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

L. N. Fletcher, Z. Zhang, S. Brown, F. A. Oyafuso, J. H. Rogers, M. H. Wong, A. Mura, G. Eichstädt, G. S. Orton, S. Brueshaber, R. Sankar, C. Li, S. M. Levin, F. Biagiotti, T. Guillot, A. P. Ingersoll, D. Grassi, C. J. Hansen, S. Bolton, J. H. Waite

TL;DR

This study uses Juno’s multi-wavelength suite to characterize Jupiter's high-latitude Folded Filamentary Regions (FFRs), revealing deep-rooted cyclonic structures that extend to depths of at least $50$–$100$ bars and that transition from microwave-bright at $p<5$ bars to microwave-dark at $p>10$ bars near the water condensation level ($6$–$7$ bars). By combining JunoCam, JIRAM, and Microwave Radiometer (MWR) data, the authors map FFR morphology, quantify their distribution (notably forming the North Polar Filamentary Belt, NPFB), and link them to enhanced lightning activity, establishing FFRs as the dominant high-latitude moist-convective engine. The work discusses the vertical structure via isentropic deformation, the role of water availability in driving convection, and the energy transport implications for Jupiter’s internal heat flux, drawing parallels with Earth’s oceanic eddies and Saturn’s convective storms. Together, these findings advance our understanding of Jupiter’s atmospheric dynamics and establish methodological approaches for multi-instrument planetary meteorology with implications for other giant planets.

Abstract

Sprawling, turbulent cloud formations dominate the meteorology of Jupiter's mid-to-high latitudes, known as Folded Filamentary Regions (FFRs). A multi-wavelength characterisation 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 $\sim100$ 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 $40^\circ$N (all latitudes are planetocentric), particularly a North Polar Filamentary Belt (NPFB) near $66-70^\circ$N that defines the transition from organised belts/zones to the chaotic polar domain. This distribution explains the high lightning rates from $45-80^\circ$N, peaking in a belt poleward of $52.3^\circ$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.

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

TL;DR

This study uses Juno’s multi-wavelength suite to characterize Jupiter's high-latitude Folded Filamentary Regions (FFRs), revealing deep-rooted cyclonic structures that extend to depths of at least – bars and that transition from microwave-bright at bars to microwave-dark at bars near the water condensation level (– bars). By combining JunoCam, JIRAM, and Microwave Radiometer (MWR) data, the authors map FFR morphology, quantify their distribution (notably forming the North Polar Filamentary Belt, NPFB), and link them to enhanced lightning activity, establishing FFRs as the dominant high-latitude moist-convective engine. The work discusses the vertical structure via isentropic deformation, the role of water availability in driving convection, and the energy transport implications for Jupiter’s internal heat flux, drawing parallels with Earth’s oceanic eddies and Saturn’s convective storms. Together, these findings advance our understanding of Jupiter’s atmospheric dynamics and establish methodological approaches for multi-instrument planetary meteorology with implications for other giant planets.

Abstract

Sprawling, turbulent cloud formations dominate the meteorology of Jupiter's mid-to-high latitudes, known as Folded Filamentary Regions (FFRs). A multi-wavelength characterisation 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 ( bars) and microwave-dark in deep-sounding wavelengths ( 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 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 N (all latitudes are planetocentric), particularly a North Polar Filamentary Belt (NPFB) near N that defines the transition from organised belts/zones to the chaotic polar domain. This distribution explains the high lightning rates from N, peaking in a belt poleward of 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.

Paper Structure

This paper contains 31 sections, 1 equation, 29 figures.

Table of Contents

  1. Introduction
  2. FFR Studies before Juno
  3. Meteorology from Juno
  4. Overview of FFR Survey
  5. Belt/Zone Nomenclature
  6. JunoCam and JIRAM
  7. JunoCam Morphology
  8. Comparing JunoCam and JIRAM
  9. Juno Microwave Radiometer (MWR)
  10. Nadir-equivalent brightness temperature
  11. MWR as an FFR Detector
  12. FFR Microwave Brightness Inversion
  13. FFR Location Analysis
  14. Correlations between MWR Channels
  15. Depth of FFRs
  16. ...and 16 more sections

Figures (29)

  • Figure 1: JunoCam observations of FFRs. All images are credited to NASA/JPL-Caltech/SwRI/MSSS, and were processed by Kevin M. Gill. Each panel is labelled by the perijove number and image number. Illumination, spatial scale, and lightning conditions change from panel to panel, and these should not be taken as natural colour. Bright white storms are notable in PJ11-13, PJ30-17, PJ39-18, PJ35-53, PJ31-18, PJ34-54, and PJ30-21, while PJ26-22/23 and PJ24-24 are examples of more quiescent FFRs.
  • Figure 2: View of a single FFR in PJ35, located near $50^\circ$N (the N4 domain), $290^\circ$W on 2021-Jul-21 (Credit: NASA/JPL-Caltech/SwRI/MSSS/Kevin M. Gill). The north pole is downwards, the direction of sunlight approximately SSE as indicated. Key features are identified as stratiform lobes (blue boxes), dark lanes (green boxes), discrete eddies/whorls (purple boxes), cumulus clusters (red boxes), and green hazes (magenta arrows), all contained within the broad area of the FFR (orange outline). Note that cyclonic motion is anticlockwise, and anticyclonic motion is clockwise. This image spans approximately $5\times10^\circ$ in latitude and longitude. The blue inset image shows a single frame with a suspected lightning flash at the edge, and represents the yellow dotted box in the image centre.
  • Figure 3: Four examples (PJ33-39) where JunoCam RGB images (top row) were immediately preceded by CH$_4$-band images of the same feature (bottom row), revealing the vertical structure of the features within the FFRs. Visibly bright cumulus-like clusters (bright white storms) are higher than the surrounding stratiform clouds; visibly dark lanes are deeper than the stratiform lobes. All images processed by Gerald Eichstädt, and credited to NASA/JPL-Caltech/SwRI/MSSS.
  • Figure 4: North polar projections (equidistant azimuthal) of JIRAM observations at 5 $\mu$m to showcase examples of spatial coverage $20-90^\circ$N. Top row provides a combination of high-resolution coverage from multiple perijoves with limited spatial coverage (overlapping observations poleward of $80^\circ$N have been deliberately omitted). Bottom row shows examples of individual perijoves with poorer spatial resolution but near global coverage of the northern hemisphere. Brightness units are spectral radiance (Wm$^{-2}$sr$^{-1}\mu$m$^{-1}$), as shown by the logarithmic colour scale. These data have not been corrected for limb darkening effects.
  • Figure 5: Comparison of polar equidistant azimuthal projections (50-90$^\circ$N) from JIRAM 5-$\mu$m imaging and JunoCam RGB imaging, selecting four perijoves (4, 7, 9 and 38) with the best overlap in spatial coverage.  Two grey circles, connected by a horizontal line, are used to guide the eye for matching FFR features (only a subset of features are identified in this way).
  • ...and 24 more figures