Barotropic instability in the middle atmosphere of Venus by zonal-wind calculations based on the data of the Venera 15 IR Fourier spectrometer

Using the data on Venus' outgoing thermal radiation measured by the infrared (IR) Fourier spectrometer, which operated aboard the Venera 15 Automatic Interplanetary Station from October to December 1983 [1], the fields of zonal thermal wind were constructed [2]. In this work, latitude profiles of the wind velocity corresponding to the midlatitude jet altitude (about 70 km) were applied to model the barotropic instability. It was found that the duration of the phase periods lies in the range of 3 to 4 terrestrial days, while the growth time values are less than 20 days. The maximum contributions into the diurnal and nocturnal profiles are determined by modes n = 3 and n = 2, respectively. This can be considered as an argument in favor of the existence of barotropic instability in the middle atmosphere of Venus at altitudes of about 70 km.