Exoplanets & Exomoons

Clouds And Seasonality On Terrestrial Planets With Varying Rotation Rates

By Keith Cowing

Status Report

physics.ao-ph

February 12, 2024

Filed under atmosphere, Clouds, exoplanet, Ocean world, physics.ao-ph, Terrestrial Planet, weather

Clouds And Seasonality On Terrestrial Planets With Varying Rotation Rates — Left: seasonal variation of the temperature, which is defined by the difference between the Northern Hemisphere (NH) averaged surface temperature and the global annual mean surface temperature. Middle: the maximum streamfunction in NH. Right: The latitude of the maximum zonal mean precipitation (ITCZ). The filled shaded contours represent the results from no-cloud simulations and the values are shown in the colourbars, while the open contours represent the results from cloud simulations and the values are shown in inline labels. For comparison, the contours are plotted at the same levels for no-clouds and clouds simulations. To highlight the difference in seasonal transition, the zero contour lines are bold black (clouds) and gray (no-clouds) for the left and right panels. The contours of streamfunction and ITCZ latitude are smoothed by a Gaussian filter with a standard deviation of σ = 3 days. The horizontal lines represent day of vernal equinox (day 90), northern summer solstice (day 180), and autumnal equinox (day 270), and day 0 is northern winter solstice. The vertical lines represent rotation rates of Ω∗ = 1/8 and 1. — physics.ao-ph

Using an idealised climate model incorporating seasonal forcing, we investigate the impact of rotation rate on the abundance of clouds on an Earth-like aquaplanet, and the resulting impacts upon albedo and seasonality.

We show that the cloud distribution varies significantly with season, depending strongly on the rotation rate, and is well explained by the large-scale circulation and atmospheric state. Planetary albedo displays non-monotonic behaviour with rotation rate, peaking at around 1/2ΩE.

Clouds reduce the surface temperature and total precipitation relative to simulations without clouds at all rotation rates, and reduce the dependence of total precipitation on rotation rate, causing non-monotonic behaviour and a local maximum around 1/8ΩE ; these effects are related to the impacts of clouds on the net atmospheric and surface radiative energy budgets. Clouds also affect the seasonality.

The influence of clouds on the extent of the winter Hadley cell and the intertropical convergence zone is relatively minor at slow rotation rates (<1/8ΩE ), but becomes more pronounced at intermediate rotation rates, where clouds decrease their maximum latitudes. The timing of seasonal transitions varies with rotation rate, and the addition of clouds reduces the seasonal phase lag.

Daniel A. Williams, Xuan Ji, Paul Corlies, Juan M. Lora

Comments: 21 pages, 9 figures
Subjects: Atmospheric and Oceanic Physics (physics.ao-ph); Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:2402.04900 [physics.ao-ph] (or arXiv:2402.04900v1 [physics.ao-ph] for this version)
https://doi.org/10.48550/arXiv.2402.04900
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Submission history
From: Daniel Alexander Williams
[v1] Wed, 7 Feb 2024 14:30:54 UTC (4,294 KB)
https://arxiv.org/abs/2402.04900

Astrobiology

Keith Cowing

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) 🖖🏻

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