H 2 O cloud base.