Japan Geoscience Union Meeting 2019

Presentation information

[J] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS11] Aqua planetology

Tue. May 28, 2019 9:00 AM - 10:30 AM A02 (TOKYO BAY MAKUHARI HALL)

convener:Yasuhito Sekine(Earth-Life Science Insitute, Tokyo Institute of Technology), Tomohiro Usui(Earth-Life Science Institute, Tokyo Institute of Technology), Keisuke Fukushi(Institute of Nature & Environmental Technology, Kanazawa University), Takazo Shibuya(Japan Agency for Marine-Earth Science and Technology), Chairperson:Yasuhito Sekine(Dept. Earth & Planetary Sci., University of Tokyo), Takazo Shibuya(JAMSTEC), Tomohiro Usui

9:45 AM - 10:00 AM

[MIS11-16] Habitable zone for a land planet

*Takanori Kodama1, Hidenori Genda2, Ryouta O'ishi3, Ayako Abe-Ouchi3 (1.University of Bordeaux, 2.Earth-Life Science Institute, Tokyo Institute of Technology, 3.Atmosphere and Ocean Research Institute, University of Tokyo)

Keywords:Land planet, Habitable zone

Most of the studies for habitable planets have focused on Earth-like planets with globally abundant water on the planetary surface. Liquid water vaporizes entirely when planets receive the insolation above a certain critical value, which is called runaway greenhouse threshold. On the other hand, the planetary climate state lapses into a snowball state when planets receive insolation below a certain value, which is called the complete freezing threshold. The habitable zone, in which planets can maintain liquid water on their surface for a long term, is determined by these thresholds.

Abe et al. (2011) focused on so-called land planets with a very small amount of water, and investigated these thresholds using a three-dimensional general circulation model. As results, they found that land planets have a wider habitable zone than Earth-like planets have. However, it is not enough to understand the relationship between the distribution of water and the climate because their range of the amount of water is extremely narrow, leading the almost same distribution of liquid water on the planetary surface.

We assumed various types of the surface water distribution, and investigated the effect of those on both the runaway greenhouse threshold and the complete freezing threshold for Earth-sized planets using a three-dimensional general circulation model. We consider the surface water distributions as longitudinally uniform water distribution and a 1-bar atmosphere whose composition is similar to the current Earth’s atmosphere. As results, both thresholds change gradually depending on the distribution of surface water. Additionally, they are dominated by the atmospheric circulation which determines the surface condition.