Climate of high obliquity exo-terrestrial planets with a three-dimensional cloud system resolving climate model

TL;DR

This study uses a high-resolution, three-dimensional cloud-resolving climate model to explore how high obliquity affects exoplanet climates, revealing that explicit cloud microphysics significantly influence temperature and water vapor distribution.

Contribution

Introduces the NICAM model for simulating high-obliquity exoplanet climates with explicit cloud microphysics, highlighting the impact of resolution on climate outcomes.

Findings

High-resolution simulations show warmer climates due to less low cloud cover.

Explicit cloud microphysics lead to increased atmospheric water vapor.

Cloud treatment differences affect climate regimes at high obliquities.

Abstract

Planetary climates are strongly affected by planetary orbital parameters such as obliquity, eccentricity, and precession. In exoplanetary systems, exo-terrestrial planets should have various obliquities. High-obliquity planets would have extreme seasonal cycles due to the seasonal change of the distribution of the insolation. Here, we introduce the Non-hydrostatic ICosahedral Atmospheric Model(NICAM), a global cloud-resolving model, to investigate the climate of high-obliquity planets. This model can explicitly simulate a three-dimensional cloud distribution and vertical transports of water vapor. We simulated exo-terrestrial climates 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 ($0^{\circ}$, $23.5^{\circ}$, $45^{\circ}$, and $60^{\circ}$). We ran two sets of simulations: 1) low-resolution (~ 220 km-mesh as the standard resolution of a general circulation model for exoplanetary science) with parametrization for cloud formation, and 2) high-resolution (~ 14 km-mesh) with an explicit cloud microphysics scheme. Results suggest that high-resolution simulations with an explicit treatment of cloud microphysics reveal warmer climates due to less low cloud fraction and a large amount of water vapor in the atmosphere. It implies that treatments of cloud-related processes lead to a difference between different resolutions in climatic regimes in cases with high obliquities.