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首页> 外文期刊>Journal of Physical Oceanography >Local and Equatorial Forcing of Seasonal Variations of the North Equatorial Countercurrent in the Atlantic Ocean
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Local and Equatorial Forcing of Seasonal Variations of the North Equatorial Countercurrent in the Atlantic Ocean

机译：大西洋北赤道逆流的季节和局部赤道强迫

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摘要

The seasonal variation of the North Equatorial Countercurrent (NECC) in the tropical Atlantic Ocean is investigated by using a linear, one-layer reduced-gravity ocean model and by analyzing sea surface height (SSH) data from Ocean Topography Experiment (TOPEX)/Poseidon (T/P) altimeters. The T/P data indicate that the seasonal variability of the NECC geostrophic transport, between 3° and 10°N, is dominated by SSH changes in the southern flank of the current. Since the southern boundary of the NECC is located partially within the equatorial waveguide, the SSH variation there can be influenced considerably by the equatorial dynamics. Therefore, it is hypothesized that the wind stress forcing along the equator is the leading driver for the seasonal cycle of the NECC transport. The wind stress curl in the NECC region is an important but smaller contributor. This hypothesis is tested by several sensitivity experiments that are designed to separate the two forcing mechanisms. In the first sensitivity run, a wind stress field that has a zero curl is used to force the ocean model. The result shows that the NECC geostrophic transport retains most of its seasonal variability. The same happens in another experiment in which the seasonal wind stress is applied only within a narrow band along the equator outside the NECC range. To further demonstrate the role of equatorial waves, another experiment was run in which the wind stress in the Southern Hemisphere is altered so that the model excludes hemispherically symmetrical waves (Kelvin waves and odd-numbered meridional modes of equatorial Rossby waves) and instead excites only the antisymmetrical equatorial Rossby modes. The circulation in the northern tropical ocean, including the NECC, is affected considerably even though the local wind stress there remains unchanged. All these appear to support the hypothesis presented in this paper.
机译：通过使用线性的单层降重力海洋模型并通过分析海洋地形实验（TOPEX）/波塞冬的海表高度（SSH）数据，研究了热带大西洋中北赤道逆流（NECC）的季节变化。 （T / P）高度表。 T / P数据表明，NECC地转运动在3°N和10°N之间的季节性变化主要受当前南翼SSH变化的影响。由于NECC的南边界部分位于赤道波导内，因此SSH的变化可能受到赤道动力学的影响。因此，假设沿着赤道的风应力是NECC输送季节周期的主要驱动力。 NECC区域中的风应力卷曲是一个重要但较小的贡献者。通过几个旨在分离这两种强迫机制的敏感性实验来检验该假设。在第一个灵敏度运行中，使用具有零卷曲的风应力场来强制海洋模型。结果表明，NECC地转运动保留了其大部分的季节变化性。在另一个实验中也是如此，在该实验中，仅在NECC范围外沿赤道的窄带内施加季节性风应力。为了进一步证明赤道波的作用，还进行了另一项实验，其中改变了南半球的风应力，因此该模型排除了半球对称波（开尔文波和赤道Rossby波的奇数子午模），而仅激发了反对称赤道Rossby模式。即使北部的海洋风压力保持不变，北部热带海洋（包括NECC）的环流也受到很大影响。所有这些似乎都支持本文提出的假设。

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