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arxiv: 2607.00801 · v1 · pith:OE7SQUZTnew · submitted 2026-07-01 · 🌌 astro-ph.EP

Colour changes of Jupiter's Oval BA through microphysical modelling

Asier Anguiano-Arteaga , Santiago P\'erez-Hoyos , Agust\'in S\'anchez-Lavega , Patrick G. J. Irwin This is my paper

Pith reviewed 2026-07-02 05:43 UTC · model grok-4.3

classification 🌌 astro-ph.EP
keywords JupiterOval BAchromophore hazemicrophysical modelvertical transportcolor changeanticyclone
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The pith

Jupiter's Oval BA color changes result from shifts in downward vertical transport within its annulus.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper applies a one-dimensional microphysical model to the upper chromophore haze of Oval BA, using aerosol properties retrieved for its red state in 2016 and whiter state in 2020. It reproduces the observed half-year color transition timescale by incorporating changes in tropospheric vertical transport, with downwelling velocities of order 10 to the minus 4 to 10 to the minus 3 meters per second at chromophore pressures. A sympathetic reader would care because this connects visible color shifts directly to the vortex dynamics without needing adjustments to haze particle size or altitude. The small velocities also account for the absence of clear dynamical signatures in existing observations.

Core claim

The transition is best reproduced by changes in tropospheric vertical transport within a subsiding annulus, corresponding to preferred downwelling velocities of order 10^{-4}-10^{-3} m s^{-1} at chromophore-bearing pressures. These small vertical velocities may help explain why no clear dynamical signature has yet been identified.

What carries the argument

One-dimensional microphysical model of the upper chromophore haze layer constrained by retrieved aerosol properties for the red and whiter annulus states.

Load-bearing premise

Color changes occur solely via decrease in optical depth of the upper chromophore haze with no significant change in particle size or haze altitude.

What would settle it

Retrievals or direct observations showing significant changes in particle size or haze altitude during a color transition, or vertical velocities outside the 10^{-4} to 10^{-3} m s^{-1} range, would disprove the explanation.

Figures

Figures reproduced from arXiv: 2607.00801 by Agust\'in S\'anchez-Lavega, Asier Anguiano-Arteaga, Patrick G. J. Irwin, Santiago P\'erez-Hoyos.

Figure 1
Figure 1. Figure 1: JunoCam views of Oval BA obtained in February 2018 (left; Perijove 11) and [PITH_FULL_IMAGE:figures/full_fig_p003_1.png] view at source ↗
Figure 2
Figure 2. Figure 2: Response of τ (900 nm) (left) and reff (right) to imposed parameter changes at t ≈ 15 years (dashed line) for a Scenario A (upwelling) baseline case with wtrop = 1.4×10−4 m s−1 (marked case in Table S1). Blue: Cinj reduced by 30–35%. Red: wtrop reduced by 45–55%. The grey band marks the target 30–35% decrease in optical depth between 2016 and 2020, and the coloured guides indicate the elapsed time from the… view at source ↗
Figure 3
Figure 3. Figure 3: Response of τ (900 nm) (left) and reff (right) to imposed parameter changes at t ≈ 15 years (dashed line) for a Scenario B (downwelling) baseline case with wtrop = −4.7 × 10−4 m s−1 (marked case in Table S2). Blue: Cinj reduced by 25–30%. Red: |wtrop| increased by 55–70%. The grey band marks the target 30–35% decrease in optical depth between 2016 and 2020, and the coloured guides indicate the elapsed time… view at source ↗
read the original abstract

Jupiter's Oval BA undergoes recurrent colour changes whose physical origin remains uncertain. Radiative transfer retrievals indicate that these changes occur in the upper chromophore haze of the vortex annulus, around and above the 0.2-bar level, and are primarily associated with a decrease in optical depth, with no significant change in particle size or haze altitude. We apply a one-dimensional microphysical model to this haze layer, constrained by the retrieved aerosol properties of the red annulus in 2016 and the whiter annulus in 2020, and use it to reproduce the observed colour-change timescale of approximately 0.5 years. Our results indicate that this transition is best reproduced by changes in tropospheric vertical transport within a subsiding annulus, corresponding to preferred downwelling velocities of order $10^{-4}-10^{-3}$ m s$^{-1}$ at chromophore-bearing pressures. These small vertical velocities may help explain why no clear dynamical signature has yet been identified.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 1 minor

Summary. The paper applies a one-dimensional microphysical model to the upper chromophore haze in Jupiter's Oval BA, constrained by radiative transfer retrievals of aerosol properties for the red annulus in 2016 and the whiter annulus in 2020. It concludes that the observed ~0.5-year color transition timescale is best reproduced by changes in tropospheric vertical transport within a subsiding annulus, with preferred downwelling velocities of order 10^{-4}–10^{-3} m s^{-1} at chromophore-bearing pressures.

Significance. If the central claim holds, the work supplies a quantitative microphysical link between subtle dynamical subsidence and recurrent color changes in Jovian vortices, offering a plausible account for the absence of clear dynamical signatures in existing observations. Constraining the model directly with epoch-specific retrievals is a constructive approach.

major comments (2)
  1. [Abstract] Abstract: The conclusion that downwelling velocities of 10^{-4}–10^{-3} m s^{-1} best reproduce the transition rests on the assumption, taken from prior retrievals, that color changes occur solely via a decrease in optical depth of the upper haze with no significant change in particle size or altitude. This assumption is load-bearing; the manuscript does not test whether modest size or altitude shifts within retrieval uncertainties could produce the observed color shift, which would alter the required velocities.
  2. [Abstract] Abstract: The velocities are characterized as 'preferred' values chosen to reproduce the 0.5-year timescale. This renders the result circular by construction, as the model is tuned to match the input observation rather than predicting the timescale from independent dynamical constraints or first-principles microphysics.
minor comments (1)
  1. The manuscript would benefit from explicit presentation of the microphysical model equations, any validation tests, and a sensitivity analysis of timescale versus vertical velocity to improve reproducibility and reader assessment.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive comments, which highlight important aspects of our modeling assumptions and methodology. We address each major comment below and outline revisions that will be incorporated into the manuscript.

read point-by-point responses

  1. Referee: [Abstract] Abstract: The conclusion that downwelling velocities of 10^{-4}–10^{-3} m s^{-1} best reproduce the transition rests on the assumption, taken from prior retrievals, that color changes occur solely via a decrease in optical depth of the upper haze with no significant change in particle size or altitude. This assumption is load-bearing; the manuscript does not test whether modest size or altitude shifts within retrieval uncertainties could produce the observed color shift, which would alter the required velocities.

    Authors: Our analysis is grounded in the radiative transfer retrievals, which indicate that the color transition is driven primarily by a decrease in optical depth with negligible changes in particle size or altitude. To directly address this point, we will add a sensitivity analysis to the revised manuscript. This will quantify how modest variations in particle size and altitude, within the reported retrieval uncertainties, influence the downwelling velocities needed to match the observed timescale. The results of this test will be presented to demonstrate the robustness of the derived velocity range. revision: yes

  2. Referee: [Abstract] Abstract: The velocities are characterized as 'preferred' values chosen to reproduce the 0.5-year timescale. This renders the result circular by construction, as the model is tuned to match the input observation rather than predicting the timescale from independent dynamical constraints or first-principles microphysics.

    Authors: The microphysical model is used to identify the vertical velocities that reproduce the observed 0.5-year transition timescale given the retrieved aerosol properties and microphysical processes. This yields a quantitative constraint on the dynamical subsidence required, rather than a first-principles prediction of the timescale itself. The principal finding is that these velocities are small (10^{-4}–10^{-3} m s^{-1}), which is consistent with the absence of clear dynamical signatures in existing observations. We will revise the abstract and discussion to clarify that the velocities represent the values required to match the observed transition under the model assumptions, avoiding any implication of independent prediction. revision: partial

Circularity Check

1 steps flagged

Vertical velocities fitted to match observed 0.5 yr timescale by construction

specific steps
  1. fitted input called prediction [Abstract]
    "Our results indicate that this transition is best reproduced by changes in tropospheric vertical transport within a subsiding annulus, corresponding to preferred downwelling velocities of order $10^{-4}-10^{-3}$ m s$^{-1}$ at chromophore-bearing pressures."

    The model is run with the retrieved 2016/2020 aerosol properties as fixed inputs and the vertical velocity is adjusted specifically to reproduce the observed 0.5-year timescale, so the quoted 'preferred' velocities are the fitted parameter values that match the input observation by construction.

full rationale

The paper constrains the 1-D microphysical model with aerosol properties retrieved for the 2016 red and 2020 white states (taken as given from prior retrievals) and varies only the vertical velocity parameter until the model reproduces the observed ~0.5 yr color-change timescale. The reported 'preferred' downwelling velocities are therefore the fitted values that match the input observation by construction rather than an independent derivation from first principles. This matches the fitted-input-called-prediction pattern. The assumption that color change occurs solely via optical-depth decrease (with fixed particle size and altitude) is load-bearing but is imported from the cited retrievals; no self-citation chain or equation-level reduction is exhibited in the provided text.

Axiom & Free-Parameter Ledger

1 free parameters · 1 axioms · 0 invented entities

The central claim rests on prior retrievals of haze properties and on the choice of vertical velocity to match the observed timescale; no new entities are introduced.

free parameters (1)
  • downwelling velocity = 10^{-4} to 10^{-3} m s^{-1}
    Order-of-magnitude value selected to reproduce the 0.5-year color-change timescale in the microphysical model.
axioms (1)
  • domain assumption Color changes are driven exclusively by optical-depth variations in the chromophore haze with fixed particle size and altitude.
    Stated as the interpretation of the 2016 and 2020 radiative-transfer retrievals that constrain the model.

pith-pipeline@v0.9.1-grok · 5716 in / 1289 out tokens · 27080 ms · 2026-07-02T05:43:23.101105+00:00 · methodology

discussion (0)

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Reference graph

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