The latitudinal and vertical structure of Venus’ thermal tides as inferred from radio occultations

Thermal tides dominate Venus’ middle atmosphere, exhibiting a semidiurnal signature at low latitudes and a diurnal one at mid-to-high latitudes. However, their full three-dimensional structure and dynamical influence remain only partially characterized. Past studies have primarily relied on cloud-level temperatures from radio occultation and horizontal winds from cloud tracking. Recent analyses of Akatsuki radio-occultation profiles at low latitudes revealed both upward and downward propagation of the semidiurnal component, pointing to an excitation region within the cloud deck (50–65 km). It remains unclear whether this mechanism extends to higher latitudes or how it couples to the broader three-dimensional flow.

Here, we present a new analysis of over 1,000 radio-occultation soundings from Akatsuki (2016–2024) and Venus Express (2006–2014), spanning 90°S to 90°N and altitudes from 40 to 95 km. This combined dataset enables a detailed reconstruction of Venus' thermal structure across the solar day cycle, capturing the transition from semidiurnal to diurnal tides, their evolving vertical propagation, and how the altitude of peak tidal signatures varies with latitude. We also derive the zonal flow field via cyclostrophic balance, both in the time-mean state and over the solar day. Compared with cloud-level measurements, our results provide new insight into the tidal modulation of zonal winds and associated energy transport.