Spatially compounding droughts over multiple regions pose amplifying pressures on the global food system, the reinsurance industry, and the global economy. Using observations and climate model simulations, we analyze the influence of various natural Ocean variability modes on the likelihood, extent, and severity of compound droughts across ten regions that have similar precipitation seasonality and cover important breadbaskets and vulnerable populations. Although a majority of compound droughts are associated with El Niños, a positive Indian Ocean Dipole, and cold phases of the Atlantic Niño and Tropical North Atlantic (TNA) can substantially modulate their characteristics. Cold TNA conditions have the largest amplifying effect on El Niño-related compound droughts. While the probability of compound droughts is ~3 times higher during El Niño conditions relative to neutral conditions, it is ~7 times higher when cold TNA and El Niño conditions co-occur. The probability of widespread and severe compound droughts is also amplified by a factor of ~3 and ~2.5 during these co-occurring modes relative to El Niño conditions alone. Our analysis demonstrates that co-occurrences of these modes result in widespread precipitation deficits across the tropics by inducing anomalous subsidence, and reducing lower-level moisture convergence over the study regions. Our results emphasize the need for considering interactions within the larger climate system in characterizing compound drought risks rather than focusing on teleconnections from individual modes. Understanding the physical drivers and characteristics of compound droughts has important implications for predicting their occurrence and characterizing their impacts on interconnected societal systems.

多个地区的干旱在空间上更加复杂，对全球粮食系统，再保险业和全球经济构成了更大的压力。利用观测和气候模型模拟，我们分析了十个降水季节相似且覆盖重要粮仓和脆弱人群的地区，各种自然海洋变率模式对复合干旱发生的可能性，程度和严重性的影响。尽管大多数复合干旱都与厄尔尼诺现象有关，但印度洋偶极子为正，大西洋尼诺和热带北大西洋（TNA）的冷期可以大大改变其特征。寒冷的TNA条件对与厄尔尼诺有关的复合干旱具有最大的放大作用。尽管在厄尔尼诺条件下复合干旱的概率是中性条件的〜3倍，但在寒冷的TNA和厄尔尼诺条件下同时发生的概率是〜7倍。在这些同时发生的模式下，相对于单独的厄尔尼诺现象，广泛而严重的复合干旱的可能性也被放大了约3倍和约2.5倍。我们的分析表明，这些模式的共生会引起异常沉降，并降低研究区域的低层水分汇聚，从而导致整个热带地区普遍出现降水不足。我们的结果强调需要在描述复合干旱风险的特征时考虑更大气候系统内的相互作用，而不是关注各个模式的遥相关。