Although Venus is a terrestrial planet similar to Earth, its atmospheric circulation is much different and poorly characterized¹. Winds at the cloud top have been measured predominantly on the dayside. Prominent poleward drifts have been observed with dayside cloud tracking and interpreted to be caused by thermal tides and a Hadley circulation^2,3,4; however, the lack of nightside measurements over broad latitudes has prevented the unambiguous characterization of these components. Here we obtain cloud-tracked winds at all local times using thermal infrared images taken by the Venus orbiter Akatsuki, which is sensitive to an altitude of about 65 kilometres⁵. Prominent equatorward flows are found on the nightside, resulting in null meridional velocities when these are zonally averaged. The velocity structure of the thermal tides was determined without the influence of the Hadley circulation. The semidiurnal tide was found to have an amplitude large enough to contribute to the maintenance of the atmospheric superrotation. The weakness of the mean meridional flow at the cloud top implies that the poleward branch of the Hadley circulation exists above the cloud top and that the equatorward branch exists in the clouds. Our results should shed light on atmospheric superrotation in other celestial bodies.

尽管金星是与地球相似的类地行星，但它的大气环流却大不相同，特征也很差¹。云顶的风主要在白天测量。通过白天云跟踪观察到明显的极向漂移，并解释为由热潮和哈德利环流^2,3,4引起；然而，由于缺乏对大纬度的夜间测量，无法对这些组件进行明确的表征。在这里，我们使用金星轨道器 Akatsuki 拍摄的热红外图像获得了所有当地时间的云跟踪风，它对大约 65 公里的高度很敏感⁵. 在夜间发现了显着的赤道流向，当对这些流进行纬向平均时，导致经向速度为零。热潮的速度结构是在没有哈德利环流影响的情况下确定的。发现半日潮的幅度足以维持大气超自转。云顶平均经向流的弱点意味着哈德利环流的极向分支存在于云顶之上，而赤道分支存在于云中。我们的结果应该能够揭示其他天体的大气超自转。