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Espinoza J.C.,Instituto Geofisico del Peru IGP | Marengo J.A.,National Institute for Space Research | Ronchail J.,University Paris Diderot | Carpio J.M.,Higher University of San Andres | And 2 more authors.
Environmental Research Letters | Year: 2014

Unprecedented wet conditions are reported in the 2014 summer (December-March) in South-western Amazon, with rainfall about 100% above normal. Discharge in the Madeira River (the main southern Amazon tributary) has been 74% higher than normal (58 000 m3 s-1) at Porto Velho and 380% (25 000 m3 s-1) at Rurrenabaque, at the exit of the Andes in summer, while levels of the Rio Negro at Manaus were 29.47 m in June 2014, corresponding to the fifth highest record during the 113 years record of the Rio Negro. While previous floods in Amazonia have been related to La Niña and/or warmer than normal tropical South Atlantic, the 2014 rainfall and flood anomalies are associated with warm condition in the western Pacific-Indian Ocean and with an exceptionally warm Subtropical South Atlantic. Our results suggest that the tropical and subtropical South Atlantic SST gradient is a main driver for moisture transport from the Atlantic toward south-western Amazon, and this became exceptionally intense during summer of 2014. © 2014 IOP Publishing Ltd. Source

Lavado Casimiro W.S.,Servicio Nacional de Meteorologia e Hidrologia | Lavado Casimiro W.S.,University of Lima | Lavado Casimiro W.S.,French National Center for Scientific Research | Labat D.,French National Center for Scientific Research | And 4 more authors.
Hydrological Processes | Year: 2013

The hydroclimatology of the Peruvian Amazon-Andes basin (PAB) which surface corresponding to 7% of the Amazon basin is still poorly documented. We propose here an extended and original analysis of the temporal evolution of monthly rainfall, mean temperature (Tmean), maximum temperature (Tmax) and minimum temperature (Tmin) time series over two PABs (Huallaga and Ucayali) over the last 40years. This analysis is based on a new and more complete database that includes 77 weather stations over the 1965-2007 period, and we focus our attention on both annual and seasonal meteorological time series. A positive significant trend in mean temperature of 0.09°C per decade is detected over the region with similar values in the Andes and rainforest when considering average data. However, a high percentage of stations with significant Tmean positive trends are located over the Andes region. Finally, changes in the mean values occurred earlier in Tmax (during the 1970s) than in Tmin (during the 1980s). In the PAB, there is neither trend nor mean change in rainfall during the 1965-2007 period. However, annual, summer and autumn rainfall in the southern Andes presents an important interannual variability that is associated with the sea surface temperature in the tropical Atlantic Ocean while there are limited relationships between rainfall and El Niño-Southern Oscillation (ENSO) events. © 2012 John Wiley & Sons, Ltd. Source

Dale A.W.,Leibniz Institute of Marine Science | Sommer S.,Leibniz Institute of Marine Science | Lomnitz U.,Leibniz Institute of Marine Science | Montes I.,Instituto Geofisico del Peru IGP | And 9 more authors.
Biogeosciences | Year: 2015

Carbon cycling in Peruvian margin sediments (11 and 12° S) was examined at 16 stations, from 74 m water depth on the middle shelf down to 1024 m, using a combination of in situ flux measurements, sedimentary geochemistry and modelling. Bottom water oxygen was below detection limit down to ca. 400 m and increased to 53 Î1/4M at the deepest station. Sediment accumulation rates decreased sharply seaward of the middle shelf and subsequently increased at the deep stations. The organic carbon burial efficiency (CBE) was unusually low on the middle shelf (<20%) when compared to an existing global database, for reasons which may be linked to episodic ventilation of the bottom waters by oceanographic anomalies. Deposition of reworked, degraded material originating from sites higher up on the slope is proposed to explain unusually high sedimentation rates and CBE (>60%) at the deep oxygenated sites. In line with other studies, CBE was elevated under oxygen-deficient waters in the mid-water oxygen minimum zone. Organic carbon rain rates calculated from the benthic fluxes alluded to efficient mineralisation of organic matter in the water column compared to other oxygen-deficient environments. The observations at the Peruvian margin suggest that a lack of oxygen does not greatly affect the degradation of organic matter in the water column but promotes the preservation of organic matter in sediments. © Author(s) 2015. Source

Espinoza J.C.,Instituto Geofisico del Peru IGP | Ronchail J.,University Paris Diderot | Lengaigne M.,CIRAD - Agricultural Research for Development | Quispe N.,Servicio Nacional de Meteorologia e Hidrologia SENAMHI | And 4 more authors.
Climate Dynamics | Year: 2013

This study investigates the spatial and temporal characteristics of cold surges that propagates northward along the eastern flank of the Andes from subtropical to tropical South America analysing wintertime in situ daily minimum temperature observations from Argentina, Bolivia and Peru and ERA-40 reanalysis over the 1975-2001 period. Cold surges usually last 2 or 3 days but are generally less persistent in the southern La Plata basin compared to tropical regions. On average, three to four cold surges are reported each year. Our analysis reveals that 52 % of cold episodes registered in the south of La Plata basin propagate northward to the northern Peruvian Amazon at a speed of around 20 m s-1. In comparison to cold surges that do not reach the tropical region, we demonstrate that these cold surges are characterized, before they reach the tropical region, by a higher occurrence of a specific circulation pattern associated to southern low-level winds progression toward low latitudes combined with subsidence and dry condition in the middle and low troposphere that reinforce the cold episode through a radiative effect. Finally, the relationship between cold surges and atmosphere dynamics is illustrated for the two most severe cold intrusions that reached the Peruvian and Bolivian Amazon in the last 20 years. © 2012 Springer-Verlag Berlin Heidelberg. Source

Lavado Casimiro W.S.,Servicio Nacional de Meteorologia e Hidrologia | Lavado Casimiro W.S.,French National Center for Scientific Research | Lavado Casimiro W.S.,University of Lima | Ronchail J.,University of Paris Pantheon Sorbonne | And 4 more authors.
Hydrological Sciences Journal | Year: 2012

According to the Peruvian agricultural ministry, the Pacific watersheds where the great cities and intense farming are located only benefit from 1% of the available freshwater in Peru. Hence a thorough knowledge of the hydrology of this region is of particular importance. In the paper, analysis of this region and of the two other main Peruvian drainages, the Titicaca and Amazonas are reported. Rainfall and runoff data collected by the Peruvian National Service of Meteorology and Hydrology (SENAMHI) and controlled under the Hydrogeodynamics of the Amazon Basin (HyBAm) project is the basis of this basin-scale study that covers the 1969-2004 period. Beyond the strong contrasting rainfall conditions that differentiate the dry coastal basins and the wet eastern lowlands, details are given about in situ runoff and per basin rainfall distribution in these regions, and about their different altitude-rainfall relationships. Rainfall and runoff variability is strong in the coastal basins at seasonal and interannual time scales, and related to extreme El Niño events in the Pacific Ocean. However, rainfall and runoff are more regular in the Andes and Amazonas at the inter-annual time scale. Warm sea-surface temperatures in the northern tropical Atlantic tend to produce drought in the southern Andes basins. Moreover, significant trends and change-points are observed in the runoff data of Amazonas basins where rainfall and runoff decrease, especially after the mid-1980s and during the low-stage season. Almost all the coastal basins show some change in minimum runoff during the last 35 years while no change is observed in rainfall. This means that human activity may have changed runoff in this region of Peru, but this hypothesis deserves more study. © 2012 IAHS Press. Source

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