Correlation of Venusian Mesoscale Cloud Morphology Between Images Acquired at Various Wavelengths

Abstract

AbstractThe differences and similarities in morphologies acquired across various wavelengths in simultaneously obtained Venus' dayside images may provide clues on cloud/atmospheric physics and chemistry. Here, we focus on spatial scales smaller than ∼600 km, where cell‐like or streaky features seem to dominate in ultraviolet images. Using images acquired at ultraviolet wavelengths of 283 nm, 365 nm, and infrared wavelengths of 0.90, 2.02, and 10 μm by the Venus orbiter Akatsuki, correlation coefficient maps between pairs of wavelengths, such as 2.02 μm/10 μm, 2.02 μm/283 nm, 2.02 μm/365 nm, 283 nm/365 nm, and 0.90 μm/2.02 μm were created. Our results show a clear negative correlation between images obtained at 2.02 μm (CO2 absorption) and 10 μm (cloud top temperature), meaning that elevated clouds are cooled by adiabatic expansion or the ambient air. A clear negative correlation was found between 2.02 μm and 283 nm (SO2 absorption), suggesting that SO2 is transported to the cloud top region during cloud ascent. We observed a clear positive correlation between images obtained at 283 and 365 nm (unknown absorber), implying a close relationship between the unknown absorber and SO2 or a non‐negligible contribution of the unknown absorber at 283 nm. We found a low correlation between images obtained at 0.90 μm (middle/lower cloud) and 2.02 μm, suggesting a weak vertical coupling in the clouds.