TY - JOUR A1 - Zehe, E. A1 - Ehret, U. A1 - Pfister, L. A1 - Blume, Theresa A1 - Schroeder, Boris A1 - Westhoff, M. A1 - Jackisch, C. A1 - Schymanski, Stanislauv J. A1 - Weiler, M. A1 - Schulz, K. A1 - Allroggen, Niklas A1 - Tronicke, Jens A1 - van Schaik, Loes A1 - Dietrich, Peter A1 - Scherer, U. A1 - Eccard, Jana A1 - Wulfmeyer, Volker A1 - Kleidon, Axel T1 - HESS Opinions: From response units to functional units: a thermodynamic reinterpretation of the HRU concept to link spatial organization and functioning of intermediate scale catchments JF - Hydrology and earth system sciences : HESS N2 - According to Dooge (1986) intermediate-scale catchments are systems of organized complexity, being too organized and yet too small to be characterized on a statistical/conceptual basis, but too large and too heterogeneous to be characterized in a deterministic manner. A key requirement for building structurally adequate models precisely for this intermediate scale is a better understanding of how different forms of spatial organization affect storage and release of water and energy. Here, we propose that a combination of the concept of hydrological response units (HRUs) and thermodynamics offers several helpful and partly novel perspectives for gaining this improved understanding. Our key idea is to define functional similarity based on similarity of the terrestrial controls of gradients and resistance terms controlling the land surface energy balance, rainfall runoff transformation, and groundwater storage and release. This might imply that functional similarity with respect to these specific forms of water release emerges at different scales, namely the small field scale, the hillslope, and the catchment scale. We thus propose three different types of "functional units" - specialized HRUs, so to speak - which behave similarly with respect to one specific form of water release and with a characteristic extent equal to one of those three scale levels. We furthermore discuss an experimental strategy based on exemplary learning and replicate experiments to identify and delineate these functional units, and as a promising strategy for characterizing the interplay and organization of water and energy fluxes across scales. We believe the thermodynamic perspective to be well suited to unmask equifinality as inherent in the equations governing water, momentum, and energy fluxes: this is because several combinations of gradients and resistance terms yield the same mass or energy flux and the terrestrial controls of gradients and resistance terms are largely independent. We propose that structurally adequate models at this scale should consequently disentangle driving gradients and resistance terms, because this optionally allow sequifinality to be partly reduced by including available observations, e. g., on driving gradients. Most importantly, the thermodynamic perspective yields an energy-centered perspective on rainfall-runoff transformation and evapotranspiration, including fundamental limits for energy fluxes associated with these processes. This might additionally reduce equifinality and opens up opportunities for testing thermodynamic optimality principles within independent predictions of rainfall-runoff or land surface energy exchange. This is pivotal to finding out whether or not spatial organization in catchments is in accordance with a fundamental organizing principle. Y1 - 2014 U6 - https://doi.org/10.5194/hess-18-4635-2014 SN - 1027-5606 SN - 1607-7938 VL - 18 IS - 11 SP - 4635 EP - 4655 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Allroggen, Niklas A1 - van Schaik, N. Loes M. B. A1 - Tronicke, Jens T1 - 4D ground-penetrating radar during a plot scale dye tracer experiment JF - Journal of applied geophysics N2 - Flow phenomena in the unsaturated zone are highly variable in time and space. Thus, it is challenging to measure and monitor such processes under field conditions. Here, we present a new setup and interpretation approach for combining a dye tracer experiment with a 4D ground-penetrating radar (GPR) survey. Therefore, we designed a rainfall experiment during which we measured three surface-based 3D GPR surveys using a pair of 500 MHz antennas. Such a survey setup requires accurate acquisition and processing techniquesto extract time-lapse information supporting the interpretation of selected cross-sections photographed after excavating the site. Our results reveal patterns of traveltime changes in the measured GPR data, which are associated with soil moisture changes. As distinct horizons are present at our site, such changes can be quantified and transferred into changes in total soil moisture content. Our soil moisture estimates are similar to the amount of infiltrated water, which confirms our experimental approach and makes us confident for further developing this strategy, especially, with respect to improving the temporal and spatial resolution. (C) 2015 Elsevier B.V. All rights reserved. KW - Ground penetrating radar KW - Time-lapse imaging KW - Brilliant blue Y1 - 2015 U6 - https://doi.org/10.1016/j.jappgeo.2015.04.016 SN - 0926-9851 SN - 1879-1859 VL - 118 SP - 139 EP - 144 PB - Elsevier CY - Amsterdam ER - TY - JOUR A1 - Allroggen, Niklas A1 - Tronicke, Jens A1 - Delock, Marcel A1 - Böniger, Urs T1 - Topographic migration of 2D and 3D ground-penetrating radar data considering variable velocities JF - Near surface geophysics N2 - We present a 2D/3D topographic migration scheme for ground-penetrating radar (GPR) data which is able to account for variable velocities by using the root mean square (rms) velocity approximation. We test our migration scheme using a synthetic 2D example and compare our migrated image to the results obtained using common GPR migration approaches. Furthermore, we apply it to 2D and 3D field data. These examples are recorded across common subsurface settings including surface topography and variations in the GPR subsurface velocity field caused by a shallow ground water table. In such field settings, our migration strategy provides well focused images of commonoffset GPR data without the need for a detailed interval velocity model. The synthetic and field examples demonstrate that our topographic migration scheme allows for accurate GPR imaging in the presence of variations in surface topography and subsurface velocity. Y1 - 2015 U6 - https://doi.org/10.3997/1873-0604.2014037 SN - 1569-4445 SN - 1873-0604 VL - 13 IS - 3 PB - European Association of Geoscientists & Engineers CY - Houten ER - TY - JOUR A1 - Tronicke, Jens A1 - Allroggen, Niklas T1 - Toward automated delineation of ground-penetrating radar facies in clastic sediments: An example from stratified glaciofluvial deposits JF - Geophysics N2 - Ground-penetrating radar (GPR) is an established geophysical method to explore near-surface sedimentary environments. Interpreting GPR images is largely based on manual procedures following concepts known as GPR facies analysis. We have developed a novel strategy to distinguish GPR facies in a largely automated and more objective manner. First, we calculate 13 textural attributes to quantify GPR reflection characteristics. Then, this database is reduced using principal component analysis. Finally, we image the dominating principal components using composite imaging and classify them using standard clustering methods. The potential of this work-flow is evaluated using a 2D GPR field example collected across stratified glaciofluvial deposits. Our results demonstrate that the derived facies images are well correlated with the composition and the porosity of the sediments as known from independent borehole logs. Our analysis strategy eases and improves the interpretability of GPR data and will help in a variety of geologic and hydrological problems. Y1 - 2015 U6 - https://doi.org/10.1190/GEO2015-0188.1 SN - 0016-8033 SN - 1942-2156 VL - 80 IS - 4 SP - A89 EP - A94 PB - Society of Exploration Geophysicists CY - Tulsa ER - TY - THES A1 - Allroggen, Niklas T1 - Observation of subsurface flow from the surface : applications of ground-penetrating radar BT - non-invasive time-lapse observation of subsurface flow by using ground-penetrating radar Y1 - 2015 ER - TY - JOUR A1 - Allroggen, Niklas A1 - Tronicke, Jens T1 - Attribute-based analysis of time-lapse ground-penetrating radar data JF - Geophysics N2 - Analysis of time-lapse ground-penetrating radar (GPR) data can provide information regarding subsurface hydrological processes, such as preferential flow. However, the analysis of time-lapse data is often limited by data quality; for example, for noisy input data, the interpretation of difference images is often difficult. Motivated by modern image-processing tools, we have developed two robust GPR attributes, which allow us to distinguish amplitude (contrast similarity) and time-shift (structural similarity) variations related to differences between individual time-lapse GPR data sets. We tested and evaluated our attributes using synthetic data of different complexity. Afterward, we applied them to a field data example, in which subsurface flow was induced by an artificial rainfall event. For all examples, we identified our structural similarity attribute to be a robust measure for highlighting time-lapse changes also in data with low signal-to-noise ratios. We determined that our new attribute-based workflow is a promising tool to analyze time-lapse GPR data, especially for imaging subsurface hydrological processes. Y1 - 2016 U6 - https://doi.org/10.1190/GEO2015-0171.1 SN - 0016-8033 SN - 1942-2156 VL - 81 SP - H1 EP - H8 PB - Society of Exploration Geophysicists CY - Tulsa ER - TY - JOUR A1 - Elling, Felix J. A1 - Spiegel, Cornelia A1 - Estrada, Solveig A1 - Davis, Donald W. A1 - Reinhardt, Lutz A1 - Henjes-Kunst, Friedhelm A1 - Allroggen, Niklas A1 - Dohrmann, Reiner A1 - Piepjohn, Karsten A1 - Lisker, Frank T1 - Origin of Bentonites and Detrital Zircons of the Paleocene Basilika Formation, Svalbard JF - Frontiers in Earth Science N2 - The Paleocene was a time of transition for the Arctic, with magmatic activity of the High Arctic Large Igneous Province (HALIP) giving way to magmatism of the North Atlantic Large Igneous Province in connection to plate tectonic changes in the Arctic and North Atlantic. In this study we investigate the Paleocene magmatic record and sediment pathways of the Basilika Formation exposed in the Central Tertiary Basin of Svalbard. By means of geochemistry, SmNd isotopic signatures, and zircon UPb geochronology we investigate the characteristics of several bentonite layers contained in the Basilika Formation, as well as the provenance of the intercalated clastic sediments. Our data show that the volcanic ash layers of the Basilika Formation, which were diagenetically altered to bentonites, originate from alkaline continental-rift magmatism such as the last, explosive stages of the HALIP in North Greenland and the Canadian Arctic. The volcanic ash layers were deposited on Svalbard in a flat shelf environment with dominant sediment supply from the east. Dating of detrital zircons suggests that the detritus was derived from Siberian sources, primarily from the Verkhoyansk Fold-and-Thrust Belt, which would require transport over similar to 3000 km across the Arctic. KW - Paleogene KW - Svalbard KW - Central Tertiary Basin KW - Basilika formation KW - bentonite KW - zircon provenance KW - High Arctic Large Igneous Province KW - North Atlantic Large Igneous Province Y1 - 2016 U6 - https://doi.org/10.3389/feart.2016.00073 SN - 2296-6463 VL - 4 PB - Frontiers Research Foundation CY - Lausanne ER - TY - JOUR A1 - Schennen, Stephan A1 - Tronicke, Jens A1 - Wetterich, Sebastian A1 - Allroggen, Niklas A1 - Schwamborn, Georg A1 - Schirrmeister, Lutz T1 - 3D ground-penetrating radar imaging of ice complex deposits in northern East Siberia JF - Geophysics N2 - Ice complex deposits are characteristic, ice-rich formations in northern East Siberia and represent an important part in the arctic carbon pool. Recently, these late Quaternary deposits are the objective of numerous investigations typically relying on outcrop and borehole data. Many of these studies can benefit from a 3D structural model of the subsurface for upscaling their observations or for constraining estimations of inventories, such as the local carbon stock. We have addressed this problem of structural imaging by 3D ground-penetrating radar (GPR), which, in permafrost studies, has been primarily used for 2D profiling. We have used a 3D kinematic GPR surveying strategy at a field site located in the New Siberian Archipelago on top of an ice complex. After applying a 3D GPR processing sequence, we were able to trace two horizons at depths below 20 m. Taking available borehole and outcrop data into account, we have interpreted these two features as interfaces of major lithologic units and derived a 3D cryostratigraphic model of the subsurface. Our data example demonstrated that a 3D surveying and processing strategy was crucial at our field site and showed the potential of 3D GPR to image geologic structures in complex ice-rich permafrost landscapes. Y1 - 2016 U6 - https://doi.org/10.1190/GEO2015-0129.1 SN - 0016-8033 SN - 1942-2156 VL - 81 SP - WA195 EP - WA202 PB - Society of Exploration Geophysicists CY - Tulsa ER - TY - JOUR A1 - Loritz, Ralf A1 - Hassler, Sibylle K. A1 - Jackisch, Conrad A1 - Allroggen, Niklas A1 - van Schaik, Loes A1 - Wienhöfer, Jan A1 - Zehe, Erwin T1 - Picturing and modeling catchments by representative hillslopes JF - Hydrology and earth system sciences : HESS N2 - This study explores the suitability of a single hillslope as a parsimonious representation of a catchment in a physically based model. We test this hypothesis by picturing two distinctly different catchments in perceptual models and translating these pictures into parametric setups of 2-D physically based hillslope models. The model parametrizations are based on a comprehensive field data set, expert knowledge and process-based reasoning. Evaluation against streamflow data highlights that both models predicted the annual pattern of streamflow generation as well as the hydrographs acceptably. However, a look beyond performance measures revealed deficiencies in streamflow simulations during the summer season and during individual rainfall-runoff events as well as a mismatch between observed and simulated soil water dynamics. Some of these shortcomings can be related to our perception of the systems and to the chosen hydrological model, while others point to limitations of the representative hillslope concept itself. Nevertheless, our results confirm that representative hillslope models are a suitable tool to assess the importance of different data sources as well as to challenge our perception of the dominant hydrological processes we want to represent therein. Consequently, these models are a promising step forward in the search for the optimal representation of catchments in physically based models. Y1 - 2017 U6 - https://doi.org/10.5194/hess-21-1225-2017 SN - 1027-5606 SN - 1607-7938 VL - 21 IS - 2 SP - 1225 EP - 1249 PB - Copernicus CY - Göttingen ER - TY - GEN A1 - Loritz, Ralf A1 - Hassler, Sibylle K. A1 - Jackisch, Conrad A1 - Allroggen, Niklas A1 - van Schaik, Loes A1 - Wienhöfer, Jan A1 - Zehe, Erwin T1 - Picturing and modeling catchments by representative hillslopes T2 - Postprints der Universität Potsdam : Mathematisch Naturwissenschaftliche Reihe N2 - This study explores the suitability of a single hillslope as a parsimonious representation of a catchment in a physically based model. We test this hypothesis by picturing two distinctly different catchments in perceptual models and translating these pictures into parametric setups of 2-D physically based hillslope models. The model parametrizations are based on a comprehensive field data set, expert knowledge and process-based reasoning. Evaluation against streamflow data highlights that both models predicted the annual pattern of streamflow generation as well as the hydrographs acceptably. However, a look beyond performance measures revealed deficiencies in streamflow simulations during the summer season and during individual rainfall-runoff events as well as a mismatch between observed and simulated soil water dynamics. Some of these shortcomings can be related to our perception of the systems and to the chosen hydrological model, while others point to limitations of the representative hillslope concept itself. Nevertheless, our results confirm that representative hillslope models are a suitable tool to assess the importance of different data sources as well as to challenge our perception of the dominant hydrological processes we want to represent therein. Consequently, these models are a promising step forward in the search for the optimal representation of catchments in physically based models. T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 635 KW - soil-moisture dynamics KW - hydrologic-response simulation KW - rainfall-runoff response KW - preferential flow KW - subsurface stormflow KW - water-uptake KW - field-scale KW - transport KW - system KW - basin Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-419082 IS - 635 SP - 1225 EP - 1249 ER -