A three-dimensional view of Venus thermal tides from radio occultations

Thermal tides dominate the dynamics of Venus’ middle atmosphere and are believed to play a major role in maintaining atmospheric superrotation. However, their global three-dimensional structure and associated circulation remain only partially constrained observationally. Previous studies have primarily characterized either temperature variability from radio occultations or horizontal winds near the cloud tops from cloud tracking, leaving the vertical coupling between thermal structure and atmospheric dynamics only partially resolved.

Here we analyze more than 1,000 radio-occultation profiles from Venus Express (2006–2014) and Akatsuki (2016–2024), spanning latitudes from 90°S to 90°N and altitudes between 40 and 95 km. Using the combined dataset, we reconstruct the temperature field as a function of latitude, altitude, and local solar time, and decompose it into diurnal and semidiurnal tidal components.

The reconstructed temperature field reveals a clear latitudinal transition in the dominant tidal regime: semidiurnal tides dominate at low latitudes, while diurnal tides become increasingly important toward mid and high latitudes. Vertical phase tilts indicate vertically propagating modes originating near the cloud region, consistent with thermal excitation within the main solar-heating layer.

Building on the observed thermal structure, we derive the associated three-dimensional tidal circulation using a dynamically consistent inversion based on the linearized momentum, continuity, and thermodynamic equations in the cyclostrophic regime. The diagnosed wind field reveals coherent zonal, meridional, and vertical tidal circulations. Zonal wind perturbations reach amplitudes of ~10–15 m/s, while vertical velocities are of order 0.1 m/s. Comparison with wind measurements near the cloud tops shows good agreement in both magnitude and large-scale structure.

These results provide a unified observational view of Venus thermal tides and new constraints on vertical coupling, wave propagation, and the dynamical structure of the Venusian atmosphere.