The 2020–2023 La Niña event, the third triple-dip occurrence since 1950, stands out for its unique characteristics when compared to the preceding events in 1973–1976 and 1998–2001. Unlike its predecessors, the latest event emerged without a preceding strong El Niño episode, starting from a state of weak discharge. Moreover, the resurgence of cold sea surface temperature (SST) anomalies during 2020–2023 showed a loose link to ocean-atmosphere variability in the northern subtropical Pacific. The spatial pattern of anomalous conditions in this recent event featured persistent SST cooling in the southeast tropical Pacific, accompanied by pronounced meridional southerly wind anomalies. Our comprehensive investigation indicates a minimal role of subsurface ocean dynamics, underscoring the exceptional strength of cross-equatorial meridional southerly wind anomalies as a primary driver of sustained negative sea surface temperature anomalies. By considering the influences of intra-basin and inter-basin factors, we propose that the observed patterns may be the combined outcome of interannual variability within the tropical Pacific and decadal variations beyond the tropics. Noteworthy contributions from the low-frequency components of the South Pacific Meridional Mode and the Atlantic Warm Pool further shape the dynamics of this event. Our findings underline the increasing importance of meridional winds in shaping the evolution of ENSO in recent decades.

中文翻译：

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2020-2023年三重拉尼娜期间前所未有的跨赤道南风异常：影响和机制

2020-2023年拉尼娜事件是自1950年以来的第三次三次探底事件，与之前的1973-1976年和1998-2001年事件相比，其独特的特征显得尤为突出。与之前的事件不同的是，最近的事件发生时没有出现强烈的厄尔尼诺现象，而是从弱放电状态开始的。此外，2020年至2023年期间冷海表面温度（SST）异常的重新出现表明与北副热带太平洋海洋大气变化之间存在松散的联系。最近这次事件的异常条件的空间格局特征是东南热带太平洋海温持续变冷，并伴有明显的经向南风异常。我们的全面调查表明，地下海洋动力学的作用微乎其微，这突显了跨赤道经向南风异常作为持续负海面温度异常的主要驱动因素的异常强度。通过考虑流域内和流域间因素的影响，我们认为观测到的模式可能是热带太平洋内的年际变化和热带以外的年代际变化的综合结果。南太平洋经向模和大西洋暖池的低频分量的值得注意的贡献进一步塑造了这一事件的动态。我们的研究结果强调了近几十年来经向风在塑造 ENSO 演变过程中的重要性日益增加。