Pressure gradient across the Luzon Strait, or depth-integrated dynamic height difference (DHD) between its northern end at the continental slope southwest of Taiwan and its southern end at the continental slope northwest of Luzon, is commonly regarded as the most direct dynamics of the intrusion of waters from the Pacific into the South China Sea through the Luzon Strait. Such a positive DHD is determined by seasonal occurrence of a meso-scale cyclonic cold eddy off west Luzon (Luzon cold eddy, LCE), and a positive wind stress curl (WSC) over the LCE active area or direct Ekman pumping may play a major role in generating the LCE. Based on the above ideas, prominent interannual (roughly 3 years and 7 years) and decadal (roughly 14 years) variability in the upper-layer Luzon Strait transport (LST) was first revealed using the 62-year (1950-2011) hindcast outputs from an eddy-resolving ocean general circulation model. To seek local factors affecting the interannual and decadal variability of LST, deseasonalized anomaly field of WSC over the LCE active area was analyzed using empirical orthogonal function (EOF). Dominant EOF modes of WSC anomaly were obtained. Spatio-temporal variability of the first EOF mode is of prominent decadal oscillation with a period of roughly 14.2 years and decadal southward shift of positive phase of the WSC anomaly, while the second EOF mode is of interannual oscillation of roughly 3.3 years and interannual northward shift of positive phase of the WSC anomaly. On the other hand, the near 7-year interannual oscillation was noticeable and can be regarded as an imprint of the variability of Kuroshio volume transport at its origin.%一般认为,吕宋海峡北南两端压力梯度或深度积分的动力高度差是太平洋水通过吕宋海峡西侵南海最直接的动力学。这一动力高度差与吕宋岛西部外海气旋式中尺度涡(即吕宋冷涡, Luzon cold eddy, LCE)的季节性出现有关,而LCE活跃区上空正的风应力旋度(wind stress curl, WSC)在LCE的产生中起主要作用。基于上述思路,利用涡分辨力海洋环流模式OFES[oceanic general circulation model (OGCM) for the Earth Simulator]的62年(1950—2011)后报结果首先得出吕宋海峡水体输运量(Luzon Strait transport, LST)不仅有约3年和7年显著的年际振荡,而且有约14年显著的年代际变化。然后分析LCE活跃区上空WSC异常场主要模态低频振荡特征以寻找影响LST年际和年代际变化的局地因子。结果表明,对LCE活跃区上空WSC去除季节性信号的异常场做经验正交函数(empirical orthogonal function, EOF)分析取得了典型的年际以上尺度的主要模态特征,其第一模态时空变化表现为约14年显著的年代际振荡和 WSC 异常场正位相区年代际尺度上的南移,而第二模态表现为约3年显著的年际振荡和WSC异常场正位相区年际尺度上的北移。另一方面, LST约7年的变化特征可视为源区黑潮水体输运量低频变化在该尺度上的印记。
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