Sudden stratospheric warmings are amongst the most dramatic events in the Earth's atmosphere and they drive extreme surface weather conditions. They have been recently linked to the hot and dry weather conditions that favour wildfires over Australia. However, the chance of a southern hemisphere event is unknown because it has only been observed once. Legitimate estimation of the frequency of sudden stratospheric warming events requires a large sample of realistic model simulations. Here we show that the chance of an event is close to 4% per year, implying that an event will occur, on average, every 25 years, using a state-of-the-art model that simulates sudden stratospheric warmings accurately. It is thus not surprising that there was a near miss in the September prior to the Australian wildfire of 2019, given the 40 years of comprehensive satellite records and just one observed Antarctic event. According to this new estimate, it would also not be surprising to see a second sudden stratospheric warming event in the coming years in the southern hemisphere. Such a stratospheric warming event might bring further extreme surface weather conditions and natural hazards, as it may raise the risk of increased rainfall in the latitudinal band of 35–50°S. Meanwhile, the associated hot and dry weather conditions over austral subtropical continents might increase the risk of wildfires over these regions.

中文翻译：

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南半球平流层突然变暖的可能性有多大？

平流层突然变暖是地球大气中最引人注目的事件之一，它们会导致极端的地表天气条件。最近，它们与有利于澳大利亚发生野火的炎热干燥天气条件有关。然而，南半球事件发生的可能性是未知的，因为它只被观察到过一次。对突然平流层变暖事件频率的合法估计需要大量真实模型模拟样本。在这里，我们表明事件发生的几率接近每年 4%，这意味着事件将平均每 25 年发生一次，使用最先进的模型来准确模拟平流层突然变暖。因此，在 2019 年澳大利亚野火之前的 9 月发生险情也就不足为奇了，鉴于 40 年的综合卫星记录和仅观察到一次南极事件。根据这一新估计，未来几年南半球出现第二次突然的平流层变暖事件也就不足为奇了。这种平流层变暖事件可能会带来进一步的极端地表天气条件和自然灾害，因为它可能会增加 35-50°S 纬度带降雨量增加的风险。同时，与南亚热带大陆相关的炎热干燥天气条件可能会增加这些地区发生野火的风险。这种平流层变暖事件可能会带来进一步的极端地表天气条件和自然灾害，因为它可能会增加 35-50°S 纬度带降雨量增加的风险。同时，与南亚热带大陆相关的炎热干燥天气条件可能会增加这些地区发生野火的风险。这种平流层变暖事件可能会带来进一步的极端地表天气条件和自然灾害，因为它可能会增加 35-50°S 纬度带降雨量增加的风险。同时，与南亚热带大陆相关的炎热干燥天气条件可能会增加这些地区发生野火的风险。