The Inhomogeneity Effect. I. Inhomogeneous Surface and Atmosphere Accelerate Planetary Cooling
We propose a general principle that under radiative-convective equilibrium, the spatial and temporal variations in a planet’s surface and atmosphere tend to increase its cooling. This principle is based on Jensen’s inequality and the curvature of the response functions of surface temperature and out...
| Main Author: | |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2023-01-01
|
| Series: | The Astrophysical Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/1538-4357/acee66 |
| _version_ | 1797648907397758976 |
|---|---|
| author | Xi Zhang |
| author_facet | Xi Zhang |
| author_sort | Xi Zhang |
| collection | DOAJ |
| description | We propose a general principle that under radiative-convective equilibrium, the spatial and temporal variations in a planet’s surface and atmosphere tend to increase its cooling. This principle is based on Jensen’s inequality and the curvature of the response functions of surface temperature and outgoing cooling flux to changes in incoming stellar flux and atmospheric opacity. We use an analytical model to demonstrate that this principle holds for various planet types: (1) on an airless planet, the mean surface temperature is lower than its equilibrium temperature; (2) on terrestrial planets with atmospheres, the inhomogeneity of incoming stellar flux and atmospheric opacity reduces the mean surface temperature; (3) on giant planets, inhomogeneously distributed stellar flux and atmospheric opacity increase the outgoing infrared flux, cooling the interior. Although the inhomogeneity of visible opacity might sometimes heat the atmosphere, the effect is generally much smaller than the inhomogeneous cooling effect of infrared opacity. Compared with the homogeneous case, the mean surface temperature on inhomogeneous terrestrial planets can decrease by more than 20%, and the internal heat flux on giant planets can increase by over an order of magnitude. Despite simplifications in our analytical framework, the effect of stellar flux inhomogeneity appears to be robust, while further research is needed to fully understand the effects of opacity inhomogeneity in more realistic situations. This principle impacts our understanding of planetary habitability and the evolution of giant planets using low-resolution and one-dimensional frameworks that may have previously overlooked the role of inhomogeneity. |
| first_indexed | 2024-03-11T15:38:48Z |
| format | Article |
| id | doaj.art-03714e56cd124f879decce07ff1fd826 |
| institution | Directory Open Access Journal |
| issn | 1538-4357 |
| language | English |
| last_indexed | 2024-03-11T15:38:48Z |
| publishDate | 2023-01-01 |
| publisher | IOP Publishing |
| record_format | Article |
| series | The Astrophysical Journal |
| spelling | doaj.art-03714e56cd124f879decce07ff1fd8262023-10-26T12:15:18ZengIOP PublishingThe Astrophysical Journal1538-43572023-01-0195712010.3847/1538-4357/acee66The Inhomogeneity Effect. I. Inhomogeneous Surface and Atmosphere Accelerate Planetary CoolingXi Zhang0https://orcid.org/0000-0002-8706-6963Department of Earth and Planetary Sciences, University of California Santa Cruz , Santa Cruz, CA 95064, USA ; xiz@ucsc.eduWe propose a general principle that under radiative-convective equilibrium, the spatial and temporal variations in a planet’s surface and atmosphere tend to increase its cooling. This principle is based on Jensen’s inequality and the curvature of the response functions of surface temperature and outgoing cooling flux to changes in incoming stellar flux and atmospheric opacity. We use an analytical model to demonstrate that this principle holds for various planet types: (1) on an airless planet, the mean surface temperature is lower than its equilibrium temperature; (2) on terrestrial planets with atmospheres, the inhomogeneity of incoming stellar flux and atmospheric opacity reduces the mean surface temperature; (3) on giant planets, inhomogeneously distributed stellar flux and atmospheric opacity increase the outgoing infrared flux, cooling the interior. Although the inhomogeneity of visible opacity might sometimes heat the atmosphere, the effect is generally much smaller than the inhomogeneous cooling effect of infrared opacity. Compared with the homogeneous case, the mean surface temperature on inhomogeneous terrestrial planets can decrease by more than 20%, and the internal heat flux on giant planets can increase by over an order of magnitude. Despite simplifications in our analytical framework, the effect of stellar flux inhomogeneity appears to be robust, while further research is needed to fully understand the effects of opacity inhomogeneity in more realistic situations. This principle impacts our understanding of planetary habitability and the evolution of giant planets using low-resolution and one-dimensional frameworks that may have previously overlooked the role of inhomogeneity.https://doi.org/10.3847/1538-4357/acee66Planetary atmospheresExoplanet atmospheresAtmospheric evolution |
| spellingShingle | Xi Zhang The Inhomogeneity Effect. I. Inhomogeneous Surface and Atmosphere Accelerate Planetary Cooling The Astrophysical Journal Planetary atmospheres Exoplanet atmospheres Atmospheric evolution |
| title | The Inhomogeneity Effect. I. Inhomogeneous Surface and Atmosphere Accelerate Planetary Cooling |
| title_full | The Inhomogeneity Effect. I. Inhomogeneous Surface and Atmosphere Accelerate Planetary Cooling |
| title_fullStr | The Inhomogeneity Effect. I. Inhomogeneous Surface and Atmosphere Accelerate Planetary Cooling |
| title_full_unstemmed | The Inhomogeneity Effect. I. Inhomogeneous Surface and Atmosphere Accelerate Planetary Cooling |
| title_short | The Inhomogeneity Effect. I. Inhomogeneous Surface and Atmosphere Accelerate Planetary Cooling |
| title_sort | inhomogeneity effect i inhomogeneous surface and atmosphere accelerate planetary cooling |
| topic | Planetary atmospheres Exoplanet atmospheres Atmospheric evolution |
| url | https://doi.org/10.3847/1538-4357/acee66 |
| work_keys_str_mv | AT xizhang theinhomogeneityeffectiinhomogeneoussurfaceandatmosphereaccelerateplanetarycooling AT xizhang inhomogeneityeffectiinhomogeneoussurfaceandatmosphereaccelerateplanetarycooling |