Small-scale gravity waves in the Venus Atmosphere as seen by Radio Occultation Experiments

Waves of varying scales permeate the atmosphere of Venus, spanning a wide range of spatial dimensions and potentially playing a major role in the planet’s energy and momentum balance. Among these phenomena, small-scale temperature fluctuations—commonly attributed to gravity waves—are a ubiquitous feature of planetary atmospheres throughout the Solar System. Gravity waves are particularly important because they redistribute energy and momentum between atmospheric layers. Although such waves have been observed in the mesosphere and upper cloud deck of Venus, their precise contribution to maintaining the planet’s characteristic atmospheric superrotation remains unclear.

Between 2006 and 2014, the Venus Express mission conducted the Radio Science Experiment (VeRa) to investigate Venus’s neutral atmosphere and ionosphere using Earth occultation measurements. During these observations, radio signals transmitted at two coherent frequencies—X-band (8.4 GHz) and S-band (2.3 GHz)—passed behind the planet relative to Earth. The resulting measurements provided radial profiles of neutral particle density over an altitude range of approximately 40–90 km. Assuming hydrostatic equilibrium, these density profiles were subsequently used to derive vertical temperature and pressure profiles. In addition, reprocessed data from the Pioneer Venus Orbiter will be incorporated to extend the dataset.

The atmospheric profiles obtained from VeRa reveal substantial variability in the upper troposphere and mesosphere, reflecting the combined influence of atmospheric waves and turbulence. Importantly, VeRa possesses sufficient vertical resolution to detect fine-scale temperature perturbations associated with internal gravity waves, characterized by vertical wavelengths of only a few kilometers.

The high vertical resolution of the VeRa temperature measurements enables the investigation of subtle atmospheric fluctuations, which are crucial for improving our understanding of Venus’s still poorly constrained energy and momentum budgets.

To better characterize the observed wave structures, we apply standard gravity wave theory to analyze their vertical and horizontal properties as functions of latitude, altitude, and local time. Their relationship with thermal tides is also examined in order to assess the role of gravity waves in sustaining Venusian superrotation.