Browsing by Author "Rau, Pedro"
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Item Restricted Can artificial neural networks estimate potential evapotranspiration in Peruvian highlands?(Springer Link, 2019) Laqui, Wilber; Zubieta Barragán, Ricardo; Rau, Pedro; Mejía, Abel; Lavado, Waldo; Ingol, EusebioEvapotranspiration (ETo) is one of the most important variables of the water cycle when water requirements for irrigation, water resource planning or hydrological applications are analyzed. In this context, models based on artificial neural networks (ANN) of the retro-propagation type can be an alternative method to estimate ETo in highland regions using a number of input variables limited. The objective of this study is to develop ANN models to estimate ETo for the Peruvian highlands using input variables such as maximum air temperature (Tmax), minimum air temperature (Tmin), hours of sunshine (Sh), relative humidity (Rh) and wind speed (Wv), as an alternative method to FAO Penman–Monteith method (FAO-PM56) and Hargreaves–Samani (HS). Daily climatic datasets recorded at 12 meteorological stations between 1963 and 2015 were selected in this study. For evaluation reason, the ETo calculated using the FAO-PM56 was also considered. The main input variable to ANN modeling is Tmax, followed by Sh and Wv or combinations between them. Hargreaves–Samani (HS) showed a poor performance in the estimation of the ETo in the Peruvian highlands compared to the 13 ANN models. Additionally, it was determined that in stations with lower thermal amplitude (< 14.2 °C) the lowest performance levels are presented in the estimation of the ETo with HS equation, which does not occur markedly with the ANN models that they estimate adequately ETo. Therefore, ANN models represent a great option to replace the FAO-PM56 and HS method, when ETo data series are scarce.Item Restricted Climate control on silicate weathering and physical erosion rates in young orogenic belts: Case study along a runoff gradient in Pacific and Amazonian Andean basins based on SNO-HYBAM Monitoring Program data(EGU General Assembly, 2017-04) Moquet, Jean Sébastien; Guyot, Jean-Loup; Viers, Jérôme; Crave, Alain; Morera Julca, Sergio Byron; Rau, Pedro; Armijos Cardenas, Elisa Natalia; Lagane, Christelle; Lavado Casimiro, Waldo Sven; Pombosa, Rodrigo; Fraizy, Pascal; Santini, William; Timouk, Franck; Vauchel, Philippe; Martinez, Jean-MichelAt the global scale and on geological time scales, mechanical erosion and chemical weathering budgets are linked. Together, these processes contribute to the formation and the degradation of the Earth's critical zone and to the biogeochemical cycles of elements. In young orogenic belts, climate and tectonic subsidence control together the rate of these matter balance budget and their relationships. The climate gradient observed along the Andean basin in both the Pacific and the Atlantic slopes offers the opportunity to explore the role of the climate variability on the erosion and weathering budgets and on their reciprocal relationships. Based on the SNO-HYBAM Monitoring Program database (Geodynamical, hydrological and Biogeochemical control of erosion/weathering and material transport in the Amazon, Orinoco and Congo basins), we explore the relationship between climate, the lithology, silicate weathering rates and physical erosion rates along a runoff gradient in Andean basins of the Amazon River (13 gauging stations) and Pacific drainage rivers (5 gauging stations). No homogenous relationship between erosion rates (E) and chemical weathering rate (W) is observed over the monitored basins. Only the volcanic basins respond to a global relationship defined in the literature while the other basins budget may depend on anthropogenic interferences on erosion/sedimentation budget, a lithology dependence of the W-E relationship parameters or/and on the existence of a threshold in this relationship. The results presented here contribute to better understanding the role of mountains belt formation in the biogeochemical cycles and in particular in the long-term carbon cycle.Your presentation type preference.Item Restricted Correction of TRMM 3B43 monthly precipitation data over the mountainous areas of Peru during the period 1998-2007(Wiley, 2011-01-13) Condom, Thomas; Rau, Pedro; Espinoza, Jhan CarloIn an attempt to estimate the spatial and temporal behaviour of rainfall over the mountainous areas of the Peruvian Andes, a new in situ monthly rainfall dataset has been collected (1998–2007) and compared with Tropical Rainfall Measuring Mission (TRMM) 3B43 monthly precipitation data for regions located above 3000 m. The reliability of the TRMM 3B43 data varies depending on the root mean squared error ratio (%RMSE) and correlation coefficient. Because of the discrepancy between the two datasets, the use of additive and multiplicative correction models is proposed for the TRMM 3B43 data. In the Peruvian mountain ranges, these correction models better approximate TRMM rainfall monthly values, as already verified for annual values.Item Open Access La distribución de las lluvias en la vertiente del Pacífico peruano y su relación con El Niño(Instituto Geofísico del Perú, 2017-01) Rau, Pedro; Bourrel, Luc; Dewitte, Boris; Labat, DavidEn 1892, se difundió la primera observación documentada de la corriente costera “El Niño”, denominada por aquel entonces: “Contracorriente marítima en Paita y Pacasmayo” (Carranza, 1892) y donde se intentaba explicar las lluvias torrenciales acaecidas en 1891. Un siglo y cuarto después, aun continúa el reto de poder comprender el efecto de este fenómeno sobre las lluvias a diferentes escalas de espacio y tiempo, especialmente en regiones del planeta como la Vertiente del Pacífico Peruano (VPP), donde sus efectos son experimentados frecuentemente. En el presente artículo se responde a preguntas comunes sobre la distribución de las lluvias en la VPP y el impacto del Fenómeno El Niño o ENSO (El Niño Oscilación del Sur en inglés), basándose en una revisión del estado del arte en la temática, las metodologías y los nuevos aportes.Item Restricted Temporal variability and annual budget of inorganic dissolved matter in Andean Pacific Rivers located along a climate gradient from northern Ecuador to southern Peru(Elsevier, 2018) Moquet, Jean Sébastien; Guyot, Jean-Loup; Morera Julca, Sergio Byron; Crave, Alain; Rau, Pedro; Vauchel, Philippe; Lagane, Christelle; Sondag, Francis; Lavado, Casimiro Waldo; Pombosa, Rodrigo; Martinez, Jean-MichelIn Ecuador and Peru, geochemical information from Pacific coastal rivers is limited and scarce. Here, we present an unedited database of major element concentrations from five HYBAM observatory stations monitored monthly between 4 and 10 years, and the discrete sampling of 23 Andean rivers distributed along the climate gradient of the Ecuadorian and Peruvian Pacific coasts. Concentration (C) vs. discharge (Q) relationships of the five monitored basins exhibit a clear dilution behavior for evaporites and/or pyrite solutes, while the solute concentrations delivered by other endmembers are less variable. Spatially, the annual specific fluxes for total dissolved solids (TDS), Ca²⁺, HCO₃, K+, Mg²⁺, and SiO₂ are controlled on the first order by runoff variability, while Cl, Na⁺ and SO₄² are controlled by the occurrence of evaporites and/or pyrite. The entire Pacific basin in Ecuador and Peru exported 30 Mt TDS·yr ¹, according to a specific flux of ∼70 t·km ²·yr ¹. This show that, even under low rainfall conditions, this orogenic context is more active, in terms of solute production, than the global average.Item Restricted Updating regionalization of precipitation in Ecuador(Springer, 2021-01-07) Ilbay-Yupa, Mercy; Lavado-Casimiro, Waldo; Rau, Pedro; Zubieta Barragán, Ricardo; Castillón, FiorelaThis article identifies homogeneous precipitation regions in Ecuador and their relationship to the El Niño-Southern Oscillation (ENSO), using monthly records from 215 rain stations for the 1968–2014 period. A k-means clustering analysis was used to divide the study area into k regions based on monthly and annual precipitation variables and geographic location (latitude, longitude, and altitude). The robustness of each cluster was evaluated using the “silhouette” coefficient. The groupings were then validated using the regional vector method (RVM). Twenty-two regions of homogeneous precipitation were identified. Seven regions are related to regional climate processes on the Pacific coast (unimodal precipitation). Two regions in the western foothills of the Andes show significant orographic rainfall. Eight regions in the inter-Andean region present a bimodal precipitation regime characterized by a reduction of precipitation from north to south and local variability. Five regions were identified in the Amazon area: three on the outer flanks of the eastern mountain range, one sub-Andean area, and one in the Amazon plain with regular rainfall throughout the year, influenced by the Amazon basin. Although Tropical Pacific sea surface temperature (SST) is strongly related to precipitation in the coastal regions of Ecuador, our findings indicate that SST influence varies among the regions of the country because Ecuador is influenced by the modes of precipitation variability in Colombia and Peru.