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Item type:Publication, Performance of regional climate model precipitation simulations over the terrain-complex Andes-Amazon transition region(John Wiley and Sons Inc, 2024-01-16)Regional climate models (RCMs) are widely used to assess future impacts associated with climate change at regional and local scales. RCMs must represent relevant climate variables in the present-day climate to be considered fit-for-purpose for impact assessment. This condition is particularly difficult to meet over complex regions such as the Andes-Amazon transition region, where the Andean topography and abundance of tropical rainfall regimes remain a challenge for numerical climate models. In this study, we evaluate the ability of 30 regional climate simulations (6 RCMs driven by 10 global climate models) to reproduce historical (1981–2005) rainfall climatology and temporal variability over the Andes-Amazon transition region. We assess spatio-temporal features such as spatial distribution of rainfall, focusing on the orographic effects over the Andes-Amazon “rainfall hotspots” region, and seasonal and interannual precipitation variability. The Eta RCM exhibits the highest spatial correlation (up to 0.6) and accurately reproduces mean annual precipitation and orographic precipitation patterns across the region, while some other RCMs have good performances at specific locations. Most RCMs simulate a wet bias over the highlands, particularly at the eastern Andean summits, as evidenced by the 100%–2,500% overestimations of precipitation in these regions. Annual cycles are well represented by most RCMs, but peak seasons are exaggerated, especially at equatorial locations. No RCM is particularly skillful in reproducing the interannual variability patterns. Results highlight skills and weaknesses of the different regional climate simulations, and can assist in the selection of regional climate simulations for impact studies in the Andes-Amazon transition zone. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, The Andes–Amazon–Atlantic pathway: A foundational hydroclimate system for social–ecological system sustainability(National Academy of Sciences, 2024-05-28)The Amazon River Basin’s extraordinary social–ecological system is sustained by various water phases, fluxes, and stores that are interconnected across the tropical Andes mountains, Amazon lowlands, and Atlantic Ocean. This “Andes–Amazon–Atlantic” (AAA) pathway is a complex hydroclimatic system linked by the regional water cycle through atmospheric circulation and continental hydrology. Here, we aim to articulate the AAA hydroclimate pathway as a foundational system for research, management, conservation, and governance of aquatic systems of the Amazon Basin. We identify and describe the AAA pathway as an interdependent, multidirectional, and multiscale hydroclimate system. We then present an assessment of recent (1981 to 2020) changes in the AAA pathway, primarily reflecting an acceleration in the rates of hydrologic fluxes (i.e., water cycle intensification). We discuss how the changing AAA pathway orchestrates and impacts social–ecological systems. We conclude with four recommendations for the sustainability of the AAA pathway in ongoing research, management, conservation, and governance. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, The role of global warming trend and tropical interannual variability as drivers of South America’s 2022–2024 climate extremes(Springer Science and Business Media Deutschland GmbH, 2026-09-01)From 2022 to 2024, South America experienced unprecedented regional climate extremes with severe socioeconomic impacts. These included extreme anomalies in temperature and precipitation, causing extreme drought conditions in southeastern South America and the Altiplano during spring 2022; extreme fire weather in central Chile in summer 2023; flooding in Rio Grande do Sul during autumn 2024; and the multiyear Amazon drought persisting throughout the springs 2022–2024. While these events were linked to the Global warming trend (GWT), Tropical interannual variability (TIV), and synoptic-scale processes, their contributions need to be clarified. Using linear regression, we decomposed the observed climate anomalies during 1998–2024 into GWT and TIV components and derived a Residual component representing anomalies not explained by either. This approach clarifies, through seasonal spatial patterns and contributions from regional variance, the roles of GWT and TIV in observed climate extremes across South America. From spring 2022 to spring 2024, GWT exhibited a strong background warming anomaly, while TIV displayed unusually robust teleconnections, particularly during its positive phases. As a result, a significant part of precipitation variability associated with climate extremes across the continent was driven by TIV, whereas GWT dominated in central-southern Chile. Both TIV and GWT contributed substantially to widespread South American warming, with GWT becoming the dominant influence as TIV weakened, except in central-southern Chile, where other factors prevailed. The unprecedented concurrence of strong GWT and combined TIV forcing amplified and prolonged climate extremes across the continent. The framework presented here can support climate extremes attribution worldwide. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Recent changes in the dry-to-wet transition season in the Andean Altiplano and related atmospheric circulation patterns (1981–2022)(Springer Science+Business Media, 2025-01-01)Drought-related impacts in the southern Tropical Andes are crucial for economic activities. Here, precipitation decreases (p < 0.1) during the dry-to-wet transition season (SON) based on CHIRPS (1981–2023) and meteorological stations (1973–2016). In addition, a decline in specific humidity and moisture flux is detected (1979–2022). The precipitation trend is stronger (p < 0.05) in the southern Titicaca, Desaguadero, Poopó and Coipasa Salt Pan hydrological system (TDPS) and extends southwards (20°S-30°S). A delayed onset and a reduced duration of the wet season are observed in the TDPS (p < 0.05), although precipitation intensifies during DJF in the southwestern TDPS (p < 0.05).To analyze the atmospheric features related to these changes, we derive atmospherics circulation patterns (CPs) from standardized anomalies of daily 200-hPa winds (1979–2022) using a weather classification technique. We identify 9 CPs, characterized by four ‘‘dry’’ (D1, D2, D3, and D4), three ‘‘wet’’ (W1, W2 and W3), and two ‘‘transitional’’ patterns (T1 and T2). During SON, the frequency of the W1 (D3) is negatively (positively) correlated with the onset date of the wet season (p < 0.05). Through the period 1979–2022, the frequencies of the D3 and the predominantly dry T1 increase (p < 0.1 and p < 0.05, respectively). Conversely, W1 frequency diminishes substantially since 2010. The physical mechanisms associated are discussed. In conclusion, increased D3 and T1 frequencies, and decreased W1 are related to the diminution of precipitation during SON and to the shortening of the wet season length. We also show that the extreme drought of 2022 was characterized by an unprecedented frequency of dry CPs, particularly during November.2