Zonal wind in the middle atmosphere of Venus

The zonal circulation in the atmosphere of Venus is investigated. As a result of reprocessing the infrared Fourier spectrometry data aboard the Venera-15 spacecraft, three-dimensional fields of the thermal wind are obtained in the coordinates latitude-altitude-solar longitude. A midlatitude jet located near the upper boundary of clouds is the main feature of the thermal wind fields. It is shown that the wind velocity in the jet is variable with time. These variations are solar-related and can be represented by superposition of cosines with periods of 1, 1/2, 1/3, and 1/4 of a Venusian day. The semidiurnal mode of the thermal tide has the highest amplitude. In the midlatitude jet, the wind velocity reaches its maximum value of 115 m/s at about 9 a.m in the second symmetrical maximum, at 9 p.m., the wind velocity is 7-10 m/s lower. A minimum velocity of 90 m/s is observed in the afternoon. On the night side, the wind velocity is systematically lower than on the dayside (by about 10 m/s). Along with changing wind velocity, the midlatitude jet changes its position: latitude (from 45 degrees to 65 degrees) and altitude (from 70 to 65 km). A con elation between the velocity of wind in the midlatitude jet and the jet position was discovered, which is indicative of the angular momentum and flux being conserved when the jet changes its position. In a single observation for the southern hemisphere, a low-latitude jet was discovered. It is observed at a latitude of 10 degrees and altitude of about 80 km, more than 10 km higher than the upper boundary of the clouds with a maximum wind velocity of about 160 m/s.