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Search Results: 1 - 10 of 4583 matches for " Klaus Scipal "
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Temporal Stability of Soil Moisture and Radar Backscatter Observed by the Advanced Synthetic Aperture Radar (ASAR)
Wolfgang Wagner,Carsten Pathe,Marcela Doubkova,Daniel Sabel,Annett Bartsch,Stefan Hasenauer,Günter Bl?schl,Klaus Scipal,José Martínez-Fernández,Alexander L?w
Sensors , 2008, DOI: 10.3390/s8021174
Abstract: The high spatio-temporal variability of soil moisture is the result of atmosphericforcing and redistribution processes related to terrain, soil, and vegetation characteristics.Despite this high variability, many field studies have shown that in the temporal domainsoil moisture measured at specific locations is correlated to the mean soil moisture contentover an area. Since the measurements taken by Synthetic Aperture Radar (SAR)instruments are very sensitive to soil moisture it is hypothesized that the temporally stablesoil moisture patterns are reflected in the radar backscatter measurements. To verify this hypothesis 73 Wide Swath (WS) images have been acquired by the ENVISAT AdvancedSynthetic Aperture Radar (ASAR) over the REMEDHUS soil moisture network located inthe Duero basin, Spain. It is found that a time-invariant linear relationship is well suited forrelating local scale (pixel) and regional scale (50 km) backscatter. The observed linearmodel coefficients can be estimated by considering the scattering properties of the terrainand vegetation and the soil moisture scaling properties. For both linear model coefficients,the relative error between observed and modelled values is less than 5 % and thecoefficient of determination (R2) is 86 %. The results are of relevance for interpreting anddownscaling coarse resolution soil moisture data retrieved from active (METOP ASCAT)and passive (SMOS, AMSR-E) instruments.
Soil moisture-runoff relation at the catchment scale as observed with coarse resolution microwave remote sensing
K. Scipal, C. Scheffler,W. Wagner
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2005,
Abstract: Microwave remote sensing offers emerging capabilities to monitor global hydrological processes. Instruments like the two dedicated soil moisture missions SMOS and HYDROS or the Advanced Scatterometer onboard METOP will provide a flow of coarse resolution microwave data, suited for macro-scale applications. Only recently, the scatterometer onboard of the European Remote Sensing Satellite, which is the precursor instrument of the Advanced Scatterometer, has been used successfully to derive soil moisture information at global scale with a spatial resolution of 50 km. Concepts of how to integrate macro-scale soil moisture data in hydrologic models are however still vague. In fact, the coarse resolution of the data provided by microwave radiometers and scatterometers is often considered to impede hydrological applications. Nevertheless, even if most hydrologic models are run at much finer scales, radiometers and scatterometers allow monitoring of atmosphere-induced changes in regional soil moisture patterns. This may prove to be valuable information for modelling hydrological processes in large river basins (>10 000 km2. In this paper, ERS scatterometer derived soil moisture products are compared to measured runoff of the Zambezi River in south-eastern Africa for several years (1992–2000). This comparison serves as one of the first demonstrations that there is hydrologic relevant information in coarse resolution satellite data. The observed high correlations between basin-averaged soil moisture and runoff time series (R2>0.85) demonstrate that the seasonal change from low runoff during the dry season to high runoff during the wet season is well captured by the ERS scatterometer. It can be expected that the high correlations are to a certain degree predetermined by the pronounced inter-annual cycle observed in the discharge behaviour of the Zambezi. To quantify this effect, time series of anomalies have been compared. This analysis showed that differences in runoff from year to year could, to some extent, be explained by soil moisture anomalies.
Structural and statistical properties of the collocation technique for error characterization
S. Zwieback, K. Scipal, W. Dorigo,W. Wagner
Nonlinear Processes in Geophysics (NPG) , 2012,
Abstract: The validation of geophysical data sets (e.g. derived from models, exploration techniques or remote sensing) presents a formidable challenge as all products are inherently different and subject to errors. The collocation technique permits the retrieval of the error variances of different data sources without the need to specify one data set as a reference. In addition calibration constants can be determined to account for biases and different dynamic ranges. The method is frequently applied to the study and comparison of remote sensing, in-situ and modelled data, particularly in hydrology and oceanography. Previous studies have almost exclusively focussed on the validation of three data sources; in this paper it is shown how the technique generalizes to an arbitrary number of data sets. It turns out that only parts of the covariance structure can be resolved by the collocation technique, thus emphasizing the necessity of expert knowledge for the correct validation of geophysical products. Furthermore the bias and error variance of the estimators are derived with particular emphasis on the assumptions necessary for establishing those characteristics. Important properties of the method, such as the structural deficiencies, dependence of the accuracy on the number of measurements and the impact of violated assumptions, are illustrated by application to simulated data.
An Enduring Concept for Security Council Reform  [PDF]
Klaus Schlichtmann
Beijing Law Review (BLR) , 2011, DOI: 10.4236/blr.2011.22010
Abstract: UN Security Council reform has been lingering over the years, since it was first seriously considered in the 1990s, after the collapse of the Soviet Union. This paper argues that enlarging the Security Council by adding new permanent and non-permanent members, while many of the Charter provisions vital for the maintenance of international peace and security and disarmament are not in effect, would be counterproductive. Instead, the composition of the Council should be reshuffled and expanded by giving a seat to a prominent member of the Global South, i.e. India, and replacing the seats of France and Britain with a single European representation. While there would be no increase or change in the number of permanent and non-permanent members, the result will be a dramatic increase in the numbers of people represented by the Permanent Five, which then will, in effect, comprise half of the world’s population projected for 2012. The underlying logic is that increasing the number of permanent members (P5) would make the Security Council not only less effective, but also prevent the realization of a fundamental purpose of the United Nations, i.e. the transition from an armed to an unarmed peace. By maintaining the number 5, the effective operation of the consensus principle required for the maintenance of international peace and security during the transition is ensured. It is maintained that the changes proposed in this paper may be regarded as “purely procedural” under Article 27 paragraph 2 of the Charter. It will be seen, however, that to trigger the process of the transition, UN Member states (other than the P5, who bear responsibility under the Charter to guarantee safe passage during the transition) must begin, one by one, to delegate “Security Sovereignty” to the Council.
Digital Technology to Support the Trade Union Movement  [PDF]
Klaus Schoemann
Open Journal of Social Sciences (JSS) , 2018, DOI: 10.4236/jss.2018.61005
Abstract:
New digital technologies have a potential to bypass traditional forms of labour organization. We summarize the academic and trade union literature on the potential of new digital technologies for trade unions. Building on the literature of the social construction of technology and democracy at work we present the concept of the technology-supported construction of the social sphere. A review of digital technologies allows us to identify the potential innovator role of trade unions and work councils in digital forms of employee participation. Digital technologies are an important way to attract younger generations of trade union members. For experienced members, bridging the digital divide becomes a vital issue, too. Finally, we highlight the active interplay and mutually reinforcing effect of online and offline communication in networking.
Assimilating scatterometer soil moisture data into conceptual hydrologic models at the regional scale
J. Parajka, V. Naeimi, G. Bl schl, W. Wagner, R. Merz,K. Scipal
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2006,
Abstract: This paper examines the potential of scatterometer data from ERS satellites for improving hydrological simulations in both gauged and ungauged catchments. We compare the soil moisture dynamics simulated by a semidistributed hydrologic model in 320 Austrian catchments with the soil moisture dynamics inferred from the satellite data. The most apparent differences occur in the Alpine areas. Assimilating the scatterometer data into the hydrologic model during the calibration phase improves the relationship between the two soil moisture estimates without any significant decrease in runoff model efficiency. For the case of ungauged catchments, assimilating scatterometer data does not improve the daily runoff simulations but does provide more consistent soil moisture estimates. If the main interest is in obtaining estimates of catchment soil moisture, reconciling the two sources of soil moisture information seems to be of value because of the different error structures.
Error characterisation of global active and passive microwave soil moisture data sets
W. A. Dorigo,K. Scipal,R. M. Parinussa,Y. Y. Liu
Hydrology and Earth System Sciences Discussions , 2010, DOI: 10.5194/hessd-7-5621-2010
Abstract: Understanding the error structures of remotely sensed soil moisture products is essential for correctly interpreting observed variations and trends in the data or assimilating them in hydrological or numerical weather prediction models. Nevertheless, a spatially coherent assessment of the quality of the various globally available data sets is often hampered by the limited availability over space and time of reliable in-situ measurements. This study explores the triple collocation error estimation technique for assessing the relative quality of several globally available soil moisture products from active (ASCAT) and passive (AMSR-E and SSM/I) microwave sensors. The triple collocation technique is a powerful tool to estimate the root mean square error while simultaneously solving for systematic differences in the climatologies of a set of three independent data sources. In addition to the scatterometer and radiometer data sets, we used the ERA-Interim and GLDAS-NOAH reanalysis soil moisture data sets as a third, independent reference. The prime objective is to reveal trends in uncertainty related to different observation principles (passive versus active), the use of different frequencies (C-, X-, and Ku-band) for passive microwave observations, and the choice of the independent reference data set (ERA-Interim versus GLDAS-NOAH). The results suggest that the triple collocation method provides realistic error estimates. Observed spatial trends agree well with the existing theory and studies on the performance of different observation principles and frequencies with respect to land cover and vegetation density. In addition, if all theoretical prerequisites are fulfilled (e.g. a sufficiently large number of common observations is available and errors of the different data sets are uncorrelated) the errors estimated for the remote sensing products are hardly influenced by the choice of the third independent data set. The results obtained in this study can help us in developing adequate strategies for the combined use of various scatterometer and radiometer-based soil moisture data sets, e.g. for improved flood forecast modelling or the generation of superior multi-mission long-term soil moisture data sets.
Ultraviolet Laser Based Gas Phase Fluorination of Polystyrene  [PDF]
Simon Kibben, Klaus Vogelsang
Journal of Surface Engineered Materials and Advanced Technology (JSEMAT) , 2014, DOI: 10.4236/jsemat.2014.45034
Abstract:

A novel hybrid process for surface fluorination of polymers is being introduced. The process is based on ultra violet (UV) laser radiation, which on the one hand forms radicals out of an atmosphere of a partially fluorinated benzene, and on the other hand activates a polymer surface in the areas where the UV radiation hits the surface. The radicals can react with the polymer surface, hence altering the surface energy. With this process, a fluorine content of over 30% on the surface of bulk polystyrene can be achieved, while the smallest possible structure size was smaller than 1 mm.

Planck-Scale Gravity Test at PETRA  [PDF]
Vahagn Gharibyan, Klaus Balewski
Journal of Modern Physics (JMP) , 2016, DOI: 10.4236/jmp.2016.79088
Abstract: Quantum or torsion gravity models predict unusual properties of space-time at very short distances. In particular, near the Planck length, around 10-35 m, empty space may behave as a crystal, singly or doubly refractive. This hypothesis, however, remains uncheckable for any direct measurement since the smallest distance accessible in experiment is about 10-19 m at the LHC. Here we propose a laboratory test to measure space birefringence or refractivity induced by gravity. A sensitivity 10-31 m for doubly and 10-28 m for singly refractive vacuum could be reached with PETRA 6 GeV beam exploring UV laser Compton scattering.
Assessment of soil moisture fields from imperfect climate models with uncertain satellite observations
G. Schumann, D. J. Lunt, P. J. Valdes, R. A. M. de Jeu, K. Scipal,P. D. Bates
Hydrology and Earth System Sciences (HESS) & Discussions (HESSD) , 2009,
Abstract: We demonstrate that global satellite products can be used to evaluate climate model soil moisture predictions but conclusions should be drawn with care. The quality of a limited area climate model (LAM) was compared to a general circulation model (GCM) using soil moisture data from two different Earth observing satellites within a model validation scheme that copes with the presence of uncertain data. Results showed that in the face of imperfect models and data, it is difficult to investigate the quality of current land surface schemes in simulating hydrology accurately. Nevertheless, a LAM provides, in general, a better representation of spatial patterns and dynamics of soil moisture compared to a GCM. However, in months when data uncertainty is higher, particularly in colder months and in periods when vegetation cover is too dense (e.g. August in the case of Western Europe), it is not possible to draw firm conclusions about model acceptability. For periods of higher confidence in observation data, our work indicates that a higher resolution LAM has more benefits to soil moisture prediction than are due to the resolution alone and can be attributed to an overall enhanced representation of precipitation relative to the GCM. Consequently, heterogeneity of rainfall patterns is better represented in the LAM and thus adequate representation of wet and dry periods leads to an improved acceptability of soil moisture (with respect to uncertain satellite observations), particularly in spring and early summer. Our results suggest that remote sensing, albeit with its inherent uncertainties, can be used to highlight which model should be preferred and as a diagnostic tool to pinpoint regions where the hydrological budget needs particular attention.
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