TY  - JOUR
A1  - Abdrakhmatov, Kanatbek E.
A1  - Walker, R. T.
A1  - Campbell, G. E.
A1  - Carr, A. S.
A1  - Elliott, A.
A1  - Hillemann, Christian
A1  - Hollingsworth, J.
A1  - Landgraf, Angela
A1  - Mackenzie, D.
A1  - Mukambayev, A.
A1  - Rizza, M.
A1  - Sloan, R. A.
T1  - Multisegment rupture in the 11 July 1889 Chilik earthquake (M-w 8.0-8.3), Kazakh Tien Shan, interpreted from remote sensing, field survey, and paleoseismic trenching
JF  - Journal of geophysical research : Solid earth
N2  - The 11 July 1889 Chilik earthquake (M-w 8.0-8.3) forms part of a remarkable sequence of large earthquakes in the late nineteenth and early twentieth centuries in the northern Tien Shan. Despite its importance, the source of the 1889 earthquake remains unknown, though the macroseismic epicenter is sited in the Chilik valley, similar to 100 km southeast of Almaty, Kazakhstan (similar to 2 million population). Several short fault segments that have been inferred to have ruptured in 1889 are too short on their own to account for the estimated magnitude. In this paper we perform detailed surveying and trenching of the similar to 30 km long Saty fault, one of the previously inferred sources, and find that it was formed in a single earthquake within the last 700 years, involving surface slip of up to 10 m. The scarp-forming event, likely to be the 1889 earthquake, was the only surface-rupturing event for at least 5000 years and potentially for much longer. From satellite imagery we extend the mapped length of fresh scarps within the 1889 epicentral zone to a total of similar to 175 km, which we also suggest as candidate ruptures from the 1889 earthquake. The 175 km of rupture involves conjugate oblique left-lateral and right-lateral slip on three separate faults, with step overs of several kilometers between them. All three faults were essentially invisible in the Holocene geomorphology prior to the last slip. The recurrence interval between large earthquakes on any of these faults, and presumably on other faults of the Tien Shan, may be longer than the timescale over which the landscape is reset, providing a challenge for delineating sources of future hazard.
Y1  - 2016
U6  - https://doi.org/10.1002/2015JB012763
SN  - 2169-9313
SN  - 2169-9356
VL  - 121
SP  - 4615
EP  - 4640
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - THES
A1  - Abon, Catherine Cristobal
T1  - Radar-based rainfall retrieval for flood forecasting in a meso-scale catchment
BT  - the Philippines
Y1  - 2015
ER  - 
TY  - JOUR
A1  - Abon, Catherine Cristobal
A1  - Kneis, David
A1  - Crisologo, Irene
A1  - Bronstert, Axel
A1  - David, Carlos Primo Constantino
A1  - Heistermann, Maik
T1  - Evaluating the potential of radar-based rainfall estimates for streamflow and flood simulations in the Philippines
JF  - GEOMATICS NATURAL HAZARDS & RISK
N2  - This case study evaluates the suitability of radar-based quantitative precipitation estimates (QPEs) for the simulation of streamflow in the Marikina River Basin (MRB), the Philippines. Hourly radar-based QPEs were produced from reflectivity that had been observed by an S-band radar located about 90 km from the MRB. Radar data processing and precipitation estimation were carried out using the open source library wradlib. To assess the added value of the radar-based QPE, we used spatially interpolated rain gauge observations (gauge-only (GO) product) as a benchmark. Rain gauge observations were also used to quantify rainfall estimation errors at the point scale. At the point scale, the radar-based QPE outperformed the GO product in 2012, while for 2013, the performance was similar. For both periods, estimation errors substantially increased from daily to the hourly accumulation intervals. Despite this fact, both rainfall estimation methods allowed for a good representation of observed streamflow when used to force a hydrological simulation model of the MRB. Furthermore, the results of the hydrological simulation were consistent with rainfall verification at the point scale: the radar-based QPE performed better than the GO product in 2012, and equivalently in 2013. Altogether, we could demonstrate that, in terms of streamflow simulation, the radar-based QPE can perform as good as or even better than the GO product - even for a basin such as the MRB which has a comparatively dense rain gauge network. This suggests good prospects for using radar-based QPE to simulate and forecast streamflow in other parts of the Philippines where rain gauge networks are not as dense.
Y1  - 2016
U6  - https://doi.org/10.1080/19475705.2015.1058862
SN  - 1947-5705
SN  - 1947-5713
VL  - 7
SP  - 1390
EP  - 1405
PB  - Routledge, Taylor & Francis Group
CY  - Abingdon
ER  - 
TY  - JOUR
A1  - Abouserie, Ahed
A1  - Zehbe, Kerstin
A1  - Metzner, Philipp
A1  - Kelling, Alexandra
A1  - Günter, Christina
A1  - Schilde, Uwe
A1  - Strauch, Peter
A1  - Körzdörfer, Thomas
A1  - Taubert, Andreas
T1  - Alkylpyridinium Tetrahalidometallate Ionic Liquids and Ionic Liquid Crystals: Insights into the Origin of Their Phase Behavior
JF  - European journal of inorganic chemistry : a journal of ChemPubSoc Europe
N2  - Six N-alkylpyridinium salts [CnPy](2)[MCl4] (n = 4 or 12 and M = Co, Cu, Zn) were synthesized, and their structure and thermal properties were studied. The [C4Py](2)[MCl4] compounds are monoclinic and crystallize in the space group P2(1)/n. The crystals of the longer chain analogues [C12Py](2)[MCl4] are triclinic and crystallize in the space group P (1) over bar. Above the melting temperature, all compounds are ionic liquids (ILs). The derivatives with the longer C12 chain exhibit liquid crystallinity and the shorter chain compounds only show a melting transition. Consistent with single-crystal analysis, electron paramagnetic resonance spectroscopy suggests that the [CuCl4](2-) ions in the Cu-based ILs have a distorted tetrahedral geometry.
KW  - Ionic liquids
KW  - Alkylpyridinium salts
KW  - Structure elucidation
KW  - Phase transitions
Y1  - 2017
U6  - https://doi.org/10.1002/ejic.201700826
SN  - 1434-1948
SN  - 1099-0682
SP  - 5640
EP  - 5649
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Abouserie, Ahed
A1  - Zehbe, Kerstin
A1  - Metzner, Philipp
A1  - Kelling, Alexandra
A1  - Günter, Christina
A1  - Schilde, Uwe
A1  - Strauch, Peter
A1  - Körzdörfer, Thomas
A1  - Taubert, Andreas
T1  - Alkylpyridinium Tetrahalidometallate Ionic Liquids and Ionic Liquid Crystals: Insights into the Origin of Their Phase Behavior
JF  - European journal of inorganic chemistry : a journal of ChemPubSoc Europe
N2  - Six N-alkylpyridinium salts [CnPy](2)[MCl4] (n = 4 or 12 and M = Co, Cu, Zn) were synthesized, and their structure and thermal properties were studied. The [C4Py](2)[MCl4] compounds are monoclinic and crystallize in the space group P2(1)/n. The crystals of the longer chain analogues [C12Py](2)[MCl4] are triclinic and crystallize in the space group P (1) over bar. Above the melting temperature, all compounds are ionic liquids (ILs). The derivatives with the longer C12 chain exhibit liquid crystallinity and the shorter chain compounds only show a melting transition. Consistent with single-crystal analysis, electron paramagnetic resonance spectroscopy suggests that the [CuCl4](2-) ions in the Cu-based ILs have a distorted tetrahedral geometry.
KW  - Ionic liquids
KW  - Alkylpyridinium salts
KW  - Structure elucidation
KW  - Phase transitions
Y1  - 2017
U6  - https://doi.org/10.1002/ejic.201700826
SN  - 1434-1948
SN  - 1099-0682
SP  - 5640
EP  - 5649
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Acosta, Veronica Torres
A1  - Schildgen, Taylor F.
A1  - Clarke, Brian A.
A1  - Scherler, Dirk
A1  - Bookhagen, Bodo
A1  - Wittmann, Hella
A1  - von Blanckenburg, Friedhelm
A1  - Strecker, Manfred
T1  - Effect of vegetation cover on millennial-scale landscape denudation rates in East Africa
JF  - Lithosphere
N2  - The mechanisms by which climate and vegetation affect erosion rates over various time scales lie at the heart of understanding landscape response to climate change. Plot-scale field experiments show that increased vegetation cover slows erosion, implying that faster erosion should occur under low to moderate vegetation cover. However, demonstrating this concept over long time scales and across landscapes has proven to be difficult, especially in settings complicated by tectonic forcing and variable slopes. We investigate this problem by measuring cosmogenic Be-10-derived catchment-mean denudation rates across a range of climate zones and hillslope gradients in the Kenya Rift, and by comparing our results with those published from the Rwenzori Mountains of Uganda. We find that denudation rates from sparsely vegetated parts of the Kenya Rift are up to 0.13 mm/yr, while those from humid and more densely vegetated parts of the Kenya Rift flanks and the Rwenzori Mountains reach a maximum of 0.08 mm/yr, despite higher median hillslope gradients. While differences in lithology and recent land-use changes likely affect the denudation rates and vegetation cover values in some of our studied catchments, hillslope gradient and vegetation cover appear to explain most of the variation in denudation rates across the study area. Our results support the idea that changing vegetation cover can contribute to complex erosional responses to climate or land-use change and that vegetation cover can play an important role in determining the steady-state slopes of mountain belts through its stabilizing effects on the land surface.
Y1  - 2015
U6  - https://doi.org/10.1130/L402.1
SN  - 1941-8264
SN  - 1947-4253
VL  - 7
IS  - 4
SP  - 408
EP  - 420
PB  - American Institute of Physics
CY  - Boulder
ER  - 
TY  - JOUR
A1  - Adhikari, Rishi Ram
A1  - Glombitza, Clemens
A1  - Nickel, Julia C.
A1  - Anderson, Chloe H.
A1  - Dunlea, Ann G.
A1  - Spivack, Arthur J.
A1  - Murray, Richard W.
A1  - Kallmeyer, Jens
T1  - Hydrogen Utilization Potential in Subsurface Sediments
JF  - Frontiers in microbiology
N2  - Subsurface microbial communities undertake many terminal electron-accepting processes, often simultaneously. Using a tritium-based assay, we measured the potential hydrogen oxidation catalyzed by hydrogenase enzymes in several subsurface sedimentary environments (Lake Van, Barents Sea, Equatorial Pacific, and Gulf of Mexico) with different predominant electron-acceptors. Hydrogenases constitute a diverse family of enzymes expressed by microorganisms that utilize molecular hydrogen as a metabolic substrate, product, or intermediate. The assay reveals the potential for utilizing molecular hydrogen and allows qualitative detection of microbial activity irrespective of the predominant electron-accepting process. Because the method only requires samples frozen immediately after recovery, the assay can be used for identifying microbial activity in subsurface ecosystems without the need to preserve live material. We measured potential hydrogen oxidation rates in all samples from multiple depths at several sites that collectively span a wide range of environmental conditions and biogeochemical zones. Potential activity normalized to total cell abundance ranges over five orders of magnitude and varies, dependent upon the predominant terminal electron acceptor. Lowest per-cell potential rates characterize the zone of nitrate reduction and highest per-cell potential rates occur in the methanogenic zone. Possible reasons for this relationship to predominant electron acceptor include (i) increasing importance of fermentation in successively deeper biogeochemical zones and (ii) adaptation of H(2)ases to successively higher concentrations of H-2 in successively deeper zones.
KW  - hydrogenase
KW  - tritium assay
KW  - deep biosphere
KW  - microbial activity
KW  - Lake Van
KW  - Barents Sea
KW  - Equatorial Pacific
KW  - Gulf of Mexico
Y1  - 2016
U6  - https://doi.org/10.3389/fmicb.2016.00008
SN  - 1664-302X
VL  - 7
PB  - Frontiers Research Foundation
CY  - Lausanne
ER  - 
TY  - JOUR
A1  - Adhikari, Rishi Ram
A1  - Kallmeyer, Jens
T1  - Detection and quantification of microbial activity in the subsurface
N2  - The subsurface harbors a large fraction of Earth's living biomass, forming complex microbial ecosystems. Without a profound knowledge of the ongoing biologically mediated processes and their reaction to anthropogenic changes it is difficult to assess the long-term stability and feasibility of any type of geotechnical utilization, as these influence subsurface ecosystems. Despite recent advances in many areas of subsurface microbiology, the direct quantification of turnover processes is still in its infancy, mainly due to the extremely low cell abundances. We provide an overview of the currently available techniques for the quantification of microbial turnover processes and discuss their specific strengths and limitations. Most techniques employed so far have focused on specific processes, e.g. sulfate reduction or methanogenesis. Recent studies show that processes that were previously thought to exclude each other can occur simultaneously, albeit at very low rates. Without the identification of the respective processes it is impossible to quantify total microbial activity. Even in cases where all simultaneously occurring processes can be identified, the typically very low rates prevent quantification. In many cases a simple measure of total microbial activity would be a better and more robust measure than assays for several specific processes. Enzyme or molecular assays provide a more general approach as they target key metabolic compounds. Depending on the compound targeted a broader spectrum of microbial processes can be quantified. The two most promising compounds are ATP and hydrogenase, as both are ubiquitous in microbes. Technical constraints limit the applicability of currently available ATP-assays for subsurface samples. A recently developed hydrogenase radiotracer assay has the potential to become a key tool for the quantification of subsurface microbial activity.
Y1  - 2010
UR  - http://www.sciencedirect.com/science/journal/00092819
U6  - https://doi.org/10.1016/j.chemer.2010.05.003
SN  - 0009-2819
ER  - 
TY  - JOUR
A1  - Aerts, J. C. J. H.
A1  - Botzen, W. J. Wouter
A1  - Clarke, K. C.
A1  - Cutter, S. L.
A1  - Hall, J. W.
A1  - Merz, Bruno
A1  - Michel-Kerjan, E.
A1  - Mysiak, J.
A1  - Surminski, Swenja
A1  - Kunreuther, H.
T1  - Integrating human behaviour dynamics into flood disaster risk assessment
JF  - Nature climate change
N2  - The behaviour of individuals, businesses, and government entities before, during, and immediately after a disaster can dramatically affect the impact and recovery time. However, existing risk-assessment methods rarely include this critical factor. In this Perspective, we show why this is a concern, and demonstrate that although initial efforts have inevitably represented human behaviour in limited terms, innovations in flood-risk assessment that integrate societal behaviour and behavioural adaptation dynamics into such quantifications may lead to more accurate characterization of risks and improved assessment of the effectiveness of risk-management strategies and investments. Such multidisciplinary approaches can inform flood-risk management policy development.
Y1  - 2018
U6  - https://doi.org/10.1038/s41558-018-0085-1
SN  - 1758-678X
SN  - 1758-6798
VL  - 8
IS  - 3
SP  - 193
EP  - 199
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Agada, S.
A1  - Chen, F.
A1  - Geiger, S.
A1  - Toigulova, G.
A1  - Agar, Susan M.
A1  - Shekhar, R.
A1  - Benson, Gregory S.
A1  - Hehmeyer, O.
A1  - Amour, Frédéric
A1  - Mutti, Maria
A1  - Christ, Nicolas
A1  - Immenhauser, A.
T1  - Numerical simulation of fluid-flow processes in a 3D high-resolution carbonate reservoir analogue
JF  - Petroleum geoscience
N2  - A high-resolution three-dimensional (3D) outcrop model of a Jurassic carbonate ramp was used in order to perform a series of detailed and systematic flow simulations. The aim of this study was to test the impact of small- and large-scale geological features on reservoir performance and oil recovery. The digital outcrop model contains a wide range of sedimentological, diagenetic and structural features, including discontinuity surfaces, shoal bodies, mud mounds, oyster bioherms and fractures. Flow simulations are performed for numerical well testing and secondary oil recovery. Numerical well testing enables synthetic but systematic pressure responses to be generated for different geological features observed in the outcrops. This allows us to assess and rank the relative impact of specific geological features on reservoir performance. The outcome documents that, owing to the realistic representation of matrix heterogeneity, most diagenetic and structural features cannot be linked to a unique pressure signature. Instead, reservoir performance is controlled by subseismic faults and oyster bioherms acting as thief zones. Numerical simulations of secondary recovery processes reveal strong channelling of fluid flow into high-permeability layers as the primary control for oil recovery. However, appropriate reservoir-engineering solutions, such as optimizing well placement and injection fluid, can reduce channelling and increase oil recovery.
Y1  - 2014
U6  - https://doi.org/10.1144/petgeo2012-096
SN  - 1354-0793
VL  - 20
IS  - 1
SP  - 125
EP  - 142
PB  - Geological Soc. Publ. House
CY  - Bath
ER  - 
TY  - JOUR
A1  - Agarwal, Ankit
A1  - Caesar, Levke
A1  - Marwan, Norbert
A1  - Maheswaran, Rathinasamy
A1  - Merz, Bruno
T1  - Network-based identification and characterization of teleconnections on different scales
JF  - Scientific Reports
N2  - Sea surface temperature (SST) patterns can – as surface climate forcing – affect weather and climate at large distances. One example is El Niño-Southern Oscillation (ENSO) that causes climate anomalies around the globe via teleconnections. Although several studies identified and characterized these teleconnections, our understanding of climate processes remains incomplete, since interactions and feedbacks are typically exhibited at unique or multiple temporal and spatial scales. This study characterizes the interactions between the cells of a global SST data set at different temporal and spatial scales using climate networks. These networks are constructed using wavelet multi-scale correlation that investigate the correlation between the SST time series at a range of scales allowing instantaneously deeper insights into the correlation patterns compared to traditional methods like empirical orthogonal functions or classical correlation analysis. This allows us to identify and visualise regions of – at a certain timescale – similarly evolving SSTs and distinguish them from those with long-range teleconnections to other ocean regions. Our findings re-confirm accepted knowledge about known highly linked SST patterns like ENSO and the Pacific Decadal Oscillation, but also suggest new insights into the characteristics and origins of long-range teleconnections like the connection between ENSO and Indian Ocean Dipole.
Y1  - 2019
U6  - https://doi.org/10.1038/s41598-019-45423-5
SN  - 2045-2322
VL  - 9
PB  - Macmillan Publishers Limited
CY  - London
ER  - 
TY  - JOUR
A1  - Agarwal, Ankit
A1  - Guntu, Ravikumar
A1  - Banerjee, Abhirup
A1  - Gadhawe, Mayuri Ashokrao
A1  - Marwan, Norbert
T1  - A complex network approach to study the extreme precipitation patterns in a river basin
JF  - Chaos : an interdisciplinary journal of nonlinear science
N2  - The quantification of spatial propagation of extreme precipitation events is vital in water resources planning and disaster mitigation. However, quantifying these extreme events has always been challenging as many traditional methods are insufficient to capture the nonlinear interrelationships between extreme event time series. Therefore, it is crucial to develop suitable methods for analyzing the dynamics of extreme events over a river basin with a diverse climate and complicated topography. Over the last decade, complex network analysis emerged as a powerful tool to study the intricate spatiotemporal relationship between many variables in a compact way. In this study, we employ two nonlinear concepts of event synchronization and edit distance to investigate the extreme precipitation pattern in the Ganga river basin. We use the network degree to understand the spatial synchronization pattern of extreme rainfall and identify essential sites in the river basin with respect to potential prediction skills. The study also attempts to quantify the influence of precipitation seasonality and topography on extreme events. The findings of the study reveal that (1) the network degree is decreased in the southwest to northwest direction, (2) the timing of 50th percentile precipitation within a year influences the spatial distribution of degree, (3) the timing is inversely related to elevation, and (4) the lower elevation greatly influences connectivity of the sites. The study highlights that edit distance could be a promising alternative to analyze event-like data by incorporating event time and amplitude and constructing complex networks of climate extremes.
Y1  - 2022
U6  - https://doi.org/10.1063/5.0072520
SN  - 1054-1500
SN  - 1089-7682
VL  - 32
IS  - 1
PB  - American Institute of Physics
CY  - Woodbury, NY
ER  - 
TY  - JOUR
A1  - Agarwal, Ankit
A1  - Maheswaran, Rathinasamy
A1  - Kurths, Jürgen
A1  - Khosa, R.
T1  - Wavelet Spectrum and Self-Organizing Maps-Based Approach for Hydrologic Regionalization -a Case Study in the Western United States
JF  - Water Resources Management
N2  - Hydrologic regionalization deals with the investigation of homogeneity in watersheds and provides a classification of watersheds for regional analysis. The classification thus obtained can be used as a basis for mapping data from gauged to ungauged sites and can improve extreme event prediction. This paper proposes a wavelet power spectrum (WPS) coupled with the self-organizing map method for clustering hydrologic catchments. The application of this technique is implemented for gauged catchments. As a test case study, monthly streamflow records observed at 117 selected catchments throughout the western United States from 1951 through 2002. Further, based on WPS of each station, catchments are classified into homogeneous clusters, which provides a representative WPS pattern for the streamflow stations in each cluster.
KW  - Wavelet power spectrum
KW  - Regionalization
KW  - Ungauged catchments
KW  - K-means technique
KW  - Self-organizing map
Y1  - 2016
U6  - https://doi.org/10.1007/s11269-016-1428-1
SN  - 0920-4741
SN  - 1573-1650
VL  - 30
SP  - 4399
EP  - 4413
PB  - Springer
CY  - Dordrecht
ER  - 
TY  - JOUR
A1  - Agarwal, Ankit
A1  - Marwan, Norbert
A1  - Maheswaran, Rathinasamy
A1  - Merz, Bruno
A1  - Kurths, Jürgen
T1  - Multi-scale event synchronization analysis for unravelling climate processes: a wavelet-based approach
JF  - Nonlinear processes in geophysics
N2  - The temporal dynamics of climate processes are spread across different timescales and, as such, the study of these processes at only one selected timescale might not reveal the complete mechanisms and interactions within and between the (sub-) processes. To capture the non-linear interactions between climatic events, the method of event synchronization has found increasing attention recently. The main drawback with the present estimation of event synchronization is its restriction to analysing the time series at one reference timescale only. The study of event synchronization at multiple scales would be of great interest to comprehend the dynamics of the investigated climate processes. In this paper, the wavelet-based multi-scale event synchronization (MSES) method is proposed by combining the wavelet transform and event synchronization. Wavelets are used extensively to comprehend multi-scale processes and the dynamics of processes across various timescales. The proposed method allows the study of spatio-temporal patterns across different timescales. The method is tested on synthetic and real-world time series in order to check its replicability and applicability. The results indicate that MSES is able to capture relationships that exist between processes at different timescales.
Y1  - 2017
U6  - https://doi.org/10.5194/npg-24-599-2017
SN  - 1023-5809
VL  - 24
SP  - 599
EP  - 611
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Agarwal, Ankit
A1  - Marwan, Norbert
A1  - Maheswaran, Rathinasamy
A1  - Merz, Bruno
A1  - Kurths, Jürgen
T1  - Quantifying the roles of single stations within homogeneous regions using complex network analysis
JF  - Journal of hydrology
N2  - Regionalization and pooling stations to form homogeneous regions or communities are essential for reliable parameter transfer, prediction in ungauged basins, and estimation of missing information. Over the years, several clustering methods have been proposed for regional analysis. Most of these methods are able to quantify the study region in terms of homogeneity but fail to provide microscopic information about the interaction between communities, as well as about each station within the communities. We propose a complex network-based approach to extract this valuable information and demonstrate the potential of our approach using a rainfall network constructed from the Indian gridded daily precipitation data. The communities were identified using the network-theoretical community detection algorithm for maximizing the modularity. Further, the grid points (nodes) were classified into universal roles according to their pattern of within- and between-community connections. The method thus yields zoomed-in details of individual rainfall grids within each community.
KW  - Complex network
KW  - Event synchronization
KW  - Rainfall network
KW  - Z-P approach
Y1  - 2018
U6  - https://doi.org/10.1016/j.jhydrol.2018.06.050
SN  - 0022-1694
SN  - 1879-2707
VL  - 563
SP  - 802
EP  - 810
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Agarwal, Ankit
A1  - Marwan, Norbert
A1  - Maheswaran, Rathinasamy
A1  - Öztürk, Ugur
A1  - Kurths, Jürgen
A1  - Merz, Bruno
T1  - Optimal design of hydrometric station networks based on complex network analysis
JF  - Hydrology and Earth System Sciences
N2  - Hydrometric networks play a vital role in providing information for decision-making in water resource management. They should be set up optimally to provide as much information as possible that is as accurate as possible and, at the same time, be cost-effective. Although the design of hydrometric networks is a well-identified problem in hydrometeorology and has received considerable attention, there is still scope for further advancement. In this study, we use complex network analysis, defined as a collection of nodes interconnected by links, to propose a new measure that identifies critical nodes of station networks. The approach can support the design and redesign of hydrometric station networks. The science of complex networks is a relatively young field and has gained significant momentum over the last few years in different areas such as brain networks, social networks, technological networks, or climate networks. The identification of influential nodes in complex networks is an important field of research. We propose a new node-ranking measure – the weighted degree–betweenness (WDB) measure – to evaluate the importance of nodes in a network. It is compared to previously proposed measures used on synthetic sample networks and then applied to a real-world rain gauge network comprising 1229 stations across Germany to demonstrate its applicability. The proposed measure is evaluated using the decline rate of the network efficiency and the kriging error. The results suggest that WDB effectively quantifies the importance of rain gauges, although the benefits of the method need to be investigated in more detail.
KW  - identifying influential nodes
KW  - climate networks
KW  - rainfall
KW  - streamflow
KW  - synchronization
KW  - precipitation
KW  - classification
KW  - events
Y1  - 2020
U6  - https://doi.org/10.5194/hess-24-2235-2020
SN  - 1027-5606
SN  - 1607-7938
VL  - 24
IS  - 5
SP  - 2235
EP  - 2251
PB  - Copernicus Publ.
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Aich, Valentin
A1  - Liersch, Stefan
A1  - Vetter, T.
A1  - Huang, S.
A1  - Tecklenburg, J.
A1  - Hoffmann, P.
A1  - Koch, H.
A1  - Fournet, S.
A1  - Krysanova, Valentina
A1  - Mueller, N.
A1  - Hattermann, Fred
T1  - Comparing impacts of climate change on streamflow in four large African river basins
JF  - Hydrology and earth system sciences : HESS
N2  - This study aims to compare impacts of climate change on streamflow in four large representative African river basins: the Niger, the Upper Blue Nile, the Oubangui and the Limpopo. We set up the eco-hydrological model SWIM (Soil and Water Integrated Model) for all four basins individually. The validation of the models for four basins shows results from adequate to very good, depending on the quality and availability of input and calibration data.
 For the climate impact assessment, we drive the model with outputs of five bias corrected Earth system models of Coupled Model Intercomparison Project Phase 5 (CMIP5) for the representative concentration pathways (RCPs) 2.6 and 8.5. This climate input is put into the context of climate trends of the whole African continent and compared to a CMIP5 ensemble of 19 models in order to test their representativeness. Subsequently, we compare the trends in mean discharges, seasonality and hydrological extremes in the 21st century. The uncertainty of results for all basins is high. Still, climate change impact is clearly visible for mean discharges but also for extremes in high and low flows. The uncertainty of the projections is the lowest in the Upper Blue Nile, where an increase in streamflow is most likely. In the Niger and the Limpopo basins, the magnitude of trends in both directions is high and has a wide range of uncertainty. In the Oubangui, impacts are the least significant. Our results confirm partly the findings of previous continental impact analyses for Africa. However, contradictory to these studies we find a tendency for increased streamflows in three of the four basins (not for the Oubangui). Guided by these results, we argue for attention to the possible risks of increasing high flows in the face of the dominant water scarcity in Africa. In conclusion, the study shows that impact intercomparisons have added value to the adaptation discussion and may be used for setting up adaptation plans in the context of a holistic approach.
Y1  - 2014
U6  - https://doi.org/10.5194/hess-18-1305-2014
SN  - 1027-5606
SN  - 1607-7938
VL  - 18
IS  - 4
SP  - 1305
EP  - 1321
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Aich, Valentin
A1  - Liersch, Stefan
A1  - Vetter, Tobias
A1  - Andersson, Jafet C. M.
A1  - Müller, Eva Nora
A1  - Hattermann, Fred
T1  - Climate or Land Use?
BT  - Attribution of Changes in River Flooding in the Sahel Zone
JF  - Water
N2  - This study intends to contribute to the ongoing discussion on whether land use and land cover changes (LULC) or climate trends have the major influence on the observed increase of flood magnitudes in the Sahel. A simulation-based approach is used for attributing the observed trends to the postulated drivers. For this purpose, the ecohydrological model SWIM (Soil and Water Integrated Model) with a new, dynamic LULC module was set up for the Sahelian part of the Niger River until Niamey, including the main tributaries Sirba and Goroul. The model was driven with observed, reanalyzed climate and LULC data for the years 1950-2009. In order to quantify the shares of influence, one simulation was carried out with constant land cover as of 1950, and one including LULC. As quantitative measure, the gradients of the simulated trends were compared to the observed trend. The modeling studies showed that for the Sirba River only the simulation which included LULC was able to reproduce the observed trend. The simulation without LULC showed a positive trend for flood magnitudes, but underestimated the trend significantly. For the Goroul River and the local flood of the Niger River at Niamey, the simulations were only partly able to reproduce the observed trend. In conclusion, the new LULC module enabled some first quantitative insights into the relative influence of LULC and climatic changes. For the Sirba catchment, the results imply that LULC and climatic changes contribute in roughly equal shares to the observed increase in flooding. For the other parts of the subcatchment, the results are less clear but show, that climatic changes and LULC are drivers for the flood increase; however their shares cannot be quantified. Based on these modeling results, we argue for a two-pillar adaptation strategy to reduce current and future flood risk: Flood mitigation for reducing LULC-induced flood increase, and flood adaptation for a general reduction of flood vulnerability.
Y1  - 2015
U6  - https://doi.org/10.3390/w7062796
SN  - 2073-4441
VL  - 7
IS  - 6
SP  - 2796
EP  - 2820
PB  - MDPI
CY  - Basel
ER  - 
TY  - JOUR
A1  - Aich, Valentin
A1  - Zimmermann, Alexander
A1  - Elsenbeer, Helmut
T1  - Quantification and interpretation of suspended-sediment discharge hysteresis patterns: How much data do we need?
JF  - Catena : an interdisciplinary journal of soil science, hydrology, geomorphology focusing on geoecology and landscape evolution
N2  - Sediment-discharge hysteresis loops are frequently analyzed to facilitate the understanding of sediment transport processes. Hysteresis patterns, however, are often complex and their interpretation can be complicated. Particularly, quantifying hysteresis patterns remains a problematic issue. Moreover, it is currently unknown how much data is required for analyzing sediment-discharge hysteresis loops in a given area. These open questions and challenges motivated us to develop a new method for quantifying suspended-sediment hysteresis. Subsequently, we applied the new hysteresis index to three suspended-sediment and discharge datasets from a small tropical rainforest catchment. The datasets comprised a different number of events and sampling sites. Our analyses show three main findings: (1) datasets restricted to only few events, which is typical for rapid assessment surveys, were always sufficient to identify the dominating hysteresis pattern in our research area. Furthermore, some of these small datasets contained multiple-peak events that allowed identifying intra-event exhaustion effects and hence, limitations in sediment supply. (2) Datasets comprising complete hydrological years were particularly useful for analyzing seasonal dynamics of hysteresis. These analyses revealed an exhaustion of hysteresis on the inter-event scale which also points to a limited sediment supply. (3) Datasets comprising measurements from two consecutive gauges installed at the catchment outlet and on a slope within that catchment allowed analyzing the change of hysteresis patterns along the flowpath. On the slope, multiple-peak events showed a stronger intra-event exhaustion of hysteresis than at the catchment outlet. Furthermore, exhaustion of hysteresis on the inter-event scale was not evident on the slope but occurred at the catchment outlet. Our results indicate that even small sediment datasets can provide valuable insights into sediment transport processes of small catchments. Furthermore, our results may serve as a first guideline on what to expect from an analysis of hysteresis patterns for datasets of varying quality and quantity. (c) 2014 Elsevier B.V. All rights reserved.
KW  - Suspended sediment
KW  - Hysteresis index
KW  - Sediment monitoring
KW  - Overland flow
KW  - Tropical forest
Y1  - 2014
U6  - https://doi.org/10.1016/j.catena.2014.06.020
SN  - 0341-8162
SN  - 1872-6887
VL  - 122
SP  - 120
EP  - 129
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Bussian, Bernd M.
A1  - Lehnik-Habrink, Petra
A1  - Hein, Sebastian
T1  - Regionalized concentrations and fingerprints of polycyclic aromatic hydrocarbons (PAHs) in German forest soils
JF  - Environmental pollution
N2  - Samples of 474 forest stands in Germany were analysed for concentrations of polycyclic aromatic hydrocarbons (PAHs) in three sampling depths. Enhanced concentrations were mainly found at spots relatively close to densely industrialized and urbanized regions and at some topographically elevated areas. Average enrichment factors between mineral soil and humic layer depend on humus type i.e. decrease from mull via moder to more Based on their compound-patterns, the observed samples could be assigned to three main clusters. For some parts of our study area a uniform assignment of samples to clusters over larger regions could be identified. For instance, samples taken at vicinity to brown-coal strip-mining districts are characterized by high relative abundances of low-molecular-weight PAHs. These results suggest that PAHs are more likely originated from local and regional emitters rather than from long-range transport and that specific source-regions can be identified based on PAH fingerprints. (C) 2015 Elsevier Ltd. All rights reserved.
KW  - Organic pollutants
KW  - PAHs
KW  - Soil
KW  - Emissions
KW  - Long-range transport
KW  - Enrichment factor
KW  - Humic layer
KW  - Mineral soil
KW  - O horizon
Y1  - 2015
U6  - https://doi.org/10.1016/j.envpol.2015.03.026
SN  - 0269-7491
SN  - 1873-6424
VL  - 203
SP  - 31
EP  - 39
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Feakins, Sarah J.
A1  - Lee, J. E.
A1  - Herzschuh, Ulrike
A1  - Liu, X.
T1  - High-resolution leaf wax carbon and hydrogen isotopic record of the late Holocene paleoclimate in arid Central Asia
JF  - Climate of the past : an interactive open access journal of the European Geosciences Union
N2  - Central Asia is located at the confluence of large-scale atmospheric circulation systems. It is thus likely to be highly susceptible to changes in the dynamics of those systems; however, little is still known about the regional paleoclimate history. Here we present carbon and hydrogen isotopic compositions of n-alkanoic acids from a late Holocene sediment core from Lake Karakuli (eastern Pamir, Xinjiang Province, China). Instrumental evidence and isotopeenabled climate model experiments with the Laboratoire de Meteorologie Dynamique Zoom model version 4 (LMDZ4) demonstrate that delta D values of precipitation in the region are influenced by both temperature and precipitation amount. We find that these parameters are inversely correlated on an annual scale, i.e., the climate has varied between relatively cool and wet and more warm and dry over the last 50 years. Since the isotopic signals of these changes are in the same direction and therefore additive, isotopes in precipitation are sensitive recorders of climatic changes in the region. Additionally, we infer that plants use year-round precipitation (including snowmelt), and thus leaf wax delta D values must also respond to shifts in the proportion of moisture derived from westerly storms during late winter and early spring. Downcore results give evidence for a gradual shift to cooler and wetter climates between 3.5 and 2.5 cal kyr BP, interrupted by a warm and dry episode between 3.0 and 2.7 kyr BP. Further cool and wet episodes occur between 1.9 and 1.5 and between 0.6 and 0.1 kyr BP, the latter coeval with the Little Ice Age. Warm and dry episodes from 2.5 to 1.9 and 1.5 to 0.6 kyr BP coincide with the Roman Warm Period and Medieval Climate Anomaly, respectively. Finally, we find a drying tend in recent decades. Regional comparisons lead us to infer that the strength and position of the westerlies, and wider northern hemispheric climate dynamics, control climatic shifts in arid Central Asia, leading to complex local responses. Our new archive from Lake Karakuli provides a detailed record of the local signatures of these climate transitions in the eastern Pamir.
Y1  - 2015
U6  - https://doi.org/10.5194/cp-11-619-2015
SN  - 1814-9324
SN  - 1814-9332
VL  - 11
IS  - 4
SP  - 619
EP  - 633
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Herzschuh, Ulrike
A1  - Wilkes, Heinz
A1  - Schulz, Hans-Martin
A1  - Wang, Yongbo
A1  - Plessen, Birgit
A1  - Mischke, Steffen
A1  - Diekmann, Bernhard
A1  - Zhang, Chengjun
T1  - Ecological development of Lake Donggi Cona, north-eastern Tibetan Plateau, since the late glacial on basis of organic geochemical proxies and non-pollen palynomorphs
JF  - Palaeogeography, palaeoclimatology, palaeoecology : an international journal for the geo-sciences
N2  - Organic geochemical proxy data from surface sediment samples and a sediment core from Lake Donggi Cona were used to infer environmental changes on the northeastern Tibetan Plateau spanning the last 18.4 kyr. Long-chain n-alkanes dominate the aliphatic hydrocarbon fraction of the sediment extract from most surface sediment samples and the sediment core. Unsaturated mid-chain n-alkanes (nC(23:1) and nC(25:1)) have high abundances in some samples, especially in core samples from the late glacial and early Holocene. TOC contents, organic biomarker and non-pollen-palynomorph concentrations and results from organic petrologic analysis on selected samples suggest three major episodes in the history of Lake Donggi Cona. Before ca. 12.6 cal ka BP samples contain low amounts of organic matter due to cold and arid conditions during the late glacial. After 12.6 cal ka BP, relatively high contents of TOC and concentrations of Botryococcus fossils, as well as enhanced concentrations of mid-chain n-alkanes and n-alkenes suggest a higher primary and macrophyte productivity than at present This is supported by high contents of palynomorphs derived from higher plants and algae and was possibly triggered by a decrease of salinity and amelioration of climate during the early Holocene. Since 6.8 cal ka BP Lake Donggi Cona has been an oligotrophic freshwater lake. Proxy data suggest that variations in insolation drive ecological changes in the lake, with increased aquatic productivity during the early Holocene summer insolation maximum. Short-term drops of TOC contents or biomarker concentrations (at 9.9 cal ka BP, after 8.0 and between 3.5 and 1.7 cal ka BP) can possibly be related to relatively cool and dry episodes reported from other sites on the north-eastern Tibetan Plateau, which are hypothesized to occur in phase with Northern Hemisphere cooling events.
KW  - Biomarker
KW  - Holocene
KW  - n-alkanes
KW  - Total organic carbon
KW  - Organic matter
KW  - Macerals
KW  - Aquatic macrophytes
Y1  - 2012
U6  - https://doi.org/10.1016/j.palaeo.2011.10.015
SN  - 0031-0182
VL  - 313
IS  - 2
SP  - 140
EP  - 149
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Hilt, Sabine
A1  - Perillon, Cecile
A1  - Gillefalk, Mikael
A1  - Sachse, Dirk
T1  - Biosynthetic hydrogen isotopic fractionation factors during lipid synthesis in submerged aquatic macrophytes: Effect of groundwater discharge and salinity
JF  - Organic geochemistry : the international journal for rapid publication of current research in organic geochemistry and biochemistry
N2  - Sedimentary lipid biomarkers have become widely used tools for reconstructing past climatic and ecological changes due to their ubiquitous occurrence in lake sediments. In particular, the hydrogen isotopic composition (expressed as delta D values) of leaf wax lipids derived from terrestrial plants has been a focus of research during the last two decades and the understanding of competing environmental and plant physiological factors influencing the delta D values has greatly improved. Comparatively less attention has been paid to lipid biomarkers derived from aquatic plants, although these compounds are abundant in many lacustrine sediments. We therefore conducted a field and laboratory experiment to study the effect of salinity and groundwater discharge on the isotopic composition of aquatic plant biomarkers. We analyzed samples of the common submerged plant species, Potamogeton pectinatus (sago pondweed), which has a wide geographic distribution and can tolerate high salinity. We tested the effect of groundwater discharge (characterized by more negative delta D values relative to lake water) and salinity on the delta D values of n-alkanes from P. pectinatus by comparing plants (i) collected from the oligotrophic freshwater Lake Stechlin (Germany) at shallow littoral depth from locations with and without groundwater discharge, and (ii) plants grown from tubers collected from the eutrophic Lake Muggelsee in nutrient solution at four salinity levels. Isotopically depleted groundwater did not have a significant influence on the delta D values of n-alkanes in Lake Stechlin P. pectinatus and calculated isotopic fractionation factors epsilon(l/w) between lake water and n-alkanes averaged -137 +/- 9%(n-C-23), -136 +/- 7%(n-C-25) and -131 +/- 6%(n-C-27), respectively. Similar epsilon values were calculated for plants from Lake Muggelsee grown in freshwater nutrient solution (-134 +/- 11% for n-C-23), while greater fractionation was observed at increased salinity values of 10 (163 +/- 12%) and 15(-172 +/- 15%). We therefore suggest an average e value of -136 +/- 9% between source water and the major n-alkanes in P. pectinatus grown under freshwater conditions. Our results demonstrate that isotopic fractionation can increase by 30-40% at salinity values 10 and 15. These results could be explained either by inhibited plant growth at higher salinity, or by metabolic adaptation to salt stress that remain to be elucidated. A potential salinity effect on dD values of aquatic lipids requires further examination, since this would impact on the interpretation of downcore isotopic data in paleohydrologic studies. (C) 2017 Elsevier Ltd. All rights reserved.
Y1  - 2017
U6  - https://doi.org/10.1016/j.orggeochem.2017.07.021
SN  - 0146-6380
VL  - 113
SP  - 10
EP  - 16
PB  - Elsevier
CY  - Oxford
ER  - 
TY  - JOUR
A1  - Aichner, Bernhard
A1  - Makhmudov, Zafar
A1  - Rajabov, Iljomjon
A1  - Zhang, Qiong
A1  - Pausata, Francesco Salvatore R.
A1  - Werner, Martin
A1  - Heinecke, Liv
A1  - Kuessner, Marie L.
A1  - Feakins, Sarah J.
A1  - Sachse, Dirk
A1  - Mischke, Steffen
T1  - Hydroclimate in the Pamirs Was Driven by Changes in Precipitation-Evaporation Seasonality Since theLast Glacial Period
JF  - Geophysical research letters
N2  - The Central Asian Pamir Mountains (Pamirs) are a high-altitude region sensitive to climatic change, with only few paleoclimatic records available. To examine the glacial-interglacial hydrological changes in the region, we analyzed the geochemical parameters of a 31-kyr record from Lake Karakul and performed a set of experiments with climate models to interpret the results. delta D values of terrestrial biomarkers showed insolation-driven trends reflecting major shifts of water vapor sources. For aquatic biomarkers, positive delta D shifts driven by changes in precipitation seasonality were observed at ca. 31-30, 28-26, and 17-14 kyr BP. Multiproxy paleoecological data and modelling results suggest that increased water availability, induced by decreased summer evaporation, triggered higher lake levels during those episodes, possibly synchronous to northern hemispheric rapid climate events. We conclude that seasonal changes in precipitation-evaporation balance significantly influenced the hydrological state of a large waterbody such as Lake Karakul, while annual precipitation amount and inflows remained fairly constant.
KW  - climate
KW  - biomarker
KW  - geochemistry
KW  - modelling
KW  - paleoclimate
KW  - hydrology
Y1  - 2019
U6  - https://doi.org/10.1029/2019GL085202
SN  - 0094-8276
SN  - 1944-8007
VL  - 46
IS  - 23
SP  - 13972
EP  - 13983
PB  - American Geophysical Union
CY  - Washington
ER  - 
TY  - JOUR
A1  - Aiken, John M.
A1  - Aiken, Chastity
A1  - Cotton, Fabrice
T1  - A python library for teaching computation to seismology students
JF  - Seismological research letters
N2  - Python is at the forefront of scientific computation for seismologists and therefore should be introduced to students interested in becoming seismologists. On its own, Python is open source and well designed with extensive libraries. However, Python code can also be executed, visualized, and communicated to others with "Jupyter Notebooks". Thus, Jupyter Notebooks are ideal for teaching students Python and scientific computation. In this article, we designed an openly available Python library and collection of Jupyter Notebooks based on defined scientific computation learning goals for seismology students. The Notebooks cover topics from an introduction to Python to organizing data, earthquake catalog statistics, linear regression, and making maps. Our Python library and collection of Jupyter Notebooks are meant to be used as course materials for an upper-division data analysis course in an Earth Science Department, and the materials were tested in a Probabilistic Seismic Hazard course. However, seismologists or anyone else who is interested in Python for data analysis and map making can use these materials.
Y1  - 2018
U6  - https://doi.org/10.1785/0220170246
SN  - 0895-0695
SN  - 1938-2057
VL  - 89
IS  - 3
SP  - 1165
EP  - 1171
PB  - Seismological Society of America
CY  - Albany
ER  - 
TY  - JOUR
A1  - Akal, Cuneyt
A1  - Koralay, O. Ersin
A1  - Candan, Osman
A1  - Oberhänsli, Roland
A1  - Chen, Fukun
T1  - Geodynamic significance of the early triassic karaburun granitoid (Western Turkey) for the opening history of Neo-Tethys
JF  - Turkish journal of earth sciences = Türk yerbilimleri dergisi
N2  - The Karaburun Peninsula, which is considered part of the Anatolide-Tauride Block of Turkey, contains clastic and carbonate sequences deposited on the northern margin of Gondwana. The Palaeozoic clastic sequence, which is intruded by the Early Triassic granitoid and tectonically overlies a Mesozoic melange sequence, can be divided into three subunits: a lower clastic subunit consisting of a sandstone-shale alternation, an upper clastic subunit consisting of black chert-bearing shales, sandstone and conglomerate, and a Permo-Carboniferous carbonate subunit. The lower Triassic Karaburun I-type granitoid has a high initial Sr-87/Sr-86 ratio (0.709021-0.709168), and low Nd-143/Nd-144 ratio (0.512004-0.512023) and epsilon Nd (-5.34 to -5.70) isotopic values. Geochronological data indicate a crystallization (intrusion) age of 247.1 +/- 2.0 Ma (Scythian). Geochemically, the acidic magmatism reflects a subduction-related continental-arc basin tectonic setting, which can be linked to the opening of the northern branch of Neo-Tethys as a continental back-arc rifting basin on the northern margin of Gondwana. This can be related to the closure through southward subduction of the Palaeotethys Ocean beneath Gondwana.
KW  - Karaburun
KW  - Neo-Tethys
KW  - Palaeo-Tethys
KW  - diorite
KW  - Triassic
KW  - magmatism
Y1  - 2011
U6  - https://doi.org/10.3906/yer-1008-1
SN  - 1300-0985
VL  - 20
IS  - 3
SP  - 255
EP  - 271
PB  - Tübitak
CY  - Ankara
ER  - 
TY  - JOUR
A1  - Akal, Cüneyt
A1  - Candan, Osman
A1  - Koralay, O. Ersin
A1  - Oberhänsli, Roland
A1  - Chen, Fukun
A1  - Prelevic, Dejan
T1  - Early Triassic potassic volcanism in the Afyon Zone of the Anatolides/Turkey - implications for the rifting of the Neo-Tethys
JF  - International journal of earth sciences
N2  - Afyon Zone, which was derived from the Anatolide-Tauride platform during closure of the Neo-Tethys, is made up of pre-Mesozoic basement and unconformably overlying Triassic-Early Tertiary cover series. The Afyon Zone contains widespread metavolcanic rocks, which are dominated by rhyolite, dacite, and trachyandesite. They form a distinct volcanic succession, which is separated from the underlying Silurian-Lower Carboniferous metacarbonates and meta-siliciclastics by a regional unconformity. Trachyandesitic metavolcanics are made up of massive lava flows, pyroclastics and epiclastics, less frequently, domes and dikes, which were developed on a deeply eroded subaerial landmass. U/Pb and Pb/Pb zircon geochronology yielded Lower Triassic (similar to 250 Ma) ages, which are interpreted as extrusion age of trachyandesitic volcanics. Based on the stratigraphic, geochronological, and geochemical data, we suggest that these Lower Triassic magmatic rocks represent an extensional tectonic setting on the northern active margin of the Gondwana, which led to the development of the northern branch of the Neo-Tethys.
KW  - Meta-trachyandesite
KW  - Afyon Zone
KW  - Turkey
KW  - Neo-Tethys
KW  - Paleo-tethys
Y1  - 2012
U6  - https://doi.org/10.1007/s00531-011-0654-2
SN  - 1437-3254
VL  - 101
IS  - 1
SP  - 177
EP  - 194
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Al Atik, Linda
A1  - Abrahamson, Norman A.
A1  - Bommer, Julian J.
A1  - Scherbaum, Frank
A1  - Cotton, Fabrice
A1  - Kuehn, Nicolas
T1  - The variability of ground-motion prediction models and its components
Y1  - 2010
UR  - http://srl.geoscienceworld.org/
U6  - https://doi.org/10.1785/gssrl.81.5.794
SN  - 0895-0695
ER  - 
TY  - JOUR
A1  - Al-Halbouni, Djamil
A1  - Holohan, Eoghan P.
A1  - Taheri, Abbas
A1  - Schöpfer, Martin P. J.
A1  - Emam, Sacha
A1  - Dahm, Torsten
T1  - Geomechanical modelling of sinkhole development using distinct elements
BT  - model verification for a single void space and application to the Dead Sea area
JF  - Solid earth
N2  - Mechanical and/or chemical removal of material from the subsurface may generate large subsurface cavities, the destabilisation of which can lead to ground collapse and the formation of sinkholes. Numerical simulation of the interaction of cavity growth, host material deformation and overburden collapse is desirable to better understand the sinkhole hazard but is a challenging task due to the involved high strains and material discontinuities. Here, we present 2-D distinct element method numerical simulations of cavity growth and sinkhole development. Firstly, we simulate cavity formation by quasi-static, stepwise removal of material in a single growing zone of an arbitrary geometry and depth. We benchmark this approach against analytical and boundary element method models of a deep void space in a linear elastic material. Secondly, we explore the effects of properties of different uniform materials on cavity stability and sinkhole development. We perform simulated biaxial tests to calibrate macroscopic geotechnical parameters of three model materials representative of those in which sinkholes develop at the Dead Sea shoreline: mud, alluvium and salt. We show that weak materials do not support large cavities, leading to gradual sagging or suffusion-style subsidence. Strong materials support quasi-stable to stable cavities, the overburdens of which may fail suddenly in a caprock or bedrock collapse style. Thirdly, we examine the consequences of layered arrangements of weak and strong materials. We find that these are more susceptible to sinkhole collapse than uniform materials not only due to a lower integrated strength of the overburden but also due to an inhibition of stabilising stress arching. Finally, we compare our model sinkhole geometries to observations at the Ghor Al-Haditha sinkhole site in Jordan. Sinkhole depth / diameter ratios of 0.15 in mud, 0.37 in alluvium and 0.33 in salt are reproduced successfully in the calibrated model materials. The model results suggest that the observed distribution of sinkhole depth / diameter values in each material type may partly reflect sinkhole growth trends.
Y1  - 2018
U6  - https://doi.org/10.5194/se-9-1341-2018
SN  - 1869-9510
SN  - 1869-9529
VL  - 9
IS  - 6
SP  - 1341
EP  - 1373
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Al-Halbouni, Djamil
A1  - Holohan, Eoghan P.
A1  - Taheri, Abbas
A1  - Watson, Robert A.
A1  - Polom, Ulrich
A1  - Schoepfer, Martin P. J.
A1  - Emam, Sacha
A1  - Dahm, Torsten
T1  - Distinct element geomechanical modelling of the formation of sinkhole clusters within large-scale karstic depressions
JF  - Solid earth
N2  - The 2-D distinct element method (DEM) code (PFC2D_V5) is used here to simulate the evolution of subsidence-related karst landforms, such as single and clustered sinkholes, and associated larger-scale depressions. Subsurface material in the DEM model is removed progressively to produce an array of cavities; this simulates a network of subsurface groundwater conduits growing by chemical/mechanical erosion. The growth of the cavity array is coupled mechanically to the gravitationally loaded surroundings, such that cavities can grow also in part by material failure at their margins, which in the limit can produce individual collapse sinkholes. Two end-member growth scenarios of the cavity array and their impact on surface subsidence were examined in the models: (1) cavity growth at the same depth level and growth rate; (2) cavity growth at progressively deepening levels with varying growth rates. These growth scenarios are characterised by differing stress patterns across the cavity array and its overburden, which are in turn an important factor for the formation of sinkholes and uvalalike depressions. For growth scenario (1), a stable compression arch is established around the entire cavity array, hindering sinkhole collapse into individual cavities and favouring block-wise, relatively even subsidence across the whole cavity array. In contrast, for growth scenario (2), the stress system is more heterogeneous, such that local stress concentrations exist around individual cavities, leading to stress interactions and local wall/overburden fractures. Consequently, sinkhole collapses occur in individual cavities, which results in uneven, differential subsidence within a larger-scale depression. Depending on material properties of the cavity-hosting material and the overburden, the larger-scale depression forms either by sinkhole coalescence or by widespread subsidence linked geometrically to the entire cavity array. The results from models with growth scenario (2) are in close agreement with surface morphological and subsurface geophysical observations from an evaporite karst area on the eastern shore of the Dead Sea.
Y1  - 2019
U6  - https://doi.org/10.5194/se-10-1219-2019
SN  - 1869-9510
SN  - 1869-9529
VL  - 10
IS  - 4
SP  - 1219
EP  - 1241
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Al-Mashaikhi, K.
A1  - Oswald, Sascha
A1  - Attinger, Sabine
A1  - Büchel, G.
A1  - Knöller, K.
A1  - Strauch, G.
T1  - Evaluation of groundwater dynamics and quality in the Najd aquifers located in the Sultanate of Oman
JF  - Environmental earth sciences
N2  - The Najd, Oman, is located in one of the most arid environments in the world. The groundwater in this region is occurring in four different aquifers A to D of the Hadhramaut Group consisting mainly of different types of limestone and dolomite. The quality of the groundwater is dominated by the major ions sodium, calcium, magnesium, sulphate, and chloride, but the hydrochemical character is varying among the four aquifers. Mineralization within the separate aquifers increases along the groundwater flow direction from south to north-northeast up to high saline sodium-chloride water in aquifer D in the northeast area of the Najd. Environmental isotope analyses of hydrogen and oxygen were conducted to monitor the groundwater dynamics and to evaluate the recharge conditions of groundwater into the Najd aquifers. Results suggest an earlier recharge into these aquifers as well as ongoing recharge takes place in the region down to present day. Mixing of modern and submodern waters was detected by water isotopes in aquifer D in the mountain chain (Jabal) area and along the northern side of the mountain range. In addition, delta H-2 and delta O-18 variations suggest that aquifers A, B, and C are assumed to be connected by faults and fractures, and interaction between the aquifers may occur. Low tritium concentrations support the mixing assumption in the recharge area. The knowledge about the groundwater development is an important factor for the sustainable use of water resources in the Dhofar region.
KW  - Environmental isotopes
KW  - Groundwater
KW  - Najd aquifer
KW  - Oman
KW  - Recharge
KW  - Water quality
Y1  - 2012
U6  - https://doi.org/10.1007/s12665-011-1331-2
SN  - 1866-6280
VL  - 66
IS  - 4
SP  - 1195
EP  - 1211
PB  - Springer
CY  - New York
ER  - 
TY  - JOUR
A1  - Alawi, Mashal
A1  - Schneider, Beate
A1  - Kallmeyer, Jens
T1  - A procedure for separate recovery of extra- and intracellular DNA from a single marine sediment sample
JF  - Journal of microbiological methods
N2  - Extracellular DNA (eDNA) is a ubiquitous biological compound in aquatic sediment and soil. Previous studies suggested that eDNA plays an important role in biogeochemical element cycling, horizontal gene transfer and stabilization of biofilm structures. Previous methods for eDNA extraction were either not suitable for oligotrophic sediments or only allowed quantification but no genetic analyses. Our procedure is based on cell detachment and eDNA liberation from sediment particles by sequential washing with an alkaline sodium phosphate buffer followed by a separation of cells and eDNA. The separated eDNA is then bound onto silica particles and purified, whereas the intracellular DNA from the separated cells is extracted using a commercial kit. The method provides extra- and intracellular DNA of high purity that is suitable for downstream applications like PCR. Extracellular DNA was extracted from organic-rich shallow sediment of the Baltic Sea, glacially influenced sediment of the Barents Sea and from the oligotrophic South Pacific Gyre. The eDNA concentration in these samples varied from 23 to 626 ng g(-1) wet weight sediment. A number of experiments were performed to verify each processing step. Although extraction efficiency is higher than other published methods, it is not fully quantitative. (C) 2014 Elsevier B.V. All rights reserved.
KW  - Extracellular DNA
KW  - eDNA
KW  - Intracellular DNA
KW  - South Pacific Gyre
KW  - Ancient DNA
KW  - Fossil DNA
Y1  - 2014
U6  - https://doi.org/10.1016/j.mimet.2014.06.009
SN  - 0167-7012
SN  - 1872-8359
VL  - 104
SP  - 36
EP  - 42
PB  - Elsevier
CY  - Amsterdam
ER  - 
TY  - JOUR
A1  - Albrecht, Tanja
A1  - Martin, M.
A1  - Haseloff, M.
A1  - Winkelmann, Ricarda
A1  - Levermann, Anders
T1  - Parameterization for subgrid-scale motion of ice-shelf calving fronts
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - A parameterization for the motion of ice-shelf fronts on a Cartesian grid in finite-difference land-ice models is presented. The scheme prevents artificial thinning of the ice shelf at its edge, which occurs due to the finite resolution of the model. The intuitive numerical implementation diminishes numerical dispersion at the ice front and enables the application of physical boundary conditions to improve the calculation of stress and velocity fields throughout the ice-sheet-shelf system. Numerical properties of this subgrid modification are assessed in the Potsdam Parallel Ice Sheet Model (PISM-PIK) for different geometries in one and two horizontal dimensions and are verified against an analytical solution in a flow-line setup.
Y1  - 2011
U6  - https://doi.org/10.5194/tc-5-35-2011
SN  - 1994-0416
VL  - 5
IS  - 1
SP  - 35
EP  - 44
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Albrecht, Torsten
A1  - Winkelmann, Ricarda
A1  - Levermann, Anders
T1  - Glacial-cycle simulations of the Antarctic Ice Sheet with the Parallel Ice Sheet Model (PISM)
BT  - Part 1: boundary conditions and climatic forcing
JF  - The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union
N2  - Simulations of the glacial-interglacial history of the Antarctic Ice Sheet provide insights into dynamic threshold behavior and estimates of the ice sheet's contributions to global sea-level changes for the past, present and future. However, boundary conditions are weakly constrained, in particular at the interface of the ice sheet and the bedrock. Also climatic forcing covering the last glacial cycles is uncertain, as it is based on sparse proxy data. <br /> We use the Parallel Ice Sheet Model (PISM) to investigate the dynamic effects of different choices of input data, e.g., for modern basal heat flux or reconstructions of past changes of sea level and surface temperature. As computational resources are limited, glacial-cycle simulations are performed using a comparably coarse model grid of 16 km and various parameterizations, e.g., for basal sliding, iceberg calving, or for past variations in precipitation and ocean temperatures. In this study we evaluate the model's transient sensitivity to corresponding parameter choices and to different boundary conditions over the last two glacial cycles and provide estimates of involved uncertainties. We also discuss isolated and combined effects of climate and sea-level forcing. Hence, this study serves as a "cookbook" for the growing community of PISM users and paleo-ice sheet modelers in general. <br /> For each of the different model uncertainties with regard to climatic forcing, ice and Earth dynamics, and basal processes, we select one representative model parameter that captures relevant uncertainties and motivates corresponding parameter ranges that bound the observed ice volume at present. The four selected parameters are systematically varied in a parameter ensemble analysis, which is described in a companion paper.
Y1  - 2020
U6  - https://doi.org/10.5194/tc-14-599-2020
SN  - 1994-0416
SN  - 1994-0424
VL  - 14
IS  - 2
SP  - 599
EP  - 632
PB  - Copernicus
CY  - Göttingen
ER  - 
TY  - JOUR
A1  - Albrich, Sergi
A1  - Frijia, Gianluca
A1  - Parente, Mariano
A1  - Caus, Esmeralda
T1  - The evolution of the earliest representatives of the genus Orbitoides: Implications for Upper Cretaceous biostratigraphy
JF  - Cretaceous research
N2  - The biostratigraphy of Campanian-Maastrichtian carbonate platforms is largely based on the larger foraminiferal genus Orbitoides. However, while the taxonomy and the chronostratigraphic age of the younger species of this genus are well established, there are still many controversies on the earliest species. We have restudied their morphological characters using a large collection of samples from the type-localities and from continuous sections in the southern Pyrenees. Based on these new observations, the long forgotten species O. sanctae-pelagiae is reinstated, while O. dordoniensis is considered a junior synonym. Successive populations of O. hottingeri, O. sanctae-pelagiae and O. douvillei show gradual morphological changes in time marked by an increase in the size and complexity of the macrospheric embryonal apparatus, an increase of the size of the adult specimens of both generations and the progressive appearance and development of true lateral chamberlets. The Font de les Bagasses Unit in the southern Pyrenees preserves a high-resolution archive of the evolution of the earliest Orbitoides. Strontium isotope stratigraphy indicates that the oldest species, O. hottingeri, made its first appearance in the earliest Campanian, close to the Santonian-Campanian boundary, and was replaced by O. sanctae-pelagiae at a level closely corresponding to the boundary between the Placenticeras bidorsatum and Menabites delawarensis ammonite zones. (C) 2014 Elsevier Ltd. All rights reserved.
KW  - Larger foraminifera
KW  - Biostratigraphy
KW  - Strontium isotope stratigraphy
KW  - Late cretaceous
KW  - Orbitoides
Y1  - 2014
U6  - https://doi.org/10.1016/j.cretres.2014.04.013
SN  - 0195-6671
SN  - 1095-998X
VL  - 51
SP  - 22
EP  - 34
PB  - Elsevier
CY  - London
ER  - 
TY  - JOUR
A1  - Ali, Saleem H.
A1  - Giurco, Damien
A1  - Arndt, Nicholas
A1  - Nickless, Edmund
A1  - Brown, Graham
A1  - Demetriades, Alecos
A1  - Durrheim, Ray
A1  - Enriquez, Maria Amelia
A1  - Kinnaird, Judith
A1  - Littleboy, Anna
A1  - Meinert, Lawrence D.
A1  - Oberhänsli, Roland
A1  - Salem, Janet
A1  - Schodde, Richard
A1  - Schneider, Gabi
A1  - Vidal, Olivier
A1  - Yakovleva, Natalia
T1  - Mineral supply for sustainable development requires resource governance
JF  - Nature : the international weekly journal of science
N2  - Successful delivery of the United Nations sustainable development goals and implementation of the Paris Agreement requires technologies that utilize a wide range of minerals in vast quantities. Metal recycling and technological change will contribute to sustaining supply, but mining must continue and grow for the foreseeable future to ensure that such minerals remain available to industry. New links are needed between existing institutional frameworks to oversee responsible sourcing of minerals, trajectories for mineral exploration, environmental practices, and consumer awareness of the effects of consumption. Here we present, through analysis of a comprehensive set of data and demand forecasts, an interdisciplinary perspective on how best to ensure ecologically viable continuity of global mineral supply over the coming decades.
Y1  - 2017
U6  - https://doi.org/10.1038/nature21359
SN  - 0028-0836
SN  - 1476-4687
VL  - 543
SP  - 367
EP  - 372
PB  - Nature Publ. Group
CY  - London
ER  - 
TY  - JOUR
A1  - Alinaghi, Alireza
A1  - Kruger, Frank
T1  - Seismic array analysis and redetermination of depths of earthquakes in Tien-Shan: implications for strength of the crust and lithosphere
JF  - Geophysical journal international
N2  - We have redetermined focal depths of moderate and major earthquakes with reported lower-crust and upper-mantle depths that have occurred in Tien-Shan, since the availability of broad-band array data. Records of earthquakes at global arrays have been used for identification and modelling of depth phases in order to make accurate estimation of focal depths. Our results show that half of the purportedly deep earthquakes are indeed originating from depths attributable to middle-crust and lower-crust regions. Also one exceptional event in the northern foreland of Tien-Shan in Junggar Basin is located in the upper mantle at the depth of 64 km. Such unusually deep earthquakes for intraplate continental tectonic domain are all located at the margin of Tien-Shan with its adjacent stable blocks and at least some of them have occurred where the brittle behaviour of continental rocks is not highly expected. The reverse mechanisms of all these earthquakes and their proximity to formerly subducting and later colliding and underplating stable blocks and their interactions with overlying Tien-Shan are clues to explain this extremity.
KW  - Earthquake source observations
KW  - Seismicity and tectonics
KW  - Body waves
Y1  - 2014
U6  - https://doi.org/10.1093/gji/ggu141
SN  - 0956-540X
SN  - 1365-246X
VL  - 198
IS  - 2
SP  - 1111
EP  - 1129
PB  - Oxford Univ. Press
CY  - Oxford
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  - Beiter, Daniel
A1  - Tronicke, Jens
T1  - Ground-penetrating radar monitoring of fast subsurface processes
JF  - Geophysics
N2  - Earth and environmental sciences rely on detailed information about subsurface processes. Whereas geophysical techniques typically provide highly resolved spatial images, monitoring subsurface processes is often associated with enormous effort and, therefore, is usually limited to point information in time or space. Thus, the development of spatial and temporal continuous field monitoring methods is a major challenge for the understanding of subsurface processes. We have developed a novel method for ground-penetrating-radar (GPR) reflection monitoring of subsurface flow processes under unsaturated conditions and applied it to a hydrological infiltration experiment performed across a periglacial slope deposit in northwest Luxembourg. Our approach relies on a spatial and temporal quasicontinuous data recording and processing, followed by an attribute analysis based on analyzing differences between individual time steps. The results demonstrate the ability of time-lapse GPR monitoring to visualize the spatial and temporal dynamics of preferential flow processes with a spatial resolution in the order of a few decimeters and temporal resolution in the order of a few minutes. We observe excellent agreement with water table information originating from different boreholes. This demonstrates the potential of surface-based GPR reflection monitoring to observe the spatiotemporal dynamics of water movements in the subsurface. It provides valuable, and so far not accessible, information for example in the field of hydrology and pedology that allows studying the actual subsurface processes rather than deducing them from point information.
Y1  - 2020
U6  - https://doi.org/10.1190/GEO2019-0737.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 85
IS  - 3
SP  - A19
EP  - A23
PB  - Society of Exploration Geophysicists
CY  - Tulsa
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas
A1  - Heincke, Bjorn H.
A1  - Koyan, Philipp
A1  - Wheeler, Walter
A1  - Ronning, Jan S.
T1  - 3D ground-penetrating radar attribute classification
BT  - a case study from a paleokarst breccia pipe in the Billefjorden area on Spitsbergen, Svalbard
JF  - Geophysics
N2  - Ground-penetrating radar (GPR) is a method that can provide detailed information about the near subsurface in sedimentary and carbonate environments. 
The classical interpretation of GPR data (e.g., based on manual feature selection) often is labor-intensive and limited by the experience of the intercally used for seismic interpretation, can provide faster, more repeatable, and less biased interpretations. We have recorded a 3D GPD data set collected across a paleokarst breccia pipe in the Billefjorden area on Spitsbergen, Svalbard. After performing advanced processing, we compare the results of a classical GPR interpretation to the results of an attribute-based classification. 

Our attribute classification incorporates a selection of dip and textural attributes as the input for a k-means clustering approach. Similar to the results of the classical interpretation, the resulting classes differentiate between undisturbed strata and breccias or fault zones. 
The classes also reveal details inside the breccia pipe that are not discerned in the classical fer that the intrapipe GPR facies result from subtle differences, such as breccia lithology, clast size, or pore-space filling.
Y1  - 2022
U6  - https://doi.org/10.1190/GEO2021-0651.1
SN  - 0016-8033
SN  - 1942-2156
VL  - 87
IS  - 4
SP  - WB19
EP  - WB30
PB  - Society of Exploration Geophysicists
CY  - Tulsa
ER  - 
TY  - JOUR
A1  - Allroggen, Niklas Robin
A1  - Booth, Adam D.
A1  - Baker, Sandra E.
A1  - Ellwood, Stephen A.
A1  - Tronicke, Jens
T1  - High-resolution imaging and monitoring of animal tunnels using 3D ground-penetrating radar
JF  - Near surface geophysics
N2  - Ground-penetrating radar is widely used to provide highly resolved images of subsurface sedimentary structures, with implications for processes active in the vadose zone. Frequently overlooked among these structures are tunnels excavated by fossorial animals (e.g., moles). We present two repeated ground-penetrating radar surveys performed a year apart in 2016 and 2017. Careful three-dimensional data processing reveals, in each data set, a pattern of elongated structures that are interpreted as a subsurface mole tunnel network. Our data demonstrate the ability of three-dimensional ground-penetrating radar imaging to non-invasively delineate the small animal tunnels (similar to 5 cm diameter) at a higher spatial and geolocation resolution than has previously been achieved. In turn, this makes repeated surveys and, therefore, long-term monitoring possible. Our results offer valuable insight into the understanding of the near-surface and showcase a potential new application for a geophysical method as well as a non-invasive method of ecological surveying.
KW  - Ground-penetrating radar
KW  - Shallow subsurface
KW  - Environmental
Y1  - 2019
U6  - https://doi.org/10.1002/nsg.12039
SN  - 1569-4445
SN  - 1873-0604
VL  - 17
IS  - 3
SP  - 291
EP  - 298
PB  - Wiley
CY  - Hoboken
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  - 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  - 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  - Alonso, Ricardo N.
A1  - Bookhagen, Bodo
A1  - Carrapa, Barbara
A1  - Coutand, Isabelle
A1  - Haschke, Michael
A1  - Hilley, George E.
A1  - Schoenbohm, Lindsay M.
A1  - Sobel, Edward
A1  - Strecker, Manfred
A1  - Trauth, Martin H.
A1  - Villanueva, Arturo
T1  - Tectonics, climate and landscape evolution of the Southern Central Andes : the Argentine Puna Plateau and adjacent regions between 22 and 30°S
Y1  - 2006
SN  - 978-3-540- 24329-8
ER  - 
TY  - JOUR
A1  - Alonzo, Michael
A1  - Bookhagen, Bodo
A1  - McFadden, Joseph P.
A1  - Sun, Alex
A1  - Roberts, Dar A.
T1  - Mapping urban forest leaf area index with airborne lidar using penetration metrics and allometry
JF  - Remote sensing of environment : an interdisciplinary journal
N2  - In urban areas, leaf area index (LAI) is a key ecosystem structural attribute with implications for energy and water balance, gas exchange, and anthropogenic energy use. In this study, we estimated LAI spatially using airborne lidar in downtown Santa Barbara, California, USA. We implemented two different modeling approaches. First, we directly estimated effective LAI (LAIe) using scan angle- and clump-corrected lidar laser penetration metrics (LPM). Second, we adapted existing allometric equations to estimate crown structural metrics including tree height and crown base height using lidar. The latter approach allowed for LAI estimates at the individual tree-crown scale. The LPM method, at both high and decimated point densities, resulted in good linear agreement with estimates from ground-based hemispherical photography (r(2) = 0.82, y = 0.99x) using a model that assumed a spherical leaf angle distribution. Within individual tree crown segments, the lidar estimates of crown structure closely paralleled field measurements (e.g., r(2) = 0.87 for crown length). LAI estimates based on the lidar crown measurements corresponded well with estimates from field measurements (r(2) = 0.84, y = 0.97x + 0.10). Consistency of the LPM and allometric lidar methods was also strong at 71 validation plots (r(2) = 0.88) and at 450 additional sample locations across the entire study area (r(2) = 0.72). This level of correspondence exceeded that of the canopy hemispherical photography and allometric, ground-based estimates (r(2) = 0.53). The first-order alignment of these two disparate methods may indicate that the error bounds for mapping LAI in cities are small enough to pursue large scale, spatially explicit estimation. (C) 2015 Elsevier Inc All rights reserved.
KW  - Airborne lidar
KW  - Leaf area index
KW  - Urban ecosystem analysis
KW  - Hemispherical photography
KW  - Allometry
KW  - Vegetation structure
Y1  - 2015
U6  - https://doi.org/10.1016/j.rse.2015.02.025
SN  - 0034-4257
SN  - 1879-0704
VL  - 162
SP  - 141
EP  - 153
PB  - Elsevier
CY  - New York
ER  - 
TY  - GEN
A1  - Alsemgeest, Jitse
A1  - Schröder, S.
A1  - Boettger, Ute
A1  - Pavlov, S. G.
A1  - Weber, I.
A1  - Greshake, A.
A1  - Knöfler, H. -R.
A1  - Altenberger, Uwe
A1  - Hübers, H. -W.
T1  - COMBINED RAMAN-LIBS STUDIES ON IRON SULFIDES TO INVESTIGATE THE EFECTS OF THE LIBS PLASMA ON THE MINERAL COMPOSITION.
T2  - Monthly notices of the Royal Astronomical Society
Y1  - 2016
SN  - 1086-9379
SN  - 1945-5100
VL  - 51
SP  - A147
EP  - A147
PB  - Wiley-Blackwell
CY  - Hoboken
ER  - 
TY  - JOUR
A1  - Altenbach, Alexander V.
A1  - Pflaum, U.
A1  - Scheibel, Thomas R.
A1  - Thies, A.
A1  - Timm, M.
A1  - Trauth, Martin H.
T1  - Scaling percentages of benthic forminifera with flux rates of organic carbon
Y1  - 1999
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
T1  - Strain localization mechanisms in deep seated layered rocks
Y1  - 1997
ER  - 
TY  - JOUR
A1  - Altenberger, Uwe
T1  - Material transport in channelized fluids-examples from hightemperature shear zones and its comparsion with minor deformed ares of the Mid-European Variscan belt
Y1  - 1996
ER  -