Can zonally symmetric inertial waves drive an oscillating zonal mean flow?
Can zonally symmetric inertial waves drive an oscillating zonal mean flow?
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DOI：
10.1080/03091929.2015.1094064
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发表时间：
2015-10
影响因子：
1.3
通讯作者：
T. Seelig;U. Harlander
中科院分区：
文献类型：
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作者：
T. Seelig;U. Harlander
本文研究了赤道大气中惯性波对纬向平均气流的激发，并类比于重力波对纬向平均气流的激发，重力波对纬向平均气流的激发在赤道大气准两年振荡中起着重要作用。在分层旋转的地球物理流中，纯重力波和惯性波对应于两种极限情况：重力波忽略旋转，惯性波忽略分层。前者与大气层等流体更相关，其中分层占主导地位，后者与深海或行星核心更相关，其中旋转占主导地位。在本研究中，一个层次的简单的分析和数值模式的纬向对称的惯性波平均流相互作用被认为是从实验室实验的数据和结果进行了比较。主要的发现可以总结如下：（i）当波浪与平均流解耦时，它们只是驱动一个逆行（向东）纬向平均气流，与纬向相速度的符号无关;（ii）当耦合存在且纬向平均流被假定为稳定时，波可以驱动垂直交替的射流，但是，与重力波情况相反，该结构是独立的符号的纬向相速度;（iii）当耦合存在和时间依赖的纬向平均流被认为是波可以驱动垂直和暂时振荡的平均流。与实验室数据的比较，从旋转环实验表明定性协议。看来，实验捕捉到的惯性波平均流耦合的基本要素。结果可能是相关的，以了解如何赤道深喷流可以保持对耗散，目前讨论的过程有争议。
In the present paper zonal mean flow excitation by inertial waves is studied in analogy to mean flow excitation by gravity waves that plays an important role for the quasi-biennial oscillation in the equatorial atmosphere. In geophysical flows that are stratified and rotating, pure gravity and inertial waves correspond to the two limiting cases: gravity waves neglect rotation, inertial waves neglect stratification. The former are more relevant for fluids like the atmosphere, where stratification is dominant, the latter for the deep oceans or planet cores, where rotation dominates. In the present study a hierarchy of simple analytical and numerical models of zonally symmetric inertial wave-mean flow interactions is considered and the results are compared with data from a laboratory experiment. The main findings can be summarised as follows: (i) when the waves are decoupled from the mean flow they just drive a retrograde (eastward) zonal mean flow, independent of the sign of the meridional phase speed; (ii) when coupling is present and the zonal mean flow is assumed to be steady, the waves can drive vertically alternating jets, but still, in contrast to the gravity wave case, the structure is independent of the sign of the meridional phase speed; (iii) when coupling is present and time-dependent zonal mean flows are considered the waves can drive vertically and temporarily oscillating mean flows. The comparison with laboratory data from a rotating annulus experiment shows a qualitative agreement. It appears that the experiment captures the basic elements of the inertial wave mean flow coupling. The results might be relevant to understand how the Equatorial Deep Jets can be maintained against dissipation, a process currently discussed controversially.