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Abstract 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. The LLJ represents a synoptic weather event characterized by different types (Central, Northern, and Andes). Given that numerous characteristics of the LLJ are sensitive to large-scale climate forcing originating remotely, this study aims to understand how tropical forcings, such as the El Niño/Southern Oscillation (ENSO) and Pacific Decadal Oscillation (PDO), regulate the duration and frequency of each LLJ type on low-frequency time scales and related impacts in precipitation changes based on reanalysis and gauge-based datasets. Our analysis reveals that ENSO and PDO are pivotal in driving the variability of LLJs over the past sixty years. Specifically, the central LLJ type is more prevalent during El Niño years and warm 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 and southeastern parts of the Amazon. Typically, LLJs tend to persist longer during these favored conditions, causing more pronounced precipitation events in the areas under the influence of the LLJs. This study enhances our understanding of the influence of large-scale atmospheric forcings on the regional precipitation dynamics in South America.
Mu et al. (Wed,) studied this question.