Resolved Convection in Hydrogen-rich Atmospheres
In hydrogen-rich atmospheres with low mean molecular weight (MMW), an air parcel containing a higher-molecular-weight condensible can be negatively buoyant even if its temperature is higher than the surrounding environment. This should fundamentally alter the dynamics of moist convection, but the lo...
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IOP Publishing
2025-01-01
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| Series: | The Planetary Science Journal |
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| Online Access: | https://doi.org/10.3847/PSJ/ad9b1a |
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| author | Jacob T. Seeley Robin D. Wordsworth |
| author_facet | Jacob T. Seeley Robin D. Wordsworth |
| author_sort | Jacob T. Seeley |
| collection | DOAJ |
| description | In hydrogen-rich atmospheres with low mean molecular weight (MMW), an air parcel containing a higher-molecular-weight condensible can be negatively buoyant even if its temperature is higher than the surrounding environment. This should fundamentally alter the dynamics of moist convection, but the low-MMW regime has previously been explored primarily via 1D theories that cannot capture the complexity of moist turbulence. Here, we use a 3D cloud-resolving model to simulate moist convection in atmospheres with a wide range of background MMWs and confirm that a humidity threshold for buoyancy reversal first derived by T. Guillot coincides with an abrupt change in tropospheric structure. Crossing the “Guillot threshold” in near-surface humidity causes the dry (subcloud) boundary layer to collapse and be replaced by a very cloudy layer with a temperature lapse rate that exceeds the dry adiabatic rate. Simulations with reduced surface moisture availability in the lower atmosphere feature a deeper dry subcloud layer, which allows the superadiabatic cloud layer to remain aloft. Our simulations support a potentially observable systematic trend toward increased cloudiness for atmospheres with near-surface moisture concentrations above the Guillot threshold. This should apply to H _2 O and potentially to other condensible species on hotter worlds. We also find evidence for episodic convective activity and associated variability in cloud cover in some of our low-MMW simulations, which should be investigated further with global-scale simulations. |
| format | Article |
| id | doaj-art-fece97750f5d4b9fa59adb10f9f422e4 |
| institution | Kabale University |
| issn | 2632-3338 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Planetary Science Journal |
| spelling | doaj-art-fece97750f5d4b9fa59adb10f9f422e42025-01-07T07:56:20ZengIOP PublishingThe Planetary Science Journal2632-33382025-01-0161610.3847/PSJ/ad9b1aResolved Convection in Hydrogen-rich AtmospheresJacob T. Seeley0https://orcid.org/0000-0003-0769-292XRobin D. Wordsworth1https://orcid.org/0000-0003-1127-8334Department of Earth and Planetary Sciences, Harvard University , Cambridge, MA 02461, USADepartment of Earth and Planetary Sciences, Harvard University , Cambridge, MA 02461, USAIn hydrogen-rich atmospheres with low mean molecular weight (MMW), an air parcel containing a higher-molecular-weight condensible can be negatively buoyant even if its temperature is higher than the surrounding environment. This should fundamentally alter the dynamics of moist convection, but the low-MMW regime has previously been explored primarily via 1D theories that cannot capture the complexity of moist turbulence. Here, we use a 3D cloud-resolving model to simulate moist convection in atmospheres with a wide range of background MMWs and confirm that a humidity threshold for buoyancy reversal first derived by T. Guillot coincides with an abrupt change in tropospheric structure. Crossing the “Guillot threshold” in near-surface humidity causes the dry (subcloud) boundary layer to collapse and be replaced by a very cloudy layer with a temperature lapse rate that exceeds the dry adiabatic rate. Simulations with reduced surface moisture availability in the lower atmosphere feature a deeper dry subcloud layer, which allows the superadiabatic cloud layer to remain aloft. Our simulations support a potentially observable systematic trend toward increased cloudiness for atmospheres with near-surface moisture concentrations above the Guillot threshold. This should apply to H _2 O and potentially to other condensible species on hotter worlds. We also find evidence for episodic convective activity and associated variability in cloud cover in some of our low-MMW simulations, which should be investigated further with global-scale simulations.https://doi.org/10.3847/PSJ/ad9b1aAtmospheric cloudsPlanetary atmospheres |
| spellingShingle | Jacob T. Seeley Robin D. Wordsworth Resolved Convection in Hydrogen-rich Atmospheres The Planetary Science Journal Atmospheric clouds Planetary atmospheres |
| title | Resolved Convection in Hydrogen-rich Atmospheres |
| title_full | Resolved Convection in Hydrogen-rich Atmospheres |
| title_fullStr | Resolved Convection in Hydrogen-rich Atmospheres |
| title_full_unstemmed | Resolved Convection in Hydrogen-rich Atmospheres |
| title_short | Resolved Convection in Hydrogen-rich Atmospheres |
| title_sort | resolved convection in hydrogen rich atmospheres |
| topic | Atmospheric clouds Planetary atmospheres |
| url | https://doi.org/10.3847/PSJ/ad9b1a |
| work_keys_str_mv | AT jacobtseeley resolvedconvectioninhydrogenrichatmospheres AT robindwordsworth resolvedconvectioninhydrogenrichatmospheres |