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Climates of Warm Earth-like Planets. III. Fractional Habitability from a Water Cycle PerspectiveThe habitable fraction of a planet's surface is important for the detectability of surface biosignatures. The extent and distribution of habitable areas are influenced by external parameters that control the planet's climate, atmospheric circulation, and hydrological cycle. We explore these issues using the ROCKE-3D general circulation model, focusing on terrestrial water fluxes and thus the potential for the existence of complex life on land. Habitability is examined as a function of insolation and planet rotation for an Earth-like world with zero obliquity and eccentricity orbiting the Sun. We assess fractional habitability using an aridity index that measures the net supply of water to the land. Earth-like planets become "superhabitable" (a larger habitable surface area than Earth) as insolation and day-length increase because their climates become more equable, reminiscent of past warm periods on Earth when complex life was abundant and widespread. The most slowly rotating, most highly irradiated planets, though, occupy a hydrological regime unlike any on Earth, with extremely warm, humid conditions at high latitudes but little rain and subsurface water storage. Clouds increasingly obscure the surface as insolation increases, but visibility improves for modest increases in rotation period. Thus, moderately slowly rotating rocky planets with insolation near or somewhat greater than modern Earth's appear to be promising targets for surface characterization by a future direct imaging mission.
Document ID
20205001008
Acquisition Source
Goddard Space Flight Center
Document Type
Accepted Manuscript (Version with final changes)
Authors
Anthony D. Del Genio ORCID
(Goddard Institute for Space Studies New York, New York, United States)
M.J. Way ORCID
(Goddard Institute for Space Studies New York, New York, United States)
Nancy Y Kiang ORCID
(GISS New York, New York, United States)
Igor Aleinov ORCID
(Columbia University New York, New York, United States)
Michael J. Puma ORCID
(Columbia University New York, New York, United States)
Benjamin Cook
(Goddard Institute for Space Studies New York, New York, United States)
Date Acquired
April 16, 2020
Publication Date
December 19, 2019
Publication Information
Publication: The Astrophysical Journal
Publisher: American Astronomical Society and IOP Publishing
Volume: 887
Issue: 2
Issue Publication Date: December 20, 2019
ISSN: 0004-637X
e-ISSN: 1538-4357
Subject Category
Space Sciences (General)
Funding Number(s)
WBS: 811073.02.52.01.08.16
WBS: 811073.02.36.01.56
WBS: 811073.02.10.03.10
Distribution Limits
Public
Copyright
Portions of document may include copyright protected material.
Technical Review
External Peer Committee
Keywords
Exoplanet atmospheric variability
Exoplanets
Habitable planets
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