arXivDaily arXiv每日学术速递 周一至周五更新
arXiv周末暂无论文更新,休息一下吧,周末愉快~~
arXiv 2004.08414astro-ph.EPphysics.ao-ph
收藏

全球超自转对行星自转速率的依赖性

The dependence of global super-rotation on planetary rotation rate

Neil T. Lewis, Greg J. Colyer, Peter L. Read

摘要:

如果一个大气层的总纬向角动量超过了与下面的行星固体共同旋转的角动量,那么它就可以被描述为全球超旋转的。本文讨论了地球大气中的全球超自转对行星自转速率的依赖性。这种依赖性是通过分析全球超旋转的理想化的大气环流模式实验与时间无关的轴对称强迫,相比,全球超旋转的估计在太阳系大气。轴对称和三维实验进行。我们发现,三维实验中的整体超旋转程度与轴对称实验中的整体超旋转程度密切相关,只是在细节上有所不同。本文从Held-Hou模型出发,导出了轴对称大气中全球超旋转的标度理论。在高旋转速率,我们的数值实验居住的制度,全球超旋转尺度地转,我们认为,地球和火星占据这一制度。在低旋转速率下,我们的实验占据了由角动量守恒决定的区域,其中全局超旋转与旋转速率无关。在我们的实验中,全球超旋转的饱和值显着低于金星和泰坦大气层中达到的饱和值,而金星和泰坦大气层则占据了全球超旋转循环的制度。这种制度只能访问时,涡流引起的向上梯度角动量传输是足够大的,这是不是在我们理想化的数值实验的情况下。我们认为,一个缓慢旋转的行星的“默认”制度是角动量守恒制度,其特点是温和的全球(和本地)超旋转。

英文摘要:

An atmosphere may be described as globally super-rotating if its total zonal angular momentum exceeds that associated with solid-body co-rotation with the underlying planet. In this paper, we discuss the dependence of global super-rotation in terrestrial atmospheres on planetary rotation rate. This dependence is revealed through analysis of global super-rotation in idealised General Circulation Model experiments with time-independent axisymmetric forcing, compared with estimates for global super-rotation in Solar System atmospheres. Axisymmetric and three-dimensional experiments are conducted. We find that the degree of global super-rotation in the three-dimensional experiments is closely related to that of the axisymmetric experiments, with some differences in detail. A scaling theory for global super-rotation in an axisymmetric atmosphere is derived from the Held-Hou model. At high rotation rate, our numerical experiments inhabit a regime where global super-rotation scales geostrophically, and we suggest that the Earth and Mars occupy this regime. At low rotation rate, our experiments occupy a regime determined by angular momentum conservation, where global super-rotation is independent of rotation rate. Global super-rotation in our experiments saturates at a value significantly lower than that achieved in the atmospheres of Venus and Titan, which instead occupy a regime where global super-rotation scales cyclostrophically. This regime can only be accessed when eddy induced up-gradient angular momentum transport is sufficiently large, which is not the case in our idealised numerical experiments. We suggest that the 'default' regime for a slowly rotating planet is the angular momentum conserving regime, characterised by mild global (and local) superrotation.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑