La precipitación en la cuenca del Amazonas (AB) es el resultado de interacciones compleja de varios procesos dinámicos y termodinámicos a gran escala, así como de características locales, que son responsables de la distribución temporal y espacial de la precipitación (Figueroa y Nobre, 1990; Satyamurty et al., 1998). Se sabe que en las escalas de tiempo intraestacional (IE), la Oscilación de Madden y Julian (MJO por sus siglas en inglés; Madden y Julian, 1994; Zhang, 2005) es el modo más dominante de la variabilidad en los trópicos. Esta perturbación ondulatoria tiene una propagación hacia el este de anomalías convectivas tropicales, desde el océano Índico hasta el Pacífico occidental y, posteriormente, a América del Sur y África, con un período de oscilación de entre 30 y 60 días (Kiladis y Weickmann, 1992; Hendon y Salby, 1994; Madden y Julian, 1994). Durante su t...

Descargue el texto completo en el repositorio institucional de la Universidade de São Paulo: https://doi.org/10.11606/T.14.2019.tde-06082019-134442

Lowest events in Lake Titicaca’s water level (LTWL) significantly impact local ecosystems and the drinking water supply in Peru and Bolivia. However, the hydroclimatic mechanisms driving extreme lake-level lowstands remain poorly understood. To investigate these low lake-level events, we analyzed detrended monthly LTWL anomalies, sea Surface temperature (SST) datasets covering the period 1921–2023. ERA5 reanalysis covers the period 1940–2023. A multiple linear regression model was developed to compute detrended LTWL anomalies, excluding multidecadal and residual components. Interdecadal Pacific Oscillation (IPO) and Pacific Decadal Oscillation (PDO) índices were also analyzed for the same period. Results indicate that 25% of all LTWL minima events have a short duration of <5 months, while the remaining 75% of all events have a long duration of more than 9 months, respectively. All...

A better understanding of the relative roles of internal climate variability and external contributions, from both natural (solar, volcanic) and anthropogenic greenhouse gas forcing, is important to better project future hydrologic changes. Changes in the evaporative demand play a central role in this context, particularly in tropical areas characterized by high precipitation seasonality, such as the tropical savannah and semi-desertic biomes. Here we present a set of geochemical proxies in speleothems from a well-ventilated cave located in central-eastern Brazil which shows that the evaporative demand is no longer being met by precipitation, leading to a hydrological deficit. A marked change in the hydrologic balance in central-eastern Brazil, caused by a severe warming trend, can be identified, starting in the 1970s. Our findings show that the current aridity has no analog over the las...