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<p>The El Niño–Southern Oscillation (ENSO) is a key driver in modulating interannual variability of tropical cyclone genesis frequency (TCGF) over the North Atlantic (NA). While climate models generally capture the observed negative correlation between ENSO and NA TCGF, large uncertainty remains in simulating the TCGF response to ENSO in this region. In this study, we use 100 ensemble members from a high-resolution climate model to quantify the uncertainty in ENSO-induced TCGF anomalies and to investigate its underlying sources. Results reveal a large intermember spread over the tropical eastern NA, particularly near the west African coast. This uncertainty primarily stems from pronounced differences among the ensemble members in simulated local vertical wind shear and mid-level vertical velocity during ENSO years. Further analysis indicates that these differences in dynamic conditions are closely related to those in the simulated Pacific–Atlantic Walker Circulation (PAWC), which modulates the large-scale environment for cyclogenesis via changes in subsidence and vertical shear. By introducing a PAWC intensity index, we show that ensemble members with a stronger PAWC response exhibit greater suppression of TCGF through enhanced subsidence and shear, while weaker PAWC responses lead to more favorable conditions for cyclogenesis. This finding may help further improve the seasonal simulations and predictions of NA TCGF.</p>

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Quantifying and attributing model uncertainty in ENSO-induced North Atlantic tropical cyclone genesis using large ensemble simulations

  • 期刊论文

  • 发表日期：

    2026年2月13日

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  • Liang Shi,
  • Ruifen Zhan,
  • Jiuwei Zhao

摘要

The El Niño–Southern Oscillation (ENSO) is a key driver in modulating interannual variability of tropical cyclone genesis frequency (TCGF) over the North Atlantic (NA). While climate models generally capture the observed negative correlation between ENSO and NA TCGF, large uncertainty remains in simulating the TCGF response to ENSO in this region. In this study, we use 100 ensemble members from a high-resolution climate model to quantify the uncertainty in ENSO-induced TCGF anomalies and to investigate its underlying sources. Results reveal a large intermember spread over the tropical eastern NA, particularly near the west African coast. This uncertainty primarily stems from pronounced differences among the ensemble members in simulated local vertical wind shear and mid-level vertical velocity during ENSO years. Further analysis indicates that these differences in dynamic conditions are closely related to those in the simulated Pacific–Atlantic Walker Circulation (PAWC), which modulates the large-scale environment for cyclogenesis via changes in subsidence and vertical shear. By introducing a PAWC intensity index, we show that ensemble members with a stronger PAWC response exhibit greater suppression of TCGF through enhanced subsidence and shear, while weaker PAWC responses lead to more favorable conditions for cyclogenesis. This finding may help further improve the seasonal simulations and predictions of NA TCGF.