Seasonal variation of the surface North Equatorial Countercurrent (NECC) in the western Pacific Ocean
Seasonal variation of the surface North Equatorial Countercurrent (NECC) in the western Pacific Ocean
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DOI：
10.1007/s00343-016-5119-9
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发表时间：
2016-03
影响因子：
--
通讯作者：
Jun Zhao;Yuanlong Li;Fan Wang
中科院分区：
文献类型：
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作者：
Jun Zhao;Yuanlong Li;Fan Wang
北赤道逆流（NECC）是热带太平洋上层环流中重要的纬向流，在西太平洋暖池热收支中起着至关重要的作用。利用1992 - 2011年卫星海流和海面高度资料，研究了热带西太平洋海面NECC的季节变化。在上游（128°~ 136°E）和下游（145°~ 160°E）区域，地表NECC的强度（INT）和轴位（Y CM）表现出明显不同的季节波动。其中，上游NECC的季节周期表现出较大的年际变化。它的INT和ycm受棉兰老涡旋、棉兰老巨蛋（MD）和其南部赤道罗斯比波变化的影响很大。INT和ycm也显示了由中太平洋赤道罗斯比波和西太平洋局地风强迫的共同作用引起的半年一次的信号。在下游区域，NECC的变率受赤道中部太平洋和太平洋海温异常的影响。MD区域的基因对于调节下游NECC的ycm尤为重要。除了与海sh相关的地转流外，经向风应力驱动的纬向Ekman流也发挥了一定的作用，对地面NECC的INT变率有相当大的影响。NECC在上游和下游区域的变化特征对比反映了区域海洋动力学的高度复杂性。
The North Equatorial Countercurrent (NECC) is an important zonal flow in the upper circulation of the tropical Pacific Ocean, which plays a vital role in the heat budget of the western Pacific warm pool. Using satellite-derived data of ocean surface currents and sea surface heights (SSHs) from 1992 to 2011, the seasonal variation of the surface NECC in the western tropical Pacific Ocean was investigated. It was found that the intensity (INT) and axis position (Y CM ) of the surface NECC exhibit strikingly different seasonal fluctuations in the upstream (128°–136°E) and downstream (145°–160°E) regions. Of the two regions, the seasonal cycle of the upstream NECC shows the greater interannual variability. Its INT and YCMare greatly influenced by variations of the Mindanao Eddy, Mindanao Dome (MD), and equatorial Rossby waves to its south. Both INT and Y CM also show semiannual signals induced by the combined effects of equatorial Rossby waves from the Central Pacific and local wind forcing in the western Pacific Ocean. In the downstream region, the variability of the NECC is affected by SSH anomalies in the MD and the central equatorial Pacific Ocean. Those in the MD region are especially important in modulating the YCMof the downstream NECC. In addition to the SSH-related geostrophic flow, zonal Ekman flow driven by meridional wind stress also plays a role, having considerable impact on INT variability of the surface NECC. The contrasting features of the variability of the NECC in the upstream and downstream regions reflect the high complexity of regional ocean dynamics.