Three dimensional temporal evolution of photochemical haze in exoplanet atmospheres I. Description and test application to HD 189733b
Reviewed by Pith2026-06-26 19:17 UTCgrok-4.3pith:PXNFHSLCopen to challenge →
The pith
Haze particles in HD 189733b stay below 30 nm and accumulate at east and west limbs following vertical winds.
A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.
Core claim
The paper claims that for the chosen haze formation efficiency, particles do not grow beyond ~30 nm. The haze spatial distribution follows the vertical velocity structure of the atmosphere, with equatorial convergence patterns of material deeper in the atmosphere at ~10^{-2} bar. The resulting global distribution leads to enhanced haze opacity at the east and west limbs. Radiative feedback from haze opacity can strongly affect the temperature-pressure structures in the upper atmosphere depending on the production rate. Longer haze-production timescales give rise to stronger haze opacity effects on the observed transmission spectra compared to short-timescale dayside formation, but the strong
What carries the argument
The mini-haze microphysical scheme, which uses a simple activation timescale mechanism to emulate delayed formation of solid particles and is coupled to the Exo-FMS GCM to track 3D particle growth, transport, and radiative feedback.
If this is right
- Particles remain no larger than ~30 nm under the chosen formation efficiency.
- Haze follows vertical velocity structure with equatorial convergence at ~10^{-2} bar.
- Global distribution produces enhanced opacity specifically at the east and west limbs.
- Haze radiative feedback modifies upper-atmosphere temperature-pressure profiles in a production-rate-dependent way.
- Longer production timescales strengthen transmission-spectrum opacity effects while nightside formation increases dayside emission flux.
Where Pith is reading between the lines
- The time-dependent 3D approach could be extended to model orbital-phase variability in haze properties on other hot Jupiters.
- Similar wind-driven convergence patterns may appear in sub-Neptune atmospheres when the same scheme is applied there.
- Future versions that add chemical feedback loops would allow self-consistent tests of how haze production alters the underlying chemistry.
- The limb-enhanced opacity could be tested against phase-resolved or eclipse-mapping data even if full spectra are not yet available.
Load-bearing premise
The simple activation timescale mechanism accurately emulates a delayed formation of solid haze particles from photochemical processes without requiring a full chemical network.
What would settle it
Direct measurements showing haze particles larger than 30 nm or transmission spectra of HD 189733b lacking enhanced east-west limb opacity would contradict the reported particle sizes and spatial distribution.
Figures
read the original abstract
The formation and global spatial distribution of photochemically produced haze particles remain a key process in exoplanet atmospheres for understanding their observed properties. We aim to develop a flexible haze particle formation and evolution model suitable for time-dependent exoplanet atmosphere simulations. Inspired by recent 2D photochemical modelling efforts, we include a simple activation timescale mechanism to emulate a delayed formation of solid haze particles. We couple our new microphysical haze formation scheme, mini-haze, to the Exo-FMS general circulation model (GCM) and simulate an idealised HD 189733b case study to examine the 3D spatial distribution and sizes of haze particles. Our results suggest that for our chosen haze formation efficiency, particles do not grow beyond $\sim$30 nm, in line with previous detailed 1D modelling. We find the haze spatial distribution follows the vertical velocity structure of the atmosphere, with equatorial convergence patterns of material deeper in the atmosphere at $\sim$10$^{-2}$ bar. The resulting global distribution leads to enhanced haze opacity at the east and west limbs of the atmosphere. In our test cases, radiative feedback from haze opacity can strongly affect the temperature-pressure structures in the upper atmosphere depending on the production rate. Our synthetic spectra results suggest that longer haze-production timescales give rise to stronger haze opacity effects on the observed transmission spectra compared to short-timescale dayside formation, but the stronger thermal feedback from nightside formation leads to an overall larger dayside emission flux. Our current simulations represent a step towards investigating self-consistent haze formation and evolution with chemical feedback effects in 3D, and can be readily applied to other objects of interest, such as sub-Neptune atmospheres.
Editorial analysis
A structured set of objections, weighed in public.
Referee Report
Summary. The paper introduces the mini-haze microphysical scheme, which employs a simple activation timescale parameterization (inspired by 2D photochemical models) to emulate delayed solid haze particle formation without a full chemical network. This is coupled to the Exo-FMS GCM for time-dependent 3D simulations of HD 189733b. Key results include: particles remaining below ~30 nm for the chosen formation efficiency; haze spatial distribution tracking vertical velocities with equatorial convergence at ~10^{-2} bar; enhanced limb opacities; and production-rate-dependent radiative feedback on upper-atmosphere T-P profiles. Synthetic spectra indicate that longer haze-production timescales strengthen transmission effects while nightside formation yields larger dayside emission fluxes due to thermal feedback.
Significance. If the activation timescale faithfully captures photochemical delays under 3D advection, the work supplies a computationally tractable route to self-consistent haze-radiation-dynamics coupling in GCMs. It extends prior 1D microphysics and 2D chemistry results to three dimensions and supplies a reusable framework for sub-Neptune and other atmospheres. The explicit test application to HD 189733b and the reported east-west limb asymmetry constitute concrete, falsifiable predictions.
major comments (1)
- [Abstract / model description] Abstract and model description: the headline claims on particle sizes (≤30 nm), equatorial convergence at ~10^{-2} bar, limb-enhanced opacity, and T-P feedback all rest on the activation timescale mechanism accurately standing in for full photochemical production rates once vertical and horizontal transport are active. No quantitative comparison to the 2D photochemical benchmarks that motivated the parameterization, nor sensitivity tests under 3D advection, are reported; if the effective formation delay differs materially, the reported spatial distribution and opacity maps would shift.
minor comments (1)
- [Abstract] The abstract states results for 'our chosen haze formation efficiency' and 'production rate' but does not list the numerical values or ranges explored; these should be stated explicitly in the methods or a table for reproducibility.
Simulated Author's Rebuttal
We thank the referee for their constructive review and recommendation of major revision. We address the major comment below and commit to the necessary changes.
read point-by-point responses
-
Referee: [Abstract / model description] Abstract and model description: the headline claims on particle sizes (≤30 nm), equatorial convergence at ~10^{-2} bar, limb-enhanced opacity, and T-P feedback all rest on the activation timescale mechanism accurately standing in for full photochemical production rates once vertical and horizontal transport are active. No quantitative comparison to the 2D photochemical benchmarks that motivated the parameterization, nor sensitivity tests under 3D advection, are reported; if the effective formation delay differs materially, the reported spatial distribution and opacity maps would shift.
Authors: We agree that the submitted manuscript lacks a direct quantitative comparison of the activation timescale parameterization against the 2D photochemical benchmarks that motivated it, as well as explicit sensitivity tests under 3D advection. The timescale was chosen to reproduce the characteristic formation delays reported in those 2D studies while remaining computationally tractable for GCM coupling; our reported particle sizes are consistent with prior 1D microphysical results. However, we acknowledge that without the requested benchmarks and tests, the robustness of the spatial distribution, limb opacity enhancements, and T-P feedback cannot be fully demonstrated. In the revised manuscript we will add (i) a direct comparison of effective production rates and delays between the mini-haze scheme and the original 2D models, and (ii) a set of sensitivity experiments varying the activation timescale under the 3D flow to quantify any shifts in haze distribution and opacity maps. These additions will directly address the concern raised. revision: yes
Circularity Check
No significant circularity in derivation chain
full rationale
The paper introduces a new mini-haze microphysical scheme that adopts an activation timescale parameterization (inspired by prior 2D photochemical work) as a modeling simplification to enable 3D GCM coupling, then reports forward simulation outputs for particle sizes, spatial distributions, limb opacities, and radiative feedback on HD 189733b. These results are generated by integrating the chosen parameters through the time-dependent dynamical model rather than being forced by definition, self-citation chains, or renaming of inputs. No load-bearing steps reduce to fitted quantities called predictions or to self-referential uniqueness theorems; the derivation remains self-contained against external benchmarks.
Axiom & Free-Parameter Ledger
free parameters (2)
- haze formation efficiency
- haze production rate
axioms (1)
- ad hoc to paper Simple activation timescale mechanism emulates delayed formation of solid haze particles
Reference graph
Works this paper leans on
-
[1]
Ackerman, A. S. & Marley, M. S. 2001, ApJ, 556, 872
2001
-
[2]
Adams, D., Gao, P., de Pater, I., & Morley, C. V . 2019, ApJ, 874, 61
2019
-
[3]
J., Wittenmyer, R
Addison, B., Wright, D. J., Wittenmyer, R. A., et al. 2019, PASP, 131, 115003
2019
-
[4]
B., Knutson, H
Agol, E., Cowan, N. B., Knutson, H. A., et al. 2010, ApJ, 721, 1861
2010
-
[5]
2025, ApJ, 985, L10
Ahrer, E.-M., Radica, M., Piaulet-Ghorayeb, C., et al. 2025, ApJ, 985, L10
2025
-
[6]
S., Tremblin, P., Manners, J., Baraffe, I., & Mayne, N
Amundsen, D. S., Tremblin, P., Manners, J., Baraffe, I., & Mayne, N. J. 2017, A&A, 598, A97
2017
-
[7]
& Lavvas, P
Arfaux, A. & Lavvas, P. 2024, MNRAS, 530, 482
2024
-
[8]
& Forget, F
Bertrand, T. & Forget, F. 2017, Icarus, 287, 72
2017
-
[9]
Bohren, C. F. & Huffman, D. R. 1983, Absorption and scattering of light by small particles (New York: John Wiley & Sons)
1983
-
[10]
2005, A&A, 444, L15
Bouchy, F., Udry, S., Mayor, M., et al. 2005, A&A, 444, L15
2005
-
[11]
Brande, J., Crossfield, I. J. M., Kreidberg, L., et al. 2024, ApJ, 961, L23
2024
-
[12]
1943, Reviews of Modern Physics, 15, 1
Chandrasekhar, S. 1943, Reviews of Modern Physics, 15, 1
1943
-
[13]
A., Mayne, N
Christie, D. A., Mayne, N. J., Gillard, R. M., et al. 2022, MNRAS, 517, 1407
2022
-
[14]
L., Tennyson, J., & Yurchenko, S
Chubb, K. L., Tennyson, J., & Yurchenko, S. N. 2020, MNRAS, 493, 1531
2020
-
[15]
I., Paradise, A., Bollasina, M
Cohen, M., Palmer, P. I., Paradise, A., Bollasina, M. A., & Tiranti, P. I. 2024, AJ, 167, 97
2024
-
[16]
A., Yurchenko, S
Coles, P. A., Yurchenko, S. N., & Tennyson, J. 2019, MNRAS, 490, 4638
2019
-
[17]
J., & Kempton, E
Corrales, L., Gavilan, L., Teal, D. J., & Kempton, E. M. R. 2023, ApJ, 943, L26
2023
-
[18]
E., Fossati, L., Koskinen, T., et al
Cubillos, P. E., Fossati, L., Koskinen, T., et al. 2023, A&A, 671, A170
2023
-
[19]
1993, A Simple and Accurate Method for Calculating Viscosity of Gaseous Mixtures, Report of investigations (U.S
Davidson, T. 1993, A Simple and Accurate Method for Calculating Viscosity of Gaseous Mixtures, Report of investigations (U.S. Department of the Interior, Bureau of Mines, Amarillo, TX) Désert, J.-M., Sing, D., Vidal-Madjar, A., et al. 2011, A&A, 526, A12
1993
-
[20]
J., et al
Drummond, B., Hébrard, E., Mayne, N. J., et al. 2020, A&A, 636, A68
2020
-
[21]
W., Xin, Y ., et al
Finnerty, L., Xuan, J. W., Xin, Y ., et al. 2024, AJ, 167, 43
2024
-
[22]
S., Henderson, B
Fleury, B., Gudipati, M. S., Henderson, B. L., & Swain, M. 2019, ApJ, 871, 158
2019
-
[23]
2024, Nature, 632, 752
Fu, G., Welbanks, L., Deming, D., et al. 2024, Nature, 632, 752
2024
-
[24]
& Benneke, B
Gao, P. & Benneke, B. 2018, ApJ, 863, 165
2018
-
[25]
Gao, P., Piette, A. A. A., Steinrueck, M. E., et al. 2023, ApJ, 951, 96
2023
-
[26]
P., Lee, E
Gao, P., Thorngren, D. P., Lee, E. K. H., et al. 2020, Nature Astronomy, 4, 951
2020
-
[27]
J., Charbonneau, D., Burrows, A., et al
Grillmair, C. J., Charbonneau, D., Burrows, A., et al. 2007, ApJ, 658, L115
2007
-
[28]
Guillot, T., Ida, S., & Ormel, C. W. 2014, A&A, 572, A72
2014
-
[29]
2019, in EPSC-DPS Joint Meeting 2019, V ol
Hargreaves, R., Gordon, I., Kochanov, R., & Rothman, L. 2019, in EPSC-DPS Joint Meeting 2019, V ol. 2019, EPSC–DPS2019–919
2019
-
[30]
J., Gordon, I
Hargreaves, R. J., Gordon, I. E., Rey, M., et al. 2020, ApJS, 247, 55
2020
-
[31]
J., Tennyson, J., Kaminsky, B
Harris, G. J., Tennyson, J., Kaminsky, B. M., Pavlenko, Y . V ., & Jones, H. R. A. 2006, MNRAS, 367, 400
2006
-
[32]
M., Lewis, N
He, C., Hörst, S. M., Lewis, N. K., et al. 2018, AJ, 156, 38
2018
-
[33]
M., Lewis, N
He, C., Hörst, S. M., Lewis, N. K., et al. 2020, Planetary Science Journal, 1, 51
2020
-
[34]
M., Radke, M., & Yant, M
He, C., Hörst, S. M., Radke, M., & Yant, M. 2022, The Planetary Science Journal, 3, 25
2022
-
[35]
E., et al
He, C., Radke, M., Moran, S. E., et al. 2024, Nature Astronomy, 8, 182
2024
-
[36]
Helling, C., Woitke, P., & Thi, W. F. 2008, A&A, 485, 547 Hörst, S. M., He, C., Lewis, N. K., et al. 2018, Nature Astronomy, 2, 303
2008
-
[37]
E., Pearson, N., et al
Huseby, L., Moran, S. E., Pearson, N., et al. 2025, Planetary Science Journal, 6, 145
2025
-
[38]
E., Lewis, N
Inglis, J., Batalha, N. E., Lewis, N. K., et al. 2024, ApJ, 973, L41
2024
-
[39]
Jacobson, M. Z. 2005, Fundamentals of Atmospheric Modeling, 2nd edn. (Cam- bridge University Press, Cambridge)
2005
-
[40]
E., van der Avoird, A., et al
Karman, T., Gordon, I. E., van der Avoird, A., et al. 2019, Icarus, 328, 160
2019
-
[41]
P., Lewis, N
Kataria, T., Showman, A. P., Lewis, N. K., et al. 2013, ApJ, 767, 76
2013
-
[42]
& Ikoma, M
Kawashima, Y . & Ikoma, M. 2018, ApJ, 853, 7
2018
-
[43]
M.-R., Bean, J
Kempton, E. M.-R., Bean, J. L., Louie, D. R., et al. 2018, PASP, 130, 114401
2018
-
[44]
Kempton, E. M. R., Zhang, M., Bean, J. L., et al. 2023, Nature, 620, 67 Article number, page 13 A&A proofs:manuscript no. aa60641-26
2023
-
[45]
N., Sagan, C., Arakawa, E
Khare, B. N., Sagan, C., Arakawa, E. T., et al. 1984, Icarus, 60, 127
1984
-
[46]
2005, Journal of Research of the National Institute of Standards and Technology, 110, 1
Kim, J., Mulholland, G., Kukuck, S., & Pui, D. 2005, Journal of Research of the National Institute of Standards and Technology, 110, 1
2005
-
[47]
& Heng, K
Kitzmann, D. & Heng, K. 2018, MNRAS, 475, 94
2018
-
[48]
A., Lewis, N., Fortney, J
Knutson, H. A., Lewis, N., Fortney, J. J., et al. 2012, ApJ, 754, 22
2012
-
[49]
L., Désert, J.-M., et al
Kreidberg, L., Bean, J. L., Désert, J.-M., et al. 2014, Nature, 505, 69
2014
-
[50]
Larson, E. J. L., Toon, O. B., West, R. A., & Friedson, A. J. 2015, Icarus, 254, 122
2015
-
[51]
& Koskinen, T
Lavvas, P. & Koskinen, T. 2017, ApJ, 847, 32
2017
-
[52]
2024, arXiv e-prints, arXiv:2410.09981
Lavvas, P., Paraskevaidou, S., & Arfaux, A. 2024, arXiv e-prints, arXiv:2410.09981
-
[53]
V ., & Griffith, C
Lavvas, P., Yelle, R. V ., & Griffith, C. A. 2010, Icarus, 210, 832
2010
-
[54]
2012, Icarus, 218, 707
Lebonnois, S., Burgalat, J., Rannou, P., & Charnay, B. 2012, Icarus, 218, 707
2012
-
[55]
Lee, E. K. H. 2023, MNRAS, 524, 2918
2023
-
[56]
Lee, E. K. H. 2025, A&A, 698, A220
2025
-
[57]
Lee, E. K. H. & Ohno, K. 2025, A&A, 695, A111
2025
-
[58]
Lee, E. K. H., Parmentier, V ., Hammond, M., et al. 2021, MNRAS, 506, 2695
2021
-
[59]
Lee, E. K. H., Tan, X., & Tsai, S.-M. 2024, MNRAS, 529, 2686
2024
-
[60]
Lee, E. K. H., Tsai, S.-M., Hammond, M., & Tan, X. 2023, A&A, 672, A110
2023
-
[61]
Lee, E. K. H., Wardenier, J. P., Prinoth, B., et al. 2022, ApJ, 929, 180
2022
-
[62]
E., Rothman, L
Li, G., Gordon, I. E., Rothman, L. S., et al. 2015, ApJS, 216, 15
2015
-
[63]
T., Mayne, N
Mak, M. T., Mayne, N. J., Sergeev, D. E., et al. 2023, Journal of Geophysical Research (Atmospheres), 128, e2023JD039343
2023
-
[64]
T., Sergeev, D
Mak, M. T., Sergeev, D. E., Mayne, N., et al. 2024, MNRAS, 529, 3971
2024
-
[65]
T., Sergeev, D
Mak, M. T., Sergeev, D. E., Mayne, N. J., et al. 2025, MNRAS, 542, 1873
2025
-
[66]
2025, AJ, 169, 221
Malsky, I., Rauscher, E., Stevenson, K., et al. 2025, AJ, 169, 221
2025
-
[67]
W., Carslaw, K
Mann, G. W., Carslaw, K. S., Spracklen, D. V ., et al. 2010, Geoscientific Model Development, 3, 519 Moosmüller, H. & Sorensen, C. M. 2018, J. Quant. Spectr. Rad. Transf., 219, 333
2010
-
[68]
E., Hörst, S
Moran, S. E., Hörst, S. M., Vuitton, V ., et al. 2020, Planetary Science Journal, 1, 17
2020
-
[69]
V ., Fortney, J
Morley, C. V ., Fortney, J. J., Kempton, E. M. R., et al. 2013, ApJ, 775, 33
2013
-
[70]
V ., Fortney, J
Morley, C. V ., Fortney, J. J., Marley, M. S., et al. 2015, ApJ, 815, 110 Morán, J. 2022, Fractal and Fractional, 6, 529
2015
-
[71]
& Kawashima, Y
Ohno, K. & Kawashima, Y . 2020, ApJ, 895, L47
2020
-
[72]
& Okuzumi, S
Ohno, K. & Okuzumi, S. 2017, ApJ, 835, 261
2017
-
[73]
& Okuzumi, S
Ohno, K. & Okuzumi, S. 2018, ApJ, 859, 34
2018
-
[74]
2020, ApJ, 891, 131
Ohno, K., Okuzumi, S., & Tazaki, R. 2020, ApJ, 891, 131
2020
-
[75]
J., et al
Ohno, K., Schlawin, E., Bell, T. J., et al. 2025, ApJ, 979, L7
2025
-
[76]
Owen, J. E. & Murray-Clay, R. A. 2025, MNRAS, 543, 587
2025
-
[77]
O., Murga, M
Pentsak, E. O., Murga, M. S., & Ananikov, V . P. 2024, ACS Earth and Space Chemistry, 8, 798
2024
-
[78]
M., Radke, M
Pesciotta, C., Hörst, S. M., Radke, M. J., et al. 2026, ApJ, 1002, 221
2026
-
[79]
L., Kyuberis, A
Polyansky, O. L., Kyuberis, A. A., Zobov, N. F., et al. 2018, MNRAS, 480, 2597
2018
-
[80]
K., Gibson, N
Pont, F., Sing, D. K., Gibson, N. P., et al. 2013, MNRAS, 432, 2917
2013
discussion (0)
Sign in with ORCID, Apple, or X to comment. Anyone can read and Pith papers without signing in.