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<p>The South Pacific Subtropical Dipole (SPSD) is a thermodynamically coupled climate mode characterized by dipolar sea surface temperature anomalies (SSTA). It links subtropical South Pacific oceanic and atmospheric anomalies to the equatorial Pacific, potentially initiating or affecting El Niño-Southern Oscillation (ENSO) events. This study evaluates the simulation of SPSD in 49 Coupled Model Intercomparison Project Phase 6 (CMIP6) models. The historical simulations (1850–2014) successfully reproduce the observed spatiotemporal characteristics of SPSD, with maturing in austral summer and the pattern correlation ranging from 0.67 to 0.95. Most models also accurately capture the dominant contributions of latent heat flux and shortwave radiation to SPSD formation. Among the 49 models, 37 replicate the observed positive correlation between SPSD and subsequent winter ENSO events. However, the residual 12 models exhibit an inverse SPSD-ENSO relationship compared to observations. This intermodel discrepancy in the SPSD-ENSO connection relates to differences in how models simulate the concurrent interaction between SPSD and the North Pacific Oscillation (NPO). In models where positive SPSD phases coincide with positive (negative) NPO phases, the subtropical North Pacific is dominated by anomalous anticyclonic (cyclonic) circulation. These contrasting atmospheric patterns lead to opposing impacts on the SPSD-triggered ENSO development. These results deepen our understanding of how interactions across the extratropical North and South Pacific collectively influence ENSO dynamics.</p>

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The South Pacific Subtropical Dipole and its relationship to ENSO in CMIP6 models

  • 期刊论文

  • 发表日期：

    2026年3月27日

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  • Jian Zheng,
  • Yuanlong Li,
  • Faming Wang

摘要

The South Pacific Subtropical Dipole (SPSD) is a thermodynamically coupled climate mode characterized by dipolar sea surface temperature anomalies (SSTA). It links subtropical South Pacific oceanic and atmospheric anomalies to the equatorial Pacific, potentially initiating or affecting El Niño-Southern Oscillation (ENSO) events. This study evaluates the simulation of SPSD in 49 Coupled Model Intercomparison Project Phase 6 (CMIP6) models. The historical simulations (1850–2014) successfully reproduce the observed spatiotemporal characteristics of SPSD, with maturing in austral summer and the pattern correlation ranging from 0.67 to 0.95. Most models also accurately capture the dominant contributions of latent heat flux and shortwave radiation to SPSD formation. Among the 49 models, 37 replicate the observed positive correlation between SPSD and subsequent winter ENSO events. However, the residual 12 models exhibit an inverse SPSD-ENSO relationship compared to observations. This intermodel discrepancy in the SPSD-ENSO connection relates to differences in how models simulate the concurrent interaction between SPSD and the North Pacific Oscillation (NPO). In models where positive SPSD phases coincide with positive (negative) NPO phases, the subtropical North Pacific is dominated by anomalous anticyclonic (cyclonic) circulation. These contrasting atmospheric patterns lead to opposing impacts on the SPSD-triggered ENSO development. These results deepen our understanding of how interactions across the extratropical North and South Pacific collectively influence ENSO dynamics.