Instituto Geofisico del Peru IGP

Lima, Peru

Instituto Geofisico del Peru IGP

Lima, Peru
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Condori C.,University of Brasilia | Condori C.,Instituto Geofisico del Peru IGP | Franca G.S.,University of Brasilia | Tavera H.J.,Instituto Geofisico del Peru IGP | And 3 more authors.
Journal of South American Earth Sciences | Year: 2017

In this study, we present results from teleseismic receiver functions, in order to investigate the crustal thickness and Vp/Vs ratio beneath northern Peru. A total number of 981 receiver functions were analyzed, from data recorded by 28 broadband seismic stations from the Peruvian permanent seismic network, the regional temporary SisNort network and one CTBTO station. The Moho depth and average crustal Vp/Vs ratio were determined at each station using the H-k stacking technique to identify the arrival times of primary P to S conversion and crustal reverberations (PpPms, PpSs + PsPms). The results show that the Moho depth correlates well with the surface topography and varies significantly from west to east, showing a shallow depth of around 25 km near the coast, a maximum depth of 55–60 km beneath the Andean Cordillera, and a depth of 35–40 km further to the east in the Amazonian Basin. The bulk crustal Vp/Vs ratio ranges between 1.60 and 1.88 with the mean of 1.75. Higher values between 1.75 and 1.88 are found beneath the Eastern and Western Cordilleras, consistent with a mafic composition in the lower crust. In contrast values vary from 1.60 to 1.75 in the extreme flanks of the Eastern and Western Cordillera indicating a felsic composition. We find a positive relationship between crustal thickness, Vp/Vs ratio, the Bouguer anomaly, and topography. These results are consistent with previous studies in other parts of Peru (central and southern regions) and provide the first crustal thickness estimates for the high cordillera in northern Peru. © 2017 Elsevier Ltd

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.

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.

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 Andrés | 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.

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.

Belmadani A.,University Pierre and Marie Curie | Belmadani A.,University of Hawaii at Manoa | Belmadani A.,University of Concepción | Echevin V.,University Pierre and Marie Curie | And 4 more authors.
Climate Dynamics | Year: 2013

The dynamics of the Peru–Chile upwelling system (PCUS) are primarily driven by alongshore wind stress and curl, like in other eastern boundary upwelling systems. Previous studies have suggested that upwelling-favorable winds would increase under climate change, due to an enhancement of the thermally-driven cross-shore pressure gradient. Using an atmospheric model on a stretched grid with increased horizontal resolution in the PCUS, a dynamical downscaling of climate scenarios from a global coupled general circulation model (CGCM) is performed to investigate the processes leading to sea-surface wind changes. Downscaled winds associated with present climate show reasonably good agreement with climatological observations. Downscaled winds under climate change show a strengthening off central Chile south of 35°S (at 30°S–35°S) in austral summer (winter) and a weakening elsewhere. An alongshore momentum balance shows that the wind slowdown (strengthening) off Peru and northern Chile (off central Chile) is associated with a decrease (an increase) in the alongshore pressure gradient. Whereas the strengthening off Chile is likely due to the poleward displacement and intensification of the South Pacific Anticyclone, the slowdown off Peru may be associated with increased precipitation over the tropics and associated convective anomalies, as suggested by a vorticity budget analysis. On the other hand, an increase in the land–sea temperature difference is not found to drive similar changes in the cross-shore pressure gradient. Results from another atmospheric model with distinct CGCM forcing and climate scenarios suggest that projected wind changes off Peru are sensitive to concurrent changes in sea surface temperature and rainfall. © 2013, Springer-Verlag Berlin Heidelberg.

Mosquera-Vasquez K.,Instituto Geofisico del Peru IGP | Dewitte B.,Instituto Geofisico del Peru IGP | Illig S.,Instituto Geofisico del Peru IGP | Takahashi K.,Instituto Geofisico del Peru IGP | Garric G.,MERCATOR
Journal of Geophysical Research: Oceans | Year: 2013

[1] The recent decades have experienced changes in the characteristics of the El Niño phenomenon, with in particular an increased occurrence of so-called Modoki or Central Pacific El Niños. Here the 2002/2003 El Niño, characterized as a Central Pacific El Niño, is studied from an Ocean General Circulation Model simulation. The focus is on the sequence of equatorial waves and their impact on zonal and vertical advection. The wave amplitude according to the most energetic baroclinic modes are first estimated, which allows inferring the sequence of the intraseasonal equatorial Kelvin (IKW) and Rossby (IRW) waves. It is shown that energetic downwelling IKWs, forced in the western-central Pacific, crossed the equatorial Pacific. Reflections of IKWs into IRWs onto the zonally varying thermocline and eastern boundary are also observed. A simplified heat budget of the surface layer is then carried out to infer the dominant processes at work during the evolution of this event focusing on the wave-induced advection terms. The results indicate that the warming phase (April-November 2002) is mainly controlled by zonal advection of mean temperature (accounted for by IKWs and locally wind-driven current) and by vertical advection in the eastern Pacific. The cooling phase (December 2002 to April 2003) is dominated by a reduction in solar radiation and the IRW-induced zonal advection of mean temperature respectively in the central and eastern equatorial Pacific. The recharge-discharge process is also showed to be at work with the recharge (discharge) process operating mainly through the second (first) baroclinic mode. © 2012. American Geophysical Union. All Rights Reserved.

Junquas C.,Instituto Geofisico del Peru IGP | Junquas C.,Joseph Fourier University | Li L.,Institute Pierre Simon Laplace | Vera C.S.,CONICET | And 2 more authors.
Climate Dynamics | Year: 2015

Impacts of the main South American orographic structures (the Andes, the Brazilian Plateau and the Guiana shield) on the regional climate and associated global teleconnection are investigated through numerical experiments in which some of these features are suppressed. Simulations are performed with a ‘‘two-way nesting’’ system coupling interactively the regional and global versions of the LMDZ4 atmospheric general circulation model. At regional scale, the simulations confirm previous studies, showing that both the Andes and the Brazilian Plateau exert a control on the position and strength of the South Atlantic convergence zone (SACZ), mainly through their impact on the low-level jet and the coastal branch of the subtropical anticyclones. The northern topography of South America appears to be crucial to determine the leading mode of rainfall variability in eastern South America, which manifests itself as a dipole-like pattern between Southeastern South America and the SACZ region. The suppression of South America orography also shows global-scale effects, corresponding to an adjustment of the global circulation system. Changes in atmospheric circulation and precipitation are found in remote areas on the globe, being the consequences of various teleconnection mechanisms. When the Brazilian Plateau and the Andes are suppressed, there is a decrease of precipitation in the SACZ region, associated with a weakening of the large-scale ascendance. Changes are described in terms of anomalies in the Walker circulation, meridional displacements of the mid-latitude jet stream, Southern annular mode anomalies and modifications of Rossby wave train teleconnection processes. © 2015 Springer-Verlag Berlin Heidelberg

Segura H.,Instituto Geofisico Del Peru IGP | Espinoza J.C.,Instituto Geofisico Del Peru IGP | Junquas C.,Grenoble Institute of Technology | Takahashi K.,Instituto Geofisico Del Peru IGP
Environmental Research Letters | Year: 2016

In this study we identified a significant low frequency variability (8 to 20 years) that characterizes the hydroclimatology over the Central Andes. Decadal-interdecadal variability is related to the central-western Pacific Ocean (R 2 = 0.50) and the zonal wind at 200 hPa above the Central Andes (R 2 = 0.66). These two oceanic-atmospheric variables have a dominant decadal-interdecadal variability, and there is a strong relationship between them at a low frequency time scale (R 2 = 0.66). During warming decades in the central-western Pacific Ocean, westerlies are intensified at 200 hPa above the Central Andes, which produce decadal periods of hydrological deficit over this region. In contrast, when the central-western Pacific Ocean is cooler than usual, easterly anomalies prevail over the Central Andes, which are associated with decades of positive hydrological anomalies over this region. Our results indicate that impacts of El Niǹo on hydrology over the Central Andes could be influenced by the low frequency variability documented in this study. © 2016 IOP Publishing Ltd.

Zubieta R.,Instituto Geofisico del Peru IGP | Zubieta R.,Agrarian National University | Saavedra M.,Instituto Geofisico del Peru IGP | Silva Y.,Instituto Geofisico del Peru IGP | Giraldez L.,Instituto Geofisico del Peru IGP
Stochastic Environmental Research and Risk Assessment | Year: 2016

The analysis of annual or seasonal data can lead to misinterpretation of spatio-temporal rainfall distribution. A high percentage of total annual precipitation can fall in just a few days, causing floods or landslides. Large economic losses from these events are particularly common in Peru, where the daily precipitation has been poorly investigated. This study presents a spatio-temporal analysis of concentration index over the Mantaro River basin in the central Peruvian Andes. Daily rainfall data recorded at 46 rainfall stations between 1974 and 2004 were selected in this study. In terms of average values, the analysis of daily rainfall indicates that low-intensity events account for 38 % of rainy days but only approximately 9 % of the total rain amount. In contrast, high- and very high-intensity events account for 35 % of rainy days and approximately 71 % of the total rain amount. The results also indicate higher concentration and lower intensity over the Northern and Central regions, compared to Southern region of the basin. Rainfall concentration gives evidence of why some of these places are more likely to be affected by extreme weather events; spatial distribution of event intensity can be partly explained by daily rainfall heterogeneity and orography. Moreover, Mann–Kendall test mostly shows a significant change toward a weaker seasonality of daily precipitation distribution over high-mountain regions. © 2016 Springer-Verlag Berlin Heidelberg

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