Superrotation in Planetary Atmospheres
Superrotation in Planetary Atmospheres
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DOI：
10.1007/s11214-020-00703-9
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发表时间：
2020-07
影响因子：
10.3
通讯作者：
T. Imamura;Jonathan L. Mitchell;S. Lebonnois;Y. Kaspi;A. Showman;O. Korablev
中科院分区：
文献类型：
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作者：
T. Imamura;Jonathan L. Mitchell;S. Lebonnois;Y. Kaspi;A. Showman;O. Korablev
超自转是大气在赤道地区以过量的角动量沿行星自转方向绕行星运行的一种动力学状态。在太阳系中，金星、土卫六、木星和土星的大气层中都存在超自转现象。一些系外行星也表现出超旋转。由于数值模式的发展，我们在类地行星大气环流制度框架下对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，而动力学状态取决于罗斯比数，一种衡量惯性和科里奥利力相对重要性的方法，以及大气的热惯性。最近的金星和土卫六大气环流模型证明了水平波在这些大气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，这些超旋转流延伸到地球深处，但目前还没有确定驱动这种超旋转的单一机制。此外，潮汐锁定的强辐射系外行星的大气环流模式早就预测了其大气中存在赤道超旋转，这被归因于强烈的昼夜热强迫的结果。正如预测的那样，最近的多普勒观测和热木星的红外相位曲线似乎证实了这些物体上超旋转的存在。
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.