Venus Cloud Morphology: Vertical Coupling and Temporal Evolution from Venus Express Multispectral Imaging

The atmosphere of Venus is entirely shrouded in a global, dense cloud deck with a vertical optical depth of 20–40 at visible wavelengths. This cloud system is the primary regulator of the planet’s radiative energy budget, a key driver of its extreme atmospheric super-rotation, and hosts an as-yet unknown ultraviolet (UV) absorber in its upper layer. While numerous studies  by early mission characterized the morphology of Venus’s cloud tops, the structural properties of deep cloud layers, their vertical coupling with the upper cloud system, and their connection to large-scale atmospheric dynamics remain poorly constrained. This critical knowledge gap limits a holistic understanding of the Venusian atmospheric system.

In this work we present a preliminary analysis of Venus cloud morphology using multi-band observations  by the European Space Agency (ESA) Venus Express mission. We employ a complementary dual-sounding approach to probe the vertical cloud structure.Daytime 0.35 μm UV images from the Venus Monitoring Camera (VMC) are used to map the spatial distribution of the unknown UV absorber at the cloud top (~65–70 km altitude), while nighttime observations in the 1.74 μm near-infrared (NIR) transparency window from the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) are used to characterize large scale morphology of the deep cloud (48-55 km altitude) and retrieve the total cloud opacity. Our analysis leverages full-orbit observations from the mission’s 24-hour polar orbit.

This work aims at revealing spatial coupling between morphology of the cloud-top UV features and deep cloud, clarify the polar vortex’s full-column vertical coherence, resolve the evolution of the global cloud morphology, and establish relation of the cloud morphology  to the atmospheric circulation to further quantify cloud regulation of radiative energy balance and constrain the properties of the unknown UV absorber.