The response of Iberian rivers to the North Atlantic Oscillation

In this study we analyzed the influence of the North Atlantic Oscillation (NAO) on the streamflow in 187 sub-basins of the Iberian Peninsula. Monthly and one-month lagged correlations were conducted to assess the spatio-temporal extent of the NAO influence on Iberian river discharges. Analysis of the persistence of the winter NAO throughout the year was also undertaken, together with analysis of streamflow anomalies during positive and negative NAO phases. Moving-window correlation analyses were conducted to assess potential changes in the temporal evolution of the NAO influence on Iberian streamflows. The results show that the NAO has a large impact on surface water resources throughout the Iberian Peninsula during winter, and in the Atlantic watershed during autumn. We showed that water resources management and snowmelt are causing the persistent dependence of streamflows on the previous winter NAO. We found that strongly positive streamflow anomalies occurred during winter, especially in the Atlantic watershed, and provide evidence of non-stationarity and spatial variability in the NAO influence on Iberian water resources

NAUTILUS-DTU10 MW Floating Offshore Wind Turbine at Gulf of Maine: Public numerical models of an actively ballasted semisubmersible

This study presents two numerical multiphysics models of the NAUTILUS-10 floating support structure mounting the DTU10 MW Reference Wind Turbine at Gulf of Maine site, and analyses its dynamics. With the site conditions and the FAST model of the onshore turbine as the starting point, the floating support structure: tower, floating substructure with its corresponding active ballast system and station keeping system, was designed by NAUTILUS. The numerical models were developed and the onshore DTU wind energy controller was tuned to avoid the resonance of the operating FOWT by TECNALIA, in the framework of H2020 LIFES50+ project. This concept and its subsystems are fully characterised throughout this paper and implemented in opensource code, FAST v8.16. Here, the mooring dynamics are solved using MoorDyn, and the hydrodynamic properties are computed using HydroDyn. Viscous effects, not captured by radiation-diffraction theory, are modelled using two different approaches: (1) through linear and quadratic additional hydrodynamic damping matrices and (2) by means of Morison elements. A set of simulations (such as, decay, wind only and broadband irregular waves tests) were carried out with system identification purposes and to analyse the differences between the two models presented. Then, a set of simulations in stochastic wind and waves were carried out to characterise the global response of the FOWT.European Union Horizon2020 programme under the agreement H2020-LCE-2014-1-640741, LIFES50+ projec

Cluster variation method and disorder varieties of two-dimensional Ising-like models

I show that the cluster variation method, long used as a powerful hierarchy of approximations for discrete (Ising-like) two-dimensional lattice models, yields exact results on the disorder varieties which appear when competitive interactions are put into these models. I consider, as an example, the plaquette approximation of the cluster variation method for the square lattice Ising model with nearest-neighbor, next-nearest-neighbor and plaquette interactions, and, after rederiving known results, report simple closed-form expressions for the pair and plaquette correlation functions.Comment: 10 revtex pages, 1 postscript figur

PRODUCCIÓN DE ADSORBENTES A PARTIR DE BAGAZO DE CAÑA DE AZÚCAR PARA LA ELIMINACIÓN DE COLORANTES EN FASE ACUOSA

En este trabajo se realizaron pruebas de adsorción para tres colorantesdiferentes: azul de metileno, Basic Blue 41 y Acid Red 266. Se utilizó como material adsorbente carbón activo preparado a partir de bagazo de caña de azúcar. Utilizando como activantes: ácido sulfúrico, ácido ortofosfórico y cloruro de zinc, con este último en dos relaciones diferentes. La pirolisis se realizó al material activado químicamente y además se preparó material sin activación previa para comparar los resultados. El carbón activo se utilizó en pruebas en discontinuo y bajo agitación con los tres colorantes mencionados. Se logra una mayor adsorción en general con todos los carbones activos frente al azul de metileno, excepto para el carbón activo fabricado a partir de bagazo de caña de azúcar activado con cloruro de zinc en relación 1-1, que adsorbe el Basic Blue 41 en gran cantidad; con este carbón activo se obtienen los mejores resultados tanto en las pruebas cinéticas como en las de adsorción

Small scale spatial variability of snow density and depth over complex alpine terrain: Implications for estimating snow water equivalent

This study analyzes spatial variability of snow depth and density from measurements made in February and April of 2010 and 2011 in three 1–2 km2 areas within a valley of the central Spanish Pyrenees. Snow density was correlated with snow depth and different terrain characteristics. Regression models were used to predict the spatial variability of snow density, and to assess how the error in computed densities might influence estimates of snow water equivalent (SWE). The variability in snow depth was much greater than that of snow density. The average snow density was much greater in April than in February. The correlations between snow depth and density were generally statistically significant but typically not very high, and their magnitudes and signs were highly variable among sites and surveys. The correlation with other topographic variables showed the same variability in magnitude and sign, and consequently the resulting regression models were very inconsistent, and in general explained little of the variance. Antecedent climatic and snow conditions prior to each survey help highlight the main causes of the contrasting relation shown between snow depth, density and terrain. As a consequence of the moderate spatial variability of snow density relative to snow depth, the absolute error in the SWE estimated from computed densities using the regression models was generally less than 15%. The error was similar to that obtained by relating snow density measurements directly to adjacent snow depths.This work was supported by research projects CGL2011-27536/HID: “Hidrologia nival en el Pirineo central español: variabilidad espacial, importancia hidrológica y su respuesta a la variabilidad y cambio climático”, financed by the Spanish Commission of Science and Technology, and FEDER; ACQWA (FP7-ENV- 2008-1-212250); the projects “La nieve en el Pirineo aragonés: Distribución especial y su respuesta a las condiciones climáticas” and “Efecto de los escenarios de cambio climático sobre la hidrología superficial y la gestión de embalses del Pirineo Aragonés”, financed by “Obra Social La Caixa”; and “Influencia del cambio climático en el turismo de nieve-CTTP1/10”, financed by the Comunidad de Trabajo de los Pirineos, CTP.Peer Reviewe

Recent evolution and associated hydrological dynamics of a vanishing tropical Andean glacier: Glaciar de Conejeras, Colombia

Glaciers in the inner tropics are rapidly retreating due to atmospheric warming. In Colombia, this retreat is accelerated by volcanic activity, and most glaciers are in their last stages of existence. There is general concern about the hydrological implications of receding glaciers, as they constitute important freshwater reservoirs and, after an initial increase in melting flows due to glacier retreat, a decrease in water resources is expected in the long term as glaciers become smaller. In this paper, we perform a comprehensive study of the evolution of a small Colombian glacier, Conejeras (Parque Nacional Natural de los Nevados) that has been monitored since 2006, with a special focus on the hydrological response of the glacierized catchment. The glacier shows great sensitivity to changes in temperature and especially to the evolution of the El Niño–Southern Oscillation (ENSO) phenomenon, with great loss of mass and area during El Niño warm events. Since 2006, it has suffered a 37&thinsp;% reduction, from 22.45&thinsp;ha in 2006 to 12&thinsp;ha in 2017, with an especially abrupt reduction since 2014. During the period of hydrological monitoring (June 2013 to December 2017), streamflow at the outlet of the catchment experienced a noticeable cycle of increasing flows up to mid-2016 and decreasing flows afterwards. The same cycle was observed for other hydrological indicators, including the slope of the rising flow limb and the monthly variability of flows. We observed an evident change in the daily hydrograph, from a predominance of days with a purely melt-driven hydrograph up to mid-2016, to an increase in the frequency of days with flows less influenced by melt after 2016. Such a hydrological cycle is not directly related to fluctuations of temperature or precipitation; therefore, it is reasonable to consider that it is the response of the glacierized catchment to retreat of the glacier. Results confirm the necessity for small-scale studies at a high temporal resolution, in order to understand the hydrological response of glacier-covered catchments to glacier retreat and imminent glacier extinction.</p

Response of vegetation to drought time-scales across global land biomes

We evaluated the response of the Earth land biomes to drought by correlating a drought indexwith three global indicators of vegetation activity and growth: vegetation indices from satellite imagery, tree-ring growth series, and Aboveground Net Primary Production (ANPP) records. Arid and humid biomes are both affected by drought, and we suggest that the persistence of thewater deficit (i.e., the drought time-scale) could be playing a key role in determining the sensitivity of land biomes to drought. We found that arid biomes respond to drought at short time-scales; that is, there is a rapid vegetation reaction as soon as water deficits below normal conditions occur. This may be due to the fact that plant species of arid regions havemechanisms allowing them to rapidly adapt to changing water availability. Humid biomes also respond to drought at short time-scales, but in this case the physiological mechanisms likely differ fromthose operating in arid biomes, as plants usually have a poor adaptability to water shortage. On the contrary, semiarid and subhumid biomes respond to drought at long time-scales, probably because plants are able to withstand water deficits, but they lack the rapid response of arid biomes to drought. These results are consistent among three vegetation parameters analyzed and across different land biomes, showing that the response of vegetation to drought depends on characteristic drought time-scales for each biome. Understanding the dominant time-scales at which drought most influences vegetation might help assessing the resistance and resilience of vegetation and improving our knowledge of vegetation vulnerability to climate change

Spatio-temporal variability of droughts in Bolivia: 1955-2012

In this study, the spatio-temporal variability and trends of droughts across Bolivia between 1955 and 2012 were investigated using two climate drought indices: the Standardized Precipitation Index (SPI), which is based on precipitation data, and the Standardized Precipitation Evapotranspiration Index (SPEI), which is based on the difference between the precipitation and the reference evapotranspiration (ETo). We found that the average drought conditions across the country showed a temporal behaviour mainly characterized by decadal variations. The spatial pattern of drought evolution showed marked differences between the Amazonian region and the Bolivian Altiplano. Both regions showed different drought periods, a lower frequency of drought variability in the Amazon region and trends towards drier conditions in the Altiplano, mainly due to a higher atmospheric water demand as a consequence of increased ETo. We also showed that inclusion of ETo, obtained from maximum and minimum temperature records, increased the spatial heterogeneity of the drought evolution in relation to the evolution observed when only precipitation droughts were considered. The SPEI, the calculation of which includes precipitation and ETo, indicated intensification in drought severity in the last years analysed relative to the pattern found when precipitation droughts alone were considered, and also indicated an increase in the magnitude and duration of drought events. The potential for increasing drought conditions under various climate change scenarios is discussed. © 2015 Royal Meteorological Society.This work has been supported by research projects I-COOP H2O 2013CD0006: ‘Test multisectorial y actividades demostrativa sobre el potencial desarrollo de sistemas de monitorización de sequías en tiempo real en la región del oeste de Sudamérica’ financed by the Spanish National Research Council (CSIC), CGL2011-27574-CO2-02 financed by the Spanish Commission of Science and Technology and FEDER, ‘Demonstration and validation of innovative methodology for regional climate change adaptation in the Mediterranean area (LIFE MEDACC)’ financed by the LIFE programme of the European Commission, C.A.-M. received a postdoctoral fellowship # JCI-2011-10263. A.S.-L. is supported by the ‘Secretaria per a Universitats i Recerca del Departament d'Economia i Coneixement, de la Generalitat de Catalunya i del programa Cofund de les Accions Marie Curie del 7è Programa marc d'R + D de la Unió Europea’ (2011 BP-B 00078) and the postdoctoral fellowship # JCI-2012-12508.Peer Reviewe

Secondary REE-minerals in the karst bauxites of the Bahoruco Peninsula (Dominican Republic)

Rare earth elements (REE) are essential for numerous technological applications. Currently about 90% of the worldwide REE demand is supplied by China (Hatch, 2012), and therefore REE are defined as critical metals (Dutta et al., 2016). Bauxites, the main source for Al in the world, gained interest since they are capable of concentrating significant amounts of REE (Liu et al., 2016), and have been recently considered unconventional deposits for REE (Goodenough et al., 2017). Two types of bauxitic deposits are defined: a) lateritic bauxites (formed after intense weathering of an Al-bearing protolith), and b) karst bauxites (of controversial origin, hosted in carbonaceous rocks). One hypothesis of karst bauxite formation suggests dissolution of the carbonates, whereas the other implies an external contribution of Al-bearing minerals during or after carbonate deposition (Bárdossy, 1982)

Caracterización y origen de las dolomías del sector sudeste de Picos de Europa (Norte de España)

In this work we focus on the dolomitization processes which affected the southeastern sector of Picos de Europa Unit. The dolostones formed consequently with this process are rocks with a varied and irregular geometry, wich reminds that observed in intrusive rocks. Their chemical composition show a slight excess of calcium in relation to stoichiometric dolomite. Their iron and strontium contents are low in relation to other comparable dolomites. The abundance of dolostones is much bigger at the Frontal Unit than in upper structural Units. The dolomitization processes respond to an epigenetic dolomitization model and they are previous to the formation of Pb-Zn orebodies. We suggest a per ascensum dolomitization model tiggered by formation waters of the Pisuerga-Carrion Unit. With regard to age, the dolomitization was later than Lower Estephanian B and possibly earlier than some undetermined time during the Permian.En el presente trabajo se pone de manifiesto la existencia de un proceso de dolomitización que afectó al sector sudeste de la región de Picos de Europa. Las dolomías formadas como consecuencia de este proceso son rocas de geometría muy variada e irregular, que recuerda a la de las masas intrusivas. Su composición química muestra un ligero exceso en calcio respecto a la fórmula estequiométrica de la dolomita. Sus contenidos en hierro y estroncio son bajos respecto a los de otras dolomías comparables. El volumen de dolomías formado es mucho mayor en la Unidad Frontal de Picos de Europa que en Unidades estructurales superiores. Los procesos dolomitizadores obedecen a un modelo de dolomitización epigenético y son previos a la deposición de mineralizaciones de Pb-Zn. Se propone un modelo de dolomitización per ascensum a partir de aguas de formación de los sedimentos de la región de Pisuerga-Carrión. En cuanto a la edad, la dolomitización es posterior al Estefaniense B inferior y posiblemente anterior a un momento del Pérmico no determinado