DRAMATIC Planets: Simulation of water cycle on Mars with cloud microphysics, and extensions to the climate evolution of Venus and beyond

We are conducting climate simulations of rocky planets using a Global Climate Model (GCM) named DRAMATIC (Dynamics, RAdiation, MAterial Transport and their mutual InteraCtions). The model is based on the spectral dynamical core of MIROC (Model for Interdisciplinary Research On Climate) developed in Japan, and has been applied to a range of planetary climates, including present-day Mars (e.g., Kuroda et al., 2005, 2013, 2015, 2020), paleo-Mars (Kamada et al., 2020, 2021, 2022), and present-day Venus (Karyu et al., 2023). Applications to paleo-Venus and TRAPPIST-1 planets are currently ongoing.

Among these, the DRAMATIC Mars GCM (MGCM) has been extensively used to investigate atmospheric dynamics and material transport on present-day Mars. A recent advancement includes the implementation of regolith adsorption properties, enabling the model to simulate atmosphere-subsurface water interactions (Kobayashi et al., 2025). The MGCM has also supported collaborations with observational data, enhancing the model’s validation and utility. In addition, we are implementing a data assimilation system into the MGCM, to further improve consistency with observations and enable more comprehensive climate reconstructions.

The current version of DRAMATIC MGCM is based on MIROC6 (Tatebe et al., 2019), and we have updated the vertical layers to use a hybrid sigma-pressure coordinate. Additionally, we have implemented a dust cycle featuring 6 particle mode radii (0.0625, 0.125, 0.25, 0.5, 1, and 2 µm). Dust is injected from the surface according to three-dimensional scenarios (latitude, longitude, and time) based on past observations (Montabone et al., 2015, 2020), which also serve as nuclei for the formation of water ice clouds. The microphysics governing the formation of water ice clouds is newly implemented based on the work of Navarro et al. (2014), as well as the radiative effects of water ice clouds, CO₂ ice clouds, and water vapor. With the updated MGCM we have successfully reproduced the zonal-mean distributions of water ice clouds aligning with observations from the MRO-MCS (McCleese et al., 2010), including their day-night variations. Additionally, we have effectively replicated the seasonal changes in water vapor column densities and water ice cloud opacities observed by MGS-TES (Smith, 2008). The implementation of cloud microphysics to reproduce supersaturation is particularly important for accurately representing observed features.

Looking ahead, such cloud formation processes are expected to significantly influence the climate of Venus. Especially, our interest lies in their effects on the cooling of atmosphere from early magma-ocean state. In the presentaion our future directions and broader implications for planetary climate evolution will also be discussed.