The Impact of Turbulent Vertical Mixing in the Venus Clouds on Chemical Tracers

TL;DR

This study uses a 3D convection-resolving model to quantify how turbulent vertical mixing in Venus's clouds influences chemical tracers like SO$_2$ and H$_2$O, revealing significant effects on their distribution.

Contribution

First application of a 3D convection-resolving model with passive tracers to study chemical mixing in Venus clouds, providing new insights into turbulent effects on atmospheric chemistry.

Findings

Vertical mixing is strong, with a relaxation timescale around 4 hours.

Turbulent activity causes spatial structures of several kilometers.

Vertical eddy diffusion estimates align with in-situ measurements but are higher than 1D models.

Abstract

Venus clouds host a convective layer between roughly 50 and 60 km that mixes heat, momentum, and chemical species. Observations and numerical modelling have helped to understand the complexity of this region. However, the impact on chemistry is still not known. Here, we use for the first time a three-dimensional convection-resolving model with passive tracers to mimic SO$_2$ and H$_2$O for two latitudinal cases. The tracers are relaxed towards a vertical profile in agreement with measured values, with a timescale varying over several orders of magnitude. The vertical mixing is quantified, it is strong for a relaxation timescale high in front of the convective timescale, around 4 hours. The spatial and temporal variability of the tracer due to the convective activity is estimated, with horizontal structures of several kilometres. At the Equator, the model is resolving a convective layer at the cloud top (70 km) suggested by some observations, the impact of such turbulent activity on chemical species is accounted for the first time. From the resolved convective plumes, a vertical eddy diffusion is estimated, consistent with past estimations from in-situ measurements, but several orders of magnitude higher than values used in 1D chemistry modelling. The results are compared to observations, with some spatial and temporal variability correlation, suggesting an impact of the convective layer on the chemical species.