Jager-Waldau A.,European Commission - Joint Research Center Ispra
Solar Energy Materials and Solar Cells | Year: 2011
This paper gives an overview of the main research directions in chalcopyrite material research and the application of results for the improvement and fabrication of solar cells. So far the copper indium gallium sulphur selenide material family is the base for the highest efficiency thin-film solar cells and the most advanced in terms of actual commercialisation. The transfer of research results into actual production from its early stage and the development of the chalcopyrite thin-film solar cell industry are sketched. The last part of the review shortly describes a number of current industrial players involved in the manufacturing of chalcopyrite solar cells. © 2011 Elsevier B.V. All rights reserved. All rights reserved.
Mayaux P.,European Commission - Joint Research Center Ispra
Philosophical transactions of the Royal Society of London. Series B, Biological sciences | Year: 2013
This paper presents a map of Africa's rainforests for 2005. Derived from moderate resolution imaging spectroradiometer data at a spatial resolution of 250 m and with an overall accuracy of 84%, this map provides new levels of spatial and thematic detail. The map is accompanied by measurements of deforestation between 1990, 2000 and 2010 for West Africa, Central Africa and Madagascar derived from a systematic sample of Landsat images-imagery from equivalent platforms is used to fill gaps in the Landsat record. Net deforestation is estimated at 0.28% yr(-1) for the period 1990-2000 and 0.14% yr(-1) for the period 2000-2010. West Africa and Madagascar exhibit a much higher deforestation rate than the Congo Basin, for example, three times higher for West Africa and nine times higher for Madagascar. Analysis of variance over the Congo Basin is then used to show that expanding agriculture and increasing fuelwood demands are key drivers of deforestation in the region, whereas well-controlled timber exploitation programmes have little or no direct influence on forest-cover reduction at present. Rural and urban population concentrations and fluxes are also identified as strong underlying causes of deforestation in this study.
Tasdemir K.,European Commission - Joint Research Center Ispra
Pattern Recognition | Year: 2012
Spectral partitioning, recently popular for unsupervised clustering, is infeasible for large datasets due to its computational complexity and memory requirement. Therefore, approximate spectral clustering of data representatives (selected by various sampling methods) was used. Alternatively, we propose to use neural networks (self-organizing maps and neural gas), which are shown successful in quantization with small distortion, as preliminary sampling for approximate spectral clustering (ASC). We show that they usually outperform k-means sampling (which was shown superior to various sampling methods), in terms of clustering accuracy obtained by ASC. More importantly, for quantization based ASC, we introduce a local density-based similarity measure constructed without any user-set parameter which achieves accuracies superior to the accuracies of commonly used distance based similarity. © 2012 Elsevier Ltd. All rights reserved.
De Longueville Bertrand B.,European Commission - Joint Research Center Ispra
Computers, Environment and Urban Systems | Year: 2010
User-generated content, interoperability and the social dimension are the cornerstones of an emerging paradigm for the creation and sharing of information: Web 2.0. This article studies how geoportals can benefit from the Web 2.0 features. Geoportals are World Wide Web gateways that organize content and services related to geographic information. They are the most visible part of Spatial Data Infrastructures (i.e. distributed systems that aid acquisition, processing, distribution, use, maintenance, and preservation of spatial data). Today's geoportals are focusing on interoperability through the implementation of standards for discovery and use of geographic data and services. Will tomorrow's Geoportals focus more on organising communities of users sharing common interests? Recent papers are arguing for deeper integration of the Web 2.0 paradigm within the geospatial web. This article aims to provide an overview supporting the next generation geoportal development by defining related concepts, by emphasising advantages and caveats of such an approach, and proposing appropriate implementation strategies. © 2010 Elsevier Ltd.
Zibordi G.,European Commission - Joint Research Center Ispra
Optics Express | Year: 2016
Determination of the water-leaving radiance LW through abovewater radiometry requires knowledge of accurate reflectance factors ρ of the sea surface. Publicly available ρ relevant to above-water radiometry include theoretical data sets generated: i. by assuming a sky radiance distribution accounting for aerosols and multiple scattering, but neglecting polarization, and quantifying sea surface effects through Cox-Munk wave slope statistics; or differently ii. accounting for polarization, but assuming an ideal Rayleigh sky radiance distribution, and quantifying sea surface effects through modeled wave elevation and slope variance spectra. The impact on above-water data products of differences between those factors ρ was quantified through comparison of LW from the Ocean Color component of the Aerosol Robotic Network (AERONET-OC) with collocated LW from inwater radiometry. Results from the analysis of radiance measurements from the sea performed with 40 degrees viewing angle and 90 degrees azimuth offset with respect to the sun plane, indicated a slightly better agreement between above- and in-water LW determined for wind speeds tentatively lower than 4 m s-1 with ρ computed accounting for aerosols, multiple scattering and Cox-Munk surfaces. Nevertheless, analyses performed by partitioning the investigated data set also indicated that actual ρ values would exhibit dependence on sun zenith comprised between those characterizing the two sets of reflectance factors. © 2016 Optical Society of America.
Sala S.,European Commission - Joint Research Center Ispra
Integrated environmental assessment and management | Year: 2013
The development and use of footprint methodologies for environmental assessment are increasingly important for both the scientific and political communities. Starting from the ecological footprint, developed at the beginning of the 1990s, several other footprints were defined, e.g., carbon and water footprint. These footprints-even though based on a different meaning of "footprint"-integrate life cycle thinking, and focus on some challenging environmental impacts including resource consumption, CO2 emission leading to climate change, and water consumption. However, they usually neglect relevant sources of impacts, as those related to the production and use of chemicals. This article presents and discusses the need and relevance of developing a methodology for assessing the chemical footprint, coupling a life cycle-based approach with methodologies developed in other contexts, such as ERA and sustainability science. Furthermore, different concepts underpin existing footprint and this could be the case also of chemical footprint. At least 2 different approaches and steps to chemical footprint could be envisaged, applicable at the micro- as well as at the meso- and macroscale. The first step (step 1) is related to the account of chemicals use and emissions along the life cycle of a product, sector, or entire economy, to assess potential impacts on ecosystems and human health. The second step (step 2) aims at assessing to which extent actual emission of chemicals harm the ecosystems above their capability to recover (carrying capacity of the system). The latter step might contribute to the wide discussion on planetary boundaries for chemical pollution: the thresholds that should not be surpassed to guarantee a sustainable use of chemicals from an environmental safety perspective. The definition of what the planetary boundaries for chemical pollution are and how the boundaries should be identified is an on-going scientific challenge for ecotoxicology and ecology. In this article, we present a case study at the macroscale for the European Union, in which the chemical footprint according to step 1 is calculated for the year 2005. A proposal for extending this approach toward step 2 is presented and discussed, complemented by a discussion on the challenges and the use of appropriate methodologies for assessing chemical footprints to stimulate further research and discussion on the topic. © 2013 SETAC.
Zibordi G.,European Commission - Joint Research Center Ispra
Applied Optics | Year: 2012
Harmel et al. [Appl. Opt. 50, 5842 (2011)] presented an intercomparison of products from collocated above-water radiometric measurements performed with a Hyperspectral Surface Acquisition System (HyperSAS) and a multispectral Sea-viewing Wide Field of View Sensor Photometer Revision for Incident Surface Measurements (SeaPRISM). Radiometric products from HyperSAS data were determined with a processing code written by the authors, while products from SeaPRISM measurements were obtained with the standard processor of the Ocean Color component of the Aerosol Robotic Network (AERONET-OC). Despite the application of equivalent processing schemes, results exhibit spectrally averaged unbiased relative differences of +26% between HyperSAS and SeaPRISM exact normalized water leaving radiances, Lwn. Harmel et al. concluded that the sun-glint correction scheme applied for SeaPRISM data reduction is a major reason for the observed differences. This comment rejects the former conclusion as being supported by a wrong interpretation of the AERONET-OC processing scheme, and a consequent failure in describing the spectral properties of the glint radiance determined from SeaPRISM data. Afterward, the differences between HyperSAS and SeaPRISM Lwn reported by Harmel et al. are challenged with intercomparison results from collocated measurements periodically performed over almost a decade with an in-water multispectral system and SeaPRISM. Results for LWN from the in-water system show spectrally averaged unbiased relative differences of +1% with respect to SeaPRISM values. © 2012 Optical Society of America.
Alfieri L.,European Commission - Joint Research Center Ispra
Meteorological Applications | Year: 2015
Extreme rain storms are known for triggering devastating flash floods in various regions of Europe and particularly along the Mediterranean coasts. Despite recent notable advances in weather forecasting, most operational early warning systems for extreme rainstorms and flash floods are still based on rainfall measurements from rain gauges and weather radars, rather than on forecasts. As a result, warning lead times are bounded to a few hours and warnings are usually issued when the event is already taking place. This work proposes a novel early warning system for heavy precipitation events in Europe, aimed at identifying forecasts of extreme rainfall accumulations over short durations and within small-size catchments prone to flash flooding. The system is based on the recently developed European Precipitation Index based on simulated Climatology (EPIC), which is calculated using COSMO-LEPS ensemble weather forecasts and subsequently fitted with gamma distributions at each time step of the forecast horizon. Probabilistic exceedence of warning thresholds is calculated and alert points are generated where potentially extreme events are detected. Comparison of daily runs over 22 months with observed rainstorm events and flash floods in Europe denotes a probability of detection up to 90%, corresponding to 45 events correctly predicted, with average lead time of 32 h. © 2012 Royal Meteorological Society.
Toth G.,European Commission - Joint Research Center Ispra
Science of the Total Environment | Year: 2012
Spatial analyses of cropland productivity levels and land use data from 2000 and 2006 were performed to assess the loss of cropland resources for biomass production of the European Union due to land take. Productivity loss in administrative regions was calculated on the basis of the extent and quality of agricultural land resources converted to artificial surfaces. Data show that while all EU member states experience constant decrease of their production capacity, there are also considerable differences among countries and regions. Based on the analysis of 24 member states, the EU lost 0.27% of its cropland and 0.26% of its crop productive potential in the period between 2000 and 2006 due to land take. The loss of agricultural land during the study period was the highest in the Netherlands, which lost 1.57% of its crop production potential within six years. The figures are quite alarming for Cyprus (0.84%), Ireland (0.77%) and Spain (0.49%) as well. In metropolitan areas of Barcelona, Berlin, Bratislava, Bucharest, Copenhagen, Hamburg, Milan, and Vienna infrastructural investment occurred on the higher quality cropland while Budapest, Paris, and Warsaw spread their urban growth to areas of less productive cropland. Denmark had to face the largest loss of its food production capacity for each citizen, exceeding the equivalent of 4kgcapita-1year-1 of wheat, followed by Ireland with more than the equivalent of 3kg wheat and Spain, Netherlands, Hungary, Cyprus and France all above 2kg loss per capita, annually. The EU lost an amount of cropland production potential equal to approximately 700,000t of wheat grain, annually, in the study period. Results highlight the following general trends: (i) land conversion from different land cover types to artificial surfaces follows the historic trends in Europe with continuing consumption of more productive areas from its land resources; (ii) the conversion rate of croplands to artificial surfaces is growing with increased population growth; (iii) with the growing rate of population increase, increasingly higher quality croplands are converted to artificial surfaces, while with faster rates of population decline increasingly poorer quality croplands are converted; (iv) countries with more developed economies generally convert cropland at a higher speed; and (v) there is a negative correlation between annual economic growth and the rate of cropland conversion. © 2012 Elsevier B.V.
Widlowski J.-L.,European Commission - Joint Research Center Ispra
Agricultural and Forest Meteorology | Year: 2010
Global products of the fraction of absorbed photosynthetically active radiation (FAPAR) are operationally available from a variety of space agencies. A proper validation of these products is essential and hinges on the acquisition of accurate ground-based FAPAR estimates of the vegetation contained within the field of view of the space sensor at the time of satellite overpass. Often remotely sensed FAPAR products are defined with respect to theoretical rather than ambient illumination conditions which complicates in situ validation efforts. Similarly, the spatial complexity and substantial heights of certain plant environments may prevent the reliable sampling of certain radiation fluxes. As a consequence, many field campaigns are carried out on agricultural crops or within young tree plantations where canopy height is not an issue. This contribution compares different approaches for estimating instantaneous FAPAR in tall, open-canopy forest stands under a variety of architectural, spectral and illumination related conditions. The bias associated with these estimations is separated into a sampling error and a transfer bias. The former relates to the impact of both the number and location of the measurements whereas the latter addresses the quality of the theory that relates these measurements to the actual canopy FAPAR.Among the various methods tested it was the 2-flux FAPAR estimator (1-TPAR) that performs best in open forest canopies under typical summer conditions. The quality of the 1-TPAR canopy FAPAR estimator changes, however, with illumination conditions, foliage colour and especially with the background brightness. Similarly, the smaller the size of the area for which the FAPAR is to be estimated the larger the variability of the bias is going to be (and this irrespective of the choice of in situ estimation techniques). Evidence is provided that working under overcast sky conditions will reduce the sampling error but may well increase the transfer bias when compared to clear sky conditions. A parametric relationship is developed that allows to predict the instantaneous canopy FAPAR for arbitrary diffuse-to-total-incident-radiation ratios (at any given solar zenith angle). This approach has a similar transfer bias as the 1-TPAR method when the forest floor is dark but dramatically outperforms the 2-flux approach under snowy background conditions (RMSE=0.9934 versus 0.5801, respectively). The number of samples acquired was found to be crucial in reducing the variability of the bias of a given FAPAR estimator. Both random and grid-based sampling schemes result in similar FAPAR biases but do not lend themselves easily to the acquisition of hundreds of data points needed for reliable estimations under direct-only illumination conditions. Transect sampling-which is shown to deliver best results if carried out at ninety degrees to the solar azimuth angle-appears ideally suited to acquire the necessary numbers of samples enabling the generation of accurate quasi-instantaneous FAPAR estimates in open-canopy forests. © 2010 Elsevier B.V.