冬季两类厄尔尼诺事件对高纬度近地面温度影响的差异与机制分析

Impacts of two types of El Niño events on high-latitude near-surface temperature during Winter: Differences and underlying mechanisms

  • 摘要: 基于ERA5再分析资料与CPC(Climate Prediction Center)提供的逐月大气环流指数,通过合成分析和动力学诊断等方法对比分析了东太平洋(EP, Eastern Pacific)厄尔尼诺与中太平洋(CP,Central Pacific)厄尔尼诺事件对高纬度地区冬季近地面温度的影响及其物理机制。结果表明,两类厄尔尼诺事件通过激发不同的遥相关波列影响高纬度近地面温度:EP型厄尔尼诺通过激发正位相的太平洋-北美(PNA)遥相关导致加拿大地区升温,但对极区影响较弱;CP型厄尔尼诺则通过激发负位相的北大西洋涛动(NAO)引起格陵兰岛升温以及极区降温。在两类事件中,高纬度近地面温度变化均主要由温度平流过程主导。进一步分析发现,EP型厄尔尼诺从热带中东太平洋激发的强波动一直传播到北太平洋地区,继而在西风波导作用下东传,呈纬向传播特征,形成典型的PNA型遥相关波列;而CP型厄尔尼诺在热带东太平洋激发的波动较弱,无法北传至北太平洋,向东传播至大西洋之后受负位涡(PV)经向梯度的影响继续北传,呈经向传播特征,形成类NAO负位相的环流响应。此外,CP型厄尔尼诺在副热带大西洋区域伴随着明显的海温异常,该海温异常通过瞬变涡旋的涡度反馈有利于NAO负位相环流异常的维持。研究结果丰富了对厄尔尼诺影响高纬度气候变异特征和机理的认识,为高纬度地区季节-年际气候预测提供了一定的理论依据。

     

    Abstract: Based on ERA5 reanalysis data and monthly atmospheric circulation indices provided by the Climate Prediction Center (CPC), this study employs composite analysis and dynamical diagnosis methods to comparatively analyze the impacts of Eastern Pacific (EP) and Central Pacific (CP) El Niño events on winter near-surface temperature in high-latitude regions and their underlying physical mechanisms. Results show that the two types of El Niño events influence high-latitude near-surface temperature by triggering different teleconnection wave trains: EP El Niño primarily induces warming over Canada through a positive-phase Pacific-North American (PNA) teleconnection but has weaker effects on the polar region. CP El Niño, in contrast, triggers a negative-phase North Atlantic Oscillation (NAO), leading to warming over Greenland and cooling in the Arctic. In both cases, near-surface temperature anomalies are predominantly driven by temperature advection processes. Further analysis reveals distinct wave propagation mechanisms. During EP El Niño events, robust waves triggered in the central-eastern equatorial Pacific propagate zonally to the North Pacific, forming a classic PNA wave train along the westerly wave guide. CP El Niño events generate weaker waves in the eastern tropical Pacific that cannot penetrate the North Pacific but instead propagate meridionally into the Atlantic, where they amplify under the influence of negative Potential Vorticity (PV) gradients, forming a negative-phase NAO-like response. Notably, CP El Niño is accompanied by pronounced Sea Surface Temperature (SST) anomalies in the subtropical Atlantic. These SST anomalies reinforce the negative NAO phase via transient eddy vorticity feedback, sustaining the anomalous circulation. This study enriches the understanding of how El Niño diversity modulates high-latitude climate variability and provides a theoretical framework for improving seasonal-to-interannual climate predictions in polar regions.

     

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