The interannual variations of eddy kinetic energy (EKE) in the western equatorial Pacific Ocean are investigated based on satellite observations and model outputs in this study. Results reveal that the EKE exhibits vigorous interannual variations, especially in the region of North Equatorial Countercurrent (NECC) and north of New Guinea, and the variations differ between the two types of El Niño events. The energy budget diagnosis indicates that the EKE variations are mainly attributed to the barotropic instability associated with the background currents. Specifically, the energetic NECC behaves northward shift and a stronger meander path, which favors the enhancement of EKE variations due to the enhanced barotropic instability. The interannual fluctuations of the strength of the New Guinea Coastal Current/Undercurrent (NGCC/NGCUC) and the eastward current along the equator contribute to the significant EKE interannual variations north of New Guinea. Further, the distinct features of EKE variations in two types of El Niño events are as follows: EKE typically weakens in the western equatorial Pacific during Eastern Pacific El Niño (EP-El Niño) events, whereas it intensifies north of New Guinea during Central Pacific El Niño (CP-El Niño) events. The opposite features north of New Guinea are attributed to the wind work and a stronger eastward current along the equator in CP-El Niño events. These results can contribute to a better understanding of the low-frequency eddy-mean flow interactions.

中文翻译：

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西赤道太平洋年际涡动能变化特征与动力学


本研究根据卫星观测和模型输出研究了赤道太平洋西部涡动能 （EKE） 的年际变化。结果表明，EKE 表现出剧烈的年际变化，尤其是在北赤道逆流 （NECC） 地区和新几内亚北部，并且两种类型的厄尔尼诺事件之间的差异不同。能量收支诊断表明，EKE 变化主要归因于与背景电流相关的气压不稳定性。具体来说，充满活力的 NECC 表现为北移和更强的蜿蜒路径，由于增强的气压不稳定性，这有利于 EKE 变化的增强。新几内亚沿海洋流/潜流 （NGCC/NGCUC） 强度的年际波动和赤道沿线的东流导致了新几内亚以北的显著 EKE 年际变化。此外，在两种类型的厄尔尼诺事件中，EKE 变化的显著特征如下：在东太平洋厄尔尼诺 （EP-El Niño） 事件期间，EKE 通常在赤道西部太平洋减弱，而在中太平洋厄尔尼诺 （CP-El Niño） 事件期间，EKE 在新几内亚北部增强。新几内亚以北的相反特征归因于 CP-El Niño 事件中沿赤道的风作用和更强的东流。这些结果有助于更好地理解低频涡流-平均流相互作用。