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首页> 外文期刊>Journal of Physical Oceanography >Annual and Semiannual Cycle of Equatorial Atlantic Circulation Associated with Basin-Mode Resonance
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Annual and Semiannual Cycle of Equatorial Atlantic Circulation Associated with Basin-Mode Resonance

机译：与盆地模式共振相关的赤道大西洋环流的年度和半年周期

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摘要

Seasonal variability of the tropical Atlantic circulation is dominated by the annual cycle, but semiannual variability is also pronounced, despite weak forcing at that period. This study uses multiyear, full-depth velocity measurements from the central equatorial Atlantic to analyze the vertical structure of annual and semiannual variations of zonal velocity. A baroclinic modal decomposition finds that the annual cycle is dominated by the fourth mode and the semiannual cycle is dominated by the second mode. Similar local behavior is found in a high-resolution general circulation model. This simulation reveals that the annual and semiannual cycles of the respective dominant baroclinic modes are associated with characteristic basinwide structures. Using an idealized, linear, reduced-gravity model to simulate the dynamics of individual baroclinic modes, it is shown that the observed circulation variability can be explained by resonant equatorial basin modes. Corollary simulations of the reduced-gravity model with varying basin geometry (i.e., square basin vs realistic coastlines) or forcing (i.e., spatially uniform vs spatially variable wind) show a structural robustness of the simulated basin modes. A main focus of this study is the seasonal variability of the Equatorial Undercurrent (EUC) as identified in recent observational studies. Main characteristics of the observed EUC including seasonal variability of transport, core depth, and maximum core velocity can be explained by the linear superposition of the dominant equatorial basin modes as obtained from the reduced-gravity model.
机译：热带大西洋环流的季节变化主要由年度周期决定，但尽管在那个时期强迫较小，但半年变化也很明显。这项研究使用了来自赤道中部大西洋的多年，全深度速度测量数据，分析了纬向速度年度和半年度变化的垂直结构。斜压模态分解发现年周期由第四种模式主导，而半年周期则由第二种模式主导。在高分辨率的一般循环模型中发现了类似的局部行为。该模拟表明，各个主要斜压模式的年度和半年周期与典型的盆地范围结构有关。使用理想的线性降重力模型来模拟各个斜压模式的动力学，结果表明，观测到的环流变化可以用赤道盆地共模共振来解释。具有不同盆地几何形状（即方形盆地与现实海岸线）或强迫（即空间均匀与空间可变风）的重力降低模型的推论模拟显示了模拟盆地模式的结构稳健性。这项研究的主要重点是最近的观测研究确定的赤道暗流（EUC）的季节性变化。观测到的EUC的主要特征包括运输的季节性变化，岩心深度和最大岩心速度，这可以通过从重力减少模型获得的主要赤道盆地模式的线性叠加来解释。

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    《Journal of Physical Oceanography》 |2016年第10期|3011-3029|共19页
  • 作者

    Brandt Peter; Claus Martin; Greatbatch Richard J.; Kopte Robert; Toole John M.; Johns William E.; Boening Claus W.;

  • 作者单位

    GEOMAR Helmholtz Zentrum Ozeanforsch Kiel, Dusternbrooker Weg 20, D-24105 Kiel, Germany|Univ Kiel, Kiel, Germany;

    GEOMAR Helmholtz Zentrum Ozeanforsch Kiel, Dusternbrooker Weg 20, D-24105 Kiel, Germany;

    GEOMAR Helmholtz Zentrum Ozeanforsch Kiel, Dusternbrooker Weg 20, D-24105 Kiel, Germany|Univ Kiel, Kiel, Germany;

    GEOMAR Helmholtz Zentrum Ozeanforsch Kiel, Dusternbrooker Weg 20, D-24105 Kiel, Germany;

    Woods Hole Oceanog Inst, Woods Hole, MA 02543 USA;

    Univ Miami, Rosenstiel Sch Marine & Atmospher Sci Meteorol &, Miami, FL USA;

    GEOMAR Helmholtz Zentrum Ozeanforsch Kiel, Dusternbrooker Weg 20, D-24105 Kiel, Germany|Univ Kiel, Kiel, Germany;

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