Seasonal Transport Variations of the Kuroshio: An OGCM Simulation
Seasonal Transport Variations of the Kuroshio: An OGCM Simulation
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DOI：
10.1175/1520-0485(1997)027
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发表时间：
1997-03
影响因子：
3.5
通讯作者：
T. Kagimoto;T. Yamagata
中科院分区：
文献类型：
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作者：
T. Kagimoto;T. Yamagata
利用高分辨率海洋环流模式对黑潮输送的季节变化进行了数值模拟。模拟的黑潮流速廓线与ADCP观测和动力计算结果吻合得非常好。模型黑潮在南西群岛（琉球群岛）附近PN线上700 m处的输运年平均值约为25 Sv（Sv [ 106 m3 s21]），与根据长期水文观测估算的结果基本一致。模式的PN线输送变化也几乎与观测相同，输送在夏季表现出弱的最大值，在冬季表现出弱的最小值。虽然Sverdrup平衡在大范围的海盆内部是有效的，但由于黑潮回流的存在，它不能预测日本以南黑潮的变化和输送。Sverdrup理论和模型（观察，以及）之间的上述差异进行了详细研究，通过分析扭矩平衡。冬季黑潮通过PN线的输送量远小于Sverdrup理论的预测值，这是因为地形控制阻止了西边界流侵入南西群岛附近的大陆坡以西。斜压性和海底地形共同作用下的反气旋涡动活动使斜坡区的海流从冬季向夏季转变。冬季斜坡上的东北向深层海流在夏季被涡动活动抵消，从而大大减弱了陆坡与海流的相互作用。同样的涡动活动加强了黑潮的环流，使得夏季东海PN线黑潮输送增强。本研究表明，比较模型的结果与观测需要一个模型的分辨率，足以解决的观测位置，以及斜压洋流和海底地形之间的相互作用有关的基本动力学。
Numerical simulation is performed using a high-resolution ocean general circulation model to investigate seasonal variations of the Kuroshio transport. The simulated velocity profiles of the Kuroshio agree surprisingly well with ADCP observations and dynamic calculations. The annual mean of the model Kuroshio transport relative to 700 m across the PN line near the Nansei (Ryukyu) Islands is about 25 Sv (Sv [ 106 m3 s21), which is almost the same with the estimate based on the long-term hydrographic observations. The model transport variations across the PN line are also almost the same as the observation; the transport shows a weak maximum in summer and a weak minimum in winter. Although the Sverdrup balance is valid in the broad interior of the basin, it fails to predict the variations as well as the transport of the Kuroshio south of Japan due to existence of the Kuroshio recirculation. The above discrepancy between the Sverdrup theory and the model (observations, as well) is studied in detail by analyzing the torque balance. In winter the Kuroshio transport across the PN line is much smaller than expected from the Sverdrup theory because the topographic control prevents the western boundary current from intruding west of the continental slope near the Nansei Islands. The current over the slope region changes its direction from winter to summer due to anticyclonic eddy activity related to the joint effect of baroclinicity and bottom topography. The deep northeastward current over the slope in winter is canceled in summer by the eddy activity so that the interaction between the continental slope and the current is much reduced. Since the same eddy activity intensifies the Kuroshio recirculation, the Kuroshio transport across the PN line in the East China Sea is increased in summer. The present study demonstrates that comparing model results with observations requires a model resolution suitable enough to resolve locations of observations as well as essential dynamics related to the interaction between baroclinic ocean currents and bottom topography.