The El Niño-Southern Oscillation (ENSO) is a primary driver of interannual variability in extreme precipitation in many regions worldwide. Understanding the relationship between ENSO and extreme precipitation is crucial, as it has implications for understanding the interannual variability of flood risk. We investigated the frequency of extreme daily precipitation in Southwest Asia across different seasons during El Niño and La Niña using the daily GPCP and ERA5 precipitation datasets for the period 1997–2022. Extreme precipitation at each grid point is defined as daily accumulated precipitation exceeding the 95th percentile on wet days, where a wet day is defined as one with at least 0.1 mm rainfall. El Niño is associated with an overall increase in the frequency of extreme precipitation in Southwest Asia during autumn, winter, and spring, whereas La Niña shows the opposite effect. To explore the dynamics of El Niño and La Niña teleconnections to Southwest Asia, we applied a feature tracking method on the ERA5 relative velocity at 850 hPa in different seasons. Overall, the storm track density and the mean intensity of storms increase in Southwest Asia during El Niño and decrease during La Niña in autumn, winter, and spring. In summer, El Niño favors less frequent extreme precipitation in the southern parts of Southwest Asia, where the tropical summer monsoon circulation is dominated, while La Niña is associated with more frequent extreme precipitation in this region. This pattern is expected, as the monsoon circulation is weaker during El Niño and stronger during La Niña. In line with this, we identified a decrease in the mean intensity of storms in the southern parts of Southwest Asia during El Niño, with the opposite occurring during La Niña. Our findings have important implications for understanding interannual variability of extreme precipitation in Southwest Asia and providing a framework for predicting such events.

中文翻译：

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ENSO 对西南亚极端降水的影响


厄尔尼诺-南方涛动 （ENSO） 是全球许多地区极端降水年际变化的主要驱动因素。了解 ENSO 与极端降水之间的关系至关重要，因为它对理解洪水风险的年际变化具有重要意义。我们使用 1997-2022 年期间的逐日 GPCP 和 ERA5 降水数据集调查了厄尔尼诺和拉尼娜期间西南亚不同季节的极端日降水频率。每个网格点的极端降水量定义为雨天日的日累积降水量超过 95 个百分位数，其中雨天定义为降雨量至少为 0.1 毫米的日雨量。厄尔尼诺现象与西南亚秋季、冬季和春季极端降水频率的总体增加有关，而拉尼娜现象则显示出相反的效果。为了探索厄尔尼诺和拉尼娜遥相关与西南亚的动态，我们对不同季节 850 hPa 的 ERA5 相对速度应用了特征跟踪方法。总体而言，在厄尔尼诺现象期间，西南亚的风暴路径密度和风暴的平均强度增加，而在秋季、冬季和春季的拉尼娜现象期间下降。在夏季，厄尔尼诺现象有利于西南亚南部地区的极端降水频率较低，那里的热带夏季季风环流占主导地位，而拉尼娜现象与该地区更频繁的极端降水有关。这种模式是意料之中的，因为季风环流在厄尔尼诺期间较弱，而在拉尼娜期间较强。与此一致，我们发现在厄尔尼诺期间，西南亚南部地区的平均风暴强度有所降低，而在拉尼娜现象期间则相反。 我们的研究结果对于理解西南亚极端降水的年际变化以及为预测此类事件提供框架具有重要意义。