Mesoscale Stationary Features in the Dayside Clouds of Venus

Abstract We present new detections of mesoscale stationary features, which are interpreted as gravity waves, on the dayside clouds of Venus. These come from an analysis of images from two instruments onboard different spacecrafts: Visible and InfraRed Thermal Imaging Spectrometer—Mapper (VIRTIS‐M) on Venus Express (VEx) and IR2 on Akatsuki. For VIRTIS‐M we selected the period from the first extension of the mission (roughly from August 2007 to May 2009). The wavelength range selected was based on best viewing conditions to characterize waves, centered at 600 nm. For IR2 we surveyed the entire available data at 2.02 μm targeting the dayside hemisphere. Basic morphological properties of the detected features were retrieved, namely their horizontal wavelength, packet sizes and orientations. Our measurements show that the horizontal wavelengths of these features are between 100 and 500 km, their widths between 500 and 3,000 km, and mostly oriented so that the crests align with the local meridian. We also retrieve the background wind in the vicinity of the detected structures to then calculate the vertical wavelength. The inclusion of the vertical wind shear of the zonal wind at the altitudes where these waves are observed proved significant in these calculations. For the features from Akatsuki data, we find values in good agreement with previous works however, for VIRTIS‐M their dimensions appear slightly reduced. This works aims to expand the current knowledge of the distribution of stationary waves with further applications to understand dynamical connections between the surface and the cloud layer in Venus' atmosphere.