Superrotation of Titan’s stratosphere driven by the radiative heating of the haze layer
Motoki Sumi, Shin-ichi Takehiro, Wataru Ohfuchi, Hideko Nomura, Yuka Fujii
Titan’s stratosphere has been observed in a superrotation state, where the atmosphere rotates many times faster than the surface does. Another characteristics of Titan’s atmosphere is the presence of thick haze layer. In this paper, we performed numerical experiments using a General Circulation Model (GCM), to explore the effects of the haze layer on the stratospheric superrotation. We employed a semi-gray radiation model of Titan’s atmosphere following McKay et al. (1999), which takes account of the sunlight absorption by haze particles. The phase change of methane or the seasonal changes were not taken into account. Our model with the radiation parameters tuned for Titan yielded the global eastward wind around the equator with larger velocities at higher altitudes except at around 70 km after 105 Earth days. Although the atmosphere is not in an equilibrium state, the zonal wind profiles is approximately consistent with the observed one. Analysis on our experiments suggests that the quasi-stationary stratospheric superrotation is maintained by the balance between the meridional circulation decoupled from the surface, and the eddies that transport angular momentum equatorward. This is different from, but similar to, the so-called Gierasch mechanism, in which momentum is supplied from the surface. This structure may explain the no-wind region at about 80 km in altitude.
Comments: 24 pages, 14 figures, accepted to the Astrophysical Journal
Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Atmospheric and Oceanic Physics (physics.ao-ph); Fluid Dynamics (physics.flu-dyn)
Cite as: arXiv:2202.08397 [astro-ph.EP] (or arXiv:2202.08397v1 [astro-ph.EP] for this version)
https://doi.org/10.48550/arXiv.2202.08397
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Submission history
From: Wataru Ohfuchi [view email]
[v1] Thu, 17 Feb 2022 01:32:17 UTC (6,993 KB)
