bluuebunny/crossref_metadata_2025 huggingface dataset:
Recent variation of the Las Vacas Glacier Mt. Aconcagua region, Central Andes, Argentina, based on ASTER stereoscopic images
Authors: Lenzano M. G. , Leiva J. C. , Lenzano L.
Published: April 2010

Abstract. This work presents the results of the ASTER stereoscopic image processing to calculate the volume changes of Las Vacas Glacier. The processing of medium resolution satellite images (ASTER level 1A – pixel 15 m) from February 2001 and 2007 was performed applying the satellite digital photogrammetry method (Kääb, 2005). The comparison of the two generated DTM returns results that are acceptable within the parameters and precisions that can be obtained with this kind of sensor and the processing methodology.
Characterizing contributions of glacier melt and groundwater during the dry season in a poorly gauged catchment of the Cordillera Blanca (Peru)
Authors: Baraer M. , McKenzie J. M. , Mark B. G. , Bury J. , Knox S.
Published: April 2010

Abstract. The retreat of glaciers in the tropics will have a significant impact on water resources. In order to overcome limitations with discontinuous to nonexistent hydrologic measurements in remote mountain watersheds, a hydrochemical and isotopic mass balance model is used to identify and characterize dry season water origins at the glacier fed Querococha basin located in southern Cordillera Blanca, Peru. Dry season water samples, collected intermittently between 1998 and 2007, were analyzed for major ions and the stable isotopes of water (δ18O and δ2H). The hydrochemical and isotopic data are analysed using conservative characteristics of selected tracers and relative contributions are calculated based on pre-identified contributing sources at mixing points sampled across the basin. The results show that during the dry-season, groundwater is the largest contributor to basin outflow and that the flux of groundwater is temporally variable. The groundwater contribution significantly correlates (P-value=0.004 to 0.044) to the antecedent precipitation regime at 3 and 18–36 months. Assuming this indicates a maximum of 4 years of precipitation accumulation in groundwater reserves, the Querococha watershed outflows are potentially vulnerable to multi-year droughts and climate related changes in the precipitation regime. The results show that the use of hydrochemical and isotopic data can contribute to hydrologic studies in remote, data poor regions, and that groundwater contribution to tropical proglacial hydrologic systems is a critical component of dry season discharge.
Interaction of water components in the semi-arid Huasco and Limarí river basins, North Central Chile
Authors: Strauch G. , Oyarzún R. , Reinstorf F. , Oyarzún J. , Schirmer M. , Knöller K.
Published: April 2010

Abstract. For sustainable water resource management in semi-arid regions, sound information is required about interactions between the different components of the water system: rain/snow precipitation, surface/subsurface run-off, groundwater recharge. Exemplarily, the Huasco and Limarí river basins as water stressed river catchments have been studied by isotope and hydrochemical methods for (i) the origin of water, (ii) water quality, (iii) relations of surface and groundwater. Applying the complex multi-isotopic and hydrochemical methodology to the water components of the Huasco and Limarí basins, a differentiation of water components concerning subsurface flow and river water along the catchment area and by anthropogenic impacts are detected. Sulphate and nitrate concentrations indicate remarkable input from mining and agricultural activities along the river catchment. The 2H-18O relations of river water and groundwater of both catchments point to the behaviour of river waters originated in an arid to semi-arid environment. Consequently, the groundwater from several production wells in the lower parts of the catchments is related to the rivers where the wells located, however, it can be distinguished from the river water. Using the hydrological water balance and the isotope mixing model, the interaction between surface and subsurface flows and river flow is estimated.
Sahara dust, ocean spray, volcanoes, biomass burning: pathways of nutrients into Andean rainforests
Authors: Fabian P. , Rollenbeck R. , Spichtinger N. , Brothers L. , Dominguez G. , Thiemens M.
Published: April 2010

Abstract. Regular rain and fogwater sampling in the Podocarpus National Park, on the humid eastern slopes of the Ecuadorian Andes, along an altitude profile between 1960 and 3180 m, has been carried out since 2002. The samples, accumulated over about 1-week intervals, were analysed for pH, conductivity and major ions (K+, Na+, NH4+, Ca2+, Mg2+, Cl−, SO42−, NO3−, PO43−). About 35% of the weekly samples had very low ion contents, with pH mostly above 5 and conductivity below 10 μS/cm. 10-days back trajectories (FLEXTRA) showed that respective air masses originated in pristine continental areas, with little or no obvious pollution sources. About 65%, however, were significantly loaded with cations and anions, with pH as low as 3.5 to 4.0 and conductivity up to 50 μS/cm. The corresponding back trajectories clearly showed that air masses had passed over areas of intense biomass burning, active volcanoes, and the ocean, with episodic Sahara and/or Namib desert dust interference. Enhanced SO42− and NO3+ were identified, by combining satellite-based fire pixel observations with back trajectories, as predominantly resulting from biomass burning. Analyses of oxygen isotopes 16O, 17O, and 18O in nitrate show that nitrate in the samples is indeed a product of atmospheric conversion of precursors. Some SO42−, about 10% of the total input, could be identified to originate from active volcanoes, whose plumes were encountered by about 10% of all trajectories. Enhanced Na+, K+, and Cl− were found to originate from ocean spray sources. They were associated with winds providing Atlantic air masses to the receptor site within less than 5 days. Episodes of enhanced Ca2+ and Mg2+ were found to be associated with air masses from African deserts. Satellite aerosol data confirm desert sources both on the Northern (Sahara) as on the Southern Hemisphere (Namib), depending on the season. A few significant PO43− peaks are related with air masses originating from North African phosphate mining fields.
Archaeological geophysics in Israel: past, present and future
Authors: Eppelbaum L. V.
Published: April 2010

Abstract. In Israel occur a giant number of archaeological objects of various age, origin and size. Different kinds of noise complicate geophysical methods employment at archaeological sites. Geodynamical active, multi-layered, and geologically variable surrounding media in many cases damages ancient objects and disturbs their physical properties. This calls to application of different geophysical methods armed by the modern interpretation technology. The main attention is focused on the geophysical methods most frequently applying in Israeli archaeological sites: GPR and high-precise magnetic survey. Other methods (paleomagnetic, resistivity, near-surface seismics, piezoelectric, etc.) are briefly described and reviewed. The number of employed geophysical methodologies is constantly increasing, and now Israeli territory may be considered as a peculiar polygon for various geophysical methods testing. Several examples illustrate effective application of geophysical methods over some typical archaeological remains. The geophysical investigations at archaeological sites in Israel could be tentatively divided on three stages: (1) past (1990), (2) present (1990–2009), and (3) future (2010). The past stage with several archaeoseismic reviews and very limited application of geophysical methods was replaced by the present stage with the violent employment of numerous geophysical techniques. It is supposed that the future stage will be characterized by extensive development of multidiscipline physical-archaeological databases, employment of all possible indicators for 4-D monitoring and ancient sites reconstruction, as well as application of combined geophysical multilevel surveys using remote operated vehicles at low altitudes.
Undercatch of tipping-bucket gauges in high rain rate events
Authors: Duchon C. E. , Biddle C. J.
Published: April 2010

Abstract. We have investigated differences in rainfall accumulations for seven high rain rate events from three gauges: a Geonor T-200B vibrating-wire weighing gauge and two MetOne tipping-bucket gauges. The Geonor gauge and one tipping-bucket gauge are located in a pit so that their collection orifices are at ground level. Thus their measured rainfall accumulations are minimally affected by wind speed. The other tipping-bucket gauge is located 105 m from the pit and is surrounded by an Alter-type slatted wind screen. Its collection orifice is positioned 1 m above ground level. The results from the seven events show that the tipping-bucket gauges noticeably underestimated storm event rainfall totals relative to the weighing-bucket gauge when 1-min rain rates exceeded about 50 mm/h (2 in/h). In addition, we conclude that observable wind induced undercatch by the aboveground tipping bucket gauge begins when the wind speed at a height of 2 m exceeds around 5 m/s. In this paper we show and discuss time series of rain rates, differences in rain rates, and wind speeds for two of the seven events in an attempt to account for the lower storm totals from the two tipping bucket gauges relative to the weighing-bucket gauge.
The forecaster's added value in QPF
Authors: Turco M. , Milelli M.
Published: April 2010

Abstract. To the authors' knowledge there are relatively few studies that try to answer this question: "Are humans able to add value to computer-generated forecasts and warnings?". Moreover, the answers are not always positive. In particular some postprocessing method is competitive or superior to human forecast. Within the alert system of ARPA Piemonte it is possible to study in an objective manner if the human forecaster is able to add value with respect to computer-generated forecasts. Every day the meteorology group of the Centro Funzionale of Regione Piemonte produces the HQPF (Human Quantitative Precipitation Forecast) in terms of an areal average and maximum value for each of the 13 warning areas, which have been created according to meteo-hydrological criteria. This allows the decision makers to produce an evaluation of the expected effects by comparing these HQPFs with predefined rainfall thresholds. Another important ingredient in this study is the very dense non-GTS (Global Telecommunication System) network of rain gauges available that makes possible a high resolution verification. In this work we compare the performances of the latest three years of QPF derived from the meteorological models COSMO-I7 (the Italian version of the COSMO Model, a mesoscale model developed in the framework of the COSMO Consortium) and IFS (the ECMWF global model) with the HQPF. In this analysis it is possible to introduce the hypothesis test developed by Hamill (1999), in which a confidence interval is calculated with the bootstrap method in order to establish the real difference between the skill scores of two competitive forecasts. It is important to underline that the conclusions refer to the analysis of the Piemonte operational alert system, so they cannot be directly taken as universally true. But we think that some of the main lessons that can be derived from this study could be useful for the meteorological community. In details, the main conclusions are the following: – despite the overall improvement in global scale and the fact that the resolution of the limited area models has increased considerably over recent years, the QPF produced by the meteorological models involved in this study has not improved enough to allow its direct use: the subjective HQPF continues to offer the best performance for the period +24 h/+48 h (i.e. the warning period in the Piemonte system); – in the forecast process, the step where humans have the largest added value with respect to mathematical models, is the communication. In fact the human characterization and communication of the forecast uncertainty to end users cannot be replaced by any computer code; – eventually, although there is no novelty in this study, we would like to show that the correct application of appropriated statistical techniques permits a better definition and quantification of the errors and, mostly important, allows a correct (unbiased) communication between forecasters and decision makers.
Wet scavenging of SO2 emissions around India's largest lignite based power plant
Authors: Rai A. , Ghosh S. , Chakraborty S.
Published: April 2010

Abstract. The Neyveli Lignite Corporation (NLC) is among the largest lignite based power plants in South East Asia. The four elevated stacks from this power plant emanate a substantial amount of sulphur dioxide into a tropical boundary layer. Sulphur dioxide being a soluble pollutant gas is absorbed by falling raindrops. This is a first study that quantifies the scavenging action of the North Eastern monsoonal rains from a lignite based power plant. We find that although the North Eastern monsoonal rains have a preponderance of very large droplets, the contribution of the small droplets cannot be neglected. We expect that the estimated scavenging coefficients can be used by large eddy and climate models.
Heat and energy fluxes in the convective cell behind a cold front
Authors: Ivanov S. , Palamarchuk J.
Published: April 2010

Abstract. High resolution model simulations are used to estimate heat fluxes and energy conversion in the convective cell developing behind a cold front. It is found that the model is able to simulate rapid temperature changes in the low troposphere up to 1 °C for a time period of a few minutes due to latent heat release as well as horizontal acceleration up to 5 m/s at the top of convective circulation. Numerical experiments have also shown sensitivity of fine resolution simulations to parameterizations used for the description of a large-scale flow.
Spatial relationships of heavy rains in the Czech Republic
Authors: Bek S. , Ježek J. , Bližňák V.
Published: April 2010

Abstract. Study of heavy rain events and their spatial distribution are of great importance. Such events cause local flooding, accelerate soil erosion and cause damage on property. Data for this study were derived by Sokol and Bližňák (2009) from radar reflectivity and daily rain gauge measurements for the period of 2002–2008. We selected heavy rain events using spatial and intensity constrains. We studied relationships between heavy rains, altitude and terrain roughness. Heavy rain totals correlate with both altitude and terrain roughness globally over the Czech Republic. The correlation is also significant for extreme heavy rain totals. The correlation of heavy rain intensities with altitude was not proven. The highest rates of average intensities are located in the south-eastern parts of the Czech Republic. The spatial distribution of heavy rain frequencies strongly corresponds to the spatial distribution of heavy rain totals. The highest percentage of heavy rains in total precipitation is located in the north-west of the Czech Republic. The extreme heavy rains occupy higher altitudes.
Hierarchical Bayesian space-time interpolation versus spatio-temporal BME approach
Authors: Hussain I. , Pilz J. , Spoeck G.
Published: April 2010

Abstract. The restrictions of the analysis of natural processes which are observed at any point in space or time to a purely spatial or purely temporal domain may cause loss of information and larger prediction errors. Moreover, the arbitrary combinations of purely spatial and purely temporal models may not yield valid models for the space-time domain. For such processes the variation can be characterized by sophisticated spatio-temporal modeling. In the present study the composite spatio-temporal Bayesian maximum entropy (BME) method and transformed hierarchical Bayesian space-time interpolation are used in order to predict precipitation in Pakistan during the monsoon period. Monthly average precipitation data whose time domain is the monsoon period for the years 1974–2000 and whose spatial domain are various regions in Pakistan are considered. The prediction of space-time precipitation is applicable in many sectors of industry and economy in Pakistan especially; the agricultural sector. Mean field maps and prediction error maps for both methods are estimated and compared. In this paper it is shown that the transformed hierarchical Bayesian model is providing more accuracy and lower prediction error compared to the spatio-temporal Bayesian maximum entropy method; additionally, the transformed hierarchical Bayesian model also provides predictive distributions.
Using earthquakes to uncover the Earth's inner secrets: interactive exhibits for geophysical education
Authors: Nostro C. , Cultrera G. , Burrato P. , Tertulliani A. , Macrì P. , Winkler A. , Castellano C. , Casale P. , Di Felice F. , Doumaz F. , Piscini A. , Scarlato P. , Vallocchia M. , Marsili A. , Badiali L. , Bono A. , Stramondo S. , Alfonsi L. , Baroux E. , Ciaccio M. G. , Frepoli A.
Published: April 2010

Abstract. The Educational & Outreach Group (E&O Group) of the Istituto Nazionale di Geofisica e Vulcanologia (INGV) designed a portable museum to bring on the road educational activities focused on seismology, seismic hazard and Earth science. This project was developed for the first edition of the Science Festival organized in Genoa, Italy, in 2003. The museum has been mainly focused to school students of all ages and explains the main topics of geophysics through posters, movie and slide presentations, and exciting interactive experiments. This new INGV museum has been remarkably successful, being visited by more than 8000 children and adults during the 10 days of the Science Festival. It is now installed at the INGV headquarters in Rome and represents the main attraction during the visits of the schools all year round.
A public summer school on astronomy in Denmark: experience from the course in 2002, 2003 and 2004
Authors: Kjeldsen H.
Published: April 2010

Abstract. During the summers of 2002, 2003 and 2004 a one-week public course on Astronomy took place at Silkeborg Folk High School in central Jutland, Denmark. The aim of the course was to offer a possibility for students to meet research scientists and discuss central scientific questions and their answers. Researchers from the Department of Physics and Astronomy at Aarhus University in Denmark took an active part in running this summer school and the course could also be seen as a part of the Department's general public outreach activities. The main aim of those activities is to: (1) show why research is important, (2) give students and children the possibility to meet people that do research, and (3) present authentic role models.
Science, mathematics and technology education in the US: a perspective from the "frontlines of the classroom to national policy"
Authors: Pertzborn R. A.
Published: April 2010

Abstract. In the past decade significant emphasis has been placed on increasing the involvement and influence of the professional scientific community in America's K-12 classrooms. The origins of this thrust have arisen from a variety of real and perceived crises occurring in America's K-12 classrooms. Projections for the nation's future workforce needs indicate an increased demand for science and technically literate workers, while fewer of the nation's students are pursuing advanced degrees in these academic areas of expertise. In an effort to address these issues and to impact the overall understanding and quality of science, math and technology education, several of the federal agencies have increasingly included a percentage of research funding devoted to the objective of improving the quality of kindergarten through Grade 12 (K-12, see Table 1) formal education and informal public outreach. To this end, NASA's Space Science Enterprise in particular has demonstrated a successful implementation approach and has been a national leader in forging strong partnerships with the education community to address these concerns.
Incorporating level set methods in Geographical Information Systems (GIS) for land-surface process modeling
Authors: Pullar D.
Published: April 2010

Abstract. Land-surface processes include a broad class of models that operate at a landscape scale. Current modelling approaches tend to be specialised towards one type of process, yet it is the interaction of processes that is increasing seen as important to obtain a more integrated approach to land management. This paper presents a technique and a tool that may be applied generically to landscape processes. The technique tracks moving interfaces across landscapes for processes such as water flow, biochemical diffusion, and plant dispersal. Its theoretical development applies a Lagrangian approach to motion over a Eulerian grid space by tracking quantities across a landscape as an evolving front. An algorithm for this technique, called level set method, is implemented in a geographical information system (GIS). It fits with a field data model in GIS and is implemented as operators in map algebra. The paper describes an implementation of the level set methods in a map algebra programming language, called MapScript, and gives example program scripts for applications in ecology and hydrology.
Lake and climate models linkage: a 3-D hydrodynamic contribution
Authors: Leon L. F. , Lam D. , Schertzer W. , Swayne D.
Published: April 2010

Abstract. Under a Canadian Foundation for Climate and Atmospheric Sciences (CFCAS) project, targeted to study the feasibility to link regional climate models with lake models, one of the tasks was to consider such a coupling in large lakes. The objective is to provide detailed information on temperature and circulation distributions of the lake to take into account the spatial variability for temperature and the heat exchange through the water's surface. The major contribution of this work is focused on realistic representation of the heat fluxes and temperature distributions to and from lakes especially during the thermally stratified ice-free periods. This paper presents the detailed 3-D ELCOM model applied in Lake Erie in order to produce, at the surface layer of the lake, the spatial distribution of temperature and heat exchanges that eventually can be coupled with a regional climate model (CRCM). Preliminary results will be presented on how this lake model may improve the regional climate models, which currently do not consider such large lake circulation effects.
Towards an Open Modelling Interface (OpenMI) the HarmonIT project
Authors: Blind M. , Gregersen J. B.
Published: April 2010

Abstract. The Water Framework Directive (WFD) poses an immense challenge to water management in Europe. Aiming at a "good ecological status" of surface waters in 2015, integrated river basin management plans need to be in place by 2009, and broadly supported by stakeholders. Information & Communication Technology (ICT) tools, such as computational models, are very helpful in designing river basin management plans (rbmp-s). However, many scientists believe that a single integrated modelling system to support the WFD cannot be developed, and integrated systems need to be quite tailored to the local situation and evolve during a collaborative planning process. As a consequence there is an urgent need to increase the flexibility of modelling systems, such that dedicated model systems can be developed from available building blocks. In the recent past a number of initiatives have been started to develop an IT framework for modelling to meet the required flexibility. In Europe the international project HarmonIT, which is sponsored by the European Commission, is developing and implementing a standard interface for modelling components and other relevant tools: The Open Modelling Interface (OpenMI). This paper describes the HarmonIT project and objectives in general. The current progress is described. It describes the roles for different types of stakeholders in modelling, varying from software coders to non-specialized users of decision support systems. It will provide insight in the requirements imposed when using the OpenMI.
LIANA Model Integration System - architecture, user interface design and application in MOIRA DSS
Authors: Hofman D.
Published: April 2010

Abstract. The LIANA Model Integration System is the shell application supporting model integration and user interface functionality required for the rapid construction and run-time support of the environmental decision support systems (EDSS). Internally it is constructed as the framework of C++ classes and functions covering most common tasks performed by the EDSS (such as managing of and alternative strategies, running of the chain of the models, supporting visualisation of the data with tables and graphs, keeping ranges and default values for input parameters etc.). EDSS is constructed by integration of LIANA system with the models or other applications such as GIS or MAA software. The basic requirements to the model or other application to be integrated is minimal - it should be a Windows or DOS .exe file and receive input and provide output as text files. For the user the EDSS is represented as the number of data sets describing scenario or giving results of evaluation of scenario via modelling. Internally data sets correspond to the I/O files of the models. During the integration the parameters included in each the data sets as well as specifications necessary to present the data set in GUI and export or import it to/from text file are provided with MIL_LIANA language. Visual C++ version of LIANA has been developed in the frame of MOIRA project and is used as the basis for the MOIRA Software Framework - the shell and user interface component of the MOIRA Decision Support System. At present, the usage of LIANA for the creation of a new EDSS requires changes to be made in its C++ code. The possibility to use LIANA for the new EDSS construction without extending the source code is achieved by substituting MIL_LIANA with the object-oriented LIANA language.
Studies on data uncertainties of the local model of the German Meteorological Service in the catchment area of the river Ilm
Authors: Pfannschmidt K. , Döhler H.
Published: April 2010

Abstract. To assess the prognostic values concerning precipitation and air temperature in the river catchment area of the Ilm/Thuringia issued by the German Meteorological Service, the differences between the prognostic values and related measured values were statistically evaluated. The investigations covered the period from November 1999 to December 2003. The spatial resolution corresponds to the LM grid cells and the available data. The observed precipitation values were corrected with regard to systematic wind error in dependence of temperature. The forecast data were investigated comprehensively in order to quantify the statistical reliability. Therefore, the 2nd moment as the case may be the standard deviation of the differences between observed precipitation values and forecasting precipitation values have been calculated. The investigations were subdivided into the complete stretch of time, the hydrological summer and the hydrological winter. Each measured value was analysed with regard to the 12-, 24-, 36- and 48-hour forecast made by the DWD. As a result, empirical analytical functions were developed to describe adequately the statistical quantities for standard deviation of precipitation and temperature for the periods of hydrological summer and hydrological winter in dependence on forecasting time, mean ground level and roughness (fractal dimension) of the LM-grid cell.
Upscaling of land-surface parameters through direct moment propagation
Authors: Kunstmann H.
Published: April 2010

Abstract. A new methodology is presented that allows the upscaling of land surface parameters of a Soil-Vegetation-Atmosphere-Transfer (SVAT) Model. Focus is set on the proper representation of latent and sensible heat fluxes on grid scale at underlying subgrid-scale heterogeneity. The objective is to derive effective land surface parameters in the sense that they are able to yield the same heat fluxes on the grid scale as the averaged heat fluxes on the subgrid-scale. A combination of inverse modelling and Second-Order-First-Moment (SOFM) propagation is applied for the derivation of effective parameters. The derived upscaling laws relate mean and variance (first and second moment) of subgrid-scale heterogeneity to a corresponding effective parameter at grid-scale. Explicit upscaling relations are exemplary derived for a) roughness length, b) wilting point soil moisture, and c) minimal stomata resistance. It is demonstrated that the SOFM-Method yields congruent results to corresponding Monte Carlo simulations. Effective parameters were found to be independent of driving meteorology and initial conditions.
Optimising soil-hydrological predictions using effective CART models
Authors: Selle B. , Huwe B.
Published: April 2010

Abstract. There are various problems with process-based models at the landscape scale, including substantial computational requirements, a multitude of uncertain input parameters and the limited parameter identificability. Classification And Regression Trees (CART) is a recent data-based approach that is likely to yield advantages both over process-based models and simple empirical models. This non-parametric regression technique can be used to simplify process-based models by extracting key variables, which govern the process of interest at a specified scale. In other words, the model complexity can be fitted to the information content in the data. CART is applied to model spatially distributed percolation in soils using weather data and the groundwater depths specific to the site. The training data was obtained by numerical experiments with Hydrus1D. Percolation is effectively predicted using CART but the model performance is highly dependant on the available data and the boundary conditions. However, the effective CART models possess an optimal complexity that corresponds to the information content in the data and hence, are particularly suited for environmental management purposes.
Use of microwave remote sensing data to monitor spatio temporal characteristics of surface soil moisture at local and regional scales
Authors: Löw A. , Ludwig R. , Mauser W.
Published: April 2010

Abstract. Hydrologic processes, such as runoff production or evapotranspiration, largely depend on the variation of soil moisture and its spatial pattern. The interaction of electromagnetic waves with the land surface can be dependant on the water content of the uppermost soil layer. Especially in the microwave domain of the electromagnetic spectrum, this is the case. New sensors as e.g. ENVISAT ASAR, allow for frequent, synoptically and homogeneous image acquisitions over larger areas. Parameter inversion models are therefore developed to derive bio- and geophysical parameters from the image products. The paper presents a soil moisture inversion model for ENVISAT ASAR data for local and regional scale applications. The model is validated against in situ soil moisture measurements. The various sources of uncertainties, being related to the inversion process are assessed and quantified.
Topography data harmonisation and uncertainties applying SRTM, laser scanner and cartographic elevation models
Authors: Haase D. , Frotscher K.
Published: April 2010

Abstract. Only a few studies have attempted to quantify topography-depending water fluxes, to evaluate retention and reservoir capacities and surface run-off paths within large river basins because data availability and data quality are critical issues to face this objective. It becomes most relevant if water balance has to be calculated in large or transboundary river basins. The advance of space based earth observation data offers a solution to this information problem. Therefore, this paper mainly focuses on weaknesses and strengths analyzing topography with SRTM (Shuttle Radar Topography Mission) digital height data and thus provides techniques for their improved application in river network derivation, floodplain analysis, watershed hydrology in large as well as in large river basins (>1000 km2). In the analysis different types of digital elevation models (DEM), terrain models (DTM) and land cover classification data (biotope map, Corine Land Cover 1994) have been used. The DHMs are generated from Airborne Laser Scanning (0.5 m), topographic maps (10.0/50.0 m) and SRTM at 30.0 m and 90.0 m spatial resolution. SRTM digital height models are generated by Synthetic Aperture Radar (SAR) and show a high spatial variance in urban areas, regions of dense vegetation canopy, floodplains and water bodies. As study area serve the Elbe basin (Czech Republic, Germany) with its sub-basins and the Saale river basin (Germany, different federal countries Saxony-Anhalt, Saxony and Thuringia).
Quantifying the efficiency of river regulation
Authors: Rödel R. , Hoffmann T.
Published: April 2010

Abstract. Dam-affected hydrologic time series give rise to uncertainties when they are used for calibrating large-scale hydrologic models or for analysing runoff records. It is therefore necessary to identify and to quantify the impact of impoundments on runoff time series. Two different approaches were employed. The first, classic approach compares the volume of the dams that are located upstream from a station with the annual discharge. The catchment areas of the stations are calculated and then related to geo-referenced dam attributes. The paper introduces a data set of geo-referenced dams linked with 677 gauging stations in Europe. Second, the intensity of the impoundment impact on runoff times series can be quantified more exactly and directly when long-term runoff records are available. Dams cause a change in the variability of flow regimes. This effect can be measured using the model of linear single storage. The dam-caused storage change ΔS can be assessed through the volume of the emptying process between two flow regimes. As an example, the storage change ΔS is calculated for regulated long-term series of the Luleälven in northern Sweden.
A study of the sensitivity of ENSO to the mean climate
Authors: Toniazzo T.
Published: April 2010

Abstract. We study the dependence of the simulated ENSO on the mean simulated climate in the HadCM3 GCM and attempt to understand its relation with results from intermediate-complexity models (ICMs). Our aim is to bridge an existing gap between results from complex GCMs and from more readily understandable ICMs, and thereby to improve our process-based prediction skills of the potential sensitivity of observed ENSO properties (amplitude, frequency and pattern) to climate change. Although there is a suggestion that surface ENSO processes are dominating the response in HadCM3, our work also shows that the complex changes in simulated climate can have contrasting effects on the ENSO and the net result may not be robust.
The roles of ENSO on the occurrence of abruptly recurving tropical cyclones over the Western North Pacific Ocean Basin
Authors: Cheung N. K. W.
Published: April 2010

Abstract. The abruptly recurving tropical cyclones over the Western North Pacific Ocean Basin during El Niño and La Niña events are studied. Temporal and spatial variations of these anomalous tracks under different phases of ENSO are shown. The anomalies of the pressure field in relation to ENSO circulation for the occurrence of the abruptly recurving cyclone tracks are investigated using fuzzy method. These are supplemented by wind field analyses. It is found that the occurrence of recurving-left (RL) and recurving-right (RR) tropical cyclones under the modification of the steering currents, including the re-adjustment of the westerly trough, the expansion or contraction of the sub-tropical high pressure, the intensifying easterly flow and the strengthening of the cross-equatorial flow, can be in El Niño or La Niña events. Evidently, there is a higher chance of occurrence of anomalous tropical cyclone trajectories in El Niño rather than La Niña events, but there is not any pronounced spatial pattern of anomalous tropical cyclone tracks. By analyzing the pressure-field, it is seen RL (RR) tropical cyclones tend to occur when the subtropical high pressure is weak (strong) in El Niño and La Niña events. More importantly, how the internal force of tropical cyclones changed by the steering current, which relies upon the relative location of tropical cyclones to the re-adjustment of the weather systems, shows when and where RL and RR tropical cyclones occur in El Niño and La Niña events.
Sea level height, sea surface temperature, and tuna yields in the Panama bight during El Niño
Authors: Pedraza M. J. , Díaz Ochoa J. A.
Published: April 2010

Abstract. Between 1988 and 1998, annual tuna landings at Buenaventura (Colombian Pacific) are correlated with the sea surface temperature in the central Equatorial Pacific (r=0.78, p<0.05) and the sea level height at Buenaventura (r=0.76, p<0.05) and Balboa (Panama) (r=0.79, p<0.05). Seasonal oceanic upwelling is forced by the Panama wind jet, which may favour oceanic fisheries such as tuna. Here we first apply a bivariate correlation method (Pyper and Peterman, 1994) and then a multivariate approach (principal components analysis or PCA) to investigate the relationships of these environmental variables with landings. With the first method, we find that landing is best correlated with the sea surface temperature in the Niño 3 region, whereas the other relationships are less clear. In contrast, with PCA we find that PC1 explains 90.6% of the total variance and suggests that sea surface temperature plays a major role in determining tuna availability in the area (especially during El Niño events). Since PC2 is mainly correlated with sea level height at Balboa but only represents 6.8% of the total variance, we suggest that oceanic upwelling effects on tuna landings at Buenaventura are not significant at interannual scales.
Disentangling the effects of El Niño on a population of the polychaete Sigambra bassi in the Bay of Ancón, Peru
Authors: Peña T. S. , Johst K. , Grimm V. , Arntz W. E. , Tarazona J.
Published: April 2010

Abstract. The macrobenthic community in shallow soft-bottom areas in the Bay of Ancón, Peru, is characterized by low biodiversity due to low oxygen concentrations. During El Niño (EN) events, higher water temperature and higher concentrations of dissolved oxygen induce a temporary increase in biodiversity. However, the structure and dynamics of the emerging macrobenthic community and populations, especially the polychaete Sigambra bassi, vary strongly among events. The reasons for this variation are poorly understood, in particular the relative influence of abiotic versus biotic factors. To disentangle how abiotic and biotic factors influence the different responses of the population of S. bassi, population models were developed based on detailed long-term monitoring data, which include four El Niño events. The results show that S. bassi abundances are favored by abiotic environmental conditions during EN, namely high temperature and dissolved oxygen concentration, but these abiotic effects are modulated by different biotic processes. In two EN events with relatively similarly high temperature anomalies (EN 1982-1983 and 1997-1998) different biological interactions (competition, predation, facilitation) and different species composition of the community resulted in different responses of the population of S. bassi.
Robustness of the influence of El Niño on the spatial extent of tropical drought
Authors: Lyon B.
Published: April 2010

Abstract. It has been well established that drought frequently emerges in several tropical regions following the onset of El Niño. An important characteristic of such droughts is their spatial extent, which has recently been linked to the strength of a particular El Niño event. Here the robustness of this relationship is examined through comparison of results from several gridded precipitation analyses for the global tropics. It is found that there is very good agreement across these datasets, including those which incorporate satellite rainfall estimates, confirming that maximum drought extent in tropical land areas increases nearly linearly with associated maximum sea surface temperature anomalies in the east-central tropical Pacific during El Niño events.
The impact of the warm phase of ENSO (El Niño Southern Oscillation) events on water resource availability of tropical catchments in Central Sulawesi, Indonesia
Authors: Leemhuis C. , Gerold G.
Published: April 2010

Abstract. Precipitation anomalies caused by the warm phase (El Niño) of the ENSO cycle lead to a strong decrease of water resources in South-East Asia. The aim of this work is to study the impact of warm phase ENSO caused precipitation anomalies on the water balance of a mesoscale tropical catchment in Central Sulawesi, Indonesia using a scenario analysis. We applied statistically generated precipitation anomalies caused by warm phase ENSO events on a validated hydrological model of the Palu River catchment (2694 km2) to investigate the implications of the generated ENSO scenarios on the total annual water balance, the annual discharge regime and the discharge variability. Moreover we analysed the influence of various catchment characteristics during warm phase ENSO conditions on the discharge variability through a comparison of different sub-catchment types. The results of the scenario analysis proved a severe decline of the annual discharge rate during warm phase ENSO conditions and an increase of the overall discharge variability.
The Impact of El Niño - Southern Oscillation Events on South America
Authors: Santos J. L.
Published: April 2010

Abstract. The presence of ENSO Events in South America is felt in two ways: a) through its effects on both the atmosphere and ocean systems, and b) through its impacts on natural ecosystems (both marine and terrestrial) and on societal and economical sectors (like fisheries, health, and agriculture). The main effects of El Niño/La Niña are: Increment/Decrement of sea surface temperature and salinity, Increment/Decrement of sea level and wave activity, Increment/Decrement of air temperature and amount of ultra violet radiation reaching the surface of the earth, and Changes in the rainfall and evaporation patterns. It is not easy to make an "average" pattern of ENSO impacts for a variety of reasons: the impacts depend greatly of factors like geographical extent and position of the oceanic anomalies, and intensity and timing of the anomalies; also the influence of social, economic and political structures determines whether climate anomalies caused by ENSO in a particular region will lead to severe societal and economical impacts. The scientific community also plays a potential role in the extent of the impacts that ENSO can produce, if scientists can provide information on the impact of the presence of ENSO by identifying and focusing on its precursors, intervention could be taken early enough. There is however, something to be said against that: information can be misleading, target inappropriate at-risk groups, or generate a false sense of security.
ENSO impact on simulated South American hydro-climatology
Authors: Stuck J. , Güntner A. , Merz B.
Published: April 2010

Abstract. The variability of the simulated hydro-climatology of the WaterGAP Global Hydrology Model (WGHM) is analysed. Main object of this study is the ENSO-driven variability of the water storage of South America. The horizontal model resolution amounts to 0.5 degree and it is forced with monthly climate variables for 1961-1995 of the Tyndall Centre Climate Research Unit dataset (CRU TS 2.0) as a representation of the observed climate state. Secondly, the model is also forced by the model output of a global circulation model, the ECHAM4-T42 GCM. This model itself is driven by observed monthly means of the global Sea Surface Temperatures (SST) and the sea ice coverage for the period of 1903 to 1994 (GISST). Thus, the climate model and the hydrological model represent a realistic simulated realisation of the hydro-climatologic state of the last century. Since four simulations of the ECHAM4 model with the same forcing, but with different initial conditions are carried out, an analysis of variance (ANOVA) gives an impression of the impact of the varying SST on the hydro-climatology, because the variance can be separated into a SST-explained and a model internal variability (noise). Also regional multivariate analyses, like Empirical Orthogonal Functions (EOF) and Canonical Correlation Analysis (CCA) provide information of the complex time-space variability. In particular the Amazon region and the South of Brazil are significantly influenced by the ENSO-variability, but also the Pacific coastal areas of Ecuador and Peru are affected. Additionally, different ENSO-indices, based on SST anomalies (e.g. NINO3.4, NINO1+2), and its influence on the South American hydro-climatology are analysed. Especially, the Pacific coast regions of Ecuador, Peru and Chile show a very different behaviour dependant on those indices.
Inter-El Niño variability and its impact on the South American low-level jet east of the Andes during austral summer − two case studies
Authors: Silva G. A. M. , Ambrizzi T.
Published: April 2010

Abstract. The impact of the maximum convection location over eastern and central Equatorial Pacific over the intensity and positioning of the South American Low-Level Jet east of the Andes (SALLJ) during the austral summer was investigated. The Bonner criteria 1 was applied to the NCEP-NCAR circulation fields during the El Niño of 1997/1998 and 2002/2003 to identify the SALLJ episodes. The composites of the atmospheric circulation over the South America during El Niño events showed that the SALLJ can be influenced by small displacements of the quasi-stationary Rossby waves position. During the strong El Niño event of 1997/1998 the SALLJ is maintained by the eastern trade winds. A low-level anomalous anticyclonic circulation over the central part of Brazil enhanced the wind in the nucleus of the jet and displaced its axis to the Northern Argentina and South of Brazil. However, the northern trade winds seem to maintain the SALLJ during the weak El Niño of 2002/2003. The jet was weaker and displaced more southeastward of Brazil than during the strong event.
Coupled model simulations of mid-Holocene ENSO and comparisons with coral oxygen isotope records
Authors: Brown J. , Collins M. , Tudhope A.
Published: April 2010

Abstract. The sensitivity of El Niño-Southern Oscillation (ENSO) to changes in mean climate is investigated for simulations of pre-industrial and mid-Holocene (6000 years before present) climate using the Hadley Centre coupled atmosphere-ocean model, HadCM3. Orbitally-forced changes in insolation in the mid-Holocene produce changes in seasonality which may alter ENSO amplitude and frequency. The model simulations are compared with mid-Holocene fossil coral oxygen isotope records from the western Pacific Warm Pool. The coral records imply a reduction of around 60% in the amplitude of interannual variability associated with ENSO in the mid-Holocene, while the model simulates a smaller reduction in ENSO amplitude of around 10%. The model also simulates a slight shift to longer period variability and a weakening of ENSO phase-locking to the seasonal cycle in the mid-Holocene. There is little change in the pattern of ENSO tropical precipitation teleconnections in the simulated mid-Holocene climate.