16:15 〜 16:30
[PAE17-16] The threshold of the runaway greenhouse state: effect of the planetary obliquity
キーワード：ハビタブル惑星、暴走温室、自転軸傾斜角
Some detected exoplanets are expected to be rocky planets with Earth-like bulk composition within the habitable zone. The inner edge of the habitable zone is determined by the onset of the runaway greenhouse state. Most of studies for potentially habitable exoplanets estimated the atmospheric structure using a one-dimensional radiative convective equilibrium model. Recently, the climate for exoplanets has been estimated with three-dimensional general circulation models (GCMs).
The planetary climate is strongly affected by the planetary obliquity. A planet with a high obliquity would have an extreme seasonal cycle due to the distribution of the stellar radiation from the central star. In the history of the Earth, Milankovitch orbital insolation forcing controlled the glaciation-deglaciation cycle. Exoplanets should have various obliquity and seasonal climatic change.
Here, we investigate the effect of the obliquity on the onset of the runaway greenhouse state with a three-dimensional general circulation model, AGCM5.4g. We assume two types of configurations (aqua planet and land planet) with 1 bar of air as a background atmosphere with five different obliquities (0º, 15º, 30º, 45º, and 60º). For a land planet configuration, we assume the same surface water distribution as Kodama et al. (2018).
As a result, the insolation at the onset of the runaway greenhouse state is affected by the obliquity owing to the seasonal change of the distribution of cloud, snow, and ice sheet. In this presentation, we summarize the dependence of the obliquity on the threshold of the runaway greenhouse state.
The planetary climate is strongly affected by the planetary obliquity. A planet with a high obliquity would have an extreme seasonal cycle due to the distribution of the stellar radiation from the central star. In the history of the Earth, Milankovitch orbital insolation forcing controlled the glaciation-deglaciation cycle. Exoplanets should have various obliquity and seasonal climatic change.
Here, we investigate the effect of the obliquity on the onset of the runaway greenhouse state with a three-dimensional general circulation model, AGCM5.4g. We assume two types of configurations (aqua planet and land planet) with 1 bar of air as a background atmosphere with five different obliquities (0º, 15º, 30º, 45º, and 60º). For a land planet configuration, we assume the same surface water distribution as Kodama et al. (2018).
As a result, the insolation at the onset of the runaway greenhouse state is affected by the obliquity owing to the seasonal change of the distribution of cloud, snow, and ice sheet. In this presentation, we summarize the dependence of the obliquity on the threshold of the runaway greenhouse state.