PDO对ENSO非对称性的年代际调整及其机制

doi:10.11978/2022189

摘要/Abstract

摘要：

本文利用HadISST的月平均海温数据以及ORAS3再分析数据, 研究了PDO(Pacific Decadal Oscillation)不同位相对ENSO(El Niño and South Oscillation)非对称的年代际调整。对PDO不同位相的海表温度异常(SSTA, sea surface temperature anomaly)的偏度分析发现, PDO正位相期间东太平洋的ENSO非对称明显强于PDO负位相期间。同时, 通过对次表层(50~150m)海洋热量收支计算发现, 东太平洋次表层非线性动力加热项(NDH, nonlinear dynamical heating) 在PDO不同位相下也有明显的变化, PDO正位相期间东太平洋的次表层NDH明显强于PDO负位相期间, NDH的差异主要是由其纬向分量NDHx的差异引起的。东太平洋更强的次表层NDHx使PDO正位相期间El Niño事件和La Niña事件次表层温度异常(SubTA, subsurface temperature anomaly)的差距更大, 从而引起SSTA的非对称, 导致PDO正位相期间东太平洋的ENSO非对称比PDO负位相期间强。

关键词: ENSO非对称, PDO, 热收支分析, 非线性动力加热项

Abstract:

El Niño and South Oscillation (ENSO) asymmetry between El Niño and La Niña events in the positive and negative Pacific Decadal Oscillation (PDO) phases is examined using HadISST and ORAS3 ocean reanalysis products. It is found that ENSO asymmetry in the equatorial eastern Pacific is significantly weaker in the negative PDO phase than that in the positive PDO phase. It is found that the eastern Pacific's subsurface nonlinear dynamical heating (NDH) is likewise greatly affected by the various PDO phases, and it is much stronger during the PDO positive phase than that during the PDO negative phase through heat budget analysis of the ocean subsurface layer. The subsurface NDH is largely contributed by NDHx. A larger gap between the El Niño event and the La Niña event Subsurface Temperature Anomaly (SubTA) during the positive phase of the PDO is caused by the stronger subsurface NDHx in the East Pacific, which causes the asymmetry of the SSTA, and results in a stronger ENSO asymmetry in the East Pacific during the positive phase of the PDO than that during the negative phase of the PDO.

Key words: ENSO asymmetry, PDO, heat budget, NDH

李承勇, 孟祥凤, 谢瑞煌. PDO对ENSO非对称性的年代际调整及其机制[J]. 热带海洋学报, 2023, 42(4): 36-46.

LI Chengyong, MENG Xiangfeng, XIE Ruihuang. Interdecadal modulation of ENSO asymmetry by the Pacific Decadal Oscillation and its mechanism[J]. Journal of Tropical Oceanography, 2023, 42(4): 36-46.

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