An extreme positive Indian Ocean Dipole (IOD) event occurred in 2019 boreal autumn, which has induced severe climate impacts around the Indian Ocean basin. In this study, the cause for 2019 IOD event and the related mechanism are explored. We find that the remarkable strengthening of Australian high and weakening of sea level pressure over South China Sea/Philippine Sea have been evidently visible since May 2019. Such a record‐breaking interhemispheric pressure gradient (IHPG) induced northward cross‐equatorial flow over the western Maritime Continent, which triggered strong wind‐evaporation‐SST and thermocline feedbacks in 2019. In addition to 2019 case, historical IOD events are highly correlated with IHPG from boreal late spring to summer. We show that skillful IHPG prediction can be made in March by European Centre for Medium‐Range Weather Forecasts seasonal forecast system, which makes it quite possible for the early warning of extreme IOD events by two to three seasons ahead.

中文翻译：

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是什么导致了2019年印度洋极端偶极事件的发生？

印度洋偶极子（IOD）事件在2019年北方秋季发生，这在印度洋盆地周围造成了严重的气候影响。在这项研究中，探讨了2019年IOD事件的原因和相关机制。我们发现，自2019年5月以来，澳大利亚明显增强了澳大利亚的高压，而南海/菲律宾海的海平面压力减弱了。这种破纪录的半球间压力梯度（IHPG）引起了西部向北的越赤道流动海事大陆，在2019年引发了强烈的风蒸发-SST和温跃层反馈。除了2019年的案例外，从春季末到夏季，历史性IOD事件与IHPG高度相关。