Browsing by Author "Cochonneau, Gerard"

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    Sediment budget in the Ucayali river basin, an Andean tributary of the Amazon river
    (Copernicus Publications, 2015-03-03) Santini, William; Martínez, Jean-Michel; Espinoza Villar, Raúl Arnaldo; Cochonneau, Gerard; Vauchel, Philippe; Moquet, Jean Sébastien; Baby, Patrice; Espinoza, Jhan Carlo; Lavado, Waldo; Carranza, Jorge; Guyot, Jean-Loup
    Formation of mountain ranges results from complex coupling between lithospheric deformation, mechanisms linked to subduction and surface processes: weathering, erosion, and climate. Today, erosion of the eastern Andean cordillera and sub-Andean foothills supplies over 99% of the sediment load passing through the Amazon Basin. Denudation rates in the upper Ucayali basin are rapid, favoured by a marked seasonality in this region and extreme precipitation cells above sedimentary strata, uplifted during Neogene times by a still active sub-Andean tectonic thrust. Around 40% of those sediments are trapped in the Ucayali retro-foreland basin system. Recent advances in remote sensing for Amazonian large rivers now allow us to complete the ground hydrological data. In this work, we propose a first estimation of the erosion and sedimentation budget of the Ucayali River catchment, based on spatial and conventional HYBAM Observatory network.
    Palabras clave:UcayaliPachiteaAndes
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    Spatio‐temporal rainfall variability in the Amazon basin countries (Brazil, Peru, Bolivia, Colombia, and Ecuador)
    (Royal Meteorological Society, 2008-09) Espinoza, Jhan Carlo; Ronchail, Josyane; Guyot, Jean Loup; Cochonneau, Gerard; Naziano, Filizola; Lavado, Waldo; De Oliveira, Eurides; Pombosa, Rodrigo; Vauchel, Philippe
    Rainfall variability in the Amazon basin (AB) is analysed for the 1964–2003 period. It is based on 756 pluviometric stations distributed throughout the AB countries. For the first time it includes data from Bolivia, Peru, Ecuador, and Colombia. In particular, the recent availability of rainfall data from the Andean countries makes it possible to complete previous studies. The impact of mountain ranges on rainfall is pointed out. The highest rainfall in the AB is observed in low windward regions, and low rainfall is measured in leeward and elevated stations. Additionally, rainfall regimes are more diversified in the Andean regions than in the lowlands. Rainfall spatio‐temporal variability is studied based on a varimax‐rotated principal component analysis (PCA). Long‐term variability with a decreasing rainfall since the 1980s prevails in June–July–August (JJA) and September October–November (SON). During the rainiest seasons, i.e. December–January–February (DJF) and March–April–May (MAM), the main variability is at decadal and interannual time scales. Interdecadal variability is related to long‐term changes in the Pacific Ocean, whereas decadal variability, opposing the northwest and the south of the AB, is associated with changes in the strength of the low‐level jet (LLJ) along the Andes. Interannual variability characterizes more specifically the northeast of the basin and the southern tropical Andes. It is related to El Niño‐Southern Oscillation (ENSO) and to the sea surface temperature (SST) gradient over the tropical Atlantic. Mean rainfall in the basin decreases during the 1975–2003 period at an annual rate estimated to be − 0.32%. Break tests show that this decrease has been particularly important since 1982. Further insights into this phenomenon will permit to identify the impact of climate on the hydrology of the AB. Copyright © 2008 Royal Meteorological Society.
    Palabras clave:Rainfall variabilityRainfall regimesAmazon basin