A Fast, Semi-analytical Model for the Venusian Binary Cloud System

TL;DR

This paper introduces a rapid semi-analytical model for Venusian clouds, capturing vapor and cloud distributions efficiently, enabling extensive parameter exploration and potential coupling with climate and chemistry models.

Contribution

The authors develop a semi-analytical model that significantly accelerates the simulation of Venusian cloud systems compared to microphysical approaches, facilitating large-scale parameter studies.

Findings

The model predicts strong supersaturation of H₂SO₄ vapor above 60 km.

Cloud mass loading responds oppositely in upper and lower clouds to vapor ratios.

Water vapor transport affects cloud acidity across all layers.

Abstract

The Venusian clouds originate from the binary condensation of H$_{2}$SO$_{4}$ and H$_{2}$O. The two components strongly interact with each other via chemistry and cloud formation. Previous works adopted sophisticated microphysical approaches to understand the clouds. Here we show that the observed vapor and cloud distributions on Venus can be well explained by a semi-analytical model. Our model assumes local thermodynamical equilibrium for water vapor but not for sulfuric acid vapor, and includes the feedback of cloud condensation and acidity to vapor distributions. The model predicts strong supersaturation of the H$_{2}$SO$_{4}$ vapor above 60 km, consistent with our recent cloud condensation model. The semi-analytical model is 100 times faster than the condensation model and 1000 times faster than the microphysical models. This allows us to quickly explore a large parameter space of the sulfuric acid gas-cloud system. We found that the cloud mass loading in the upper clouds has an opposite response of that in the lower clouds to the vapor mixing ratios in the lower atmosphere. The transport of water vapor influences the cloud acidity in all cloud layers while the transport of sulfuric acid vapor only dominates in the lower clouds. This cloud model is fast enough to be coupled with the climate models and chemistry models to understand the cloudy atmospheres of Venus and Venus-like extra-solar planets.