Environmental hydrogeochemistry and genesis of fluoride in groundwaters of Dindigul district, Tamilnadu (India)     

S. Chidambaram  M. Bala Krishna Prasad  R. Manivannan  U. Karmegam  C. Singaraja  P. Anandhan  M. V. Prasanna  S. Manikandan 《Environmental Earth Sciences》2013,68(2):333-342

Fluoride (F^?) is an indispensable element for the human’s skeletal and dental health at prescribed levels and becomes lethal at higher levels. Spatial–temporal variability of F^? and its geochemical control/association with other dissolved ions in groundwater in the Dindigul district of Tamilnadu (India) were conducted to describe the geochemical dynamics of F^– in response to seasonal variability. High concentrations of fluoride (≥1.5 mg L^?1) were observed in the northern region of the district. High levels of F^? were observed in non-monsoon periods and low levels in monsoon, because of dilution by precipitation. Bicarbonate was well correlated with F^? which explains that both ions were derived from the weathering. While F^? has a very weak correlation with silica, this implies that the silicate weathering does not supply F^? to the groundwater system. The F^? pollution in Dindigul groundwaters is mainly driven by two factors: (1) the geogenic weathering inputs, the geology of this area mainly comprises fluoride bearing minerals (e.g. hornblende biotite gneiss and charnockite); (2) the anthropogenic inputs (agri-fertilizers and tannery waste). Further, F^? in the study area is mainly attributed to geogenic sources during pre and postmonsoons and anthropogenic sources in monsoon periods.  相似文献   

Nuclear energy response in the EMF27 study     

Son H. Kim  Kenichi Wada  Atsushi Kurosawa  Matthew Roberts 《Climatic change》2014,123(3-4):443-460

The nuclear energy response for mitigating global climate change across 18 participating models of the EMF27 study is investigated. Diverse perspectives on the future role of nuclear power in the global energy system are evident in the broad range of nuclear power contributions from participating models of the study. In the Baseline scenario without climate policy, nuclear electricity generation and shares span 0–66 EJ/year and 0–25 % in 2100 for all models, with a median nuclear electricity generation of 39 EJ/year (1,389 GWe at 90 % capacity factor) and median share of 9 %. The role of nuclear energy increased under the climate policy scenarios. The median of nuclear energy use across all models doubled in the 450 ppm CO₂e scenario with a nuclear electricity generation of 67 EJ/year (2,352 GWe at 90 % capacity factor) and share of 17 % in 2100. The broad range of nuclear electricity generation (11–214 EJ/year) and shares (2–38 %) in 2100 of the 450 ppm CO₂e scenario reflect differences in the technology choice behavior, technology assumptions and competitiveness of low carbon technologies. Greater clarification of nuclear fuel cycle issues and risk factors associated with nuclear energy use are necessary for understanding the nuclear deployment constraints imposed in models and for improving the assessment of the nuclear energy potential in addressing climate change.  相似文献   

Land-use transition for bioenergy and climate stabilization: model comparison of drivers,impacts and interactions with other land use based mitigation options   总被引：1，自引：0，他引：1  

Alexander Popp  Steven K. Rose  Katherine Calvin  Detlef P. Van Vuuren  Jan Phillip Dietrich  Marshall Wise  Elke Stehfest  Florian Humpenöder  Page Kyle  Jasper Van Vliet  Nico Bauer  Hermann Lotze-Campen  David Klein  Elmar Kriegler 《Climatic change》2014,123(3-4):495-509

In this article, we evaluate and compare results from three integrated assessment models (GCAM, IMAGE, and ReMIND/MAgPIE) regarding the drivers and impacts of bioenergy production on the global land system. The considered model frameworks employ linked energy, economy, climate and land use modules. By the help of these linkages the direct competition of bioenergy with other energy technology options for greenhouse gas (GHG) mitigation, based on economic costs and GHG emissions from bioenergy production, has been taken into account. Our results indicate that dedicated bioenergy crops and biomass residues form a potentially important and cost-effective input into the energy system. At the same time, however, the results differ strongly in terms of deployment rates, feedstock composition and land-use and greenhouse gas implications. The current paper adds to earlier work by specific looking into model differences with respect to the land-use component that could contribute to the noted differences in results, including land cover allocation, land use constraints, energy crop yields, and non-bioenergy land mitigation options modeled. In scenarios without climate change mitigation, bioenergy cropland represents 10–18 % of total cropland by 2100 across the different models, and boosts cropland expansion at the expense of carbon richer ecosystems. Therefore, associated emissions from land-use change and agricultural intensification as a result of bio-energy use range from 14 and 113 Gt CO2-eq cumulatively through 2100. Under climate policy, bioenergy cropland increases to 24–36 % of total cropland by 2100.  相似文献   

Fossil resource and energy security dynamics in conventional and carbon-constrained worlds     

David McCollum  Nico Bauer  Katherine Calvin  Alban Kitous  Keywan Riahi 《Climatic change》2014,123(3-4):413-426

Fossil resource endowments and the future development of fossil fuel prices are important factors that will critically influence the nature and direction of the global energy system. In this paper we analyze a multi-model ensemble of long-term energy and emissions scenarios that were developed within the framework of the EMF27 integrated assessment model inter-comparison exercise. The diverse nature of these models highlights large uncertainties in the likely development of fossil resource (coal, oil, and natural gas) consumption, trade, and prices over the course of the twenty-first century and under different climate policy frameworks. We explore and explain some of the differences across scenarios and models and compare the scenario results with fossil resource estimates from the literature. A robust finding across the suite of IAMs is that the cumulative fossil fuel consumption foreseen by the models is well within the bounds of estimated recoverable reserves and resources. Hence, fossil resource constraints are, in and of themselves, unlikely to limit future GHG emissions this century. Our analysis also shows that climate mitigation policies could lead to a major reallocation of financial flows between regions, in terms of expenditures on fossil fuels and carbon, and can help to alleviate near-term energy security concerns via the reductions in oil imports and increases in energy system diversity they will help to motivate. Aggressive efforts to promote energy efficiency are, on their own, not likely to lead to markedly greater energy independence, however, contrary to the stated objectives of certain industrialized countries.  相似文献   

Retrieving daily global solar radiation from routine climate variables     

Isaac Moradi  Richard Mueller  Richard Perez 《Theoretical and Applied Climatology》2014,116(3-4):661-669

Solar radiation is an important variable for studies related to solar energy applications, meteorology, climatology, hydrology, and agricultural meteorology. However, solar radiation is not routinely measured at meteorological stations; therefore, it is often required to estimate it using other techniques such as retrieving from satellite data or estimating using other geophysical variables. Over the years, many models have been developed to estimate solar radiation from other geophysical variables such as temperature, rainfall, and sunshine duration. The aim of this study was to evaluate six of these models using data measured at four independent worldwide networks. The dataset included 13 stations from Australia, 25 stations from Germany, 12 stations from Saudi Arabia, and 48 stations from the USA. The models require either sunshine duration hours (Ångstrom) or daily range of air temperature (Bristow and Campbell, Donatelli and Bellocchi, Donatelli and Campbell, Hargreaves, and Hargreaves and Samani) as input. According to the statistical parameters, Ångstrom and Bristow and Campbell indicated a better performance than the other models. The bias and root mean square error for the Ångstrom model were less than 0.25 MJ m² day^?1 and 2.25 MJ m² day^?1, respectively, and the correlation coefficient was always greater than 95 %. Statistical analysis using Student’s t test indicated that the residuals for Ångstrom, Bristow and Campbell, Hargreaves, and Hargreaves and Samani are not statistically significant at the 5 % level. In other words, the estimated values by these models are statistically consistent with the measured data. Overall, given the simplicity and performance, the Ångstrom model is the best choice for estimating solar radiation when sunshine duration measurements are available; otherwise, Bristow and Campbell can be used to estimate solar radiation using daily range of air temperature.  相似文献   

Why were some La Niñas followed by another La Niña?     

Zeng-Zhen Hu  Arun Kumar  Yan Xue  Bhaskar Jha 《Climate Dynamics》2014,42(3-4):1029-1042

This paper investigates why some La Niña events are followed by another La Niña and some others are not. We propose two preconditions that result in continuation of a La Niña. The first one is that La Niña must be a strong event (a major La Niña). This ensures that the reflected Rossby wave signal at the eastern boundary of the Pacific has a strong westward propagating cold ocean temperature anomaly over the off-equatorial region. The off-equator cold anomaly may not be conducive to the equatorial recharge process, and as a result, may favor the persistence of cold ocean subsurface temperature anomaly and prevent the transition from La Niña to El Niño. The second precondition is whether there are eastward propagating downwelling Kelvin waves during the decay phase of a major La Niña. Eastward propagating downwelling Kelvin waves could lead to demise for a tendency for a follow-up La Niña. The equatorial Kelvin wave activities are associated with fluctuations of surface wind in the equatorial far-western Pacific. The analysis suggests that both the surface wind in the equatorial far-western Pacific and the recharge/discharge of the equatorial Pacific are indicators for occurrence or no occurrence of a follow-up La Niña event.  相似文献   

Prior-knowledge-based spectral mixture analysis for impervious surface mapping     

《International Journal of Applied Earth Observation and Geoinformation》2014

In this study, we developed a prior-knowledge-based spectral mixture analysis (PKSMA) to map impervious surfaces by using endmembers derived separately for high- and low-density urban regions. First, an urban area was categorized into high- and low-density urban areas, using a multi-step classification method. Next, in high-density urban areas that were assumed to have only vegetation and impervious surfaces (ISs), the vegetation–impervious model (V–I) was used in a spectral mixture analysis (SMA) with three endmembers: vegetation, high albedo, and low albedo. In low-density urban areas, the vegetation–impervious–soil model (V–I–S) was used in an SMA analysis with four endmembers: high albedo, low albedo, soil, and vegetation. The fraction of IS with high and low albedo in each pixel was combined to produce the final IS map. The root mean-square error (RMSE) of the IS map produced using PKSMA was about 11.0%, compared to 14.52% only using four-endmember SMA. Particularly in high-density urban areas, PKSMA (RMSE = 6.47%) showed better performance than four-endmember (15.91%). The results indicate that PKSMA can improve IS mapping compared to traditional SMA by using appropriately selected endmembers and is particularly strong in high-density urban areas.  相似文献   

Slope correction for ocean radar altimetry     

David T. Sandwell  Walter H. F. Smith 《Journal of Geodesy》2014,88(8):765-771

We develop a slope correction model to improve the accuracy of mean sea surface topography models as well as marine gravity models. The correction is greatest above ocean trenches and large seamounts where the slope of the geoid exceeds 100  \(\upmu \) rad. In extreme cases, the correction to the mean sea surface height is 40 mm and the correction to the along-track altimeter slope is 1–2  \(\upmu \) rad which maps into a 1–2 mGal gravity error. Both corrections are easily applied using existing grids of sea surface slope from satellite altimetry.  相似文献   

The need for and use of socio-economic scenarios for climate change analysis: A new approach based on shared socio-economic pathways     

Elmar Kriegler  Brian C. O’Neill  Stephane Hallegatte  Tom Kram  Robert J. Lempert  Richard H. Moss  Thomas Wilbanks 《Global Environmental Change》2012,22(4):807-822

Socio-economic scenarios constitute an important tool for exploring the long-term consequences of anthropogenic climate change and available response options. A more consistent use of socio-economic scenarios that would allow an integrated perspective on mitigation, adaptation and residual climate impacts remains a major challenge. We assert that the identification of a set of global narratives and socio-economic pathways offering scalability to different regional contexts, a reasonable coverage of key socio-economic dimensions and relevant futures, and a sophisticated approach to separating climate policy from counter-factual “no policy” scenarios would be an important step toward meeting this challenge. To this end, we introduce the concept of “shared socio-economic (reference) pathways”. Sufficient coverage of the relevant socio-economic dimensions may be achieved by locating the pathways along the dimensions of challenges to mitigation and to adaptation. The pathways should be specified in an iterative manner and with close collaboration between integrated assessment modelers and impact, adaptation and vulnerability researchers to assure coverage of key dimensions, sufficient scalability and widespread adoption. They can be used not only as inputs to analyses, but also to collect the results of different climate change analyses in a matrix defined by two dimensions: climate exposure as characterized by a radiative forcing or temperature level and socio-economic development as classified by the pathways. For some applications, socio-economic pathways may have to be augmented by “shared climate policy assumptions” capturing global components of climate policies that some studies may require as inputs. We conclude that the development of shared socio-economic (reference) pathways, and integrated socio-economic scenarios more broadly, is a useful focal point for collaborative efforts between integrated assessment and impact, adaptation and vulnerability researchers.  相似文献   

Coupled 3D physical and biological modelling of the mesoscale variability observed in North-East Atlantic in spring 1997: biological processes     

《Deep Sea Research Part I: Oceanographic Research Papers》2002,49(10):1741-1768

A limited area, eddy resolving coupled physical and biological model and data assimilation are used to reproduce and analyse the ecosystem variability observed in the North-East Atlantic in April–May 1997 on Discovery cruise 227. The ecosystem was in a post-bloom grazing controlled regime. The combination of the deep mixing in the upper layer during the cruise and a deeper than average winter convection led to high-nutrient–low-chlorophyll type conditions, which are unusual for this location. These conditions and lack of strong mesoscale physical features led to low spatial variability of phyto- and zooplankton yet strong sensitivity to the variations in the vertical mixing (storm event). Modelling results show that plankton patchiness formation under these conditions was dominated by biological mechanisms (mainly predator–prey oscillations). Furthermore, this mechanism, together with mixing and stirring, are responsible in this order for the observed scales and variability of patchiness from homogeneous low winter concentrations of phyto- and zooplankton.  相似文献