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Item type:Publication, The 2022–23 drought in the South American Altiplano: ENSO effects on moisture flux in the western Amazon during the pre-wet season(Elsevier B.V., 2024-09-01)The 2022-23 hydrological year in the Lake Titicaca, Desaguadero River, and Lake Poopó hydrological system (TDPS) over the South American Altiplano constituted a historically dry period. This drought was particularly severe during the pre-wet season (October–December), when the TDPS and the adjacent Andean-Amazon region experienced as much as 60% reductions in rainfall. Consequently, Titicaca Lake water levels decreased by 0.05 m from December to January, which is part of the rising lake level period of normal conditions. Such conditions have not been seen since the El Niño-related drought of 1982-83. Using a set of hydroclimatic, Sea Surface Temperature (SST) and atmospheric reanalysis datasets, we find that this new historical drought was associated with enhanced southerly moisture flux anomalies, reducing the inflow of moisture-laden winds from the Amazon basin to the TDPS. Such anomalies in moisture transport were not seen since at least the 1950s. The atmospheric dynamics associated with this drought are related to La Niña SST anomalies via subtropical teleconnections associated with Rossby wave trains towards South America, further extended by subtropical Atlantic Ocean SST anomalies. This feature reduced the atmospheric moisture inflow from the Amazon and weakened the development of the Bolivian High in the upper troposphere. These results document a new atmospheric mechanism related to extreme droughts in the TDPS associated with La Niña SST anomalies during the pre-wet season. This goes beyond the traditional understanding of El Niño events, especially the strongest ones, being associated with dry conditions in the TDPS during the wet season (December–March). - 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, Regionalization of Rainfall in the Upper Madeira Basin Based on Interannual and Decadal Variability: A Multi-Seasonal Approach(John Wiley and Sons Ltd, 2023-11-30)Identifying rainfall regions associated with specific modes of variability is of practical interest for water resources management, seasonal forecasting, and mitigation of weather-related risks. This study aims to identify homogeneous rainfall regions within the ~1 million km2 Upper Madeira River basin—southwestern Amazon—by their interannual and decadal variability and relates this variability to ocean indices. An observed dataset of 146 ground-based rainfall stations, distributed throughout the Andes and the Amazon, and homogenized at the monthly time-step for the period 1980–2016, was used for the analysis. With no spatial constraints, hierarchical cluster analysis and principal component analysis (PCA) optimally grouped stations into 10 rainfall homogenous regions. The value of the regionalization for interpreting the rainfall variability was evaluated by relating the seasonal rainfall time series of the regions with ocean indices. Then, by applying PCA to seasonal rainfall series and linking the principal components to sea surface temperature and ocean indices, an insight into the main large-scale drivers of the rainfall spatio-temporal variability in this basin at interannual and decadal scales is provided. This analysis identified differences in the year-round influences of the tropical Pacific and/or Atlantic oceans on the 10 homogenous regions. - 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 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Climatological patterns of heatwaves during winter and spring 2023 and trends for the period 1979–2023 in central South America(Frontiers Media, 2025-01-01)In the last 40 years, trends in heat wave frequency, intensity, and duration have increased steadily around the world. These intense heat waves were characterized persistent atmospheric blocking episode, with a continuous presence of a warm air mass and lack of rain for several consecutive days, that contributed to pronounced positive temperature anomalies, reinforced by extremely low soil moisture, and warm and drought conditions. The year 2023 was the warmest year on record, and the global average temperature was +1.45°C above pre-industrial (1850–1900) values worldwide. In South America 2023 was the warmest since 1900, with 0.81°C above the 1991–2020 reference period. Central South America experienced a sequence of heatwaves series being the most intense during the autumn and spring of 2023. From August to December 2023, the meteorological services of Brazil, Argentina, Paraguay and Bolivia reported record-high maximum temperatures in this period in several stations east of the Andes and identified 7 heat waves episodes that affected all these countries. The large-scale circulation patterns show that heatwaves were characterized by an anomalously high-pressure system that facilitated the formation of a heat dome through dry, hot air columns over a warm and dry soil. Several locations experienced temperature of about 10°C above normal, and some locations reported maximum temperatures above 40°C for several days in a row. These heat waves aggravated the drought over Amazonia during the second half of 2023, during an El Niño year. Compound drought-heat favored hydrological drought, while the increased dryness amplified the risk of fires.5