Resolving Convection of CO2 Ice Clouds in the Martian Polar Nights

• Published in: Geophysical research letters 2024-06, Vol.51 (12), p.n/a
• Main Authors: Caillé, Vincent, Spiga, Aymeric, Määttänen, Anni, Falletti, Lola, Mathé, Christophe
• Format: Article
• Language: English
• Subjects: atmosphere; Atmospheric particulates; Carbon dioxide; Cloud formation; Clouds; CO2 clouds; Convection; Convective development; Cooling; Ice; Ice clouds; Ice formation; Large eddy simulation; LES Modelization; Lower atmosphere; Mars; Mars climate; Mars surface; Microphysics; Parameters; Perturbation; platenology; Sciences of the Universe; Sunlight; Troposphere; Winds
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2023GL106923

Martian CO2 ice clouds are intriguing features, representing a rare occurrence of atmospheric condensation of a major component. These clouds play a crucial role due to their radiative properties, interactions with surface, and coupling with microphysical cycles of aerosols. Observations have been limited, prompting modeling studies to understand their formation and dynamics. Here, we present the first high‐resolution 3D simulations of CO2 ice clouds using a Large‐Eddy Simulation (LES) model incorporating CO2 microphysics. We investigate cloud formation in idealized temperature perturbations in the polar night. A reference simulation with a −2K perturbation demonstrates that the formed CO2 ice cloud possesses a convective potential, leading to its ascent in the troposphere. We determine the timescales and orders of magnitude of various phenomena involved in the lifecycle of a CO2 ice cloud. Sensitivity tests show that convection can be inhibited or intensified by the thermodynamic and microphysical conditions of the simulated environment. Plain Language Summary CO2 ice clouds have been observed in the Martian polar nights in the lower atmosphere. These clouds are extremely challenging to observe due to the lack of sunlight. However, they play a significant role in Mars' climate, especially through interactions with the surface and other atmospheric species. To study the formation processes of these clouds, we use a high‐resolution model. Even a relatively weak cooling can lead to the formation of a CO2 ice cloud with convective potential, enabling it to move vertically upward. We determine the characteristic times and altitudes of this phenomenon and investigate how they respond when atmospheric parameters, such as cooling temperature, the presence of extra dust, or horizontal winds are varied. Our findings show that some of these parameters can either inhibit or enhance convection development. Key Points Coupling a convection model with a CO2 microphysics scheme can simulate the formation of convective CO2 ice clouds triggered by realistic perturbations These is a strong coupling between CO2 ice cloud convection and dust cycle in the troposphere The convective process intensity depends strongly on the number of available condensation nuclei and the temperature of the perturbation