Browsing by Author "Fraizy, P."
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Item Open Access Discharge simulation in the sub-basins of the Amazon using ORCHIDEE forced by new datasets(European Geosciences Union (EGU), 2012-03-22) Guimberteau, Matthieu; Drapeau, Guillaume; Ronchail, Josyane; Sultan, Benjamin; Polcher, Jan; Martinez, Jean-Michel; Prigent, Catherine; Guyot, Jean-Loup; Cochonneau, Gérard; Espinoza, Jhan Carlo; Filizola, N.; Fraizy, P.; Lavado, W.; De Oliveira, E.; Pombosa, R.; Noriega, L.; Vauchel, P.The aim of this study is to evaluate the ability of the ORCHIDEE land surface model to simulate streamflows over each sub-basin of the Amazon River basin. For this purpose, simulations are performed with a routing module including the influence of floodplains and swamps on river discharge and validated against on-site hydrological measurements collected within the HYBAM observatory over the 1980–2000 period. When forced by the NCC global meteorological dataset, the initial version of ORCHIDEE shows discrepancies with ORE HYBAM measurements with underestimation by 15 % of the annual mean streamflow at Obidos hydrological station. Consequently, several improvements are incrementally added to the initial simulation in order to reduce those discrepancies. First, values of NCC precipitation are substituted by ORE HYBAM daily in-situ rainfall observations from the meteorological services of Amazonian countries, interpolated over the basin. It highly improves the simulated streamflow over the northern and western parts of the basin, whereas streamflow over southern regions becomes overestimated, probably due to the extension of rainy spots that may be exaggerated by our interpolation method, or to an underestimation of simulated evapotranspiration when compared to flux tower measurements. Second, the initial map of maximal fractions of floodplains and swamps which largely underestimates floodplains areas over the main stem of the Amazon River and over the region of Llanos de Moxos in Bolivia, is substituted by a new one with a better agreement with different estimates over the basin. Simulated monthly water height is consequently better represented in ORCHIDEE when compared to Topex/Poseidon measurements over the main stem of the Amazon. Finally, a calibration of the time constant of the floodplain reservoir is performed to adjust the mean simulated seasonal peak flow at Obidos in agreement with the observations.Item Open Access Rainfall control on Amazon sediment flux: synthesis from 20 years of monitoring(IOP Publishing, 2020-05-14) Armijos Cardenas, Elisa Natalia; Crave, A.; Espinoza, Jhan Carlo; Filizola, N.; Espinoza-Villar, R.; Ayes, I.; Fonseca, P.; Fraizy, P.; Gutierrez, O.; Vauchel, P.; Camenen, B.; Martiınez, J. M.; Dos Santos, A.; Santini, W.; Cochonneau, G.; Guyot, J. L.The biodiversity and productivity of the Amazon floodplain depend on nutrients and organic matter transported with suspended sediments. Nevertheless, there are still fundamental unknowns about how hydrological and rainfall variability influence sediment flux in the Amazon River. To address this gap, we analyzed 3069 sediment samples collected every 10 days during 1995–2014 at five gauging stations located in the main rivers. We have two distinct fractions of suspended sediments, fine (clay and silt) and coarse (sand), which followed contrasting seasonal and long-term patterns. By taking these dynamics into account, it was estimated, for first time, in the Amazon plain, that the suspended sediment flux separately measured approximately 60% fine and 40% coarse sediment. We find that the fine suspended sediments flux is linked to rainfall and higher coarse suspended sediment flux is related with discharge. Additionally this work presents the time lag between rainfall and discharge, which is related to the upstream area of the gauging. This result is an important contribution to knowledge of biological and geomorphological issues in Amazon basin.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.