Origins and life cycle of Venus’ clouds investigated with a high-accuracy cloud microphysics model
(2026)
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- Authors
- Supervisors
- Crucifix, Michel
- Abstract
- Venus is globally shrouded in thick sulfuric acid clouds and represents a critical analog for studying planetary climates where the atmosphere is deeply coupled with photochemically-produced cloud processes—a regime widely observed in the Solar System and beyond. This study aims to understand the origin and life cycle of the Venus clouds. In Chapter 1, we first addressed key gaps in current modeling by constraining vertical transport using a realistic eddy diffusion profile. Based on the eddy diffusion case studies, we narrowed the best-fit eddy diffusion profile to ~2 m2 s-1 between 60 and 70 km, and ~360 m2 s-1 above 85 km. In Chapter 2, we developed a novel multi-component cloud microphysics model, Simulator of Particle Evolution, Composition, and Kinetics, (SPECK) to simulate cloud formation processes based on first principles. Our model successfully reproduced the complex, multi-layered cloud structure observed at Venus, showing good agreement with both the CARMA model results and in-situ observations conducted by the Pioneer Venus Large Probe. In Chapter 4 and 5, the initial stage of cloud formation is simulated using nucleation theory—the most fundamental approach to study the cloud origin and a substantial advancement over previous studies. In Chapter 4, we used SPECK to investigate the origin of the persistent lower haze on Venus. Our simulations revealed that the lower haze layer, observed below the main cloud deck, forms only when we include the cosmic dust influx. This result establishes cosmic material as an essential component of the Venus climate. In Chapter 5, We investigated the budget of cloud nuclei on Venus by simulating nucleation processes self-consistently. Our simulations showed that approximately 80% of the Venus clouds are sustained by the homogeneous nucleation of sulfur allotropes. Particles from the sub-cloud haze act as efficient condensation nuclei and contribute the remaining 20% to cloud formation, while the role of binary sulfuric acid nucleation is found to be negligible. Ultimately, this study provides a versatile modeling framework and foundational insights into photochemically-driven aerosol cycles, essential for interpreting future Venus mission data and understanding climates across terrestrial and giant planets in the universe.
- Affiliations
Citations
Karyu, H. (2026). Origins and life cycle of Venus’ clouds investigated with a high-accuracy cloud microphysics model. https://hdl.handle.net/2078.5/273258