Mu Ye, Jones Charles, Carvalho Leila M V, Xue Lulin, Liu Changhai, Ding Qinghua
Department of Geography, University of California Santa Barbara, Santa Barbara, CA USA.
Earth Research Institute, University of California Santa Barbara, Santa Barbara, CA USA.
NPJ Clim Atmos Sci. 2024;7(1):297. doi: 10.1038/s41612-024-00852-6. Epub 2024 Dec 4.
The hydrological cycle in South America during austral summer, including extreme precipitation and floods, is significantly influenced by northerly low-level jets (LLJs) along the eastern Andes. These synoptic weather events have been associated with three different types of LLJs (Central, Northern, and Andes) and are sensitive to remote large-scale forcings. This study investigates how tropical forcings related to El Niño/Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO) regulate the duration and frequency of each LLJ type and their impacts on extreme precipitation. Our analysis reveals that ENSO and PDO are important in driving the variability of LLJs over the past 65 years. Specifically, the Central LLJ type is more prevalent during El Niño and Warm/Neutral PDO phases, leading to heightened extreme precipitation in southern South America. Conversely, La Niña years during Cold PDO phases tend to favor the Northern and Andes LLJs, which are associated with increased precipitation extremes in the western Amazon and southeastern South America. Central and Andes LLJs tend to persist longer during these favored conditions, causing more pronounced precipitation events in the areas under their influence. This study enhances our understanding of the influence of large-scale atmospheric forcings on the regional precipitation dynamics in South America.
在南半球夏季，南美洲的水文循环，包括极端降水和洪水，受到安第斯山脉东部低空急流（LLJs）的显著影响。这些天气尺度的天气事件与三种不同类型的低空急流（中部、北部和安第斯山脉型）有关，并且对远程大尺度强迫敏感。本研究调查了与厄尔尼诺/南方涛动（ENSO）和太平洋年代际振荡（PDO）相关的热带强迫如何调节每种低空急流类型的持续时间和频率及其对极端降水的影响。我们的分析表明，ENSO和PDO在驱动过去65年低空急流的变率方面很重要。具体而言，中部低空急流类型在厄尔尼诺和暖/中性PDO阶段更为普遍，导致南美洲南部极端降水增加。相反，冷PDO阶段的拉尼娜年倾向于有利于北部和安第斯山脉低空急流，这与亚马逊西部和南美洲东南部降水极端事件增加有关。在这些有利条件下，中部和安第斯山脉低空急流往往持续更长时间，在其影响区域造成更明显的降水事件。这项研究增进了我们对大尺度大气强迫对南美洲区域降水动态影响的理解。
