ABSTRACT

Based on the subsurface mooring observations at 159°59′E, 14°40′N from July 2014 to May 2016, the vertical structure and variability of the North Equatorial Current/Undercurrent (NEC/NEUC) are investigated. The NEC flows westward stably from the sea surface down to 500 m and is strongest with the magnitude of approximately 40 cm/s in January 2016, while in several months, the eastward current occurs and attains the maximum of nearly 15 cm/s in April and September 2015. Beneath the NEC, the eastward NEUC is observed and its depth could reach at least 860 m. The Power Spectral Density function reveals surface-intensified signals of the currents at mooring site, and the period in the upper layer is around 30–155 days. AVISO products accurately describe the variability of the NEC and are consistent with the mooring observations. Further analysis with sea level anomaly data suggests that the mesoscale eddies, which move westward, may influence the intraseasonal variability measured by the mooring. A comparison of the results with other mooring observations at 130°E implies the phenomenon of western intensification and the existence of NEUC jets at different longitudes that they are not observed at 130°E, 15.5°N.

摘要

基于2014年7月至2016年5月159°59′E、14°40′N的地下系泊观测，研究了北赤道流/暗流（NEC/NEUC）的垂直结构和变化。NEC从海面稳定西流至500 m，最强，2016年1月震级约40 cm/s，几个月后出现东流，4月达到最大值近15 cm/s 2015 年 9 月，NEC 下方观测到东向的 NEUC，其深度至少可达 860 m。功率谱密度函数揭示了系泊处水流的表面增强信号，上层的周期约为 30-155 天。AVISO 产品准确地描述了 NEC 的可变性，并与系泊观测结果一致。对海平面异常数据的进一步分析表明，向西移动的中尺度涡旋可能会影响系泊所测量的季节内变化。将结果与 130°E 的其他系泊观测结果进行比较，表明存在西方增强现象，并且在不同经度存在 NEUC 急流，而在 130°E、15.5°N 未观测到它们。