Planetary Wave Response to Surface Forcing and Instability in the Presence of Mean Flow and Topography
Planetary Wave Response to Surface Forcing and Instability in the Presence of Mean Flow and Topography
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DOI：
10.1175/jpo3055.1
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发表时间：
2007-05
影响因子：
3.5
通讯作者：
P. Killworth;J. Blundell
中科院分区：
文献类型：
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作者：
P. Killworth;J. Blundell
缓慢变化的平均流量，分层和地形的海洋的本地响应的两个来源的干扰进行检查，集中在所产生的表面高程是否是可观察的。第一个是海洋对表面强迫（Ekman抽水或浮力强迫）的反应。对于随机强迫的典型振幅，虽然大部分海洋响应很小（表面高程小于1毫米），但有足够的近共振（或涉及临界层的伪共振）在大部分海洋中产生1厘米或更高的高程。第二个来源是斜压不稳定。最快的线性增长率，以及那些特定的波长，计算全局。几乎所有的海洋都是斜压不稳定的，最不稳定的波被发现具有小的波长（通常小于10 km），扰动集中在表面附近：e-折叠时间O（20天）经常被发现。然而，扰动的相速度几乎到处都比平均气流和地形的自由行星波向西慢。由于自由波的传播速度与观测结果相似，不稳定性可能是变化的一个很好的来源，但可能不是观测到的波传播的直接原因。
The local response of an ocean with slowly varying mean flow, stratification, and topography to two sources of disturbance is examined, concentrating on whether the resulting surface elevations are observable. The first is the ocean response to surface forcing (Ekman pumping or buoyancy forcing). For typical amplitudes of random forcing, while much of the ocean response is small (surface elevations less than 1 mm), there are sufficient near resonances (or pseudoresonances involving a critical layer) to produce elevations of 1 cm or more in much of the ocean. The second source is baroclinic instability. The fastest linear growth rate, as well as those for specific wavelengths, is computed globally. Almost all of the ocean is baroclinically unstable, and the most unstable waves are found to possess a small wavelength (often less than 10 km) with a disturbance concentrated near the surface: e-folding times O(20 days) are frequently found. However, the phase speed for the disturbances is almost everywhere slower westward than free planetary waves with mean flow and topography. Since the free waves propagate at speeds similar to observations, instability may be a good source of variability but is probably not responsible directly for observed wave propagation.