bluuebunny/crossref_metadata_2025 huggingface dataset:
In-situ submicron organic aerosol characterization at a boreal forest research station during HUMPPA-COPEC 2010 using soft and hard ionization mass spectrometry
Authors: Vogel A. L. , Äijälä M. , Corrigan A. L. , Junninen H. , Ehn M. , Petäjä T. , Worsnop D. R. , Kulmala M. , Russell L. M. , Williams J. , Hoffmann T.
Published: July 2013

Abstract. The chemical composition of submicron aerosol during the comprehensive field campaign HUMPPA-COPEC 2010 at Hyytiälä, Finland is presented. The focus lies on online measurements of organic acids, which was achieved by using atmospheric pressure chemical ionization (APCI) ion trap mass spectrometry (IT-MS). These measurements were accompanied by Aerosol Mass Spectrometry (AMS) measurements and Fourier-Transform Infrared Spectroscopy (FTIR) of filter samples, all showing a high degree of correlation. The soft ionization mass spectrometer alternated between gas phase measurements solely and measuring the sum of gas- and particle-phase. The AMS measurements of C, H and O elemental composition show that the aerosol during the campaign was highly oxidized, which appears reasonable due to high and prolonged radiation during the boreal summer measurement period as well as the long transport times of some of the aerosol. In order to contrast ambient and laboratory aerosol, an average organic acid pattern, measured by APCI-IT-MS during the campaign, was compared to terpene ozonolysis products in a laboratory reaction chamber. Identification of single organic acid species remains a major challenge due to the complexity of the boreal forest aerosol. Unambiguous online species identification was attempted by the combinatorial approach of identifying unique fragments in the MS2-mode of standards, and then comparing these results with MS2 field spectra. During the campaign, unique fragments of limonene derived organic acids (limonic acid and ketolimononic acid) and of the biomass burning tracer vanillic acid were detected. Other specific fragments (neutral loss of 28 Da) in the MS2 suggest the occurrence of semialdehydes. Furthermore, an approach to determine the average molecular weight of the aerosol is presented. The campaign average organic molecular weight was determined to be 300 g mol−1. However, a plume of aged biomass burning aerosol, arriving at Hyytiälä from Russia, contained organic compounds up to 800 Da (MWom ≈ 450 g mol−1), showing that the average molecular weight can vary significantly. The high measurement frequency of both, AMS and APCI-IT-MS, enabled the partitioning of selected organic acids between gas- and particle-phase as a function of the total particulate mass to be quantified. Surprisingly high fractions of the higher molecular weight organic acids were observed to reside in the gas phase. These observations might be a consequence of large equilibration timescales for semi-solid boreal forest aerosol, as it has been recently hypothesised by Shiraiwa and Seinfeld (2012).
Strong wintertime ozone events in the Upper Green River Basin, Wyoming
Authors: Rappenglück B. , Ackermann L. , Alvarez S. , Golovko J. , Buhr M. , Field R. , Soltis J. , Montague D. C. , Hauze B. , Adamson S. , Risch D. , Wilkerson G. , Bush D. , Stoeckenius T. , Keslar C.
Published: July 2013

Abstract. During recent years, elevated ozone (O3) values have been observed repeatedly in the Upper Green River Basin (UGRB), Wyoming during wintertime. This paper presents an analysis of high ozone days in late winter 2011 (1 h average up to 166 ppbv). Intensive Operational Periods (IOPs) of ambient monitoring were performed which included comprehensive surface and boundary layer measurements. On IOP days, maximum O3 values are restricted to a very shallow surface layer. Low wind speeds in combination with low mixing layer heights (~50 m a.g.l. around noontime) are essential for accumulation of pollutants within the UGRB. Air masses contain substantial amounts of reactive nitrogen (NOx) and non-methane hydrocarbons (NMHC) emitted from fossil fuel exploration activities in the Pinedale Anticline. On IOP days in the morning hours in particular, reactive nitrogen (up to 69%), aromatics and alkanes (~10–15%; mostly ethane and propane) are major contributors to the hydroxyl (OH) reactivity. Measurements at the Boulder monitoring site during these time periods under SW wind flow conditions show the lowest NMHC/NOx ratios (~50), reflecting a relatively low NMHC mixture, and a change from a NOx-limited regime towards a NMHC limited regime as indicated by photochemical indicators, e.g. O3/NOy, O3/NOz, and O3/HNO3 and the EOR (Extent of Reaction). OH production on IOP days is mainly due to nitrous acid (HONO). Until noon on IOP days, HONO photolysis contributes between 74–98% of the entire OH-production. Ozone photolysis (contributing 2–24%) is second to HONO photolysis. However, both reach about the same magnitude in the early afternoon (close to 50%). Photolysis of formaldehyde (HCHO) is not important (2–7%). High HONO levels (maximum hourly median on IOP days: 1096 pptv) are favored by a combination of shallow boundary layer conditions and enhanced photolysis rates due to the high albedo of the snow surface. HONO is most likely formed through (i) abundant nitric acid (HNO3) produced in atmospheric oxidation of NOx, deposited onto the snow surface and undergoing photo-enhanced heterogeneous conversion to HONO (estimated HONO production: 2250 pptv h−1) and (ii) combustion related emission of HONO (estimated HONO production: ~585 pptv h−1). HONO, serves as the most important precursor for OH, strongly enhanced due to the high albedo of the snow cover (HONO photolysis rate 2900 pptv h−1). OH radicals will oxidize NMHCs, mostly aromatics (toluene, xylenes) and alkanes (ethane, propane), eventually leading to an increase in ozone.
Turbulent diffusivities and energy dissipation rates in the stratosphere from GOMOS satellite stellar scintillation measurements
Authors: Gavrilov N. M.
Published: July 2013

Abstract. Parameters of anisotropic and isotropic spectra of refractivity, density and temperature perturbations obtained from GOMOS satellite measurements of stellar scintillations are used to estimate turbulent Thorpe scales, LT, diffusivities, K, and energy dissipation rates, ε, in the stratosphere. At low latitudes, average values for altitudes 30–45 km in September–November 2004 are LT~1–1.1 m, ε~(1.8–2.4)×10−5 W kg−1, and K ~ (1.2–1.6) × 10−2 m2 s−1 depending on different assumed values of parameters of anisotropic and isotropic spectra. Respective standard deviations of individual values including all kinds of variability are δLT ~ 0.6–0.7 m, δε ~(2.3–3.5)×10−5 W kg−1, and δK ~ (1.7–2.6)×10−2 m2 s−1. These values correspond to high-resolution balloon measurements of turbulent characteristics in the stratosphere, and to previous satellite stellar scintillation measurements. Distributions of turbulent characteristics at altitudes 30–45 km in low latitudes have maxima at longitudes 30–100° W, 0–60° E and 90–180° E, which correspond to continent locations. Correlations between parameters of anisotropic and isotropic spectra are studied.
Towards a stable and absolute atmospheric carbon dioxide instrument using spectroscopic null method
Authors: Xiang B. , Nelson D. D. , McManus J. B. , Zahniser M. S. , Wofsy S. C.
Published: July 2013

Abstract. We present a novel spectral method to measure atmospheric carbon dioxide (CO2) with high precision and stability without resorting to calibration tanks during long-term operation. This spectral null method improves precision by reducing spectral proportional noise associated with laser emission instabilities. We employ sealed quartz cells with known CO2 column densities to serve as the permanent internal references in the null method, which improve the instrument's stability and accuracy. A prototype instrument – ABsolute Carbon dioxide (ABC) is developed using this new approach. The instrument has a one-second precision of 0.02 ppm, which averages down to 0.007 ppm within one minute. Long-term stability of within 0.1 ppm is achieved without any calibrations for over a one-month period. These results have the potential for eliminating the need for calibration cylinders for high accuracy field measurements of carbon dioxide.
The importance of different spatial scales in determining structural and functional characteristics of deep-sea infauna communities
Authors: Ingels J. , Vanreusel A.
Published: July 2013

Abstract. The urge to understand spatial distributions of species and communities and their causative processes has continuously instigated the development and testing of conceptual models in spatial ecology. For the deep sea, there is evidence that structural and functional characteristics of benthic communities are regulated by a multitude of biotic and environmental processes that act in concert on different spatial scales, but the spatial patterns are poorly understood compared to those for terrestrial ecosystems. Deep-sea studies generally focus on very limited scale ranges, thereby impairing our understanding of which spatial scales and associated processes are most important in driving structural and functional diversity of communities. Here, we used an extensive integrated dataset of free-living nematodes from deep-sea sediments to unravel the importance of different spatial scales in determining benthic infauna communities. Multiple-factor multivariate permutational analyses were performed on different sets of community descriptors (structure, structural and functional diversity, standing stock). The different spatial scales investigated cover two margins in the northeast Atlantic, several submarine canyons/channel/slope areas, a bathymetrical range of 700–4300 m, different sampling locations at each station, and vertical sediment profiles. The results indicated that the most important spatial scale for structural and functional diversity and standing stock variability is the smallest one; infauna communities changed substantially more with differences between sediment depth layers than with differences associated to larger geographical or bathymetrical scales. Community structure differences were greatest between stations at both margins. Important regulating ecosystem processes and the scale on which they occur are discussed. The results imply that, if we are to improve our understanding of ecosystem patterns of deep-sea infauna and the relevant processes driving their structure, structural and functional diversity, and standing stock, we must pay particular attention to the small-scale heterogeneity or patchiness and the causative mechanisms acting on that scale.
Natural ocean carbon cycle sensitivity to parameterizations of the recycling in a climate model
Authors: Romanou A. , Romanski J. , Gregg W. W.
Published: July 2013

Abstract. Sensitivities of the oceanic biological pump within the GISS climate modeling system are explored here. Results are presented from twin control simulations of the air-sea CO2 gas exchange using two different ocean models coupled to the same atmosphere. The two ocean models (Russell ocean model and Hybrid Coordinate Ocean Model, HYCOM) use different vertical coordinate systems, and therefore different representations of column physics. Both variants of the GISS climate model are coupled to the same ocean biogeochemistry module (the NASA Ocean Biogeochemistry Model, NOBM) which computes prognostic distributions for biotic and abiotic fields that influence the air-sea flux of CO2 and the deep ocean carbon transport and storage. In particular, the model differences due to remineralization rate changes are compared to differences attributed to physical processes modeled differently in the two ocean models such as ventilation, mixing, eddy stirring and vertical advection. The Southern Ocean emerges as a key region where the CO2 flux is as sensitive to biological parameterizations as it is to physical parameterizations. Mixing in the Southern Ocean is shown to be a~good indicator of the magnitude of the biological pump efficiency regardless of physical model choice.
Holocene climate variations in the western Antarctic Peninsula: evidence for sea ice extent predominantly controlled by changes in insolation and ENSO variability
Authors: Etourneau J. , Collins L. G. , Willmott V. , Kim J.-H. , Barbara L. , Leventer A. , Schouten S. , Sinninghe Damsté J. S. , Bianchini A. , Klein V. , Crosta X. , Massé G.
Published: July 2013

Abstract. The West Antarctic ice sheet is particularly sensitive to global warming and its evolution and impact on global climate over the next few decades remains difficult to predict. In this context, investigating past sea ice conditions around Antarctica is of primary importance. Here, we document changes in sea ice presence, upper water column temperatures (0–200 m) and primary productivity over the last 9000 yr BP (before present) in the western Antarctic Peninsula (WAP) margin from a sedimentary core collected in the Palmer Deep Basin. Employing a multi-proxy approach, based on the combination of two biomarkers proxies (highly branched isoprenoid (HBI) alkenes for sea ice and TEX86L for temperature) and micropaleontological data (diatom assemblages), we derived new Holocene records of sea ice conditions and upper water column temperatures. The early Holocene (9000–7000 yr BP) was characterized by a cooling phase with a short sea ice season. During the mid-Holocene (~7000–3800 yr BP), local climate evolved towards slightly colder conditions and a prominent extension of the sea ice season occurred, promoting a favorable environment for intensive diatom growth. The late Holocene (the last ~2100 yr) was characterized by warmer temperatures and increased sea ice presence, accompanied by reduced local primary productivity, likely in response to a shorter growing season compared to the early or mid-Holocene. The gradual increase in annual sea ice duration over the last 7000 yr might have been influenced by decreasing mean annual and spring insolation, despite increasing summer insolation. We postulate that, in addition to precessional changes in insolation, seasonal variability, via changes in the strength of the circumpolar Westerlies and upwelling activity, was further amplified by the increasing frequency/amplitude of the El Niño–Southern Oscillation (ENSO). However, between 3800 and 2100 yr BP, the lack of correlation between ENSO and climate variability in the WAP suggests that other climatic factors might have been more important in controlling WAP climate at this time.
Mending Milankovitch theory: obliquity amplification by surface feedbacks
Authors: Tabor C. R. , Poulsen C. J. , Pollard D.
Published: July 2013

Abstract. Milankovitch theory states that orbitally induced changes in high-latitude summer insolation dictate the waxing and waning of ice-sheets. Accordingly, precession should dominate the ice-volume response because it most strongly modulates summer insolation intensity. However, Early Pleistocene (2.6–0.8 Ma) ice-volume proxy records vary almost exclusively at the frequency of the obliquity cycle. To explore this paradox, we use an Earth system model coupled with a dynamic ice-sheet to separate the climate responses to idealized transient orbits of obliquity and precession that maximize insolation changes. Our results show that positive surface albedo feedbacks between high-latitude annual-mean insolation, ocean heat flux and sea-ice coverage, and boreal forest/tundra exchange enhance the ice-volume response to obliquity forcing relative to precession forcing. These surface feedbacks, in combination with modulation of the precession cycle power by eccentricity, may explain the dominantly 41 kyr cycles in global ice volume of the Early Pleistocene.
Comparison and application of wind retrieval algorithms for small unmanned aerial systems
Authors: Bonin T. A. , Chilson P. B. , Zielke B. S. , Klein P. M. , Leeman J. R.
Published: July 2013

Abstract. Recently, there has been an increase in use of Unmanned Aerial Systems (UASs) as platforms for conducting fundamental and applied research in the lower atmosphere due to their relatively low cost and ability to collect samples with high spatial and temporal resolution. Concurrent with this development comes the need for accurate instrumentation and measurement methods suitable for small meteorological UASs. Moreover, the instrumentation to be integrated into such platforms must be small and lightweight. Whereas thermodynamic variables can be easily measured using well-aspirated sensors onboard, it is much more challenging to accurately measure the wind with a UAS. Several algorithms have been developed that incorporate GPS observations as a means of estimating the horizontal wind vector, with each algorithm exhibiting its own particular strengths and weaknesses. In the present study, the performance of three such GPS-based wind-retrieval algorithms has been investigated and compared with wind estimates from rawinsonde and sodar observations. Each of the algorithms considered agreed well with the wind measurements from sounding and sodar data. Through the integration of UAS-retrieved profiles of thermodynamic and kinematic parameters, one can investigate the static and dynamic stability of the atmosphere and relate them to the state of the boundary layer across a variety of times and locations, which might be difficult to access using conventional instrumentation.
LAPM: a tool for underwater large-area photo-mosaicking
Authors: Marcon Y. , Sahling H. , Bohrmann G.
Published: July 2013

Abstract. This paper presents a new tool for large-area photo-mosaicking (LAPM tool). This tool was developed specifically for the purpose of underwater mosaicking, and it is aimed at providing end-user scientists with an easy and robust way to construct large photo-mosaics from any set of images. It is notably capable of constructing mosaics with an unlimited number of images on any modern computer (minimum 1.30 GHz, 2 GB RAM). The mosaicking process can rely on both feature matching and navigation data. This is complemented by an intuitive graphical user interface, which gives the user the ability to select feature matches between any pair of overlapping images. Finally, mosaic files are given geographic attributes that permit direct import into ArcGIS. So far, the LAPM tool has been successfully used to construct geo-referenced photo-mosaics with photo and video material from several scientific cruises. The largest photo-mosaic contained more than 5000 images for a total area of about 105 000 m2. This is the first article to present and to provide a finished and functional program to construct large geo-referenced photo-mosaics of the seafloor using feature detection and matching techniques. It also presents concrete examples of photo-mosaics produced with the LAPM tool.
A test of numerical instability and stiffness in the parametrizations of the ARPÉGE and ALADIN models
Authors: Tudor M.
Published: July 2013

Abstract. Meteorological numerical weather prediction (NWP) models solve a system of partial differential equations in time and space. Semi-lagrangian advection schemes allow for long time steps. These longer time steps can result in instabilities occurring in the model physics. A system of differential equations in which some solution components decay more rapidly than others is stiff. In this case it is stability rather than accuracy that restricts the time step. The vertical diffusion parametrization can cause fast non-meteorological oscillations around the slowly evolving true solution (fibrillations). These are treated with an anti-fibrillation scheme, but small oscillations remain in operational weather forecasts using ARPÉGE and ALADIN models. In this paper, a simple test is designed to reveal if the formulation of particular a physical parametrization is a stiff problem or potentially numerically unstable in combination with any other part of the model. When the test is applied to a stable scheme, the solution remains stable. However, applying the test to a potentially unstable scheme yields a solution with fibrillations of substantial amplitude. The parametrizations of the NWP model ARPÉGE were tested one by one to see which one may be the source of unstable model behaviour. The test identified the set of equations in the stratiform precipitation scheme (a diagnostic Kessler-type scheme) as a stiff problem, particularly the combination of terms arising due to the evaporation of snow.
Modeling shortwave solar radiation using the JGrass-NewAge system
Authors: Formetta G. , Rigon R. , Chávez J. L. , David O.
Published: July 2013

Abstract. This paper presents two new modeling components based on the object modeling system v3 (OMS3) for the calculation of the shortwave incident radiation (Rsw↓) on complex topography settings, and the implementation of several ancillary tools. The first component, NewAGE-SwRB, accounts for elevation slope, aspect, shadow of the sites, and uses suitable parameterization for obtaining the cloudless irradiance. A second component, NewAGE-DEC-MOD's is implemented to estimate the irradiance reduction due to the presence of clouds according to three parameterizations. To obtain a working modeling composition that is comparable with ground data at measurement stations the two components are connected to a kriging component. With the help of an additional component, NewAGE-V (verification package), the performance of modeled (Rsw↓) is quantitatively evaluated. The two components (and the various parameterizations they contain) are tested using the data from three basins, and some simple verification tests were carried out to assess the goodness of the methods used. Moreover, a raster mode test is performed in order to show the capability of the system in providing solar radiation raster maps. The components are part of a larger system, JGrass-NewAGE, their input and outputs are geometrical objects immediately displayed in a geographical information system (GIS). They can be used seamlessly with the various modeling solutions available in JGrass-NewAGE for the estimation of long wave radiation, evapotranspiration, and snow melting, as well as standalone components to just estimate shortwave radiation for various uses. The modularity of the approach leads to more accurate physical-statistical studies aimed to assess in depth the components' performances and extends their results spatially, without the necessity of recoding any part of the component.
Automating the solution of PDEs on the sphere and other manifolds in FEniCS 1.2
Authors: Rognes M. E. , Ham D. A. , Cotter C. J. , McRae A. T. T.
Published: July 2013

Abstract. Differential equations posed over immersed manifolds are of particular importance in studying geophysical flows; for instance, ocean and atmosphere simulations crucially rely on the capability to solve equations over the sphere. This paper presents the extension of the FEniCS software components to the automated solution of finite element formulations of differential equations defined over general, immersed manifolds. We describe the implementation and in particular detail how the required extensions essentially reduce to the extension of the FEniCS form compiler to cover this case. The resulting implementation has all the properties of the FEniCS pipeline and we demonstrate its flexibility by an extensive range of numerical examples covering a number of geophysical benchmark examples and test cases. The results are all in agreement with the expected values. The description here relates to DOLFIN/FEniCS 1.2.
Circulation pattern based parameterization of a multiplicative random cascade for disaggregation of observed and projected daily rainfall time series
Authors: Lisniak D. , Franke J. , Bernhofer C.
Published: July 2013

Abstract. The use of multiplicative random cascades (MRCs) for temporal rainfall disaggregation has been extensively studied in the past. MRCs are appealing for rainfall disaggregation due to their formal simplicity and the possibility to extract the model parameters directly from observed high resolution rainfall data. These parameters, however, represent the rainfall characteristics of the observation period. Since rainfall characteristics of different time slices are changing due to climate variability, we propose a parameterization approach for MRCs to adjust the parameters according to past (observed) or future (projected) time series. This is done on the basis of circulation patterns (CPs) by extracting a distinct MRC parameterization from high resolution rainfall data, as observed on days governed by each individual CP. The parameterization approach is tested by comparing the statistical properties of disaggregated rainfall time series of two time slices, 1969–1979 and 1989–1999, to the results obtained by two other disaggregation methods (a conceptually similar MRC without CP-based parameterization and a recombination approach) and to the statistical properties of observed hourly rainfall data. In this context, all three approaches use rainfall data of the time slice 1989–1999 for parameterization. We found that the inclusion of CPs into the parameterization of a MRC yields hourly time series that better reproduce the properties of observed rainfall in time slice 1989–1999, as compared to the simple MRC. Despite similar results of both MRCs in the validation period of 1969–1979, we can conclude that the CP-based parameterization approach is applicable for temporal rainfall disaggregation in time slices distinct from the parameterization period. This approach accounts for changes in rainfall characteristics due to changes in the frequency of occurrence of the CPs and allows generating hourly rainfall from daily data, as often provided by a statistical downscaling of global climate change.
Runoff and Sediment load of the Yan River, China: changes over the last 60 yr
Authors: Wang F. , Mu X. , Hessel R. , Zhang W. , Ritsema C. J. , Li R.
Published: July 2013

Abstract. Runoff and sediment load changes are affected by climate change and human activities in an integrated way. Historical insight into these effects can not only improve the knowledge of river processes, but also promote more effective land and water management. In this study, we looked at runoff and sediment change in the Yan River basin, Loess Plateau, China, using data sets on land use and land cover (LUC), monthly data of precipitation and temperature, and observed data on runoff and sediment load from 1952 to 2010 at the Ganguyi Hydrologic Station. Available data on soil and water conservation structures and their effect were also studied. Five main findings emerged from the data analysis. (1) The annual runoff and sediment load varied greatly during the last 60 yr, and both had coefficients of variation that were much larger than those of precipitation and temperature. (2) Annual runoff and sediment load both showed a significant trend of linear decline over the period studied. The climate data showed a non-significant decline in precipitation over the same period, and a very significant increase in temperature; both can help explain the observed declines in runoff and soil loss. (3) Based on a mass curve analysis with anomalies of normalized runoff and sediment load, 4 stages in the change of runoff and soil loss were identified: 1951 to 1971 (Stage I), 1972 to 1986 (Stage II), 1987 to 1996 (Stage III) and 1997 to 2010 (Stage IV). (4) When years were paired based on similar precipitation and temperature condition (SPTC) and used to assess the impacts of human activities, it was found that 6 sets of paired years out of 12 (50%) showed a decline in runoff, 8 (67%) a decline in sediment load, and 9 (75%) a decline in sediment concentration. The other sets show an increasing change with time. It showed the complexity of human impacts. (5) Human impacts relating to LUC change and soil and water measures in this basin were significant because of both the transfer of sloping cropland into non-food vegetation or terraces, and the siltation in the reservoirs and behind check dams. Data indicated that about 56 Mt of sediment was deposited annually from 1960–1999 as a result of the soil and water conservation structures, which is significantly more than the average 42 Mt, leaving the Yan River basin as sediment load each year. Although the effects of climate change and human action could not be separated, analysis of the data indicated that both had a significant impact on runoff and sediment load in the area.
A decision analysis framework for stakeholder involvement and learning in groundwater management
Authors: Karjalainen T. P. , Rossi P. M. , Ala-aho P. , Eskelinen R. , Reinikainen K. , Kløve B. , Pulido-Velazquez M. , Yang H.
Published: July 2013

Abstract. Multi-criteria decision analysis (MCDA) methods are increasingly used to facilitate both rigorous analysis and stakeholder involvement in natural and water resource planning. Decision making in that context is often complex and multi-faceted with numerous trade-offs between social, environmental and economic impacts. However, practical applications of decision-support methods are often too technically oriented and hard to use, understand or interpret for all participants. The learning of participants in these processes is seldom examined, even though successful deliberation depends on learning. This paper analyzes the potential of an interactive MCDA framework, the decision analysis interview (DAI) approach, for facilitating stakeholder involvement and learning in groundwater management. It evaluates the results of an MCDA process in assessing land-use management alternatives in a Finnish esker aquifer area where conflicting land uses affect the groundwater body and dependent ecosystems. In the assessment process, emphasis was placed on the interactive role of the MCDA tool in facilitating stakeholder participation and learning. The results confirmed that the structured decision analysis framework can foster learning and collaboration in a process where disputes and diverse interests are represented. Computer-aided interviews helped the participants to see how their preferences affected the desirability and ranking of alternatives. During the process, the participants' knowledge and preferences evolved as they assess their initial knowledge with the help of fresh scientific information. The decision analysis process led to the opening of a dialogue, showing the overall picture of the problem context, and the critical issues for the further process.
A model-based assessment of the potential use of compound specific stable isotope analysis in river monitoring of diffuse pesticide pollution
Authors: Lutz S. R. , van Meerveld H. J. , Waterloo M. J. , Broers H. P. , van Breukelen B. M.
Published: July 2013

Abstract. Compound-specific stable isotope analysis (CSIA) has, in combination with model-assisted interpretation, proven a valuable approach to quantify the extent of organic contaminant degradation in groundwater systems. CSIA data may also provide insights into the origin and transformation of diffuse river pollutants such as pesticides and nitrate at the catchment scale. While CSIA methods for pesticides have increasingly become available, they have not yet been deployed to interpret isotope data of pesticides in surface water. We applied a coupled subsurface-surface reactive transport model (HydroGeoSphere) at the hillslope scale to investigate the usefulness of CSIA in the assessment of pesticide degradation. We simulated the transport and transformation of a pesticide in a hypothetical but realistic two-dimensional hillslope transect. The steady-state model results illustrate a strong increase of isotope ratios at the hillslope outlet, which resulted from degradation and long travel times through the hillslope during average hydrological conditions. In contrast, following an extreme rainfall event that induced overland flow, the simulated isotope ratios dropped to the values of soil water in the pesticide application area. These results suggest that CSIA can help to determine whether pesticides enter the stream via groundwater exfiltration or via surface runoff. Simulations with daily rainfall and evapotranspiration data and one pesticide application per year resulted in small seasonal variations of concentrations and isotope ratios at the hillslope outlet, which fell within the uncertainty range of current CSIA methods. This implies a good reliability of in-stream isotope data in the absence of transport via surface runoff or other fast transport routes, since the time of measurement appears to be of minor importance. The analysis of simulated isotope ratios also allowed quantifying the contribution of two different reaction pathways to the overall degradation, which gave further insight into transport routes in the modelled system. The simulations supported the use of the commonly applied Rayleigh equation for the interpretation of CSIA data, since this led to an underestimation of the real extent of degradation of less than 12% at the hillslope outlet. Overall, the model results emphasize the applicability and usefulness of CSIA in the assessment of diffuse river pollution.
Forcing factors of cloud-to-ground lightning over Iberia: regional-scale assessments
Authors: Santos J. A. , Reis M. A. , De Pablo F. , Rivas-Soriano L. , Leite S. M.
Published: July 2013

Abstract. Cloud-to-ground lightning in a sector covering the Iberian Peninsula, the Balearic Islands and nearby seas (36–44° N, 10° W–5° E) is analysed in the period from 2003 to 2009 (7 yr). Two Iberian lightning detection networks, composed of 18 sensors over Portugal and Spain, are combined for the first time in the present study. The selected characteristics are cloud-to-ground flashes (CGFs), first stroke peak current, polarity and multiplicity (number of strokes in a given flash). This study examines the temporal (on hourly, monthly and seasonal timescales) and spatial variability of CGFs. The influence of five forcing factors on lightning (elevation, lifted index, convective available potential energy and daily minimum and maximum near-surface air temperatures) over the Iberian sector is also assessed. For regional-scale assessments, six subsectors with different climatic conditions were analysed separately. Despite important regional differences, the strongest lightning activity occurs from late spring to early autumn, and mostly in the afternoon. Furthermore, CGFs are mainly located over high-elevation areas in late spring to summer, while they tend to occur over the sea in autumn. The results suggest that (1) orographically forced thunderstorms over mountainous areas, mostly from May to September, (2) tropospheric buoyancy forcing over western-central and northern regions in summer and over the Mediterranean regions in autumn, and (3) near-surface thermal contrasts from October to February largely control the location of lightning in Iberia. There is no evidence of different forcings by polarity. A clear correspondence between summertime precipitation patterns and CGFs is also found.
Seasonal and annual mass balances of Mera and Pokalde glaciers (Nepal Himalaya) since 2007
Authors: Wagnon P. , Vincent C. , Arnaud Y. , Berthier E. , Vuillermoz E. , Gruber S. , Ménégoz M. , Gilbert A. , Dumont M. , Shea J. M. , Stumm D. , Pokhrel B. K.
Published: July 2013

Abstract. In the Everest region, Nepal, ground-based monitoring programs were started on the debris-free Mera Glacier (27.7° N, 86.9° E; 5.1 km2, 6420 to 4940 m a.s.l.) in 2007 and on the small Pokalde Glacier (27.9° N, 86.8° E; 0.1 km2, 5690 to 5430 m a.s.l., ∼ 25 km North of Mera Glacier) in 2009. These glaciers lie on the southern flank of the central Himalaya under the direct influence of the Indian monsoon and receive more than 80% of their annual precipitation in summer (June to September). Despite a large inter-annual variability with glacier-wide mass balances ranging from −0.77± 0.40 m w.e. in 2011–2012 (Equilibrium-line altitude (ELA) at ∼ 6055 m a.s.l.) to + 0.46 ± 0.40 m w.e. in 2010–2011 (ELA at ∼ 5340 m a.s.l.), Mera Glacier has been shrinking at a moderate mass balance rate of −0.10± 0.40 m w.e. yr−1 since 2007. Ice fluxes measured at two distinct transverse cross sections at ∼ 5350 m a.s.l. and ∼ 5520 m a.s.l. confirm that the mean state of this glacier over the last one or two decades corresponds to a limited mass loss, in agreement with remotely-sensed region-wide mass balances of the Everest area. Seasonal mass balance measurements show that ablation and accumulation are concomitant in summer which in turn is the key season controlling the annual glacier-wide mass balance. Unexpectedly, ablation occurs at all elevations in winter due to wind erosion and sublimation, with remobilized snow likely being sublimated in the atmosphere. Between 2009 and 2012, the small Pokalde Glacier lost mass more rapidly than Mera Glacier with respective mean glacier-wide mass balances of −0.72 and −0.26 ± 0.40 m w.e. yr−1. Low-elevation glaciers, such as Pokalde Glacier, have been usually preferred for in-situ observations in Nepal and more generally in the Himalayas, which may explain why compilations of ground-based mass balances are biased toward negative values compared with the regional mean under the present-day climate.
Purtscher-like Retinopathy in Septicemic Disseminated Intravascular Coagulation Associated with Nephrotic Syndrome
Authors: Viola Francesco , Vezzola Diego , Villani Edoardo , Mapelli Chiara , Barteselli Giulio , Ratiglia Roberto
Published: July 2013

Purpose

To describe a case of severe Purtscher-like retinopathy during an episode of septicemic diffused intravascular coagulation (DIC) in a child with severe nephrotic syndrome.

Methods

Case report.

Results

A 5-year-old girl with a history of steroid-sensitive nephrotic syndrome was admitted for worsening symptoms of the systemic disease. Laboratory studies revealed evidence of DIC during an episode of septicemia. Ten days later, she had a sudden and severe bilateral visual loss. Her visual acuity was hand motion in either eye. Fundus examination showed ischemic retinal whitening and retinal hemorrhages. Fluorescein angiography revealed obstruction of arterioles and venules at the posterior pole. Three weeks later, ischemic retinal blanching and hemorrhages resolved in both eyes; visual acuity improved to 20/250 and 20/200 in right and left eye, respectively. No further functional improvement was noted after 3 months, due to diffuse thinning of the inner retina architecture as shown by optical coherence tomography.

Conclusions

Purtscher-like retinopathy can occur in patients with septicemic DIC and nephrotic syndrome.
Correlation between Cataract Grading by Scheimpflug Imaging and Phaco Time in Phacoemulsification using Peristaltic and Venturi Pumps
Authors: Patrício Maria Sara , Almeida Ana Catarina , Rodrigues Maria Picoto , Guedes Marta Esteves , Ferreira Tiago Bravo
Published: July 2013

Purpose

To study the correlation among cataract grading system by Scheimpflug imaging (Oculus Pentacam® Nucleus Grading System [PNS]), effective phaco time (EPT), and surgical time (ST) using peristaltic and venturi pumps on the Whitestar Signature Phaco System (Abbott Medical Optics, Inc., Santa Ana, California, USA).

Methods

Patients scheduled to have bimanual microincision phacoemulsification by the same surgeon (T.F.) had Pentacam® Scheimpflug assessment using PNS and were randomly distributed into 2 groups. In group 1, surgery was performed using peristaltic pump, and in group 2, using venturi pump. Parameters assessed in both groups included EPT and ST.

Results

Sixty eyes that had uneventful clear cornea phacoemulsification with implantation of foldable intraocular lens (IOL) were evaluated, 30 in each group. The EPT was statistically superior with higher nuclear density grades for both groups 1 and 2 (group 1 Spearman R = 0.739, p<0.001; group 2 Spearman R = 0.924, p<0.001). The ST statistically increased with nucleus density for both groups 1 and 2 (group 1 Spearman R = 0.620, p<0.001; group 2 Spearman R = 0.643, p<0.001). Group 2 presented statistically significant reduction on median ST compared with group 1 for nucleus grading 2, 3, 4, and 5.

Conclusions

The PNS is an objective and reproducible method of grading nuclear cataract density and had a correlation with EPT. Peristaltic and venturi pumps in Signature Phaco System were similar in EPT but venturi pump reduced the median ST in nucleus with higher PNS, without repercussion on complications or anterior chamber stability.
Astigmatism Prevalence and Biometric Analysis in Normal Population
Authors: Nemeth Gabor , Szalai Eszter , Berta Andras , Modis Laszlo
Published: July 2013

Purpose

To analyze the magnitude, orientation, and age-related changes of corneal astigmatism and its correlation with biometric parameters in healthy eyes.

Methods

Patients over 15 years of age were enrolled in our study. Exclusion criteria were previous ocular surgery, corneal disease, or contact lens wear. Axial length (AL), keratometric readings, and anterior chamber depth (ACD) were assessed using IOLMaster.

Results

In our study, 1092 eyes were examined. The mean age was 69.64 ± 15.25 years (range 15–100 years). The AL was 23.32 ± 1.49 mm and ACD was 3.17 ± 2.03 mm. Higher AL and ACD values were observed in male patients. The overall astigmatism was 0.89 ± 0.72 D. The magnitude of astigmatism was ≥ 0.5 D in 73.53% of the cases, ≥ 1.0 D in 32.78%, ≥ 1.5 D in 13.55%, and ≥ 2.0 D in 6.86%. In our population, 582 eyes (53.3%) showed with-the-rule astigmatism, 309 (28.3%) against-the-rule, and 201 (18.4%) oblique astigmatism, regardless of sex. Significant against-the-rule astigmatic shift was verified with aging. Significant correlation was found between age and ACD (r = −0.39, p<0.001), age and AL (r = −0.15, p<0.001), and AL and flat (r = −0.54, p<0.001) and steep keratometric readings (r = −0.49, p<0.001).

Conclusions

In order to obtain adequate refraction results, at the time of cataract surgery distinct attention should be drawn to ophthalmologic biometric parameters, which are continuously changing even in adulthood, and to astigmatism above 1.0 D, present in >32% of the population.
Ophthalmologic Findings in Russian Children with Fetal Alcohol Syndrome
Authors: Gummel Kristina , Ygge Jan
Published: July 2013

Purpose

To study functional and anatomic characteristics of eyes of Russian children with fetal alcohol syndrome (FAS).

Methods

One hundred children aged 10–16 years from Russian orphanages (St. Petersburg) were examined: 50 with verified diagnosis of FAS and 50 healthy children. All children were tested for distance visual acuity (VA) with subjective optimal correction (Sivtsev chart), skiascopy, visual inspection for FAS external ocular features, biomicroscopy, eye alignment using cover test, and indirect ophthalmoscopy.

Results

All analyzed parameters were worse in children with FAS compared with controls. Children with FAS showed a higher incidence of amblyopia, hyperopia, astigmatism, and anisometropia. In children with FAS, the incidence of blepharophimosis was 34% (8% in controls), epicanthus 14% (2% in controls), telecanthus 32% (compared to 4% in controls), eyelid ptosis 9% (none in controls), and strabismus 26% (10% in controls). Ophthalmoscopy revealed a tilted optic disc in 5 children with FAS (7%) compared with none in controls.

Conclusions

Russian children with FAS have a higher incidence of vision problems and eye pathology that needs to be taken into account and requires ophthalmologist monitoring.
Twelve-Month Follow-up of the Artiflex Toric Phakic Intraocular Lens
Authors: Guerin Marc B. , Treacy Maxwell P. , O'Keeffe Michael
Published: July 2013

Purpose

To evaluate the efficacy, safety, refractive predictability, and complications 12 months following the implantation of a foldable toric phakic intraocular lens (PIOL) for the correction of myopic astigmatism.

Methods

Uncorrected visual acuity (UCVA) and best-corrected distance visual acuity (CDVA), subjective and objective manifest refraction, endothelial cell count (ECC), intraocular pressure, biomicroscopy findings, and patient-reported symptoms were the main parameters recorded pre and post the implantation of an Artiflex toric PIOL.

Results

Twenty-eight eyes of 19 patients with preoperative myopia ranging from -1.00 D to -12.00 D and with astigmatism ranging from -1.00 D to -5.50 D had the Artiflex toric PIOL inserted to correct refractive error. Postoperatively, all eyes had UCVA of at least 6/12, 94% of at least 6/9, and 58% of at least 6/6. The CDVA improved in 38% of eyes and vision deteriorated by one line in one eye. Postoperative mean refractive spherical equivalent was -0.25 D (range -1.25 D to 0.00 D) with mean astigmatism being -0.60 D (range -1.50 D to 0.00 D). The ECC decreased by a mean of 6.17% (SD 5.63%) at 12 months when compared with the preoperative baseline.

Conclusions

The Artiflex toric PIOL is an efficacious, predictable, and safe method of treating moderate to high refractive error with astigmatism.
Measurements of Orbital Volume using Cone-Beam Computed Tomography in Eye Movement Abnormalities
Authors: Maka Erika , Lukats Olga , Vizkelety Tamas , Markella Zsolt , Kis Maria , Nemeth Janos , Barabas Jozsef
Published: July 2013

Purpose

To measure the orbital volume in adult patients with unilateral eye movement abnormalities originating in childhood.

Methods

Cone-beam computed tomography was performed in 2 patients with eye movement abnormalities. A 28-year-old woman was treated because of right divergent squint originating at 8 years of age after penetrating corneal trauma. A 38-year-old man was examined because of abnormal head posture caused by left superior oblique underaction originating at 6 years of age. Orbital scans were analyzed with Cranioviewer 3D craniofacial cephalometric program. We measured bony orbital area in 6 slices (in ventro-dorsal direction per 4.8 mm) in every orbit on coronal scans.

Results

The volume was more in the orbit with unilateral divergent squint and less in the orbit with unilateral superior oblique underaction compared to the contralateral orbital volume measurements.

Conclusions

Cranioviewer 3D craniofacial cephalometric program is suitable for volumetric analysis of the bony orbit on cone-beam computed tomography files. The development of the orbit can be influenced by extraocular muscle movements.
Preventable Visual Impairment in Children with Nonprofound Intellectual Disability
Authors: Aslan Lokman , Aslankurt Murat , Aksoy Adnan , Altun Hatice
Published: July 2013

Purpose

To assess the preventable visual impairment in children with nonprofound intellectual disability (ID).

Methods

A total of 215 children with IDs (90 Down syndrome [DS], 125 nonprofound ID) and 116 age- and sex-matched healthy subjects were enrolled in this study. All participants underwent ophthalmologic examinations including cycloplegic refraction measurements, ocular movement evaluation, screening for strabismus (Hirschberg, Krimsky, or prism cover test), slit-lamp biomicroscopy, funduscopy, and intraocular pressure measurements. All data were recorded for statistical analysis.

Results

Ocular findings in decreasing prevalence were as follows: refractive errors 55 (61.1%), strabismus 30 (33.2%), cataract 7 (7.8%), and nystagmus 7 (7.8%) in children with DS; refractive errors 57 (45.6%), strabismus 19 (15.2%), cataract 7 (6.4%), nystagmus 5 (4%), and glaucoma 1 (0.8%) in children with other ID; and refractive errors 13 (11.2%) and strabismus 4 (3.5%) in controls. Cataracts, glaucoma, and nystagmus were not observed in the control group. The most common ophthalmic findings in children with DS compared with other ID and controls were with hyperopia (p<0.03 and p<0.001, respectively) and esotropia (p<0.01 and p<0.01, respectively).

Conclusions

The pediatric population with ID has a high prevalence of preventable visual impairments, refractive errors, strabismus, and cataracts. The prevalence of strabismus and refractive errors was more frequent in children with DS. The importance of further health screenings including ophthalmic examinations should be utilized to implement appropriate care management and improve quality of life.