Analyzing the impact of ocean-atmosphere teleconnections on rainfall variability in the Brazilian Legal Amazon via the Rainfall Anomaly Index (RAI)

Abstract

Drought events are mainly associated with alterations in ocean-atmosphere patterns, leading to abnormally dry conditions due to reduced precipitation. This study aims to enhance the understanding of the spatiotemporal relationship of atmospheric teleconnections associated with droughts in the Brazilian Legal Amazon (BLA), based on the Rainfall Anomaly Index (RAI), utilizing 1675 precipitation grid points from the Global Precipitation Climatology Centre (GPCC) for the period 1970–2019. The results revealed that Principal Component Analysis (PCA) and cluster analysis of RAI demonstrated significant climatic variability, with 15 components explaining 68% of the total variance and identifying two homogeneous regions closely aligning with observed conditions. Atmospheric teleconnections showed substantial variation in spatial and temporal extent in extreme drought events in the years 2005, 2010, 2015–2016, and 2019 in the BLA. The findings indicate that on an interannual scale, the dominant teleconnections in the BLA are the Atlantic Multidecadal Oscillation (AMO), North Atlantic Oscillation (NAO), Tropical North Atlantic (TNA), Pacific North American (PNA) pattern, and Atlantic Meridional Overturning Circulation (AMOC). In contrast, on a decadal scale, the Pacific Decadal Oscillation (PDO), Southern Oscillation Index (SOI), Oceanic Niño Index (ONI), and Tropical South Atlantic (TSA) prevail. Our results provide valuable insights into the nature of drought events in the Amazon, including strategies for the early detection of their intensity and affected areas, demonstrating that atmospheric teleconnections significantly influence both interannual and decadal periods. These influences are concentrated on specific temporal scales and during particular years. Conclusively, this study underscores the critical role of atmospheric teleconnections in shaping drought dynamics in the BLA, offering a foundation for predictive models and mitigation strategies to combat climate-induced challenges in the region.