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木星大红斑和纬向风作为一种自洽的单层准地转流。

Jupiter's Great Red Spot and zonal winds as a self-consistent, one-layer, quasigeostrophic flow.

作者信息

Marcus Philip S., Lee Changhoon

机构信息

Department of Mechanical Engineering, University of California at Berkeley, Berkeley, California 94720.

出版信息

Chaos. 1994 Jun;4(2):269-286. doi: 10.1063/1.166007.

Abstract

We present the point of view that both the vortices and the east-west zonal winds of Jupiter are confined to the planet's shallow weather layer and that their dynamics is completely described by the weakly dissipated, weakly forced quasigeostrophic (QG) equation. The weather layer is the region just below the tropopause and contains the visible clouds. The forcing mimics the overshoot of fluid from an underlying convection zone. The late-time solutions of the weakly forced and dissipated QG equations appear to be a small subset of the unforced and undissipated equations and are robust attractors. We illustrate QG vortex dynamics and attempt to explain the important features of Jupiter's Great Red Spot and other vortices: their shapes, locations with respect to the extrema of the east-west winds, stagnation points, numbers as a function of latitude, mergers, break-ups, cloud morphologies, internal distributions of vorticity, and signs of rotation with respect to both the planet's rotation and the shear of their surrounding east-west winds. Initial-value calculations in which the weather layer starts at rest produce oscillatory east-west winds. Like the Jovian winds, the winds are east-west asymmetric and have Karman vortex streets located only at the west-going jets. From numerical calculations we present an empirically derived energy criterion that determines whether QG vortices survive in oscillatory zonal flows with nonzero potential vorticity gradients. We show that a recent proof that claims that all QG vortices decay when embedded in oscillatory zonal flows is too restrictive in its assumptions. We show that the asymmetries in the cloud morphologies and numbers of cyclones and anticyclones can be accounted for by a QG model of the Jovian atmosphere, and we compare the QG model with competing models.

摘要

我们提出这样一种观点

木星的涡旋和东西向纬向风都局限于该行星的浅薄天气层,并且它们的动力学完全由弱耗散、弱强迫的准地转(QG)方程描述。天气层位于对流层顶下方的区域,包含可见云层。强迫作用模拟了来自下层对流区的流体过冲。弱强迫和耗散的QG方程的后期解似乎是无强迫和无耗散方程的一个小子集,并且是稳健的吸引子。我们阐述了QG涡旋动力学,并试图解释木星大红斑和其他涡旋的重要特征:它们的形状、相对于东西风极值的位置、停滞点、作为纬度函数的数量、合并、分裂、云形态、涡度的内部分布以及相对于行星自转和其周围东西风切变的旋转方向。天气层初始静止的初值计算产生振荡的东西向风。与木星风一样,这些风在东西方向上不对称,并且只有在向西的急流处存在卡门涡街。通过数值计算,我们给出了一个根据经验得出的能量准则,该准则可确定QG涡旋在具有非零位势涡度梯度的振荡纬向流中是否能够存活。我们表明,最近一个声称所有QG涡旋在嵌入振荡纬向流时都会衰减的证明,在其假设方面过于严格。我们表明,云形态以及气旋和反气旋数量的不对称性可以由木星大气的QG模型来解释,并且我们将QG模型与其他竞争模型进行了比较。

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