Wind-Driven Oscillations in Meridional Overturning Circulations near the Equator. Part II: Idealized Simulations
Wind-Driven Oscillations in Meridional Overturning Circulations near the Equator. Part II: Idealized Simulations
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DOI：
10.1175/jpo-d-19-0297.1
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发表时间：
2021-03
影响因子：
3.5
通讯作者：
M. Bell;A. Blaker;J. Hirschi
中科院分区：
文献类型：
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作者：
M. Bell;A. Blaker;J. Hirschi
大振幅[±100 Sv (1 Sv≡106 m3 s−1)]，太平洋经向翻转环流在赤道10°范围内的高频振荡已经在NEMO海洋环流模式的积分中被发现。本文第一部分表明，这些振荡主要由周期接近4天和10天的两个频带所主导，它们是由赤道约10°内的风所驱动的。这部分表明，在水平均匀、稳定分层的静止状态下，小振幅的风力运动可以很好地模拟振荡。它的主要新颖之处在于，通过关注带状积分线性化方程，它提出了具有倾斜边边界的盆地运动的解。利用垂直正态模态和赤道经向模态表示柳井和惯性重力波，找到了解。太平洋前三个经向和垂直模态（总共9个模态）的16天时间序列片段的模拟捕获了从NEMO积分诊断出的匹配时间序列片段的85%至95%的方差。在全风力和全压力作用下驱动解，得到了最优的一致性。在大西洋和印度洋的相应模态也得到了类似的结果。由纬向风和气压驱动的准平稳解也可以很好地模拟MOC在相同经向和垂直模态中的较慢变化。
Large-amplitude [±100 Sv (1 Sv ≡ 106 m3 s−1)], high-frequency oscillations in the Pacific Ocean’s meridional overturning circulation within 10° of the equator have been found in integrations of the NEMO ocean general circulation model. Part I of this paper showed that these oscillations are dominated by two bands of frequencies with periods close to 4 and 10 days and that they are driven by the winds within about 10° of the equator. This part shows that the oscillations can be well simulated by small-amplitude, wind-driven motions on a horizontally uniform, stably stratified state of rest. Its main novelty is that, by focusing on the zonally integrated linearized equations, it presents solutions for the motions in a basin with sloping side boundaries. The solutions are found using vertical normal modes and equatorial meridional modes representing Yanai and inertia–gravity waves. Simulations of 16-day-long segments of the time series for the Pacific of each of the first three meridional and vertical modes (nine modes in all) capture between 85% and 95% of the variance of matching time series segments diagnosed from the NEMO integrations. The best agreement is obtained by driving the solutions with the full wind forcing and the full pressure forces on the bathymetry. Similar results are obtained for the corresponding modes in the Atlantic and Indian Oceans. Slower variations in the same meridional and vertical modes of the MOC are also shown to be well simulated by a quasi-stationary solution driven by zonal wind and pressure forces.