Characterising atmospheric gravity waves on the nightside lower clouds of Venus: a systematic analysis

TL;DR

This study systematically detects and characterizes atmospheric gravity waves on Venus's nightside lower clouds using multi-mission imaging data, revealing their properties and expanding understanding of Venusian atmospheric dynamics.

Contribution

It provides a comprehensive analysis of mesoscale waves on Venus's lower clouds, utilizing data from two space missions over multiple years, and offers new insights into their properties and variability.

Findings

Detected nearly 300 wave packets across 5500 images.

Waves are larger in scale than those in the upper cloud.

Results are consistent with and extend previous observations.

Abstract

We present the detection and characterisation of mesoscale waves on the lower clouds of Venus using images from the Visible Infrared Thermal Imaging Spectrometer onboard the European Venus Express space mission and from the 2 $\mu$m camera (IR2) instrument onboard the Japanese space mission Akatsuki. We used image navigation and processing techniques based on contrast enhancement and geometrical projections to characterise morphological properties of the detected waves, such as horizontal wavelength and the relative optical thickness drop between crests and troughs. Additionally, we performed phase velocity and trajectory tracking of wave packets. We combined these observations to derive other properties of the waves such as the vertical wavelength of detected packets. Our observations include 13 months of data from August 2007 to October 2008, and the entire available data set of IR2 from January to November 2016.We characterised almost 300 wave packets across more than 5500 images over a broad region of the globe of Venus. Our results show a wide range of properties and are not only consistent with previous observations but also expand upon them, taking advantage of two instruments that target the same cloud layer of Venus across multiple periods. In general, waves observed on the nightside lower cloud are of a larger scale than the gravity waves reported in the upper cloud. This paper is intended to provide a more in-depth view of atmospheric gravity waves on the lower cloud and enable follow-up works on their influence in the general circulation of Venus.