Structure of Jupiter's High-Latitude Storms: Folded Filamentary Regions Revealed by Juno

Sprawling, turbulent cloud formations dominate the meteorology of Jupiter's mid-to-high latitudes, known as Folded Filamentary Regions (FFRs). A multi-wavelength characterization by Juno reveals the spatial distribution, vertical structure, and energetics of the FFRs. The cloud tops display multiple lobes of stratiform aerosols, separated by darker, cloud-free lanes, and embedded with smaller eddies and high-altitude cumulus clouds. These cyclonic FFRs are microwave-bright in shallow-sounding wavelengths (p < 5 bars) and microwave-dark in deep-sounding wavelengths (p > 10 bars), with the transition potentially associated with the water condensation layer (6–7 bars). Associating microwave contrasts with temperature anomalies, this implies despinning of cyclonic eddies above/below their mid-planes. Despite deep roots (being detectable in wavelengths sounding ~ 100 bars), they are “pancake vortices” with horizontal extents at least an order of magnitude larger than their depth. In the northern hemisphere, FFRs are most common in cyclonic belts poleward of 40° N (all latitudes are planetocentric), particularly a North Polar Filamentary Belt (NPFB) near 66 – 70 °N that defines the transition from organized belts/zones to the chaotic polar domain. This distribution explains the high lightning rates from 45 - 80° N, peaking in a belt poleward of 52.3° N, which may trace the availability of water for moist convection. Many observed lightning flashes can be associated to specific FFRs containing bright storms, but some FFRs display no activity, suggesting quiescent periods during storm evolution. Analogies to Earth's oceanic eddies suggest that cyclones deform isentropic surfaces at their midplanes, raising deep water-rich layers upwards to promote moist convection, release latent heat, and inject clouds into the upper troposphere.

Fletcher is a Juno Participating Scientist supported by STFC Consolidated Grant reference ST/W00089X/1 and Small Grant reference UKRI1205. Wong received support from the NASA Juno Participating Scientist program (80NSSC19K1265); Wong and Sankar received support from the New Frontiers Data Analysis Program (80NSSC25K0362). For the purpose of open access, the author has applied a Creative Commons Attribution (CC BY) license to the Author Accepted Manuscript version arising from this submission. A portion of this work used the ALICE high performance computing facility at the University of Leicester. Some of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (80NM0018D0004). The JIRAM project was funded by the Italian Space Agency (ASI). JW was supported at the University of Alabama as part of NASA's Juno mission supported by NASA through contract 12029 with Southwest Research Institute. We are immensely grateful to the members of the Juno team responsible for planning, executing, and processing the data sets presented in this paper since 2016. We thank Tim Dowling, Phil Marcus, and Daphne Lemasquerier for illuminating discussions on the nature of Jovian vortices. We thank Kevin M. Gill for sharing his JunoCam compositions for Figures 1 and 2. Finally, we thank two anonymous reviewers for their careful reviews of this manuscript.