Venus – wind speed and rotation

This graph shows the variation of the wind speed (east-west component) with Venusian latitude, and its period of rotation.
The wind speeds are calculated by digitally tracking cloud features observed by the Venus Monitoring Camera (VMC) on board ESA’s Venus Express in the ultraviolet (at 365 nanometres). The observations used to obtain these results were performed during the period from 9 to 13 January 2007, (blue and green curves). Negative wind speed implies that the clouds move in the counter clockwise direction as observed from the south pole.

The blue curve was calculated using the average of speeds between 11:00 and 13:00 Local Solar Time, whereas the red curve includes all local times measured (9:00 - 15:00).

Two independent visual tracking estimates were obtained at latitudes between approximately 10º north and 45º south. But at higher latitudes the contrast in the ultraviolet images is reduced and yields far fewer targets for visual tracking.

The wind speeds are nearly constant at 90-100 m/s in low latitudes (lower than 40º south), in agreement with earlier measurements. Above 40º south, towards the south pole, the wind speeds quickly decrease.