Superrotation is a dynamical regime where the atmosphere circulates around the planet in the direction of planetary rotation with excess angular momentum in the equatorial region. Superrotation is known to exist in the atmospheres of Venus, Titan, Jupiter, and Saturn in the solar system. Some of the exoplanets also exhibit superrotation. Our understanding of superrotation in a framework of circulation regimes of the atmospheres of terrestrial planets is in progress thanks to the development of numerical models; a global instability involving planetary-scale waves seems to play a key role, and the dynamical state depends on the Rossby number, a measure of the relative importance of the inertial and Coriolis forces, and the thermal inertia of the atmosphere. Recent general circulation models of Venus’s and Titan’s atmospheres demonstrated the importance of horizontal waves in the angular momentum transport in these atmospheres and also an additional contribution of thermal tides in Venus’s atmosphere. The atmospheres of Jupiter and Saturn also exhibit strong superrotation. Recent gravity data suggests that these superrotational flows extend deep into the planet, yet currently no single mechanism has been identified as driving this superrotation. Moreover, atmospheric circulation models of tidally locked, strongly irradiated exoplanets have long predicted the existence of equatorial superrotation in their atmospheres, which has been attributed to the result of the strong day-night thermal forcing. As predicted, recent Doppler observations and infrared phase curves of hot Jupiters appear to confirm the presence of superrotation on these objects.

中文翻译：

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行星大气中的超自转

超自转是一种动力学状态，其中大气在赤道地区以行星自转的方向以过大的角动量在行星周围循环。众所周知，太阳系的金星、泰坦、木星和土星的大气中存在超自转。一些系外行星也表现出超自转。由于数值模型的发展，我们对类地行星大气环流体系框架中超自转的理解正在取得进展；涉及行星尺度波的全球不稳定性似乎起着关键作用，动态状态取决于罗斯比数，这是惯性力和科里奥利力的相对重要性的度量，以及大气的热惯性。最近的金星和泰坦大气环流模型证明了水平波在这些大气中角动量传输中的重要性，以及金星大气中热潮汐的额外贡献。木星和土星的大气层也表现出强烈的超自转。最近的重力数据表明，这些超自转流延伸到地球深处，但目前还没有发现单一的机制来驱动这种超自转。此外，潮汐锁定、强辐射系外行星的大气环流模型长期以来一直预测其大气中存在赤道超自转，这归因于强烈的昼夜热强迫的结果。正如预测的那样，