Search results

9 Pags., 4 Tabls., 4 Figs. ; Rainfall erosivity refers to the ability of precipitation to erode soil, and depends on characteristics such as its total volume, duration, and intensity and amount of energy released by raindrops. Despite the relevance of rainfall erosivity for soil degradation prevention, very few studies have addressed its spatial and temporal variability. In this study the time variation of rainfall erosivity in the Ebro Valley (NE Spain) is assessed for the period 1955–2006. The results show a general decrease in annual and seasonal rainfall erosivity, which is explained by a decrease of very intense rainfall events whilst the frequency of moderate and low events increased. This trend is related to prevailing positive conditions of the main atmospheric teleconnection indices affecting the West Mediterranean, i.e. the North Atlantic Oscillation (NAO), the Mediterranean Oscillation (MO) and the Western Mediterranean Oscillation (WeMO). ; This work has been supported by research projects CGL2011- 24185 financed by the Spanish Ministry of Science and Innovation (CICYT) and the European Regional Development Fund (ERDFFEDER), 2010CZ0021 financed by the Spanish National Research Council (Consejo Superior de Investigaciones Científicas-CSIC) and the Czech Academy of Sciences, and "Grupo de Investigación E68: Geomorfología y Cambio Global" financed by the Aragón Government and the European Social Fund (ESF-FSE). Research of M. A.-M. was supported by a JAE-Predoc grant from the Spanish National Research Council (Consejo Superior de Investigaciones Científicas-CSIC). ; Peer reviewed

A new multiscalar drought dataset, the SPEIbase, made available to the scientific and management community is presented. The multiscalar character of the dataset allows finding the most appropriate time scale of interest for a specific application, so potential uses of the dataset range over a wide variety of disciplines. The dataset (in three file formats) is distributed under an open license. Further work includes updating the dataset past December 2006, depending on the data availability. ; This work has been supported by the research projects CGL2008-01189/BTE and CGL2006-11619/HID, funded by the Spanish Commission of Science and Technology and FEDER; EUROGEOSS (FP7-ENV-2008-1-226487) and ACQWA (FP7-ENV-2007-1- 212250), funded by the VII Framework Programme of the European Commission; and "Las sequías climáticas en la cuenca del Ebro y su respuesta hidrológica" and "La nieve en el Pirineo aragonés: Distribución espacial y su respuesta a las condiciones climática," funded by "Obra Social La Caixa" and the Aragón Government. ; Peer reviewed

27 Pags., 5 Tabls., 8 Figs. The definitive version is available at: http://www.jswconline.org/ ; Assessment of the spatial distribution of soil properties has achieved considerable interest among soil scientists, both for testing hypotheses about soil formation processes and for predicting the properties of soils at nonsampled locations (mapping). In this paper, we provide a discussion of the various approaches to the modeling of spatial variates, and we propose a modeling framework that is able to incorporate the most important effects usually found in spatial variates, including fixed and random spatial effects, spatial trends, and heteroscedasticity. We provide a case study of the analysis of eight soil properties in a mountain catchment in the Spanish Pyrenees. As explanatory covariates, we use several topography parameters, which can be related to the pedogenetic processes active in the area. Several of them proved useful for explaining the variability of soil properties, explaining up to 77% of their variance. We focus on the importance of model selection in order to determine which effects are relevant for modeling each soil parameter. We find that the full model is not necessarily optimal for all the variables tested and that the model should be adapted to the complexity of each individual case. This paper is a contribution to the discussion on the modeling of spatial variates and to the eventual development of a general theory of spatial variates. ; This work has been supported by the following research projects: EROMED (CGL2011-25486) and DISDROSPEC (CGL2011–24185) financed by the Spanish Commission of Science and Technology (CICYT) and FEDER, ChangingRISKS (OPE00446/PIM2010ECR-00726) financed by EU ERA-NET CIRCLE Programme, and Grupo de Excelencia E68 financed by the Aragón Government. Research of M. A.-M. is supported by a research grant from the Spanish National Research Council (JAE-Predoc, CSIC). ; Peer reviewed

14 Pag., 4 Tabl., 5 Fig. © Author(s) 2010. This work is distributed under the Creative Commons Attribution 3.0 License. ; Sediment, Total Organic Carbon (TOC) and total nitrogen (TN) accumulation during one overbank flood (1.15 y return interval) were examined at one reach of the Middle Ebro River (NE Spain) for elucidating spatial patterns. To achieve this goal, four areas with different geomorphological features and located within the study reach were examined by using artificial grass mats. Within each area, 1 m2 study plots consisting of three pseudo-replicates were placed in a semi-regular grid oriented perpendicular to the main channel. TOC, TN and Particle-Size composition of deposited sediments were examined and accumulation rates estimated. Generalized linear mixed-effects models were used to analyze sedimentation patterns in order to handle clustered sampling units, specific-site effects and spatial self-correlation between observations. Our results confirm the importance of channel-floodplain morphology and site micro-topography in explaining sediment, TOC and TN deposition patterns, although the importance of other factors as vegetation pattern should be included in further studies to explain small-scale variability. Generalized linear mixed-effect models provide a good framework to deal with the high spatial heterogeneity of this phenomenon at different spatial scales, and should be further investigated in order to explore its validity when examining the importance of factors such as flood magnitude or suspended sediment concentration. ; Field works were funded by the Department of Environmental Science, Technology and University – Government of Aragon (Research group E-61 on Ecological Restoration)– and MEC (CGL2005-07059). The Spanish Research Council (CSIC) granted Álvaro Cabezas through the I3P program(I3P-EPD2003-2), which was financed by European Social Funds (UE). Research of M. Angulo-Martínez is supported by a JAE-Predoc Research Grant from the Spanish National Research Council (Consejo Superior de Investigaciones Científicas – CSIC). ; Peer reviewed

35 Pags., 1 Tabl., 9 Figs. The definitive version is available at: http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-0088 ; Most applications of the extreme value (EV) theory have assumed stationarity, i.e. the statistical properties of the process do not change over time. However, there is evidence suggesting that the occurrence of extreme events is not stationary but changes naturally, as it has been found for many other climate variables. Of paramount importance for hazard analysis is whether the observed precipitation time series exhibit long-term trends or cycles; such information is also relevant in climate change studies. In this study, the theory of non-stationary extreme value (NSEV) analysis was applied to data series of daily precipitation using the peaks-over-threshold (POT) approach. A Poisson/generalized Pareto (P/GP) model, in which the model parameters were allowed to vary linearly with time, was fitted to the resulting series of precipitation event's intensity and magnitude. A log-likelihood ratio test was applied to determine the existence of trends in the model parameters. The method was applied to a case study in northeast Spain, comprising a set of 64 daily rainfall series from 1930 to 2006. Statistical significance was achieved in less than 5% of the stations using a linear non-stationary model at the annual scale, indicating that there is no evidence of a generalized trend in extreme precipitation in the study area. At the seasonal scale, however, a significant number of stations along the Mediterranean (Catalonia region) showed a significant decrease of extreme rainfall intensity in winter, while experiencing an increase in spring. ; This research has been supported by the following projects: CGL2008-00831/BTE, CGL2006-11619/HID, CGL2008-01189/BTE and CGL2008-1083/CLI funded by the Spanish Commission of Science and Technology and FEDER; EUROGEOSS (FP7-ENV-2008-1-226487) and ACQWA (FP7-ENV-2007-1-212250) funded by the VII Framework Programme of the European Commission; 'Las sequías climáticas en la cuenca del Ebro y su respuesta hidrológica' and 'La nieve en el Pirineo Aragonés: distribución espacial y su respuesta a las condiciones climáticas' funded by 'Obra Social La Caixa' and the Aragón Government; and 'Programa de grupos de investigación consolidados' funded by the Aragón Government. ; Peer reviewed

A monthly global dataset of a multiscalar drought index is presented and compared in terms of spatial and temporal variability with the existing continental and global drought datasets based on the Palmer drought severity index (PDSI). The presented dataset is based on the standardized precipitation evapotranspiration index (SPEI). The index was obtained using the CRU TS3.0 dataset at a spatial resolution of 0.5°. The advantages of the new dataset are that; i) it improves the spatial resolution of the unique global drought dataset at a global scale; ii) it is spatially and temporally comparable to other datasets, given the probabilistic nature of the SPEI, and, in particular; iii) it enables identification of various drought types, given the multiscalar character of the SPEI. The dataset is freely available on the web page of the Spanish National Research Council (CSIC) in three different formats (NetCDF, binary raster, and plain text). ; This work has been supported by the research projects CGL2008-01189/BTE and CGL2006-11619/HID financed by the Spanish Commission of Science and Technology and FEDER, EUROGEOSS (FP7-ENV- 2008-1-226487) and ACQWA (FP7-ENV-2007-1- 212250) financed by the VII Framework Programme of the European Commission, "Las sequías climáticas en la cuenca del Ebro y su respuesta hidrológica" and "La nieve en el Pirineo aragonés: Distribución espacial y su respuesta a las condiciones climática" Financed by "Obra Social La Caixa" and the Aragón Government ; Peer reviewed

The definitive version is available at: http://www.agu.org/journals/jgr ; We used a novel method that combined probabilistic analysis and spatial modeling assisted by GIS to analyze the risk of extreme precipitation in northeast Spain related to three atmospheric circulation configurations: the North Atlantic Oscillation (NAO), the Mediterranean Oscillation, and the Western Mediterranean Oscillation (WeMO). The analysis was performed at an event-based scale using data obtained from daily atmospheric circulation indices. The maximum intensity and total precipitation magnitude recorded during positive and negative circulation events were obtained from the daily records of 174 observatories between 1950 and 2006. The series of both maximum intensity and magnitude for positive and negative phases of the three atmospheric circulation indices follow a generalized Pareto (GP) distribution. A regression-based interpolation procedure was used to generate distributed maps of GP parameters, enabling us to determine the probability of the magnitude and maximum intensity of precipitation and the quantile precipitation for any return period associated with the positive and negative phases of the three atmospheric circulation patterns. A high spatial variability in precipitation risk was found, depending on the positive/negative phases of the three atmospheric circulation patterns. Different phases of the circulation indices show contrasting effects on the two analyzed parameters. Thus the most extreme daily precipitation during winter months is expected for negative WeMO events, representing a markedly different result from those obtained for other events. In contrast, negative NAO events record the most extreme precipitation magnitude risk per event, although this is mainly restricted to mountainous areas. ; This work was supported by projects financed by the Spanish Commission of Science and Technology (CGL2005–04508/BOS and CGL2008–01189/BTE), the 7th framework program of the European Commission (projects ACQWA (FP7-ENV-2007-1-212250) and EUROGEOSS (FP7-ENV-2008-1-226487)), and the "Programa de grupos de investigación consolidados" financed by the Aragón Government. ; Peer reviewed

18 Pags., 7 Figs. The definitive version is available at: http://www.springerlink.com/content/978-94-007-1371-0/ ; This chapter shows the influence of the North Atlantic Oscillation (NAO) on droughts in the entire Mediterranean region between 1901 and 2006. The analysis has been based on identification of positive and negative NAO winters and also detection of the anomalies of drought severity by means of the Standardized Precipitation Evapotranspiration Index (SPEI). The analysis is focussed on the winter NAO. Nevertheless, given that the SPEI drought indicator can be obtained at different time-scales, the study shows how the effects of the winter NAO on droughts are propagated for the following months when long time scales are considered. In general, during the positive phases, the negative SPEI averages are recorded in Southern Europe (the Iberian Peninsula, Italy and the Balkans), areas of Turkey and northwest Africa. On the contrary, the SPEI averages are found positive in northeast Africa. The opposite configuration, but with some differences in the spatial patterns and the magnitude of the SPEI averages, is found during the negative NAO years. The findings of this study should be of great applicability in terms of developing early warning systems. The established relationships between NAO phases and drought indices seem appropriate for drought prediction over large areas of the Mediterranean basin. ; This work has been supported by the research projects CGL2008-01189/BTE and CGL2006-11619/HID financed by the Spanish Commission of Science and Technology and FEDER, EUROGEOSS (FP7-ENV-2008-1-226487) and ACQWA (FP7-ENV-2007-1- 212250) financed by the VII Framework Programme of the European Commission, and "La nieve en el Pirineo aragonés: Distribución espacial y su respuesta a las condiciones climáticas" Financed by "Obra Social La Caixa" and the Aragón Government. ; Peer reviewed