This study reported the unprecedented tropical cyclone (TC) activity in the western North Pacific (WNP) and North Atlantic (NA) during the developing year of the 2023/2024 El Niño. The possible causes behind these unusual features were addressed. In contrast to previous El Niño events, an unusual low/high TC genesis number in the WNP/NA was identified during the typhoon season (June–November) in 2023. Meanwhile, the mean TC genesis location in the WNP exhibited a La Niña-like northwestward shift, rarely observed in an El Niño developing year. An observational diagnosis on TC-genesis-related large-scale dynamics and thermodynamics revealed that the lower/higher TC numbers in the WNP/NA were primarily attributed to an anticyclonic/cyclonic anomaly linked to trans-basin sea surface temperature anomalies in the tropics and extratropics. Additionally, weaker intraseasonal oscillation activity compared to previous El Niños also partially contributed to fewer TCs in the WNP.

中文翻译：

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2023 年北太平洋/大西洋前所未有的低/高压热带气旋活动的可能原因厄尔尼诺现象


本研究报告了在 2023/2024 年厄尔尼诺现象的发展年度，北太平洋西部 （WNP） 和北大西洋 （NA） 前所未有的热带气旋 （TC） 活动。解决了这些不寻常特征背后的可能原因。与以往的厄尔尼诺事件相比，在 2023 年的台风季节（6 月至 11 月）期间，在 WNP/NA 中发现了不寻常的低/高 TC 生成数。同时，WNP 中 TC 的平均成因位置表现出类似拉尼娜的西北移动，这在厄尔尼诺发展年份很少观察到。对 TC 成因相关的大尺度动力学和热力学的观测诊断表明，WNP/NA 中较低/较高的 TC 值主要归因于与热带和外热带跨流域海面温度异常相关的反气旋/气旋异常。此外，与以前的厄尔尼诺现象相比，较弱的季节内振荡活动也部分导致了 WNP 中 TC 的减少。