State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China.
College of Earth Sciences, University of Chinese Academy of Sciences, Beijing, 100049, China.
Sci Rep. 2018 Nov 20;8(1):17112. doi: 10.1038/s41598-018-35469-2.
In the present study, the mean states of the North Equatorial Undercurrents (NEUCs) simulated in an eddy-resolving ocean model are evaluated, and the variability of the three NEUC jets is analyzed. This analysis provides a reference for future observations regarding how long the in-situ observations should be conducted to obtain a complete picture of NEUCs. We show that the primary features of the three eastward NEUC jets are fairly well reproduced by the high-resolution model of LICOM, such as the locations, tilting directions and widths of the three jets. However, the simulated NEUCs have slightly weaker magnitude and are located at shallower depths. In addition, two dominant time scales on interannual (2-7 years) and decadal (12-19 years) time scales for all three NEUC jets are found in a 39-year high-resolution LICOM simulation, although the latter is not statistically significant. The variation of these jets is related to the remarkable interannual and decadal variability in the Pacific Ocean. Our decomposition analysis indicates that both the small- and large-scale currents contribute to the total variation. Furthermore, the low-pass temporal filter of zonal velocity shows that the quasi-steady cross-basin NEUC jets can only emerge on time scales longer than the interannual periodicity.
在本研究中，评估了一个高分辨率海洋模式中模拟的北赤道逆流（NEUC）的平均状态，并分析了三个 NEUC 流的可变性。这项分析为未来的观测提供了参考，即需要进行多长时间的现场观测才能全面了解 NEUC。结果表明，LICOM 高分辨率模式较好地再现了三个向东的 NEUC 流的主要特征，如三个流的位置、倾斜方向和宽度。然而，模拟的 NEUC 强度略弱，位置较浅。此外，在 39 年的高分辨率 LICOM 模拟中，发现了所有三个 NEUC 流的两个主要时间尺度，即年际（2-7 年）和年代际（12-19 年），尽管后者在统计上不显著。这些流的变化与太平洋显著的年际和年代际变化有关。我们的分解分析表明，小尺度和大尺度流都对总变化有贡献。此外，纬向速度的低通时间滤波器表明，准定常的跨洋 NEUC 流只能在时间尺度大于年际周期的情况下出现。
