Atmospheres & Climate

Lorenz Energy Cycle: Another Way to Understand the Atmospheric Circulation on Tidally Locked Terrestrial Planets

By Keith Cowing
astro-ph.EP
April 24, 2023
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Lorenz Energy Cycle: Another Way to Understand the Atmospheric Circulation on Tidally Locked Terrestrial Planets
Climatic elements on three planets. (a)–(c) Temporal- and zonal-mean temperature (color shading) and zonal-mean zonal winds (contour lines) on Earth, on the rapidly rotating tidally locked terrestrial planet, and on the slowly rotating tidally locked terrestrial planet; (d)–(f) same as (a)–(c) but for deviations of temporal- and zonal-mean geopotential height from the global means (color shading), and mass stream functions (contour lines, in units of 1010 kg s−1 ). Note that the ranges of color bars in panels (d), (e), and (f) are different. Panels (a), (b), (d) and (e) are shown in the standard coordinates, and (c) and (f) are shown in the tidally locked coordinates. SP and AP are the substellar point and the antistellar point, respectively. — astro-ph.EP

In this study, we employ and modify the Lorenz energy cycle (LEC) framework as another way to understand the atmospheric circulation on tidally locked terrestrial planets.

It well describes the atmospheric general circulation in the perspective of energy transformation, involved with several dynamical processes. We find that on rapidly rotating, tidally locked terrestrial planets, mean potential energy (PM) and eddy potential energy (PE) are comparable to those on Earth, as they have similar steep meridional temperature gradients.

Mean kinetic energy (KM) and eddy kinetic energy (KE) are larger than those on Earth, related to stronger winds. The two conversion paths, PM→PE→KE and PM→KM→KE, are both efficient. The former is associated with strong baroclinic instabilities, and the latter is associated with Hadley cells. On slowly rotating, tidally locked terrestrial planets, weak temperature gradients in the free atmosphere and strong nightside temperature inversion make PM and PE are much smaller than those on Earth.

Meanwhile, large day–night surface temperature contrast and small rotation rate make the overturning circulation extend to the globe, so that the main conversion path is PM→KM→KE. This study shows that the LEC analyses improve the understanding of the atmospheric circulation on tidally locked terrestrial planets.

Shuang Wang, Jun Yang

Comments: 25 pages, 16 fugures
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2304.11627 [astro-ph.EP] (or arXiv:2304.11627v1 [astro-ph.EP] for this version)
Submission history
From: Shuang Wang
[v1] Sun, 23 Apr 2023 12:00:21 UTC (7,165 KB)
https://arxiv.org/abs/2304.11627
Astrobiology,

Explorers Club Fellow, ex-NASA Space Station Payload manager/space biologist, Away Teams, Journalist, Lapsed climber, Synaesthete, Na’Vi-Jedi-Freman-Buddhist-mix, ASL, Devon Island and Everest Base Camp veteran, (he/him) 🖖🏻