Browsing by Author "Ronchail, J."
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Item Restricted Assessment of different precipitation datasets and their impacts on the water balance of the Negro River basin(Elsevier, 2011-07-11) Getirana, A. C. V.; Espinoza, Jhan Carlo; Ronchail, J.; Rotunno Filho, O. C.With the objective of understanding the potential and limitations of available precipitation products for hydrological studies, this paper compares six daily and sub-daily precipitation datasets and their impacts on the water balance of the Negro River basin in the Amazon basin. The precipitation datasets contain gauge-based data [data derived from the Hybam Observatory Precipitation (HOP) dataset and provided by the Climate Prediction Center (CPC)], satellite-based data [the Global Precipitation Climatology Project (GPCP) one-degree daily and TRMM Multisatellite Precipitation Analysis (TMPA) datasets] and model-based data [the NCEP-DOE AMIP-II re-analysis (NCEP-2) and 40-year ECMWF Re-Analysis (ERA-40) datasets]. Each dataset has a common set of meteorological forcing data which are used to run the MGB-IPH hydrological model for the period from January 1998 to August 2002.Item Open Access Central South America(American Meteorological Society, 2017-08) Marengo, J. A.; Espinoza, Jhan Carlo; Alves, L. M.; Ronchail, J.; Baez, J.;The central South America region includes Brazil, Peru, Paraguay, and Bolivia. The 2016 climate conditions were characterized by extreme high temperatures and below-average precipitation in the Amazon and Andean regions, while above-average precipitation was observed in northern Peru and northeastern Paraguay.Item Open Access Central South America(American Meteorological Society, 2018-08) Espinoza, Jhan Carlo; Alves, L. M.; Ronchail, J.; Báez, J.; Takahashi, Ken; Lavado-Casimiro, W.The central South America region includes Brazil, Peru, Paraguay, and Bolivia.Item Open Access Drought in Bolivia: the worst in the last 25 years(American Meteorological Society, 2017-08) Marengo, J. A.; Espinoza, Jhan Carlo; Alves, L. M.; Ronchail, J.The article reports on the intense drought conditions which affected the center, southern parts and in the southern lowlands of Bolivia which affected during the first part of the year. Discussed is the hydrology of the Peruvian side of Lake Titicaca which shows low river discharge and drop in water level at Lake Titicaca. Also discussed is the extreme drought at Andean region in 2016 has led the Peruvian government Ministry of Agriculture to declare a state of emergency.Item Restricted Fluctuations in the monthly discharge of Guyana Shield rivers, related to Pacific and Atlantic climate variability(Taylor & Francis, 2012-06) Labat, D.; Espinoza, Jhan Carlo; Ronchail, J.; Cochonneau, G.; De Oliveira, E.; Doudou, J. C.; Guyot, J. L.The discharge variability of the main rivers that drain the Guyana Shield is analysed over the last 50 years using cross-wavelet, coherence and composite analysis involving oceanic and atmospheric variables. We highlight the overall hydro-climatological homogeneity of this region that allowed us to focus on the longest discharge time series available. Therefore, a wavelet cross-analysis was carried out between monthly and seasonal Maroni River discharge at the Langa Tabiki station and selected climate indices. This confirms a strong relationship between the hydrology of the Guyana Shield and the Pacific sea-surface temperature (SST) fluctuations. There is evidence of intermittent influence, of between inter-annual and near decadal scales, of the Atlantic SST fluctuations, in particular around 1970 and 1990. Finally, we show that the links between oceanic regions and high discharge in the rivers of Guyana are realized through the reinforcement of the Walker and Hadley cells between the Amazon and the adjacent oceans and through decreased trade winds and monsoon flux that favour the persistence of humidity over the Guyana Shield.Item Open Access Future changes in precipitation and impacts on extreme streamflow over Amazonian sub-basins(IOP Publishing, 2013-03-07) Guimberteau, M.; Ronchail, J.; Espinoza, Jhan Carlo; Lengaigne, M.; Sultan, B.; Polcher, J.; Drapeau, G.; Guyot, J. L.; Ducharne, A.; Ciais, P.Because of climate change, much attention is drawn to the Amazon River basin, whose hydrology has already been strongly affected by extreme events during the past 20 years. Hydrological annual extreme variations (i.e. low/high flows) associated with precipitation (and evapotranspiration) changes are investigated over the Amazon River sub-basins using the land surface model ORCHIDEE and a multimodel approach. Climate change scenarios from up to eight AR4 Global Climate Models based on three emission scenarios were used to build future hydrological projections in the region, for two periods of the 21st century. For the middle of the century under the SRESA1B scenario, no change is found in high flow on the main stem of the Amazon River (Obidos station), but a systematic discharge decrease is simulated during the recession period, leading to a 10% low-flow decrease. Contrasting discharge variations are pointed out depending on the location in the basin. In the western upper part of the basin, which undergoes an annual persistent increase in precipitation, high flow shows a 7% relative increase for the middle of the 21st century and the signal is enhanced for the end of the century (12%). By contrast, simulated precipitation decreases during the dry seasons over the southern, eastern and northern parts of the basin lead to significant low-flow decrease at several stations, especially in the Xingu River, where it reaches −50%, associated with a 9% reduction in the runoff coefficient. A 18% high-flow decrease is also found in this river. In the north, the low-flow decrease becomes higher toward the east: a 55% significant decrease in the eastern Branco River is associated with a 13% reduction in the runoff coefficient. The estimation of the streamflow elasticity to precipitation indicates that southern sub-basins (except for the mountainous Beni River), that have low runoff coefficients, will become more responsive to precipitation change (with a 5 to near 35% increase in elasticity) than the western sub-basins, experiencing high runoff coefficient and no change in streamflow elasticity to precipitation. These projections raise important issues for populations living near the rivers whose activity is regulated by the present annual cycle of waters. The question of their adaptability has already arisen.Item Open Access Relación entre la reversión de la cota del río (repiquetes), las lluvias y los vientos en niveles bajos sobre el oeste de la cuenca amazónica(Instituto Geofísico del Perú, 2020-10) Figueroa, M.; Armijos Cardenas, Elisa Natalia; Espinoza, J.; Ronchail, J.; Fraizy, P.La agricultura ribereña en épocas de recesión del caudal (junio-octubre) es una de las actividades económicas más importantes de la llanura amazónica. Sin embargo, esta labor se ve afectada por los conocidos “repiquetes”, los cuales son inundaciones repentinas que se desarrollan en plena época de recesión debido a la reversión en el nivel del río. Utilizando datos diarios de nivel del río obtenidos de las reglas limnimétricas de las estaciones localizadas en los ríos Amazonas, Marañón y Ucayali, durante el período 1996-2018; se pudo determinar que de los 73 repiquetes observados en el río Amazonas (reversión ≥ 20 cm), el 64 % de ellos fueron precedidos por repiquetes solo en el río Marañón, y el 5 % fueron repiquetes originados solo en el río Ucayali. El 21 % de los eventos fueron antecedidos por repiquetes en ambos ríos y 10 % no tuvieron precursor aguas arriba. Estos resultados indican que el río Marañón es el principal precursor de los repiquetes originados en el río Amazonas. Analizando la lluvia diaria y vientos en niveles bajos (850 hPa) se puede concluir que los repiquetes registrados en el río Amazonas se originan por las abundantes lluvias en la región de transición Andes-Amazonas entre Perú y Ecuador, las cuales acontecen de tres a cinco días antes del inicio de cada repiquete. Las lluvias precursoras se relacionan con un cambio notable en la dirección del viento meridional, de norte a sur, y a un flujo de humedad hacia el este.Item Open Access Tropical South America east of the Andes(American Meteorological Society, 2015-07) Marengo, J. A.; Espinoza, Jhan Carlo; Ronchail, J.; Alves, L. M.This subsection covers Brazil, Paraguay, and sectors of northern Argentina, Peru, and Bolivia east of the Andes.Item Open Access Tropical South America east of the Andes(American Meteorological Society, 2014-07) Marengo, J. A.; Alves, L. M.; Espinoza, Jhan Carlo; Ronchail, J.Unless otherwise noted, normals and anomalies are based on the 1961–90 average.Item Open Access Tropical South America east of the Andes(American Meteorological Society, 2016-08) Marengo, J. A.; Espinoza, Jhan Carlo; Ronchail, J.; Alves, L. M.This region includes Brazil, Paraguay, southern Venezuela, and the Amazon lowland sectors of Peru, Colombia and Bolivia.