Journal article
Atmospheric dynamics of temperate sub-neptunes. I. Dry dynamics
- Abstract:
- Sub-Neptunes (planets with radii between 2 and 4 R⊕) are abundant around M-dwarf stars, yet the atmospheric dynamics of these planets is relatively unexplored. In this paper, we aim to provide a basic underpinning of the dry dynamics of general low-mean-molecular-weight, temperate sub-Neptune atmospheres. We use the ExoFMS general circulation model (GCM) with an idealized gray-gas radiation scheme to simulate planetary atmospheres with different levels of instellation and rotation rates, using the atmosphere of K2-18b as our control. We find that the atmospheres of tidally locked (TL), temperate sub-Neptunes have weak horizontal temperature gradients owing to their slow rotation rates and hydrogen-dominated composition. The zonal wind structure is dominated by high-latitude cyclostrophic jets driven by the conservation of angular momentum. At low pressures we observe superrotating equatorial jets, which we propose are driven by a Rossby–Kelvin instability similar to the type seen in simulations of idealized atmospheres with axisymmetric forcing. By viewing the flow in TL coordinates, we find the predominant overturning circulation to be between the day side and night side, and we derive scaling relations linking the TL stream function and vertical velocities to instellation. Comparing our results to the only other GCM study of K2-18b, we find significant qualitative differences in dynamics, highlighting the need for further collaboration and investigation into the effects of different dynamical cores and physical parameterizations. This paper provides a baseline for studying the dry dynamics of temperate sub-Neptunes, which will be built on in part II with the introduction of moist effects.
- Publication status:
- Published
- Peer review status:
- Peer reviewed
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(Preview, Version of record, 3.2MB, Terms of use)
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- Publisher copy:
- 10.3847/1538-4357/ac4887
Authors
- Publisher:
- IOP Publishing
- Journal:
- The Astrophysical Journal More from this journal
- Volume:
- 927
- Issue:
- 1
- Article number:
- 38
- Publication date:
- 2022-03-03
- Acceptance date:
- 2021-12-20
- DOI:
- EISSN:
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1538-4357
- ISSN:
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0004-637X
- Language:
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English
- Keywords:
- Pubs id:
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1242522
- Local pid:
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pubs:1242522
- Deposit date:
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2022-03-05
Terms of use
- Copyright holder:
- Innes and Pierrehumbert
- Copyright date:
- 2022
- Rights statement:
- ©2022. The Author(s). Published by the American Astronomical Society. Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI.
- Licence:
- CC Attribution (CC BY)
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