Stationary Features at the Cloud Top of Venus Observed by Ultraviolet Imager Onboard Akatsuki

Abstract

AbstractStationary features indicative of topographic gravity waves were identified at the cloud top of Venus with the 283‐nm channel of the Ultraviolet Imager (UVI) onboard Akatsuki, and their geographical and local time dependences were studied. At this wavelength the absorption by SO2 dominates. To extract stationary structures with respect to the surface, we averaged multiple images to smooth out moving features and applied high‐pass filtering to emphasize small structures. We found that stationary features appear exclusively above highlands and that they tend to appear between noon and evening. The stationary features seem to be synchronized with those observed in the cloud top temperature maps taken by the Longwave Infrared Camera (LIR). It was shown using a gravity wave model that the scale height of SO2 should be smaller than that of the cloud around the cloud top to reproduce the observed phase relationship between the stationary features seen in the Ultraviolet Imager and Longwave Infrared Camera images.