Cyclostrophic winds from the Visible and Infrared Thermal Imaging Spectrometer temperature sounding: A preliminary analysis

Abstract

Visible and Infrared Thermal Imaging Spectrometer (VIRTIS) onboard the Venus Express spacecraft has been operating since April 2006 providing new observations of the temperature structure of Venus mesosphere (60–95 km). Zonal winds in the middle atmosphere of Venus have been retrieved from VIRTIS temperature profiles using the cyclostrophic approximation. The wind field is characterized by three main features: (1) a midlatitude jet connected to the thermal feature known as the cold collar; the jet reaches a maximum speed of 80–90 ± 10 m/s near the cloud top (∼70 km altitude) at 50°S latitude; (2) a strong decrease of wind from 60°S toward the pole reaching zero velocity at ∼70°S; and (3) the decrease of the wind above the jet with increasing altitude. Local time dependence of the temperature and wind field has been analyzed. Temperatures show at cloud tops a cooling of ∼15 K during the night which propagates also on the zonal wind field. Comparison with cloud‐tracked winds from Venus Monitoring Camera images indicates a first‐order agreement.