On The Relative Humidity Of Earth’s Atmosphere

Water vapour is highly subsaturated in much of the Earth’s atmosphere. This has important consequences for water vapour feedback, and also for general phenomena such as the runaway greenhouse.

In this chapter, we discuss the processes that create subsaturation, with reference to both observations, general circulation models, and a range of idealized theoretical models which produce subsaturation.

While this chapter focuses on subsaturation of water vapour in Earth’s atmosphere, the processes discussed are generic to condensible substances in all planetary atmospheres.

Raymond T. Pierrehumbert, Helene Brogniez, Remy Roca

Comments: Cite as Pierrehumbert RT, Brogniez† H, and Roca R 2007: On the relative humidity of the atmosphere. in The Global Circulation of the Atmosphere, T Schneider and A Sobel, eds. Princeton University Press 400pp
Subjects: Atmospheric and Oceanic Physics (physics.ao-ph); Earth and Planetary Astrophysics (astro-ph.EP); Geophysics (physics.geo-ph)
Cite as: arXiv:2507.08824 [physics.ao-ph] (or arXiv:2507.08824v1 [physics.ao-ph] for this version)
https://doi.org/10.48550/arXiv.2507.08824
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Submission history
From: Raymond Pierrehumbert
[v1] Mon, 30 Jun 2025 09:02:15 UTC (1,147 KB)
https://arxiv.org/abs/2507.08824
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