12:00 〜 12:15
[AAS05-12] Climate of high obliquity exo-terrestrial planets with 3D cloud resolving climate model
キーワード：系外惑星、気候、自転軸傾斜角
Many exoplanets have been detected since 1995. Some of them are expected to be rocky planets with Earth-like bulk composition within the habitable zone which is defined as the region around the central star where liquid water on the planetary surface remains stable for a long term. New space telescope observations are planned to reveal the characteristics of the atmosphere of exoplanets. In the next decade, such potential habitable exoplanets will be the primary targets for observation of life on exoplanets. Recently, the climate for exoplanets in the habitable zone has been estimated with 3D climate models. Thus, future observation and our understanding for exoplanetary climate will be an essential key on exoplanetary science.
Climates are strongly affected by the planetary orbital parameters, such as the obliquity, eccentricity, precession, and so on. On the Earth's history, glaciation and deglaciation cycle have been controlled by Milankovitch orbital insolation forcing. In our solar system, planets have a wide range of obliquity. Thanks to the presence of the Moon, our Earth has stable obliquity around 23.5º. Without the Moon, Earth's obliquity would vary due to solar tides between 0º and 90º on the timescale of less than 10 Myrs. Thus, on the exoplanetary system, exoplanets should have various obliquity. High obliquity planets would have extreme seasonal cycles due to the seasonal change of the distribution of the insolation.
Here, we introduce NICAM(Non-hydrostatic ICosahedral Atmospheric Model), known as a global cloud resolving model. This model can explicitly resolve cloud distributions and the vertical moisture transport of water vapor, and we can simulate the climate with high resolution using the supercomputer FUGAKU. We assumed aqua-planet configurations with 1 bar of air as a background atmosphere with four different obliquities (0º, 23.5º, 45º, and 60º). We ran two sets set of simulations: 1) low-resolution (~220km mesh as the standard resolution of GCM for exoplanetary science) with parametrization for cloud formation, and 2) high-resolution (~14km mesh) + explicit cloud microphysics scheme. Results suggest that high resolution simulations with an explicit treatment of cloud microphysics show warmer climates due to a large amount of water vapor in the atmosphere, leading a difference between different resolutions in climatic regimes in cases with high obliquities.
This work was supported by MEXT as “Program for Promoting Researches on the Supercomputer Fugaku” (JPMXP1020200305) and used computational resources provided by the RIKEN Center for Computational Science (Project ID: hp200128, hp210166).
Climates are strongly affected by the planetary orbital parameters, such as the obliquity, eccentricity, precession, and so on. On the Earth's history, glaciation and deglaciation cycle have been controlled by Milankovitch orbital insolation forcing. In our solar system, planets have a wide range of obliquity. Thanks to the presence of the Moon, our Earth has stable obliquity around 23.5º. Without the Moon, Earth's obliquity would vary due to solar tides between 0º and 90º on the timescale of less than 10 Myrs. Thus, on the exoplanetary system, exoplanets should have various obliquity. High obliquity planets would have extreme seasonal cycles due to the seasonal change of the distribution of the insolation.
Here, we introduce NICAM(Non-hydrostatic ICosahedral Atmospheric Model), known as a global cloud resolving model. This model can explicitly resolve cloud distributions and the vertical moisture transport of water vapor, and we can simulate the climate with high resolution using the supercomputer FUGAKU. We assumed aqua-planet configurations with 1 bar of air as a background atmosphere with four different obliquities (0º, 23.5º, 45º, and 60º). We ran two sets set of simulations: 1) low-resolution (~220km mesh as the standard resolution of GCM for exoplanetary science) with parametrization for cloud formation, and 2) high-resolution (~14km mesh) + explicit cloud microphysics scheme. Results suggest that high resolution simulations with an explicit treatment of cloud microphysics show warmer climates due to a large amount of water vapor in the atmosphere, leading a difference between different resolutions in climatic regimes in cases with high obliquities.
This work was supported by MEXT as “Program for Promoting Researches on the Supercomputer Fugaku” (JPMXP1020200305) and used computational resources provided by the RIKEN Center for Computational Science (Project ID: hp200128, hp210166).