Stability Analysis of the Labrador Current
Stability Analysis of the Labrador Current
复制标题
拉布拉多海流的稳定性分析
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
L. Czeschel
中科院分区：
文献类型：
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作者：
Soeren Thomsen;C. Eden;L. Czeschel
系泊观测和模型模拟指出，拉布拉多电流（LC）在冬季的不稳定性，增强涡动动能（EKE）在2至5天之间的周期，和更少的EKE在其他季节。使用垂直剪切和分层模型的线性稳定性分析揭示了LC中三种主要的不稳定模式：
- 平衡的内部模式，沿流波长约为30-45 km，相速度为0.3 m/s，最大增长率为1 d−1，表面增强，但深度达到振幅，
- 平衡的浅模式，其沿流波长约为0.3-1.5 km，相速度和增长率约为3倍，但振幅仅限于混合层（ML），
- 和一个不平衡的对称模式，最大的增长率，消失的相速度和沿流结构，和非常小的横流波长，也局限于ML。
这两种平衡模态都类似于斜压不稳定，但在中等到小的理查森数Ri下运行，其增长率比Ri的准地转极限大得多。内部模式被认为是负责的LC在冬季的不稳定性。弱分层和增强的垂直切变，由于当地的浮力损失和对流水团从内部平流的结果在小Ri LC内，和3倍的增长率的内部模式相比，夏季和秋季的条件。浅模式和对称模式都没有解决的模型，但有人建议，他们也可能发挥重要作用的不稳定性，在LC和横向混合。
Mooring observations and model simulations point to an instability of the Labrador Current (LC) during winter, with enhanced eddy kinetic energy (EKE) at periods between 2 to 5 days, and much less EKE during other seasons. Linear stability analysis using vertical shear and stratification from the model reveals three dominant modes of instability in the LC:
- a balanced interior mode with along-flow wavelengths of about 30–45 km, phase velocities of 0.3 m/s, maximal growth rates of 1 d−1 and surface intensified, but deep reaching amplitudes,
- a balanced shallow mode with along-flow wavelengths of about 0.3–1.5 km, about three times larger phase speeds and growth rates, but amplitudes confined to the mixed layer (ML),
- and an unbalanced symmetric mode with largest growth rates, vanishing phase speeds and along-flow structure, and very small cross-flow wavelengths, also confined to the ML.
Both balanced modes are akin to baroclinic instability, but operate at moderate to small Richardson numbers Ri with much larger growth rates as for the quasi-geostrophic limit of Ri ≫ 1. The interior mode is found to be responsible for the instability of the LC during winter. Weak stratification and enhanced vertical shear due to local buoyancy loss and the advection of convective water masses from the interior result in small Ri within the LC, and to three times larger growth rates of the interior mode in March compared to summer and fall conditions. Both the shallow and the symmetric mode are not resolved by the model, but it is suggested that they might also play an important role for the instability in the LC and for lateral mixing.
在三维大气环流海洋模型中实现线性稳定性分析的扩散性
影响因子：
3.2
作者：
通讯作者：
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