Modification of Parametric Subharmonic Instability in the Presence of Background Geostrophic Currents
Modification of Parametric Subharmonic Instability in the Presence of Background Geostrophic Currents
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DOI：
10.1029/2018gl080183
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发表时间：
2018-12
影响因子：
5.2
通讯作者：
Wei Yang;T. Hibiya;Yuki Tanaka;Liang Zhao;Hao Wei
中科院分区：
文献类型：
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作者：
Wei Yang;T. Hibiya;Yuki Tanaka;Liang Zhao;Hao Wei
尽管人们已经进行了各种数值试验来研究与参数亚谐不稳定（PSI）相关的内潮能量的级联，但大多数试验都假设理想的海洋情况，忽略了背景相对涡度的存在。在这里，我们表明，第一次，的存在下，可以显着修改PSI的行为，通过改变当地的有效科里奥利频率（feff=f+ feff 2）。一组25.4°N的数值实验表明，当正向相移feff接近M1临界频率（ω = ωM1）时，PSI效率显著增加。此外，对31°N（M1临界纬度的极向）的数值试验表明，当负的ψ足够低时，PSI的能量传输是可能的。所提出的结果提供了重要的意义，了解在海洋中的背景地转流盛行的diapycnal混合的空间分布。
Although various numerical experiments have been carried out to investigate the cascade of internal tide energy associated with parametric subharmonic instability (PSI), most of them assume idealized oceanic situations, ignoring the existence of background relative vorticity (ζ). Here we show, for the first time, that the existence of ζ can significantly modify the behavior of PSI by changing the local effective Coriolis frequency ( feff=f+ζ2 ). A set of numerical experiments for 25.4°N show that the PSI efficiency significantly increases at the position where positive ζ shifts feff close to the M1 critical frequency (ω = ωM1). Furthermore, numerical experiments for 31°N, poleward of the M1 critical latitude, show that significant PSI energy transfer is possible when negative ζ is low enough. The presented results provide important implications for understanding the spatial distribution of diapycnal mixing in the ocean where background geostrophic currents prevail.