Planetary-scale waves are thought to play a role in powering the yet-unexplained atmospheric superrotation of Venus. Puzzlingly, while Kelvin, Rossby and stationary waves manifest at the upper clouds (65--70 km), no planetary-scale waves or stationary patterns have been reported in the intervening level of the lower clouds (48--55 km), although the latter are probably Lee waves. Using observations by the Akatsuki orbiter and ground-based telescopes, we show that the lower clouds follow a regular cycle punctuated between 30$^{circ}$N--40$^{circ}$S by a sharp discontinuity or disruption with potential implications to Venuss general circulation and thermal structure. This disruption exhibits a westward rotation period of $sim$4.9 days faster than winds at this level ($sim$6-day period), alters clouds properties and aerosols, and remains coherent during weeks. Past observations reveal its recurrent nature since at least 1983, and numerical simulations show that a nonlinear Kelvin wave reproduces many of its properties.
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