@article{BubeckKreibichPenningRowselletal.2017, author = {Bubeck, Philip and Kreibich, Heidi and Penning-Rowsell, E. C. and Botzen, W. J. Wouter and de Moel, H. and Klijn, F.}, title = {Explaining differences in flood management approaches in Europe and in the USA - a comparative analysis}, series = {Journal of flood risk management}, volume = {10}, journal = {Journal of flood risk management}, publisher = {Wiley}, address = {Hoboken}, issn = {1753-318X}, doi = {10.1111/jfr3.12151}, pages = {436 -- 445}, year = {2017}, abstract = {Flood risk management in Europe and worldwide is not static but constantly in a state of flux. There has been a trend towards more integrated flood risk management in many countries. However, the initial situation and the pace and direction of change is very different in the various countries. In this paper, we will present a conceptual framework that seeks to explain why countries opt for different flood risk management portfolios. The developed framework utilises insights from a range of policy science concepts in an integrated way and considers, among others, factors such as geographical characteristics, the experience with flood disasters, as well as human behavioural aspects.}, language = {en} } @article{HansmanRingThomsonetal.2017, author = {Hansman, Reuben J. and Ring, Uwe and Thomson, Stuart N. and den Brok, Bas and Stuebner, Konstanze}, title = {Late Eocene Uplift of the Al Hajar Mountains, Oman, Supported by Stratigraphy and Low-Temperature Thermochronology}, series = {Tectonics}, volume = {36}, journal = {Tectonics}, publisher = {American Geophysical Union}, address = {Washington}, issn = {0278-7407}, doi = {10.1002/2017TC004672}, pages = {3081 -- 3109}, year = {2017}, abstract = {Uplift of the Al Hajar Mountains in Oman has been related to either Late Cretaceous ophiolite obduction or the Neogene Zagros collision. To test these hypotheses, the cooling of the central Al Hajar Mountains is constrained by 10 apatite (U-Th)/He (AHe), 15 fission track (AFT), and four zircon (U-Th)/He (ZHe) sample ages. These data show differential cooling between the two major structural culminations of the mountains. In the 3km high Jabal Akhdar culmination AHe single-grain ages range between 392 Ma and 101 Ma (2 sigma errors), AFT ages range from 518 Ma to 324 Ma, and ZHe single-grain ages range from 62 +/- 3Ma to 39 +/- 2 Ma. In the 2 km high Saih Hatat culmination AHe ages range from 26 +/- 4 to 12 +/- 4 Ma, AFT ages from 73 +/- 19Ma to 57 +/- 8 Ma, and ZHe single-grain ages from 81 +/- 4 Ma to 58 +/- 3 Ma. Thermal modeling demonstrates that cooling associated with uplift and erosion initiated at 40 Ma, indicating that uplift occurred 30 Myr after ophiolite obduction and at least 10 Myr before the Zagros collision. Therefore, this uplift cannot be related to either event. We propose that crustal thickening supporting the topography of the Al Hajar Mountains was caused by a slowdown of Makran subduction and that north Oman took up the residual fraction of N-S convergence between Arabia and Eurasia.}, language = {en} } @article{LaudanRoezerSiegetal.2017, author = {Laudan, Jonas and Roezer, Viktor and Sieg, Tobias and Vogel, Kristin and Thieken, Annegret}, title = {Damage assessment in Braunsbach 2016: data collection and analysis for an improved understanding of damaging processes during flash floods}, series = {Natural hazards and earth system sciences}, volume = {17}, journal = {Natural hazards and earth system sciences}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1561-8633}, doi = {10.5194/nhess-17-2163-2017}, pages = {2163 -- 2179}, year = {2017}, language = {en} } @article{SchwanghartScherler2017, author = {Schwanghart, Wolfgang and Scherler, Dirk}, title = {Bumps in river profiles: uncertainty assessment and smoothing using quantile regression techniques}, series = {Earth surface dynamics}, volume = {5}, journal = {Earth surface dynamics}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {2196-6311}, doi = {10.5194/esurf-5-821-2017}, pages = {821 -- 839}, year = {2017}, abstract = {The analysis of longitudinal river profiles is an important tool for studying landscape evolution. However, characterizing river profiles based on digital elevation models (DEMs) suffers from errors and artifacts that particularly prevail along valley bottoms. The aim of this study is to characterize uncertainties that arise from the analysis of river profiles derived from different, near-globally available DEMs. We devised new algorithms quantile carving and the CRS algorithm - that rely on quantile regression to enable hydrological correction and the uncertainty quantification of river profiles. We find that globally available DEMs commonly overestimate river elevations in steep topography. The distributions of elevation errors become increasingly wider and right skewed if adjacent hillslope gradients are steep. Our analysis indicates that the AW3D DEM has the highest precision and lowest bias for the analysis of river profiles in mountainous topography. The new 12m resolution TanDEM-X DEM has a very low precision, most likely due to the combined effect of steep valley walls and the presence of water surfaces in valley bottoms. Compared to the conventional approaches of carving and filling, we find that our new approach is able to reduce the elevation bias and errors in longitudinal river profiles.}, language = {en} } @article{CaoTianTelfordetal.2017, author = {Cao, Xianyong and Tian, Fang and Telford, Richard J. and Ni, Jian and Xu, Qinghai and Chen, Fahu and Liu, Xingqi and Stebich, Martina and Zhao, Yan and Herzschuh, Ulrike}, title = {Impacts of the spatial extent of pollen-climate calibration-set on the absolute values, range and trends of reconstructed Holocene precipitation}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {178}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2017.10.030}, pages = {37 -- 53}, year = {2017}, abstract = {Pollen-based quantitative reconstructions of past climate variables is a standard palaeoclimatic approach. Despite knowing that the spatial extent of the calibration-set affects the reconstruction result, guidance is lacking as to how to determine a suitable spatial extent of the pollen-climate calibration-set. In this study, past mean annual precipitation (P-ann) during the Holocene (since 11.5 cal ka BP) is reconstructed repeatedly for pollen records from Qinghai Lake (36.7 degrees N, 100.5 degrees E; north-east Tibetan Plateau), Gonghai Lake (38.9 degrees N, 112.2 degrees E; north China) and Sihailongwan Lake (42.3 degrees N, 126.6 degrees E; north-east China) using calibration-sets of varying spatial extents extracted from the modern pollen dataset of China and Mongolia (2559 sampling sites and 168 pollen taxa in total). Results indicate that the spatial extent of the calibration-set has a strong impact on model performance, analogue quality and reconstruction diagnostics (absolute value, range, trend, optimum). Generally, these effects are stronger with the modern analogue technique (MAT) than with weighted averaging partial least squares (WA-PLS). With respect to fossil spectra from northern China, the spatial extent of calibration-sets should be restricted to radii between ca. 1000 and 1500 km because small-scale calibration-sets (<800 km radius) will likely fail to include enough spatial variation in the modern pollen assemblages to reflect the temporal range shifts during the Holocene, while too broad a scale calibration-set (>1500 km radius) will include taxa with very different pollen-climate relationships. (C) 2017 Elsevier Ltd. All rights reserved.}, language = {en} } @article{FohlmeisterPlessenDudashvilietal.2017, author = {Fohlmeister, Jens Bernd and Plessen, Birgit and Dudashvili, Alexey Sergeevich and Tjallingii, Rik and Wolff, Christian Michael and Gafurov, Abror and Cheng, Hai}, title = {Winter precipitation changes during the Medieval Climate Anomaly and the Little Ice Age in arid Central Asia}, series = {Quaternary science reviews : the international multidisciplinary research and review journal}, volume = {178}, journal = {Quaternary science reviews : the international multidisciplinary research and review journal}, publisher = {Elsevier}, address = {Oxford}, issn = {0277-3791}, doi = {10.1016/j.quascirev.2017.10.026}, pages = {24 -- 36}, year = {2017}, abstract = {The strength of the North Atlantic Oscillation (NAO) is considered to be the main driver of climate changes over the European and western Asian continents throughout the last millennium. For example, the predominantly warm Medieval Climate Anomaly (MCA) and the following cold period of the Little Ice Age (LIA) over Europe have been associated with long-lasting phases with a positive and negative NAO index. Its climatic imprint is especially pronounced in European winter seasons. However, little is known about the influence of NAO with respect to its eastern extent over the Eurasian continent. Here we present speleothem records (PC, 8180 and Sr/Ca) from the southern rim of Fergana Basin (Central Asia) revealing annually resolved past climate variations during the last millennium. The age control of the stalagmite relies on radiocarbon dating as large amounts of detrital material inhibit accurate 230Th dating. Present-day calcification of the stalagmite is most effective during spring when the cave atmosphere and elevated water supply by snow melting and high amount of spring precipitation provide optimal conditions. Seasonal precipitation variations cause changes of the stable isotope and Sr/ Ca compositions. The simultaneous changes in these geochemical proxies, however, give also evidence for fractionation processes in the cave. By disentangling both processes, we demonstrate that the amount of winter precipitation during the MCA was generally higher than during the LIA, which is in line with climatic changes linked to the NAO index but opposite to the higher mountain records of Central Asia. Several events of strongly reduced winter precipitation are observed during the LIA in Central Asia. These dry winter events can be related to phases of a strong negative NAO index and all results reveal that winter precipitation over the central Eurasian continent is tightly linked to atmospheric NAO modes by the westerly wind systems. (C) 2017 Elsevier Ltd. All rights reserved.}, language = {en} } @article{SahleNiskanenSchmidtetal.2017, author = {Sahle, Christoph J. and Niskanen, Johannes and Schmidt, Christian and Stefanski, Johannes and Gilmore, Keith and Forov, Yury and Jahn, Sandro and Wilke, Max and Sternemann, Christian}, title = {Cation Hydration in Supercritical NaOH and HCl Aqueous Solutions}, series = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, volume = {121}, journal = {The journal of physical chemistry : B, Condensed matter, materials, surfaces, interfaces \& biophysical chemistry}, publisher = {American Chemical Society}, address = {Washington}, issn = {1520-6106}, doi = {10.1021/acs.jpcb.7b09688}, pages = {11383 -- 11389}, year = {2017}, abstract = {We present a study of the local atomic environment of the oxygen atoms in the aqueous solutions of NaOH and HCl under simultaneous high-temperature and high-pressure conditions. Experimental nonresonant X-ray Raman scattering core-level spectra at the oxygen K-edge show systematic changes as a function of temperature and pressure. These systematic changes are distinct for the two different solutes and are described well by calculations within the Bethe- Salpeter formalism for snapshots from ab initio molecular dynamics simulations. The agreement between experimental and simulation results allows us to use the computations for a detailed fingerprinting analysis in an effort to elucidate the local atomic structure and hydrogen-bonding topology in these relevant solutions. We observe that both electrolytes, especially NaOH, enhance hydrogen bonding and tetrahedrality in the water structure at supercritical conditions, in particular in the vicinity of the hydration shells. This effect is accompanied with the association of the HCl and NaOH molecules at elevated temperatures.}, language = {en} } @article{AbouserieZehbeMetzneretal.2017, author = {Abouserie, Ahed and Zehbe, Kerstin and Metzner, Philipp and Kelling, Alexandra and G{\"u}nter, Christina and Schilde, Uwe and Strauch, Peter and K{\"o}rzd{\"o}rfer, Thomas and Taubert, Andreas}, title = {Alkylpyridinium Tetrahalidometallate Ionic Liquids and Ionic Liquid Crystals: Insights into the Origin of Their Phase Behavior}, series = {European journal of inorganic chemistry : a journal of ChemPubSoc Europe}, journal = {European journal of inorganic chemistry : a journal of ChemPubSoc Europe}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1434-1948}, doi = {10.1002/ejic.201700826}, pages = {5640 -- 5649}, year = {2017}, abstract = {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.}, language = {en} } @article{AbouserieZehbeMetzneretal.2017, author = {Abouserie, Ahed and Zehbe, Kerstin and Metzner, Philipp and Kelling, Alexandra and G{\"u}nter, Christina and Schilde, Uwe and Strauch, Peter and K{\"o}rzd{\"o}rfer, Thomas and Taubert, Andreas}, title = {Alkylpyridinium Tetrahalidometallate Ionic Liquids and Ionic Liquid Crystals: Insights into the Origin of Their Phase Behavior}, series = {European journal of inorganic chemistry : a journal of ChemPubSoc Europe}, journal = {European journal of inorganic chemistry : a journal of ChemPubSoc Europe}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1434-1948}, doi = {10.1002/ejic.201700826}, pages = {5640 -- 5649}, year = {2017}, abstract = {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.}, language = {en} } @phdthesis{Nitze2017, author = {Nitze, Ingmar}, title = {Remote sensing of rapid permafrost landscape dynamics}, school = {Universit{\"a}t Potsdam}, pages = {151}, year = {2017}, language = {en} } @phdthesis{Irrgang2017, author = {Irrgang, Anna Maria}, title = {Temporal and spatial dynamics of Arctic coastal changes and the resulting impacts: Yukon Territory, Canada}, school = {Universit{\"a}t Potsdam}, pages = {154}, year = {2017}, language = {en} } @phdthesis{Murawski2017, author = {Murawski, Aline}, title = {Trends in precipitation over Germany and the Rhine basin related to changes in weather patterns}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-412725}, school = {Universit{\"a}t Potsdam}, pages = {112}, year = {2017}, abstract = {Niederschlag als eine der wichtigsten meteorologischen Gr{\"o}ßen f{\"u}r Landwirtschaft, Wasserversorgung und menschliches Wohlbefinden hat schon immer erh{\"o}hte Aufmerksamkeit erfahren. Niederschlagsmangel kann verheerende Auswirkungen haben, wie z.B. Missernten und Wasserknappheit. {\"U}berm{\"a}ßige Niederschl{\"a}ge andererseits bergen jedoch ebenfalls Gefahren in Form von Hochwasser oder Sturzfluten und wiederum Missernten. Daher wurde viel Arbeit in die Detektion von Niederschlags{\"a}nderungen und deren zugrundeliegende Prozesse gesteckt. Insbesondere angesichts von Klimawandel und unter Ber{\"u}cksichtigung des Zusammenhangs zwischen Temperatur und atmosph{\"a}rischer Wasserhaltekapazit{\"a}t, ist großer Bedarf an Forschung zum Verst{\"a}ndnis der Auswirkungen von Klimawandel auf Niederschlags{\"a}nderungen gegeben. Die vorliegende Arbeit hat das Ziel, vergangene Ver{\"a}nderungen in Niederschlag und anderen meteorologischen Variablen zu verstehen. F{\"u}r verschiedene Zeitr{\"a}ume wurden Tendenzen gefunden und mit entsprechenden Ver{\"a}nderungen in der großskaligen atmosph{\"a}rischen Zirkulation in Zusammenhang gebracht. Die Ergebnisse dieser Arbeit k{\"o}nnen als Grundlage f{\"u}r die Attributierung von Hochwasserver{\"a}nderungen zu Klimawandel genutzt werden. Die Annahmen f{\"u}r die Maßstabsverkleinerung („Downscaling") der Daten von großskaligen Zirkulationsmodellen auf die lokale Skala wurden hier getestet und verifziert. In einem ersten Schritt wurden Niederschlagsver{\"a}nderungen in Deutschland analysiert. Dabei lag der Fokus nicht nur auf Niederschlagssummen, sondern auch auf Eigenschaften der statistischen Verteilung, {\"U}bergangswahrscheinlichkeiten als Maß f{\"u}r Trocken- und Niederschlagsperioden und Extremniederschlagsereignissen. Den r{\"a}umlichen Fokus auf das Rheineinzugsgebiet, das gr{\"o}ßte Flusseinzugsgebiet Deutschlands und einer der Hauptwasserwege Europas, verlagernd, wurden nachgewiesene Ver{\"a}nderungen in Niederschlag und anderen meteorologischen Gr{\"o}ßen in Bezug zu einer „optimierten" Wetterlagenklassifikation analysiert. Die Wetterlagenklassifikation wurde unter der Maßgabe entwickelt, die Varianz des lokalen Klimas bestm{\"o}glich zu erkl{\"a}ren. Die letzte hier behandelte Frage dreht sich darum, ob die beobachteten Ver{\"a}nderungen im lokalen Klima eher H{\"a}ufigkeits{\"a}nderungen der Wetterlagen zuzuordnen sind oder einer Ver{\"a}nderung der Wetterlagen selbst. Eine gebr{\"a}uchliche Annahme f{\"u}r einen Downscaling-Ansatz mit Hilfe von Wetterlagen und einem stochastischen Wettergenerator ist, dass Klimawandel sich allein durch eine Ver{\"a}nderung der H{\"a}ufigkeit von Wetterlagen ausdr{\"u}ckt, die Eigenschaften der Wetterlagen dabei jedoch konstant bleiben. Diese Annahme wurde {\"u}berpr{\"u}ft und die F{\"a}higkeit der neuesten Generation von Zirkulationsmodellen, diese Wetterlagen zu reproduzieren, getestet. Niederschlagsver{\"a}nderungen in Deutschland im Zeitraum 1951-2006 lassen sich zusammenfassen als negativ im Sommer und positiv in allen anderen Jahreszeiten. Verschiedene Niederschlagscharakteristika best{\"a}tigen die Tendenz in den Niederschlagssummen: w{\"a}hrend mittlere und extreme Niederschlagstageswerte im Winter zugenommen haben, sind auch zusammenh{\"a}ngende Niederschlagsperioden l{\"a}nger geworden (ausgedr{\"u}ckt als eine gestiegene Wahrscheinlichkeit f{\"u}r einen Tag mit Niederschlag gefolgt von einem weiteren nassen Tag). Im Sommer wurde das Gegenteil beobachtet: gesunkene Niederschlagssummen, untermauert von verringerten Mittel- und Extremwerten und l{\"a}ngeren Trockenperioden. Abseits dieser allgemeinen Zusammenfassung f{\"u}r das gesamte Gebiet Deutschlands, ist die r{\"a}umliche Verteilung von Niederschlagsver{\"a}nderungen deutlich heterogener. Vermehrter Niederschlag im Winter wurde haupts{\"a}chlich im Nordwesten und S{\"u}dosten Deutschlands beobachtet, w{\"a}hrend im Fr{\"u}hling die st{\"a}rksten Ver{\"a}nderungen im Westen und im Herbst im S{\"u}den aufgetreten sind. Das saisonale Bild wiederum l{\"o}st sich f{\"u}r die zugeh{\"o}rigen Monate auf, z.B. setzt sich der Anstieg im Herbstniederschlag aus deutlich vermehrtem Niederschlag im S{\"u}dwesten im Oktober und im S{\"u}dosten im November zusammen. Diese Ergebnisse betonen die starken r{\"a}umlichen Zusammenh{\"a}nge der Niederschlags{\"a}nderungen. Der n{\"a}chste Schritt hinsichtlich einer Zuordnung von Niederschlagsver{\"a}nderungen zu {\"A}nderungen in großskaligen Zirkulationsmustern, war die Ableitung einer Wetterlagenklassifikation, die die betrachteten lokalen Klimavariablen hinreichend stratifizieren kann. Fokussierend auf Temperatur, Globalstrahlung und Luftfeuchte zus{\"a}tzlich zu Niederschlag, wurde eine Klassifikation basierend auf Luftdruck, Temperatur und spezifischer Luftfeuchtigkeit als am besten geeignet erachtet, die Varianz der lokalen Variablen zu erkl{\"a}ren. Eine vergleichsweise hohe Anzahl von 40 Wetterlagen wurde ausgew{\"a}hlt, die es erlaubt, typische Druckmuster durch die zus{\"a}tzlich verwendete Temperaturinformation einzelnen Jahreszeiten zuzuordnen. W{\"a}hrend die F{\"a}higkeit, Varianz im Niederschlag zu erkl{\"a}ren, relativ gering ist, ist diese deutlich besser f{\"u}r Globalstrahlung und nat{\"u}rlich Temperatur. Die meisten der aktuellen Zirkulationsmodelle des CMIP5-Ensembles sind in der Lage, die Wetterlagen hinsichtlich H{\"a}ufigkeit, Saisonalit{\"a}t und Persistenz hinreichend gut zu reproduzieren. Schließlich wurden dieWetterlagen bez{\"u}glich Ver{\"a}nderungen in ihrer H{\"a}ufigkeit, Saisonalit{\"a}t und Persistenz, sowie der Wetterlagen-spezifischen Niederschl{\"a}ge und Temperatur, untersucht. Um Unsicherheiten durch die Wahl eines bestimmten Analysezeitraums auszuschließen, wurden alle m{\"o}glichen Zeitr{\"a}ume mit mindestens 31 Jahren im Zeitraum 1901-2010 untersucht. Dadurch konnte die Annahme eines konstanten Zusammenhangs zwischen Wetterlagen und lokalem Wetter gr{\"u}ndlich {\"u}berpr{\"u}ft werden. Es wurde herausgefunden, dass diese Annahme nur zum Teil haltbar ist. W{\"a}hrend Ver{\"a}nderungen in der Temperatur haupts{\"a}chlich auf Ver{\"a}nderungen in der Wetterlagenh{\"a}ufigkeit zur{\"u}ckzuf{\"u}hren sind, wurde f{\"u}r Niederschlag ein erheblicher Teil von Ver{\"a}nderungen innerhalb einzelner Wetterlagen gefunden. Das Ausmaß und sogar das Vorzeichen der Ver{\"a}nderungen h{\"a}ngt hochgradig vom untersuchten Zeitraum ab. Die H{\"a}ufigkeit einiger Wetterlagen steht in direkter Beziehung zur langfristigen Variabilit{\"a}t großskaliger Zirkulationsmuster. Niederschlagsver{\"a}nderungen variieren nicht nur r{\"a}umlich, sondern auch zeitlich - Aussagen {\"u}ber Tendenzen sind nur in Bezug zum jeweils untersuchten Zeitraum g{\"u}ltig. W{\"a}hrend ein Teil der Ver{\"a}nderungen auf {\"A}nderungen der großskaligen Zirkulation zur{\"u}ckzuf{\"u}hren ist, gibt es auch deutliche Ver{\"a}nderungen innerhalb einzelner Wetterlagen. Die Ergebnisse betonen die Notwendigkeit f{\"u}r einen sorgf{\"a}ltigen Nachweis von Ver{\"a}nderungen m{\"o}glichst verschiedene Zeitr{\"a}ume zu untersuchen und mahnen zur Vorsicht bei der Anwendung von Downscaling-Ans{\"a}tzen mit Hilfe von Wetterlagen, da diese die Auswirkungen von Klimaver{\"a}nderungen durch das Vernachl{\"a}ssigen von Wetterlagen-internen Ver{\"a}nderungen falsch einsch{\"a}tzen k{\"o}nnten.}, language = {en} } @phdthesis{Golly2017, author = {Golly, Antonius}, title = {Formation and evolution of channel steps and their role for sediment dynamics in a steep mountain stream}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-411728}, school = {Universit{\"a}t Potsdam}, pages = {180}, year = {2017}, abstract = {Steep mountain channels are an important component of the fluvial system. On geological timescales, they shape mountain belts and counteract tectonic uplift by erosion. Their channels are strongly coupled to hillslopes and they are often the main source of sediment transported downstream to low-gradient rivers and to alluvial fans, where commonly settlements in mountainous areas are located. Hence, mountain streams are the cause for one of the main natural hazards in these regions. Due to climate change and a pronounced populating of mountainous regions the attention given to this threat is even growing. Although quantitative studies on sediment transport have significantly advanced our knowledge on measuring and calibration techniques we still lack studies of the processes within mountain catchments. Studies examining the mechanisms of energy and mass exchange on small temporal and spatial scales in steep streams remain sparse in comparison to low-gradient alluvial channels. In the beginning of this doctoral project, a vast amount of experience and knowledge of a steep stream in the Swiss Prealps had to be consolidated in order to shape the principal aim of this research effort. It became obvious, that observations from within the catchment are underrepresented in comparison to experiments performed at the catchment's outlet measuring fluxes and the effects of the transported material. To counteract this imbalance, an examination of mass fluxes within the catchment on the process scale was intended. Hence, this thesis is heavily based on direct field observations, which are generally rare in these environments in quantity and quality. The first objective was to investigate the coupling of the channel with surrounding hillslopes, the major sources of sediment. This research, which involved the monitoring of the channel and adjacent hillslopes, revealed that alluvial channel steps play a key role in coupling of channel and hillslopes. The observations showed that hillslope stability is strongly associated with the step presence and an understanding of step morphology and stability is therefore crucial in understanding sediment mobilization. This finding refined the way we think about the sediment dynamics in steep channels and motivated continued research of the step dynamics. However, soon it became obvious that the technological basis for developing field tests and analyzing the high resolution geometry measured in the field was not available. Moreover, for many geometrical quantities in mountain channels definitions and a clear scientific standard was not available. For example, these streams are characterized by a high spatial variability of the channel banks, preventing straightforward calculations of the channel width without a defined reference. Thus, the second and inevitable part of this thesis became the development and evaluation of scientific tools in order to investigate the geometrical content of the study reach thoroughly. The developed framework allowed the derivation of various metrics of step and channel geometry which facilitated research on the a large data set of observations of channel steps. In the third part, innovative, physically-based metrics have been developed and compared to current knowledge on step formation, suggested in the literature. With this analyses it could be demonstrated that the formation of channel steps follow a wide range of hydraulic controls. Due to the wide range of tested parameters channel steps observed in a natural stream were attributed to different mechanisms of step formation, including those based on jamming and those based on key-stones. This study extended our knowledge on step formation in a steep stream and harmonized different, often time seen as competing, processes of step formation. This study was based on observations collected at one point in time. In the fourth part of this project, the findings of the snap-shot observations were extended in the temporal dimension and the derived concepts have been utilized to investigate reach-scale step patterns in response to large, exceptional flood events. The preliminary results of this work based on the long-term analyses of 7 years of long profile surveys showed that the previously observed channel-hillslope mechanism is the responsible for the short-term response of step formation. The findings of the long-term analyses of step patterns drew a bow to the initial observations of a channel-hillslope system which allowed to join the dots in the dynamics of steep stream. Thus, in this thesis a broad approach has been chosen to gain insights into the complex system of steep mountain rivers. The effort includes in situ field observations (article I), the development of quantitative scientific tools (article II), the reach-scale analyses of step-pool morphology (article III) and its temporal evolution (article IV). With this work our view on the processes within the catchment has been advanced towards a better mechanistic understanding of these fluvial system relevant to improve applied scientific work.}, language = {en} } @phdthesis{Theuring2017, author = {Theuring, Philipp Christian}, title = {Suspended sediments in the Kharaa River, sources and impacts}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-410550}, school = {Universit{\"a}t Potsdam}, pages = {135}, year = {2017}, abstract = {Anthropogenically amplified erosion leads to increased fine-grained sediment input into the fluvial system in the 15.000 km2 Kharaa River catchment in northern Mongolia and constitutes a major stressing factor for the aquatic ecosystem. This study uniquely combines the application of intensive monitoring, source fingerprinting and catchment modelling techniques to allow for the comparison of the credibility and accuracy of each single method. High-resolution discharge data were used in combination with daily suspended solid measurements to calculate the suspended sediment budget and compare it with estimations of the sediment budget model SedNet. The comparison of both techniques showed that the development of an overall sediment budget with SedNet was possible, yielding results in the same order of magnitude (20.3 kt a- 1 and 16.2 kt a- 1). Radionuclide sediment tracing, using Be-7, Cs-137 and Pb-210 was applied to differentiate sediment sources for particles < 10μm from hillslope and riverbank erosion and showed that riverbank erosion generates 74.5\% of the suspended sediment load, whereas surface erosion contributes 21.7\% and gully erosion only 3.8\%. The contribution of the single subcatchments of the Kharaa to the suspended sediment load was assessed based on their variation in geochemical composition (e.g. in Ti, Sn, Mo, Mn, As, Sr, B, U, Ca and Sb). These variations were used for sediment source discrimination with geochemical composite fingerprints based on Genetic Algorithm driven Discriminant Function Analysis, the Kruskal-Wallis H-test and Principal Component Analysis. The contributions of the individual sub-catchment varied from 6.4\% to 36.2\%, generally showing higher contributions from the sub-catchments in the middle, rather than the upstream portions of the study area. The results indicate that river bank erosion generated by existing grazing practices of livestock is the main cause for elevated fine sediment input. Actions towards the protection of the headwaters and the stabilization of the river banks within the middle reaches were identified as the highest priority. Deforestation and by lodging and forest fires should be prevented to avoid increased hillslope erosion in the mountainous areas. Mining activities are of minor importance for the overall catchment sediment load but can constitute locally important point sources for particular heavy metals in the fluvial system.}, language = {en} } @phdthesis{Schmidt2017, author = {Schmidt, Katja}, title = {Assessing, testing, and implementing socio-cultural valuation methods to operationalise ecosystem services in land use management}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-411049}, school = {Universit{\"a}t Potsdam}, pages = {165}, year = {2017}, abstract = {Ecosystem services (ESs) are defined as the contributions that ecosystems make to human wellbeing and are increasingly being used as an approach to explore the importance of ecosystems for humans through their valuation. Although value plurality has been recognised long before the mainstreaming of ESs research, socio-cultural valuation is still underrepresented in ESs assessments. It is the central goal of this PhD dissertation to explore the ability of socio-cultural valuation methods for the operationalisation of ESs research in land management. To address this, I formulated three research objectives that are briefly outlined below and relate to the three studies conducted during this dissertation. The first objective relates to the assessment of the current role of socio-cultural valuation in ESs research. Human values are central to ESs research yet non-monetary socio-cultural valuation methods have been found underrepresented in the field of ESs science. In regard to the unbalanced consideration of value domains and conceptual uncertainties, I perform a systematic literature review aiming to answer the research question: To what extent have socio-cultural values been addressed in ESs assessments. The second objective aims to test socio-cultural valuation methods of ESs and their relevance for land use preferences by exploring their methodological opportunities and limitations. Socio-cultural valuation methods have only recently become a focus in ESs research and therefore bear various uncertainties in regard to their methodological implications. To overcome these uncertainties, I analysed responses to a visitor survey. The research questions related to the second objective were: What are the implications of different valuation methods for ESs values? To what extent are land use preferences explained by socio-cultural values of ESs? The third objective addressed in this dissertation is the implementation of ESs research into land management through socio-cultural valuation. Though it is emphasised that the ESs approach can assist decision making, there is little empirical evidence of the effect of ESs knowledge on land management. I proposed a way to implement transdisciplinary, spatially explicit research on ESs by answering the following research questions: Which landscape features underpinning ESs supply are considered in land management? How can participatory approaches accounting for ESs be operationalised in land management? The empirical research resulted in five main findings that provide answers to the research questions. First, this dissertation provides evidence that socio-cultural values are an integral part of ESs research. I found that they can be assessed for provisioning, regulating, and cultural services though they are linked to cultural services to a greater degree. Socio-cultural values have been assessed by monetary and non-monetary methods and their assessment is effectively facilitated by stakeholder participation. Second, I found that different methods of socio-cultural valuation revealed different information. Whereas rating revealed a general value of ESs, weighting was found more suitable to identify priorities across ESs. Value intentions likewise differed in the distribution of values, generally implying a higher value for others than for respondents themselves. Third, I showed that ESs values were distributed similarly across groups with differing land use preferences. Thus, I provided empirical evidence that ESs values and landscape values should not be used interchangeably. Fourth, I showed which landscape features important for ESs supply in a Scottish regional park are not sufficiently accounted for in the current management strategy. This knowledge is useful for the identification of priority sites for land management. Finally, I provide an approach to explore how ESs knowledge elicited by participatory mapping can be operationalised in land management. I demonstrate how stakeholder knowledge and values can be used for the identification of ESs hotspots and how these hotspots can be compared to current management priorities. This dissertation helps to bridge current gaps of ESs science by advancing the understanding of the current role of socio-cultural values in ESs research, testing different methods and their relevance for land use preferences, and implementing ESs knowledge into land management. If and to what extent ESs and their values are implemented into ecosystem management is mainly the choice of the management. An advanced understanding of socio-cultural valuation methods contributes to the normative basis of this management, while the proposal for the implementation of ESs in land management presents a practical approach of how to transfer this type of knowledge into practice. The proposed methods for socio-cultural valuation can support guiding land management towards a balanced consideration of ESs and conservation goals.}, language = {en} } @phdthesis{Bredow2017, author = {Bredow, Eva}, title = {Geodynamic models of plume-ridge interaction}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-411732}, school = {Universit{\"a}t Potsdam}, pages = {104}, year = {2017}, abstract = {According to the classical plume hypothesis, mantle plumes are localized upwellings of hot, buoyant material in the Earth's mantle. They have a typical mushroom shape, consisting of a large plume head, which is associated with the formation of voluminous flood basalts (a Large Igneous Province) and a narrow plume tail, which generates a linear, age-progressive chain of volcanic edifices (a hotspot track) as the tectonic plate migrates over the relatively stationary plume. Both plume heads and tails reshape large areas of the Earth's surface over many tens of millions of years. However, not every plume has left an exemplary record that supports the classical hypothesis. The main objective of this thesis is therefore to study how specific hotspots have created the crustal thickness pattern attributed to their volcanic activities. Using regional geodynamic models, the main chapters of this thesis address the challenge of deciphering the three individual (and increasingly complex) Réunion, Iceland, and Kerguelen hotspot histories, especially focussing on the interactions between the respective plume and nearby spreading ridges. For this purpose, the mantle convection code ASPECT is used to set up three-dimensional numerical models, which consider the specific local surroundings of each plume by prescribing time-dependent boundary conditions for temperature and mantle flow. Combining reconstructed plate boundaries and plate motions, large-scale global flow velocities and an inhomogeneous lithosphere thickness distribution together with a dehydration rheology represents a novel setup for regional convection models. The model results show the crustal thickness pattern produced by the plume, which is compared to present-day topographic structures, crustal thickness estimates and age determinations of volcanic provinces associated with hotspot activity. Altogether, the model results agree well with surface observations. Moreover, the dynamic development of the plumes in the models provide explanations for the generation of smaller, yet characteristic volcanic features that were previously unexplained. Considering the present-day state of a model as a prediction for the current temperature distribution in the mantle, it cannot only be compared to observations on the surface, but also to structures in the Earth's interior as imaged by seismic tomography. More precisely, in the case of the Réunion hotspot, the model demonstrates how the distinctive gap between the Maldives and Chagos is generated due to the combination of the ridge geometry and plume-ridge interaction. Further, the Rodrigues Ridge is formed as the surface expression of a long-distance sublithospheric flow channel between the upwelling plume and the closest ridge segment, confirming the long-standing hypothesis of Morgan (1978) for the first time in a dynamic context. The Réunion plume has been studied in connection with the seismological RHUM-RUM project, which has recently provided new seismic tomography images that yield an excellent match with the geodynamic model. Regarding the Iceland plume, the numerical model shows how plume material may have accumulated in an east-west trending corridor of thin lithosphere across Greenland and resulted in simultaneous melt generation west and east of Greenland. This provides an explanation for the extremely widespread volcanic material attributed to magma production of the Iceland hotspot and demonstrates that the model setup is also able to explain more complicated hotspot histories. The Iceland model results also agree well with newly derived seismic tomographic images. The Kerguelen hotspot has an extremely complex history and previous studies concluded that the plume might be dismembered or influenced by solitary waves in its conduit to produce the reconstructed variable melt production rate. The geodynamic model, however, shows that a constant plume influx can result in a variable magma production rate if the plume interacts with nearby mid-ocean ridges. Moreover, the Ninetyeast Ridge in the model is created by on-ridge activities, while the Kerguelen plume was located beneath the Australian plate. This is also a contrast to earlier studies, which described the Ninetyeast Ridge as the result of the Indian plate passing over the plume. Furthermore, the Amsterdam-Saint Paul Plateau in the model is the result of plume material flowing from the upwelling toward the Southeast Indian Ridge, whereas previous geochemical studies attributed that volcanic province to a separate deep plume. In summary, the three case studies presented in this thesis consistently highlight the importance of plume-ridge interaction in order to reconstruct the overall volcanic hotspot record as well as specific smaller features attributed to a certain hotspot. They also demonstrate that it is not necessary to attribute highly complicated properties to a specific plume in order to account for complex observations. Thus, this thesis contributes to the general understanding of plume dynamics and extends the very specific knowledge about the Réunion, Iceland, and Kerguelen mantle plumes.}, language = {en} } @phdthesis{Tanski2017, author = {Tanski, George}, title = {Fate of organic matter mobilized from eroding permafrost coasts}, school = {Universit{\"a}t Potsdam}, pages = {IX, 106, 57 S.}, year = {2017}, language = {en} } @phdthesis{Herbrich2017, author = {Herbrich, Marcus}, title = {Einfluss der erosionsbedingten Pedogenese auf den Wasserund Stoffhaushalt ackerbaulich genutzter B{\"o}den der Grundmor{\"a}nenbodenlandschaft NO-Deutschlands - hydropedologische Untersuchungen mittels w{\"a}gbarer Pr{\"a}zisionslysimeter}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-408561}, school = {Universit{\"a}t Potsdam}, pages = {186}, year = {2017}, abstract = {In the arable soil landscape of hummocky ground moraines, an erosion-affected spatial differentiation of soils can be observed. Man-made erosion leads to soil profile modifications along slopes with changed solum thickness and modified properties of soil horizons due to water erosion in combination with tillage operations. Soil erosion creates, thereby, spatial patterns of soil properties (e.g., texture and organic matter content) and differences in crop development. However, little is known about the manner in which water fluxes are affected by soil-crop interactions depending on contrasting properties of differently-developed soil horizons and how water fluxes influence the carbon transport in an eroded landscape. To identify such feedbacks between erosion-induced soil profile modifications and the 1D-water and solute balance, high-precision weighing lysimeters equipped with a wide range of sensor technique were filled with undisturbed soil monoliths that differed in the degree of past soil erosion. Furthermore, lysimeter effluent concentrations were analyzed for dissolved carbon fractions in bi-weekly intervals. The water balance components measured by high precision lysimeters varied from the most eroded to the less eroded monolith up to 83 \% (deep drainage) primarily caused due to varying amounts of precipitation and evapotranspiration for a 3-years period. Here, interactions between crop development and contrasting rainfall interception by above ground biomass could explain differences in water balance components. Concentrations of dissolved carbon in soil water samples were relatively constant in time, suggesting carbon leaching was mainly affected by water fluxes in this observation period. For the lysimeter-based water balance analysis, a filtering scheme was developed considering temporal autocorrelation. The minute-based autocorrelation analysis of mass changes from lysimeter time series revealed characteristic autocorrelation lengths ranging from 23 to 76 minutes. Thereby, temporal autocorrelation provided an optimal approximation of precipitation quantities. However, the high temporal resolution in lysimeter time series is restricted by the lengths of autocorrelation. Erosion-induced but also gradual changes in soil properties were reflected by dynamics of soil water retention properties in the lysimeter soils. Short-term and long-term hysteretic water retention data suggested seasonal wettability problems of soils increasingly limited rewetting of previously dried pore regions. Differences in water retention were assigned to soil tillage operations and the erosion history at different slope positions. The threedimensional spatial pattern of soil types that result from erosional soil profile modifications were also reflected in differences of crop root development at different landscape positions. Contrasting root densities revealed positive relations of root and aboveground plant characteristics. Differences in the spatially-distributed root growth between different eroded soil types provided indications that root development was affected by the erosion-induced soil evolution processes. Overall, the current thesis corroborated the hypothesis that erosion-induced soil profile modifications affect the soil water balance, carbon leaching and soil hydraulic properties, but also the crop root system is influenced by erosion-induced spatial patterns of soil properties in the arable hummocky post glacial soil landscape. The results will help to improve model predictions of water and solute movement in arable soils and to understand interactions between soil erosion and carbon pathways regarding sink-or-source terms in landscapes.}, language = {en} } @phdthesis{Gudipudi2017, author = {Gudipudi, Venkata Ramana}, title = {Cities and global sustainability}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-407113}, school = {Universit{\"a}t Potsdam}, pages = {xxii, 101}, year = {2017}, abstract = {In the wake of 21st century, humanity witnessed a phenomenal raise of urban agglomerations as powerhouses for innovation and socioeconomic growth. Driving much of national (and in few instances even global) economy, such a gargantuan raise of cities is also accompanied by subsequent increase in energy, resource consumption and waste generation. Much of anthropogenic transformation of Earth's environment in terms of environmental pollution at local level to planetary scale in the form of climate change is currently taking place in cities. Projected to be crucibles for entire humanity by the end of this century, the ultimate fate of humanity predominantly lies in the hands of technological innovation, urbanites' attitudes towards energy/resource consumption and development pathways undertaken by current and future cities. Considering the unparalleled energy, resource consumption and emissions currently attributed to global cities, this thesis addresses these issues from an efficiency point of view. More specifically, this thesis addresses the influence of population size, density, economic geography and technology in improving urban greenhouse gas (GHG) emission efficiency and identifies the factors leading to improved eco-efficiency in cities. In order to investigate the in uence of these factors in improving emission and resource efficiency in cities, a multitude of freely available datasets were coupled with some novel methodologies and analytical approaches in this thesis. Merging the well-established Kaya Identity to the recently developed urban scaling laws, an Urban Kaya Relation is developed to identify whether large cities are more emission efficient and the intrinsic factors leading to such (in)efficiency. Applying Urban Kaya Relation to a global dataset of 61 cities in 12 countries, this thesis identifed that large cities in developed regions of the world will bring emission efficiency gains because of the better technologies implemented in these cities to produce and utilize energy consumption while the opposite is the case for cities in developing regions. Large cities in developing countries are less efficient mainly because of their affluence and lack of efficient technologies. Apart from the in uence of population size on emission efficiency, this thesis identified the crucial role played by population density in improving building and on-road transport sector related emission efficiency in cities. This is achieved by applying the City Clustering Algorithm (CCA) on two different gridded land use datasets and a standard emission inventory to attribute these sectoral emissions to all inhabited settlements in the USA. Results show that doubling the population density would entail a reduction in the total CO2 emissions in buildings and on-road sectors typically by at least 42 \%. Irrespective of their population size and density, cities are often blamed for their intensive resource consumption that threatens not only local but also global sustainability. This thesis merged the concept of urban metabolism with benchmarking and identified cities which are eco-efficient. These cities enable better socioeconomic conditions while being less burden to the environment. Three environmental burden indicators (annual average NO2 concentration, per capita waste generation and water consumption) and two socioeconomic indicators (GDP per capita and employment ratio) for 88 most populous European cities are considered in this study. Using two different non-parametric ranking methods namely regression residual ranking and Data Envelopment Analysis (DEA), eco-efficient cities and their determining factors are identified. This in-depth analysis revealed that mature cities with well-established economic structures such as Munich, Stockholm and Oslo are eco-efficient. Further, correlations between objective eco-efficiency ranking with each of the indicator rankings and the ranking of urbanites' subjective perception about quality of life are analyzed. This analysis revealed that urbanites' perception about quality of life is not merely confined to the socioeconomic well-being but rather to their combination with lower environmental burden. In summary, the findings of this dissertation has three general conclusions for improving emission and ecological efficiency in cities. Firstly, large cities in emerging nations face a huge challenge with respect to improving their emission efficiency. The task in front of these cities is threefold: (1) deploying efficient technologies for the generation of electricity and improvement of public transportation to unlock their leap frogging potential, (2) addressing the issue of energy poverty and (3) ensuring that these cities do not develop similar energy consumption patterns with infrastructure lock-in behavior similar to those of cities in developed regions. Secondly, the on-going urban sprawl as a global phenomenon will decrease the emission efficiency within the building and transportation sector. Therefore, local policy makers should identify adequate fiscal and land use policies to curb urban sprawl. Lastly, since mature cities with well-established economic structures are more eco-efficient and urbanites' perception re ects its combination with decreasing environmental burden; there is a need to adopt and implement strategies which enable socioeconomic growth in cities whilst decreasing their environment burden.}, language = {en} } @phdthesis{OseiTutu2017, author = {Osei Tutu, Anthony}, title = {Linking global mantle dynamics with lithosphere dynamics using the geoid, plate velocities and lithosphere stress state as constraints}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-407057}, school = {Universit{\"a}t Potsdam}, pages = {108}, year = {2017}, abstract = {Lithospheric plates move over the low viscosity asthenosphere balancing several forces. The driving forces include basal shear stress exerted by mantle convection and plate boundary forces such as slab pull and ridge push, whereas the resisting forces include inter-plate friction, trench resistance, and cratonic root resistance. These generate plate motions, the lithospheric stress field and dynamic topography which are observed with different geophysical methods. The orientation and tectonic regime of the observed crustal/lithospheric stress field further contribute to our knowledge of different deformation processes occurring within the Earth's crust and lithosphere. Using numerical models previous studies were able to identify major forces generating stresses in the crust and lithosphere which also contribute to the formation of topography as well as driving lithospheric plates. They showed that the first-order stress pattern explaining about 80\,\\% of the stress field originates from a balance of forces acting at the base of the moving lithospheric plates due to convective flow in the underlying mantle. The remaining second-order stress pattern is due to lateral density variations in the crust and lithosphere in regions of pronounced topography and high gravitational potential, such as the Himalayas and mid-ocean ridges. By linking global lithosphere dynamics to deep mantle flow this study seeks to evaluate the influence of shallow and deep density heterogenities on plate motions, lithospheric stress field and dynamic topography using the geoid as a major constraint for mantle rheology. We use the global 3D lithosphere-asthenosphere model SLIM3D with visco-elasto-plastic rheology coupled at 300 km depth to a spectral model of mantle flow. The complexity of the lithosphere-asthenosphere component allows for the simulation of power-law rheology with creep parameters accounting for both diffusion and dislocation creep within the uppermost 300 km. First we investigate the influence of intra-plate friction and asthenospheric viscosity on present-day plate motions. Previous modelling studies have suggested that small friction coefficients (µ < 0.1, yield stress ~ 100 MPa) can lead to plate tectonics in models of mantle convection. Here we show that, in order to match present-day plate motions and net rotation, the frictional parameter must be less than 0.05. We are able to obtain a good fit with the magnitude and orientation of observed plate velocities (NUVEL-1A) in a no-net-rotation (NNR) reference frame with µ < 0.04 and minimum asthenosphere viscosity ~ 5*10e19 Pas to 10e20 Pas. Our estimates of net rotation (NR) of the lithosphere suggest that amplitudes ~ 0.1-0.2 °/Ma, similar to most observation-based estimates, can be obtained with asthenosphere viscosity cutoff values of ~ 10e19 Pas to 5*10e19 Pas and friction coefficient µ < 0.05. The second part of the study investigates further constraints on shallow and deep mantle heterogeneities causing plate motion by predicting lithosphere stress field and topography and validating with observations. Lithosphere stresses and dynamic topography are computed using the modelling setup and rheological parameters for prescribed plate motions. We validate our results with the World Stress Map 2016 (WSM2016) and the observed residual topography. Here we tested a number of upper mantle thermal-density structures. The one used to calculate plate motions is considered the reference thermal-density structure. This model is derived from a heat flow model combined with a sea floor age model. In addition we used three different thermal-density structures derived from global S-wave velocity models to show the influence of lateral density heterogeneities in the upper 300 km on model predictions. A large portion of the total dynamic force generating stresses in the crust/lithosphere has its origin in the deep mantle, while topography is largely influenced by shallow heterogeneities. For example, there is hardly any difference between the stress orientation patterns predicted with and without consideration of the heterogeneities in the upper mantle density structure across North America, Australia, and North Africa. However, the crust is dominant in areas of high altitude for the stress orientation compared to the all deep mantle contribution. This study explores the sensitivity of all the considered surface observables with regards to model parameters providing insights into the influence of the asthenosphere and plate boundary rheology on plate motion as we test various thermal-density structures to predict stresses and topography.}, language = {en} } @phdthesis{Schmidt2017, author = {Schmidt, Silke Regina}, title = {Analyzing lakes in the time frequency domain}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-406955}, school = {Universit{\"a}t Potsdam}, pages = {VIII, 126}, year = {2017}, abstract = {The central aim of this thesis is to demonstrate the benefits of innovative frequency-based methods to better explain the variability observed in lake ecosystems. Freshwater ecosystems may be the most threatened part of the hydrosphere. Lake ecosystems are particularly sensitive to changes in climate and land use because they integrate disturbances across their entire catchment. This makes understanding the dynamics of lake ecosystems an intriguing and important research priority. This thesis adds new findings to the baseline knowledge regarding variability in lake ecosystems. It provides a literature-based, data-driven and methodological framework for the investigation of variability and patterns in environmental parameters in the time frequency domain. Observational data often show considerable variability in the environmental parameters of lake ecosystems. This variability is mostly driven by a plethora of periodic and stochastic processes inside and outside the ecosystems. These run in parallel and may operate at vastly different time scales, ranging from seconds to decades. In measured data, all of these signals are superimposed, and dominant processes may obscure the signals of other processes, particularly when analyzing mean values over long time scales. Dominant signals are often caused by phenomena at long time scales like seasonal cycles, and most of these are well understood in the limnological literature. The variability injected by biological, chemical and physical processes operating at smaller time scales is less well understood. However, variability affects the state and health of lake ecosystems at all time scales. Besides measuring time series at sufficiently high temporal resolution, the investigation of the full spectrum of variability requires innovative methods of analysis. Analyzing observational data in the time frequency domain allows to identify variability at different time scales and facilitates their attribution to specific processes. The merit of this approach is subsequently demonstrated in three case studies. The first study uses a conceptual analysis to demonstrate the importance of time scales for the detection of ecosystem responses to climate change. These responses often occur during critical time windows in the year, may exhibit a time lag and can be driven by the exceedance of thresholds in their drivers. This can only be detected if the temporal resolution of the data is high enough. The second study applies Fast Fourier Transform spectral analysis to two decades of daily water temperature measurements to show how temporal and spatial scales of water temperature variability can serve as an indicator for mixing in a shallow, polymictic lake. The final study uses wavelet coherence as a diagnostic tool for limnology on a multivariate high-frequency data set recorded between the onset of ice cover and a cyanobacteria summer bloom in the year 2009 in a polymictic lake. Synchronicities among limnological and meteorological time series in narrow frequency bands were used to identify and disentangle prevailing limnological processes. Beyond the novel empirical findings reported in the three case studies, this thesis aims to more generally be of interest to researchers dealing with now increasingly available time series data at high temporal resolution. A set of innovative methods to attribute patterns to processes, their drivers and constraints is provided to help make more efficient use of this kind of data.}, language = {en} } @phdthesis{Siddiqui2017, author = {Siddiqui, Tarique Adnan}, title = {Long-term investigation of the lunar tide in the equatorial electrojet during stratospheric sudden warmings}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-406384}, school = {Universit{\"a}t Potsdam}, pages = {xvii, 116}, year = {2017}, abstract = {The ionosphere, which is strongly influenced by the Sun, is known to be also affected by meteorological processes. These processes, despite having their origin in the troposphere and stratosphere, interact with the upper atmosphere. Such an interaction between atmospheric layers is known as vertical coupling. During geomagnetically quiet times, when near-Earth space is not under the influence of solar storms, these processes become important drivers for ionospheric variability. Studying the link between these processes in the lower atmosphere and the ionospheric variability is important for our understanding of fundamental mechanisms in ionospheric and meteorological research. A prominent example of vertical coupling between the stratosphere and the ionosphere are the so-called stratospheric sudden warming (SSW) events that occur usually during northern winters and result in an increase in the polar stratospheric temperature and a reversal of the circumpolar winds. While the phenomenon of SSW is confined to the northern polar stratosphere, its influence on the ionosphere can be observed even at equatorial latitudes. During SSW events, the connection between the polar stratosphere and the equatorial ionosphere is believed to be through the modulation of global atmospheric tides. These tides are fundamental for the ionospheric E-region wind dynamo that generates electric fields and currents in the ionosphere. Observations of ionospheric currents indicate a large enhancement of the semidiurnal lunar tide in response to SSW events. Thus, the semidiurnal lunar tide becomes an important driver of ionospheric variability during SSW events. In this thesis, the ionospheric effect of SSW events is investigated in the equatorial region, where a narrow but an intense E-region current known as the equatorial electrojet (EEJ) flows above the dip equator during the daytime. The day-to-day variability of the EEJ can be determined from magnetic field records at geomagnetic observatories close to the dip equator. Such magnetic data are available for several decades and allows to investigate the impact of SSW events on the EEJ and, even more importantly, helps in understanding the effects of SSW events on the equatorial ionosphere. An excellent long-term record of the geomagnetic field at the equator from 1922 onwards is available for the observatory Huancayo in Peru and is extensively utilized in this study. The central subject of this thesis is the investigation of lunar tides in the EEJ during SSW events by analyzing long time series. This is done by estimating the lunar tidal amplitude in the EEJ from the magnetic records at Huancayo and by comparing them to measurements of the polar stratospheric wind and temperature, which led to the identification of the known SSW events from 1952 onwards. One goal of this thesis is to identify SSW events that predate 1952. To this end, superposed epoch analysis (SEA) is employed to establish a relationship between the lunar tidal power and the wind and temperature conditions in the lower atmosphere. A threshold value for the lunar tidal power is identified that is discriminative for the known SSW events. This threshold is then used to identify lunar tidal enhancements, which are indicative for any historic SSW events prior to 1952. It can be shown, that the number of lunar tidal enhancements and thus the occurrence frequency of historic SSW events between 1926 and 1952 is similar to the occurrence frequency of the known SSW events from 1952 onwards. Next to the classic SSW definition, the concept of polar vortex weakening (PVW) is utilized in this thesis. PVW is defined for higher latitudes and altitudes (≈ 40km) than the classical SSW definition (≈ 32km). The correlation between the timing and magnitude of lunar tidal enhancements in the EEJ and the timing and magnitude of PVW is found to be better than for the classic SSW definition. This suggests that the lunar tidal enhancements in the EEJ are closely linked to the state of the middle atmosphere. Geomagnetic observatories located in different longitudes at the dip equator allow investigating the longitudinally dependent variability of the EEJ during SSW events. For this purpose, the lunar tidal enhancements in the EEJ are determined for the Peruvian and Indian sectors during the major SSW events of the years 2006 and 2009. It is found that the lunar tidal amplitude shows similar enhancements in the Peruvian sector during both SSW events, while the enhancements are notably different for the two events in the Indian sector. In summary, this thesis shows that lunar tidal enhancements in the EEJ are indeed correlated to the occurrence of SSW events and they should be considered a prominent driver of low latitude ionospheric variability. Secondly, lunar tidal enhancements are found to be longitudinally variable. This suggests that regional effects, such as ionospheric conductivity and the geometry and strength of the geomagnetic field, also play an important role and have to be considered when investigating the mechanisms behind vertical coupling.}, language = {en} } @misc{Petersen2017, type = {Master Thesis}, author = {Petersen, Gesa Maria}, title = {Source array and receiver array analysis of Vogtland/ West Bohemia earthquake clusters}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-406671}, school = {Universit{\"a}t Potsdam}, pages = {107}, year = {2017}, abstract = {Die Region Vogtland/ West B{\"o}hmen im Grenzgebiet zwischen Deutschland und Tschechien ist bekannt f{\"u}r ihre geologische Aktivit{\"a}t. Holoz{\"a}ner Vulkanismus, Gasaustritte an Mofetten und Quellen und wiederkehrende Erdbebenschw{\"a}rme sind Ausdruck geodynamischer Prozesse im Untergrund. W{\"a}hrend des Erdbebenschwarms 2008/2009 in Nov{\´y} Kostel installierte die Universit{\"a}t Potsdam ein tempor{\"a}res Array in Rohrbach, in einer Epizentraldistanz von etwa 10 km und mit einer Aperatur von etwa 0.75 km. 22 Erdbeben wurden f{\"u}r Quellarray- beam forming ausgew{\"a}hlt. Quellarrays sind {\"o}rtliche Cluster von Erdbeben, die von einer Empf{\"a}ngerstation aufgezeichnet werden. Wegen der Reziprozit{\"a}t der Green'schen Funktionen k{\"o}nnen diese in {\"a}hnlicher Weise genutzt werden wie Empf{\"a}ngerarrays, bei denen mehrere Stationen ein einzelnes Beben aufzeichnen. Die Kreuzkorrelationskoeffizienten aller Beben des Quellarrays, aufgezeichnet an einer einzelnen Station, sind in der Regel h{\"o}her als f{\"u}r einzelne Ereignisse, die an allen Stationen des Empf{\"a}ngerarrays aufgezeichnet wurden. Dies deutet hinsichtlich der aufgel{\"o}sten Frequenzen auf einen heterogenen Untergrund unter den Array-Stationen und ein vergleichsweise homogenes Quellarray-Volumen hin. Beam forming wurde mit den horizontalen und vertikalen Spuren aller Quellarray-Beben, aufgezeichnet auf allen 11 Stationen des Empf{\"a}ngerarrays, durchgef{\"u}hrt. Die Ergebnisse wurden im Hinblick auf Konversionen und reflektierte Phasen analysiert. W{\"a}hrend die theoretische Richtung der direkten P-Welle im Falle der Quellarray-Aufzeichnungen gut {\"u}bereinstimmt, wird eine Empf{\"a}ngerarray-Missweisung von 15° bis 25° beobachtet. Eine PS Phase, die der direkten P Phase folgt und eine m{\"o}gliche SP Phase, die kurz vor der direkten S-Phase ankommt, wurden auf den summierten Spuren mehrerer Stationen interpretiert. Aus der Betrachtung der Laufzeiten resultiert eine Konversionstiefe von 0.6-0.9 km Tiefe. Ein zweites Quellarray, bestehend aus 12 tieferen Beben wurde zus{\"a}tzlich analysiert, um eine nach ca. 0.85 s ausschließlich auf den Aufzeichnungen tieferer Beben auftretende Strukturphase zu deuten. Zus{\"a}tzlich zum beam forming wurden zwei Lokalisierungsmethoden von Reflexionen und Konversionen f{\"u}r einfach reflektierte/konvertierte Phasen entwickelt und zur Auswertung verwendet. W{\"a}hrend die erste, analytische Methode eine homogene Geschwindigkeit entlang des Laufwegs annimmt, wird in der zweiten Methode eine 3-D-Rastersuche ausgef{\"u}hrt, in der ein 1-D-Geschwindigkeitsmodell verwendet wird. Auf Grund der eindeutigen beam forming Ergebnisse und der hohen {\"A}hnlichkeit der Wellenformen der Erdbeben, die f{\"u}r das Quellarray genutzt wurden, bieten Quellarrays bestehend aus Mikrobeben aus dem untersuchten Gebiet gute M{\"o}glichkeiten zur Untersuchung von Krustenstrukturen.}, language = {en} } @phdthesis{Wambura2017, author = {Wambura, Frank Joseph}, title = {Analysis of anthropogenic impacts on water resources in the Wami River basin, Tanzania}, school = {Universit{\"a}t Potsdam}, pages = {116}, year = {2017}, language = {en} } @phdthesis{Carus2017, author = {Carus, Jana}, title = {Plant-habitat interactions in brackish marshes}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-404966}, school = {Universit{\"a}t Potsdam}, pages = {VII, 103}, year = {2017}, abstract = {Estuarine marshes are ecosystems that are situated at the transition zone between land and water and are thus controlled by physical and biological interactions. Marsh vegetation offers important ecosystem services by filtrating solid and dissolved substances from the water and providing habitat. By buffering a large part of the arriving flow velocity, attenuating wave energy and serving as erosion control for riverbanks, tidal marshes furthermore reduce the destructive effects of storm surges and storm waves and thus contribute to ecosystem-based shore protection. However, in many estuaries, extensive embankments, artificial bank protection, river dredging and agriculture threaten tidal marshes. Global warming might entail additional risks, such as changes in water levels, an increase of the tidal amplitude and a resulting shift of the salinity zones. This can affect the dynamics of the shore and foreland vegetation, and vegetation belts can be narrowed or fragmented. Against this background, it is crucial to gain a better understanding of the processes underlying the spatio temporal vegetation dynamics in brackish marshes. Furthermore, a better understanding of how plant-habitat relationships generate patterns in tidal marsh vegetation is vital to maintain ecosystem functions and assess the response of marshes to environmental change as well as the success of engineering and restoration projects. For this purpose, three research objectives were addressed within this thesis: (1) to explore the possibility of vegetation serving as self-adaptive shore protection by quantifying the reduction of current velocity in the vegetation belt and the morphologic plasticity of a brackish marsh pioneer, (2) to disentangle the roles of abiotic factors and interspecific competition on species distribution and stand characteristics in brackish marshes, and (3) to develop a mechanistic vegetation model that helps analysing the influence of habitat conditions on the spatio-temporal dynamic of tidal marsh vegetation. These aspects were investigated using a combination of field studies and statistical as well as process-based modelling. To explore the possibility of vegetation serving as self-adaptive coastal protection, in the first study, we measured current velocity with and without living vegetation, recorded ramet density and plant thickness during two growing periods at two locations in the Elbe estuary and assessed the adaptive value of a larger stem diameter of plants at locations with higher mechanical stress by biomechanical measurements. The results of this study show that under non-storm conditions, the vegetation belt of the marsh pioneer Bolboschoenus maritimus is able to buffer a large proportion of the flow velocity. We were furthermore able to show that morphological traits of plant species are adapted to hydrodynamic forces by demonstrating a positive correlation between ramet thickness and cross-shore current. In addition, our measurements revealed that thicker ramets growing at the front of the vegetation belt have a significantly higher stability than ramets inside the vegetation belt. This self-adaptive effect improves the ability of B. maritimus to grow and persist in the pioneer zone and could provide an adaptive value in habitats with high mechanical stress. In the second study, we assessed the distribution of the two marsh species and a set of stand characteristics, namely aboveground and belowground biomass, ramet density, ramet height and the percentage of flowering ramets. Furthermore, we collected information on several abiotic habitat factors to test their effect on plant growth and zonation with generalised linear models (GLMs). Our results demonstrate that flow velocity is the main factor controlling the distribution of Bolboschoenus maritimus and Phragmites australis. Additionally, inundation height and duration, as well as intraspecific competition affect distribution patterns. This study furthermore shows that cross-shore flow velocity does not only directly influence the distribution of the two marsh species, but also alters the plants' occurrence relative to inun-dation height and duration. This suggests an effect of cross-shore flow velocity on their tolerance to inundation. The analysis of the measured stand characteristics revealed a negative effect of total flow velocity on all measured parameters of B. maritimus and thus confirmed our expectation that flow velocity is a decisive stressor which influences the growth of this species. To gain a better understanding of the processes and habitat factors influencing the spatio-temporal vegetation dynamics in brackish marshes, I built a spatially explicit, mechanistic model applying a pattern-oriented modelling approach. A sensitivity analysis of the para-meters of this dynamic habitat-macrophyte model HaMac suggests that rhizome growth is the key process for the lateral dynamics of brackish marshes. From the analysed habitat factors, P. australis patterns were mainly influenced by flow velocity. The competition with P. australis was of key importance for the belowground biomass of B. maritimus. Concerning vegetation dynamics, the model results emphasise that without the effect of flow velocity the B. maritimus vegetation belt would expand into the tidal flat at locations with present vegetation recession, suggesting that flow velocity is the main reason for vegetation recession at exposed locations. Overall, the results of this thesis demonstrate that brackish marsh vegetation considerably contributes to flow reduction under average flow conditions and can hence be a valuable component of shore-protection schemes. At the same time, the distribution, growth and expansion of tidal marsh vegetation is substantially influenced by flow. Altogether, this thesis provides a clear step forward in understanding plant-habitat interactions in tidal marshes. Future research should integrate studies of vertical marsh accretion with research on the factors that control the lateral position of marshes.}, language = {en} } @phdthesis{Ziegler2017, author = {Ziegler, Moritz O.}, title = {The 3D in-situ stress field and its changes in geothermal reservoirs}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-403838}, school = {Universit{\"a}t Potsdam}, pages = {VIII, 110, XV}, year = {2017}, abstract = {Information on the contemporary in-situ stress state of the earth's crust is essential for geotechnical applications and physics-based seismic hazard assessment. Yet, stress data records for a data point are incomplete and their availability is usually not dense enough to allow conclusive statements. This demands a thorough examination of the in-situ stress field which is achieved by 3D geomechanicalnumerical models. However, the models spatial resolution is limited and the resulting local stress state is subject to large uncertainties that confine the significance of the findings. In addition, temporal variations of the in-situ stress field are naturally or anthropogenically induced. In my thesis I address these challenges in three manuscripts that investigate (1) the current crustal stress field orientation, (2) the 3D geomechanical-numerical modelling of the in-situ stress state, and (3) the phenomenon of injection induced temporal stress tensor rotations. In the first manuscript I present the first comprehensive stress data compilation of Iceland with 495 data records. Therefore, I analysed image logs from 57 boreholes in Iceland for indicators of the orientation of the maximum horizontal stress component. The study is the first stress survey from different kinds of stress indicators in a geologically very young and tectonically active area of an onshore spreading ridge. It reveals a distinct stress field with a depth independent stress orientation even very close to the spreading centre. In the second manuscript I present a calibrated 3D geomechanical-numerical modelling approach of the in-situ stress state of the Bavarian Molasse Basin that investigates the regional (70x70x10km³) and local (10x10x10km³) stress state. To link these two models I develop a multi-stage modelling approach that provides a reliable and efficient method to derive from the larger scale model initial and boundary conditions for the smaller scale model. Furthermore, I quantify the uncertainties in the models results which are inherent to geomechanical-numerical modelling in general and the multi-stage approach in particular. I show that the significance of the models results is mainly reduced due to the uncertainties in the material properties and the low number of available stress magnitude data records for calibration. In the third manuscript I investigate the phenomenon of injection induced temporal stress tensor rotation and its controlling factors. I conduct a sensitivity study with a 3D generic thermo-hydro-mechanical model. I show that the key control factors for the stress tensor rotation are the permeability as the decisive factor, the injection rate, and the initial differential stress. In particular for enhanced geothermal systems with a low permeability large rotations of the stress tensor are indicated. According to these findings the estimation of the initial differential stress in a reservoir is possible provided the permeability is known and the angle of stress rotation is observed. I propose that the stress tensor rotations can be a key factor in terms of the potential for induced seismicity on pre-existing faults due to the reorientation of the stress field that changes the optimal orientation of faults.}, language = {en} } @misc{CaloHenneEugsteretal.2017, author = {Cal{\`o}, Camilla and Henne, Paul D. and Eugster, Patricia and Leeuwen, Jacqueline van and Gilli, Adrian and Hamann, Yvonne and La Mantia, Tommaso and Pasta, Salvatore and Vescovi, Elisa and Tinner, Willy}, title = {1200 years of decadal-scale variability of Mediterranean vegetation and climate at Pantelleria Island, Italy}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-403240}, pages = {10}, year = {2017}, abstract = {A new sedimentary sequence from Lago di Venere on Pantelleria Island, located in the Strait of Sicily between Tunisia and Sicily was recovered. The lake is located in the coastal infra-Mediterranean vegetation belt at 2 m a.s.l. Pollen, charcoal and sedimentological analyses are used to explore linkages among vegetation, fire and climate at a decadal scale over the past 1200 years. A dry period from ad 800 to 1000 that corresponds to the Medieval Warm Period' (WMP) is inferred from sedimentological analysis. The high content of carbonate recorded in this period suggests a dry phase, when the ratio of evaporation/precipitation was high. During this period the island was dominated by thermophilous and drought-tolerant taxa, such as Quercus ilex, Olea, Pistacia and Juniperus. A marked shift in the sediment properties is recorded at ad 1000, when carbonate content became very low suggesting wetter conditions until ad 1850-1900. Broadly, this period coincides with the Little Ice Age' (LIA), which was characterized by wetter and colder conditions in Europe. During this time rather mesic conifers (i.e. Pinus pinaster), shrubs and herbs (e.g. Erica arborea and Selaginella denticulata) expanded, whereas more drought-adapted species (e.g. Q. ilex) declined. Charcoal data suggest enhanced fire activity during the LIA probably as a consequence of anthropogenic burning and/or more flammable fuel (e.g. resinous Pinus biomass). The last century was characterized by a shift to high carbonate content, indicating a change towards drier conditions, and re-expansion of Q. ilex and Olea. The post-LIA warming is in agreement with historical documents and meteorological time series. Vegetation dynamics were co-determined by agricultural activities on the island. Anthropogenic indicators (e.g. Cerealia-type, Sporormiella) reveal the importance of crops and grazing on the island. Our pollen data suggest that extensive logging caused the local extinction of deciduous Quercus pubescens around ad1750.}, language = {en} } @phdthesis{Richter2017, author = {Richter, Nicole}, title = {Investigating hazards and the evolution of volcanic landscapes by means of terrestrial and satellite remote sensing data and modelling}, school = {Universit{\"a}t Potsdam}, pages = {169}, year = {2017}, language = {en} } @phdthesis{Zhou2017, author = {Zhou, Bin}, title = {On the assessment of surface urban heat island}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-404383}, school = {Universit{\"a}t Potsdam}, pages = {xiii, 119}, year = {2017}, abstract = {Inwiefern St{\"a}dte unter den Megatrends der Urbanisierung und des Klimawandels nachhaltig gestaltet werden k{\"o}nnen, bleibt umstritten. Dies ist zum Teil auf unzureichende Kenntnisse der Mensch-Umwelt-Interaktionen zur{\"u}ckzuf{\"u}hren. Als die am vollst{\"a}ndigsten dokumentierte anthropogene Klimamodifikation ruft der Urbane Hitzeinsel (UHI) Effekt weltweit Sorgen hinsichtlich der Gesundheit der Bev{\"o}lkerung hervor. Dazu kommt noch ein immer h{\"a}ufigeres und intensiveres Auftreten von Hitzewellen, wodurch das Wohlbefinden der Stadtbewohner weiter beeintr{\"a}chtigt wird. Trotz eines deutlichen Anstiegs der Zahl der UHI-bezogenen Ver{\"o}ffentlichungen in den letzten Jahrzehnten haben die unterschiedlichen Definitionen von st{\"a}dtischen und l{\"a}ndlichen Gebieten in bisherigen Studien die allgemeine Vergleichbarkeit der Resultate stark erschwert. Dar{\"u}ber hinaus haben nur wenige Studien den UHI-Effekt und seine Einflussfaktoren anhand einer Kombination der Landnutzungsdaten und der thermischen Fernerkundung systematisch untersucht. Diese Arbeit stellt einen allgemeinen Rahmen zur Quantifizierung von UHI-Intensit{\"a}ten mittels eines automatisierten Algorithmus vor, wobei St{\"a}dte als Agglomerationen maximal r{\"a}umlicher Kontinuit{\"a}t basierend auf Landnutzungsdaten identifiziert, sowie deren l{\"a}ndliche Umfelder analog definiert werden. Durch Verkn{\"u}pfung der Landnutzungsdaten mit Landoberfl{\"a}chentemperaturen von Satelliten kann die UHI-Intensit{\"a}t robust und konsistent berechnet werden. Anhand dieser Innovation wurde nicht nur der Zusammenhang zwischen Stadtgr{\"o}ße und UHI-Intensit{\"a}t erneut untersucht, sondern auch die Auswirkungen der Stadtform auf die UHI-Intensit{\"a}t quantifiziert. Diese Arbeit leistet vielf{\"a}ltige Beitr{\"a}ge zum tieferen Verst{\"a}ndnis des UHI-Ph{\"a}nomens. Erstens wurde eine log-lineare Beziehung zwischen UHI-Intensit{\"a}t und Stadtgr{\"o}ße unter Ber{\"u}cksichtigung der 5,000 europ{\"a}ischen St{\"a}dte best{\"a}tigt. Werden kleinere St{\"a}dte auch ber{\"u}cksichtigt, ergibt sich eine log-logistische Beziehung. Zweitens besteht ein komplexes Zusammenspiel zwischen der Stadtform und der UHI-Intensit{\"a}t: die Stadtgr{\"o}ße stellt den st{\"a}rksten Einfluss auf die UHI-Intensit{\"a}t dar, gefolgt von der fraktalen Dimension und der Anisometrie. Allerdings zeigen ihre relativen Beitr{\"a}ge zur UHI-Intensit{\"a}t eine regionale Heterogenit{\"a}t, welche die Bedeutung r{\"a}umlicher Muster w{\"a}hrend der Umsetzung von UHI-Anpassungsmaßnahmen hervorhebt. Des Weiteren ergibt sich eine neue Saisonalit{\"a}t der UHI-Intensit{\"a}t f{\"u}r individuelle St{\"a}dte in Form von Hysteresekurven, die eine Phasenverschiebung zwischen den Zeitreihen der UHI-Intensit{\"a}t und der Hintergrundtemperatur andeutet. Diese Saisonalit{\"a}t wurde anhand von Luft- und Landoberfl{\"a}chentemperaturen untersucht, indem die Satellitenbeobachtung und die Modellierung der urbanen Grenzschicht mittels des UrbClim-Modells kombiniert wurden. Am Beispiel von London ist die Diskrepanz der Saisonalit{\"a}ten zwischen den beiden Temperaturen vor allem auf die mit der einfallenden Sonnenstrahlung verbundene Besonderheit der Landoberfl{\"a}chentemperatur zur{\"u}ckzuf{\"u}hren. Dar{\"u}ber hinaus spielt das regionale Klima eine wichtige Rolle bei der Entwicklung der UHI. Diese Arbeit ist eine der ersten Studien dieser Art, die eine systematische und statistische Untersuchung des UHI-Effektes erm{\"o}glicht. Die Ergebnisse sind von besonderer Bedeutung f{\"u}r die allgemeine r{\"a}umliche Planung und Regulierung auf Meso- und Makroebenen, damit sich Vorteile der rapiden Urbanisierung nutzbar machen und zeitgleich die folgende Hitzebelastung proaktiv vermindern lassen.}, language = {en} } @phdthesis{Otto2017, author = {Otto, Christopher}, title = {Numerical analysis of thermal, hydraulic and mechanical processes in the near- and far-field of underground coal gasification reactors}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-404625}, school = {Universit{\"a}t Potsdam}, pages = {XII, 115}, year = {2017}, abstract = {Die Untertagevergasung von Kohle (UTV) erm{\"o}glicht die Erschließung konventionell nicht f{\"o}rderbarer Kohleressourcen und bietet dadurch Potenzial zur Erh{\"o}hung der weltweiten Kohlereserven. Bei der in-situ Kohleumwandlung entsteht ein hochkalorisches Synthesegas, das elektrifiziert oder zur Gewinnung chemischer Rohstoffe und synthetischer Kraftstoffe eingesetzt werden kann. Neben den wirtschaftlichen M{\"o}glichkeiten, bestehen jedoch auch standort-spezifische Umweltgef{\"a}hrdungspotentiale durch Subsidenz und Schadstoffmigration von UTV-R{\"u}ckst{\"a}nden in nutzbare Grundwasserleiter. Eine nachhaltige und effiziente UTV erfordert ein umfangreiches Verst{\"a}ndnis der thermisch, hydraulisch und mechanisch gekoppelten Prozesse im UTV-Reaktornahbereich. Aufgrund der hohen Investitionskosten von UTV-Pilotanlagen, sind numerische Simulationen gekoppelter Prozesse von entscheidender Bedeutung f{\"u}r die Bewertung m{\"o}glicher UTV-Umweltauswirkungen. Im Rahmen dieser Arbeit wird die UTV-induzierte Permeabilit{\"a}tsver{\"a}nderung, Erzeugung m{\"o}glicher hydraulischer Kurzschl{\"u}sse benachbarter Reaktoren und Dynamik nicht-isothermer Multiphasenfl{\"u}sse mit gekoppelten Simulationen analysiert. Die Simulationsergebnisse zeigen, dass eine Implementierung temperaturabh{\"a}ngiger thermo-mechanischer Gesteinsparameter nur f{\"u}r Untersuchungen von Permeabilit{\"a}ts-{\"a}nderungen im Reaktornachbereich notwendig ist. Die Ergebnisse erlauben somit eine recheneffiziente Realisierung von komplexen thermo-mechanisch gekoppelten Simulations-studien regionalskaliger Modelle mit konstanten Gesteinsparametern, bei nahezu gleichbleibender Ergebnisgenauigkeit, die zur Bewertung von UTV-Umweltgef{\"a}hrdungs-potenzialen beitragen. Simulationen zur Ausbildung hydraulischer Kurzschl{\"u}sse zwischen einzelnen UTV-Reaktoren auf regionaler Skala, verdeutlichen die Relevanz von geologischen St{\"o}rungen an einem UTV-Standort, da diese durch Reaktivierung hydraulische Verbindungen induzieren und somit einen effizienten und nachhaltigen UTV-Betrieb negativ beeintr{\"a}chtigen k{\"o}nnen. In diesem Zusammenhang kommt der Ausbildung einer Wasserdampfphase, der sogenannte „steam jacket", im Hochtemperaturnahbereich von UTV-Reaktoren, als potenzielle Barriere zur Vermeidung von UTV-Schadstoffaustritten und zur potenziellen Minimierung von Energieverlusten eine entscheidende Bedeutung zu. Diese steam jackets entstehen durch evaporiertes Formationswasser und sind komplexe nicht-isotherme Multiphasenfluss-Ph{\"a}nomene. F{\"u}r ein verbessertes Prozessverst{\"a}ndnis dieser Multiphasenfl{\"u}sse, wurde ein neuartiges Modellkonzept entwickelt, welches, validiert gegen Feldversuchsdaten, erstmals sowohl eine Quantifizierung als auch Prognose von Wasserflussraten in und aus einem UTV-Reaktor erlaubt. Die Ergebnisse der vorgelegten Doktorarbeit bilden eine wichtige Grundlage f{\"u}r eine erfolgreiche Integration gekoppelter thermo-hydro-mechanischer Simulationen in weiterf{\"u}hrende Studien. Vor dem Hintergrund hoher UTV-Umweltgef{\"a}hrdungspotentiale, k{\"o}nnen diese zur verbesserten Bewertung und Minderung von UTV-Umweltauswirkungen beitragen, sowie die UTV-Effizienz nachhaltig optimieren.}, language = {en} } @misc{LauterbachWittPlessenetal.2017, author = {Lauterbach, Stefan and Witt, Roman and Plessen, Birgit and Dulski, Peter and Prasad, Sushma and Mingram, Jens and Gleixner, Gerd and Hettler-Riedel, Sabine and Stebich, Martina and Schnetger, Bernhard and Schwalb, Antje and Schwarz, Anja}, title = {Climatic imprint of the mid-latitude Westerlies in the Central Tian Shan of Kyrgyzstan and teleconnections to North Atlantic climate variability during the last 6000 years}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-404085}, pages = {15}, year = {2017}, abstract = {In general, a moderate drying trend is observed in mid-latitude arid Central Asia since the Mid-Holocene, attributed to the progressively weakening influence of the mid-latitude Westerlies on regional climate. However, as the spatio-temporal pattern of this development and the underlying climatic mechanisms are yet not fully understood, new high-resolution paleoclimate records from this region are needed. Within this study, a sediment core from Lake Son Kol (Central Kyrgyzstan) was investigated using sedimentological, (bio) geochemical, isotopic, and palynological analyses, aiming at reconstructing regional climate development during the last 6000 years. Biogeochemical data, mainly reflecting summer moisture conditions, indicate predominantly wet conditions until 4950 cal. yr BP, succeeded by a pronounced dry interval between 4950 and 3900 cal. yr BP. In the following, a return to wet conditions and a subsequent moderate drying trend until present times are observed. This is consistent with other regional paleoclimate records and likely reflects the gradual Late Holocene diminishment of the amount of summer moisture provided by the mid-latitude Westerlies. However, climate impact of the Westerlies was apparently not only restricted to the summer season but also significant during winter as indicated by recurrent episodes of enhanced allochthonous input through snowmelt, occurring before 6000 cal. yr BP and at 5100-4350, 3450-2850, and 1900-1500 cal. yr BP. The distinct similar to 1500year periodicity of these episodes of increased winter precipitation in Central Kyrgyzstan resembles similar cyclicities observed in paleoclimate records around the North Atlantic, likely indicating a hemispheric-scale climatic teleconnection and an impact of North Atlantic Oscillation (NAO) variability in Central Asia.}, language = {en} } @misc{KorzeniowskaBuehlerMauroetal.2017, author = {Korzeniowska, Karolina and B{\"u}hler, Yves and Mauro, Marty and Korup, Oliver}, title = {Regional snow-avalanche detection using object-based image analysis of near-infrared aerial imagery}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-403942}, pages = {14}, year = {2017}, abstract = {Snow avalanches are destructive mass movements in mountain regions that continue to claim lives and cause infrastructural damage and traffic detours. Given that avalanches often occur in remote and poorly accessible steep terrain, their detection and mapping is extensive and time consuming. Nonetheless, systematic avalanche detection over large areas could help to generate more complete and up-to-date inventories (cadastres) necessary for validating avalanche forecasting and hazard mapping. In this study, we focused on automatically detecting avalanches and classifying them into release zones, tracks, and run-out zones based on 0.25 m near-infrared (NIR) ADS80-SH92 aerial imagery using an object-based image analysis (OBIA) approach. Our algorithm takes into account the brightness, the normalised difference vegetation index (NDVI), the normalised difference water index (NDWI), and its standard deviation (SDNDWI) to distinguish avalanches from other land-surface elements. Using normalised parameters allows applying this method across large areas. We trained the method by analysing the properties of snow avalanches at three 4 km-2 areas near Davos, Switzerland. We compared the results with manually mapped avalanche polygons and obtained a user's accuracy of > 0.9 and a Cohen's kappa of 0.79-0.85. Testing the method for a larger area of 226.3 km-2, we estimated producer's and user's accuracies of 0.61 and 0.78, respectively, with a Cohen's kappa of 0.67. Detected avalanches that overlapped with reference data by > 80 \% occurred randomly throughout the testing area, showing that our method avoids overfitting. Our method has potential for large-scale avalanche mapping, although further investigations into other regions are desirable to verify the robustness of our selected thresholds and the transferability of the method.}, language = {en} } @article{KorzeniowskaBuehlerMartyetal.2017, author = {Korzeniowska, Karolina and B{\"u}hler, Yves and Marty, Mauro and Korup, Oliver}, title = {Regional snow-avalanche detection using object-based image analysis of near-infrared aerial imagery}, series = {Natural hazards and earth system sciences : NHESS}, volume = {17}, journal = {Natural hazards and earth system sciences : NHESS}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1561-8633}, doi = {10.5194/nhess-17-1823-2017}, pages = {1823 -- 1836}, year = {2017}, abstract = {Snow avalanches are destructive mass movements in mountain regions that continue to claim lives and cause infrastructural damage and traffic detours. Given that avalanches often occur in remote and poorly accessible steep terrain, their detection and mapping is extensive and time consuming. Nonetheless, systematic avalanche detection over large areas could help to generate more complete and up-to-date inventories (cadastres) necessary for validating avalanche forecasting and hazard mapping. In this study, we focused on automatically detecting avalanches and classifying them into release zones, tracks, and run-out zones based on 0.25 m near-infrared (NIR) ADS80-SH92 aerial imagery using an object-based image analysis (OBIA) approach. Our algorithm takes into account the brightness, the normalised difference vegetation index (NDVI), the normalised difference water index (NDWI), and its standard deviation (SDNDWI) to distinguish avalanches from other land-surface elements. Using normalised parameters allows applying this method across large areas. We trained the method by analysing the properties of snow avalanches at three 4 km-2 areas near Davos, Switzerland. We compared the results with manually mapped avalanche polygons and obtained a user's accuracy of > 0.9 and a Cohen's kappa of 0.79-0.85. Testing the method for a larger area of 226.3 km-2, we estimated producer's and user's accuracies of 0.61 and 0.78, respectively, with a Cohen's kappa of 0.67. Detected avalanches that overlapped with reference data by > 80 \% occurred randomly throughout the testing area, showing that our method avoids overfitting. Our method has potential for large-scale avalanche mapping, although further investigations into other regions are desirable to verify the robustness of our selected thresholds and the transferability of the method.}, language = {en} } @misc{SmithBookhagenRheinwalt2017, author = {Smith, Taylor and Bookhagen, Bodo and Rheinwalt, Aljoscha}, title = {Spatiotemporal patterns of High Mountain Asia's snowmelt season identified with an automated snowmelt detection algorithm, 1987-2016}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-403911}, pages = {15}, year = {2017}, abstract = {High Mountain Asia (HMA) - encompassing the Tibetan Plateau and surrounding mountain ranges - is the primary water source for much of Asia, serving more than a billion downstream users. Many catchments receive the majority of their yearly water budget in the form of snow, which is poorly monitored by sparse in situ weather networks. Both the timing and volume of snowmelt play critical roles in downstream water provision, as many applications - such as agriculture, drinking-water generation, and hydropower - rely on consistent and predictable snowmelt runoff. Here, we examine passive microwave data across HMA with five sensors (SSMI, SSMIS, AMSR-E, AMSR2, and GPM) from 1987 to 2016 to track the timing of the snowmelt season - defined here as the time between maximum passive microwave signal separation and snow clearance. We validated our method against climate model surface temperatures, optical remote-sensing snow-cover data, and a manual control dataset (n = 2100, 3 variables at 25 locations over 28 years); our algorithm is generally accurate within 3-5 days. Using the algorithm-generated snowmelt dates, we examine the spatiotemporal patterns of the snowmelt season across HMA. The climatically short (29-year) time series, along with complex interannual snowfall variations, makes determining trends in snowmelt dates at a single point difficult. We instead identify trends in snowmelt timing by using hierarchical clustering of the passive microwave data to determine trends in self-similar regions. We make the following four key observations. (1) The end of the snowmelt season is trending almost universally earlier in HMA (negative trends). Changes in the end of the snowmelt season are generally between 2 and 8 days decade 1 over the 29-year study period (5-25 days total). The length of the snowmelt season is thus shrinking in many, though not all, regions of HMA. Some areas exhibit later peak signal separation (positive trends), but with generally smaller magnitudes than trends in snowmelt end. (2) Areas with long snowmelt periods, such as the Tibetan Plateau, show the strongest compression of the snowmelt season (negative trends). These trends are apparent regardless of the time period over which the regression is performed. (3) While trends averaged over 3 decades indicate generally earlier snowmelt seasons, data from the last 14 years (2002-2016) exhibit positive trends in many regions, such as parts of the Pamir and Kunlun Shan. Due to the short nature of the time series, it is not clear whether this change is a reversal of a long-term trend or simply interannual variability. (4) Some regions with stable or growing glaciers - such as the Karakoram and Kunlun Shan - see slightly later snowmelt seasons and longer snowmelt periods. It is likely that changes in the snowmelt regime of HMA account for some of the observed heterogeneity in glacier response to climate change. While the decadal increases in regional temperature have in general led to earlier and shortened melt seasons, changes in HMA's cryosphere have been spatially and temporally heterogeneous.}, language = {en} } @article{SmithBookhagenRheinwalt2017, author = {Smith, Taylor and Bookhagen, Bodo and Rheinwalt, Aljoscha}, title = {Spatiotemporal patterns of High Mountain Asia's snowmelt season identified with an automated snowmelt detection algorithm, 1987-2016}, series = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, volume = {11}, journal = {The Cryosphere : TC ; an interactive open access journal of the European Geosciences Union}, issn = {1994-0416}, doi = {10.5194/tc-11-2329-2017}, pages = {2329 -- 2343}, year = {2017}, abstract = {High Mountain Asia (HMA) - encompassing the Tibetan Plateau and surrounding mountain ranges - is the primary water source for much of Asia, serving more than a billion downstream users. Many catchments receive the majority of their yearly water budget in the form of snow, which is poorly monitored by sparse in situ weather networks. Both the timing and volume of snowmelt play critical roles in downstream water provision, as many applications - such as agriculture, drinking-water generation, and hydropower - rely on consistent and predictable snowmelt runoff. Here, we examine passive microwave data across HMA with five sensors (SSMI, SSMIS, AMSR-E, AMSR2, and GPM) from 1987 to 2016 to track the timing of the snowmelt season - defined here as the time between maximum passive microwave signal separation and snow clearance. We validated our method against climate model surface temperatures, optical remote-sensing snow-cover data, and a manual control dataset (n = 2100, 3 variables at 25 locations over 28 years); our algorithm is generally accurate within 3-5 days. Using the algorithm-generated snowmelt dates, we examine the spatiotemporal patterns of the snowmelt season across HMA. The climatically short (29-year) time series, along with complex interannual snowfall variations, makes determining trends in snowmelt dates at a single point difficult. We instead identify trends in snowmelt timing by using hierarchical clustering of the passive microwave data to determine trends in self-similar regions. We make the following four key observations. (1) The end of the snowmelt season is trending almost universally earlier in HMA (negative trends). Changes in the end of the snowmelt season are generally between 2 and 8 days decade 1 over the 29-year study period (5-25 days total). The length of the snowmelt season is thus shrinking in many, though not all, regions of HMA. Some areas exhibit later peak signal separation (positive trends), but with generally smaller magnitudes than trends in snowmelt end. (2) Areas with long snowmelt periods, such as the Tibetan Plateau, show the strongest compression of the snowmelt season (negative trends). These trends are apparent regardless of the time period over which the regression is performed. (3) While trends averaged over 3 decades indicate generally earlier snowmelt seasons, data from the last 14 years (2002-2016) exhibit positive trends in many regions, such as parts of the Pamir and Kunlun Shan. Due to the short nature of the time series, it is not clear whether this change is a reversal of a long-term trend or simply interannual variability. (4) Some regions with stable or growing glaciers - such as the Karakoram and Kunlun Shan - see slightly later snowmelt seasons and longer snowmelt periods. It is likely that changes in the snowmelt regime of HMA account for some of the observed heterogeneity in glacier response to climate change. While the decadal increases in regional temperature have in general led to earlier and shortened melt seasons, changes in HMA's cryosphere have been spatially and temporally heterogeneous.}, language = {en} } @misc{BoessenkoolBruegerHeistermann2017, author = {Boessenkool, Berry and Br{\"u}ger, Gerd and Heistermann, Maik}, title = {Effects of sample size on estimation of rainfall extremes at high temperatures}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-403897}, pages = {7}, year = {2017}, abstract = {High precipitation quantiles tend to rise with temperature, following the so-called Clausius-Clapeyron (CC) scaling. It is often reported that the CC-scaling relation breaks down and even reverts for very high temperatures. In our study, we investigate this reversal using observational climate data from 142 stations across Germany. One of the suggested meteorological explanations for the breakdown is limited moisture supply. Here we argue that, instead, it could simply originate from undersampling. As rainfall frequency generally decreases with higher temperatures, rainfall intensities as dictated by CC scaling are less likely to be recorded than for moderate temperatures. Empirical quantiles are conventionally estimated from order statistics via various forms of plotting position formulas. They have in common that their largest representable return period is given by the sample size. In small samples, high quantiles are underestimated accordingly. The small-sample effect is weaker, or disappears completely, when using parametric quantile estimates from a generalized Pareto distribution (GPD) fitted with L moments. For those, we obtain quantiles of rainfall intensities that continue to rise with temperature.}, language = {en} } @article{BoessenkoolBruegerHeistermann2017, author = {Boessenkool, Berry and Br{\"u}ger, Gerd and Heistermann, Maik}, title = {Effects of sample size on estimation of rainfall extremes at high temperatures}, series = {Natural hazards and earth system sciences}, volume = {17}, journal = {Natural hazards and earth system sciences}, number = {9}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1561-8633}, doi = {10.5194/nhess-17-1623-2017}, pages = {1623 -- 1629}, year = {2017}, abstract = {High precipitation quantiles tend to rise with temperature, following the so-called Clausius-Clapeyron (CC) scaling. It is often reported that the CC-scaling relation breaks down and even reverts for very high temperatures. In our study, we investigate this reversal using observational climate data from 142 stations across Germany. One of the suggested meteorological explanations for the breakdown is limited moisture supply. Here we argue that, instead, it could simply originate from undersampling. As rainfall frequency generally decreases with higher temperatures, rainfall intensities as dictated by CC scaling are less likely to be recorded than for moderate temperatures. Empirical quantiles are conventionally estimated from order statistics via various forms of plotting position formulas. They have in common that their largest representable return period is given by the sample size. In small samples, high quantiles are underestimated accordingly. The small-sample effect is weaker, or disappears completely, when using parametric quantile estimates from a generalized Pareto distribution (GPD) fitted with L moments. For those, we obtain quantiles of rainfall intensities that continue to rise with temperature.}, language = {en} } @incollection{Serwene2017, author = {Serwene, Pola}, title = {Mentor Texts}, series = {Sprache im Geographieunterricht Bilinguale und sprachsensible Materialien und Methoden}, booktitle = {Sprache im Geographieunterricht Bilinguale und sprachsensible Materialien und Methoden}, editor = {Budke, Alexandra and Kuckuck, Miriam}, publisher = {Waxmann}, address = {M{\"u}nster}, publisher = {Universit{\"a}t Potsdam}, pages = {101 -- 114}, year = {2017}, language = {de} } @misc{PilzFranckeBronstert2017, author = {Pilz, Tobias and Francke, Till and Bronstert, Axel}, title = {lumpR 2.0.0: an R package facilitating landscape discretisation for hillslope-based hydrological models}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-402880}, pages = {23}, year = {2017}, abstract = {The characteristics of a landscape pose essential factors for hydrological processes. Therefore, an adequate representation of the landscape of a catchment in hydrological models is vital. However, many of such models exist differing, amongst others, in spatial concept and discretisation. The latter constitutes an essential pre-processing step, for which many different algorithms along with numerous software implementations exist. In that context, existing solutions are often model specific, commercial, or depend on commercial back-end software, and allow only a limited or no workflow automation at all. Consequently, a new package for the scientific software and scripting environment R, called lumpR, was developed. lumpR employs an algorithm for hillslope-based landscape discretisation directed to large-scale application via a hierarchical multi-scale approach. The package addresses existing limitations as it is free and open source, easily extendible to other hydrological models, and the workflow can be fully automated. Moreover, it is user-friendly as the direct coupling to a GIS allows for immediate visual inspection and manual adjustment. Sufficient control is furthermore retained via parameter specification and the option to include expert knowledge. Conversely, completely automatic operation also allows for extensive analysis of aspects related to landscape discretisation. In a case study, the application of the package is presented. A sensitivity analysis of the most important discretisation parameters demonstrates its efficient workflow automation. Considering multiple streamflow metrics, the employed model proved reasonably robust to the discretisation parameters. However, parameters determining the sizes of subbasins and hillslopes proved to be more important than the others, including the number of representative hillslopes, the number of attributes employed for the lumping algorithm, and the number of sub-discretisations of the representative hillslopes.}, language = {en} } @article{PilzFranckeBronstert2017, author = {Pilz, Tobias and Francke, Till and Bronstert, Axel}, title = {lumpR 2.0.0: an R package facilitating landscape discretisation for hillslope-based hydrological models}, series = {Geoscientific model development}, volume = {10}, journal = {Geoscientific model development}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1991-959X}, doi = {10.5194/gmd-10-3001-2017}, pages = {3001 -- 3023}, year = {2017}, abstract = {The characteristics of a landscape pose essential factors for hydrological processes. Therefore, an adequate representation of the landscape of a catchment in hydrological models is vital. However, many of such models exist differing, amongst others, in spatial concept and discretisation. The latter constitutes an essential pre-processing step, for which many different algorithms along with numerous software implementations exist. In that context, existing solutions are often model specific, commercial, or depend on commercial back-end software, and allow only a limited or no workflow automation at all. Consequently, a new package for the scientific software and scripting environment R, called lumpR, was developed. lumpR employs an algorithm for hillslope-based landscape discretisation directed to large-scale application via a hierarchical multi-scale approach. The package addresses existing limitations as it is free and open source, easily extendible to other hydrological models, and the workflow can be fully automated. Moreover, it is user-friendly as the direct coupling to a GIS allows for immediate visual inspection and manual adjustment. Sufficient control is furthermore retained via parameter specification and the option to include expert knowledge. Conversely, completely automatic operation also allows for extensive analysis of aspects related to landscape discretisation. In a case study, the application of the package is presented. A sensitivity analysis of the most important discretisation parameters demonstrates its efficient workflow automation. Considering multiple streamflow metrics, the employed model proved reasonably robust to the discretisation parameters. However, parameters determining the sizes of subbasins and hillslopes proved to be more important than the others, including the number of representative hillslopes, the number of attributes employed for the lumping algorithm, and the number of sub-discretisations of the representative hillslopes.}, language = {en} } @misc{Heistermann2017, author = {Heistermann, Maik}, title = {HESS Opinions: A planetary boundary on freshwater use is misleading}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-402854}, pages = {7}, year = {2017}, abstract = {In 2009, a group of prominent Earth scientists introduced the "planetary boundaries" (PB) framework: they suggested nine global control variables, and defined corresponding "thresholds which, if crossed, could generate unacceptable environmental change". The concept builds on systems theory, and views Earth as a complex adaptive system in which anthropogenic disturbances may trigger non-linear, abrupt, and irreversible changes at the global scale, and "push the Earth system outside the stable environmental state of the Holocene". While the idea has been remarkably successful in both science and policy circles, it has also raised fundamental concerns, as the majority of suggested processes and their corresponding planetary boundaries do not operate at the global scale, and thus apparently lack the potential to trigger abrupt planetary changes. This paper picks up the debate with specific regard to the planetary boundary on "global freshwater use". While the bio-physical impacts of excessive water consumption are typically confined to the river basin scale, the PB proponents argue that water-induced environmental disasters could build up to planetary-scale feedbacks and system failures. So far, however, no evidence has been presented to corroborate that hypothesis. Furthermore, no coherent approach has been presented to what extent a planetary threshold value could reflect the risk of regional environmental disaster. To be sure, the PB framework was revised in 2015, extending the planetary freshwater boundary with a set of basin-level boundaries inferred from environmental water flow assumptions. Yet, no new evidence was presented, either with respect to the ability of those basin-level boundaries to reflect the risk of regional regime shifts or with respect to a potential mechanism linking river basins to the planetary scale. So while the idea of a planetary boundary on freshwater use appears intriguing, the line of arguments presented so far remains speculative and implicatory. As long as Earth system science does not present compelling evidence, the exercise of assigning actual numbers to such a boundary is arbitrary, premature, and misleading. Taken as a basis for water-related policy and management decisions, though, the idea transforms from misleading to dangerous, as it implies that we can globally offset water-related environmental impacts. A planetary boundary on freshwater use should thus be disapproved and actively refuted by the hydrological and water resources community.}, language = {en} } @article{Heistermann2017, author = {Heistermann, Maik}, title = {HESS Opinions: A planetary boundary on freshwater use is misleading}, series = {Hydrology and earth system sciences}, volume = {21}, journal = {Hydrology and earth system sciences}, publisher = {Copernicus}, address = {G{\"o}ttingen}, issn = {1027-5606}, doi = {10.5194/hess-21-3455-2017}, pages = {3455 -- 3461}, year = {2017}, abstract = {In 2009, a group of prominent Earth scientists introduced the "planetary boundaries" (PB) framework: they suggested nine global control variables, and defined corresponding "thresholds which, if crossed, could generate unacceptable environmental change". The concept builds on systems theory, and views Earth as a complex adaptive system in which anthropogenic disturbances may trigger non-linear, abrupt, and irreversible changes at the global scale, and "push the Earth system outside the stable environmental state of the Holocene". While the idea has been remarkably successful in both science and policy circles, it has also raised fundamental concerns, as the majority of suggested processes and their corresponding planetary boundaries do not operate at the global scale, and thus apparently lack the potential to trigger abrupt planetary changes. This paper picks up the debate with specific regard to the planetary boundary on "global freshwater use". While the bio-physical impacts of excessive water consumption are typically confined to the river basin scale, the PB proponents argue that water-induced environmental disasters could build up to planetary-scale feedbacks and system failures. So far, however, no evidence has been presented to corroborate that hypothesis. Furthermore, no coherent approach has been presented to what extent a planetary threshold value could reflect the risk of regional environmental disaster. To be sure, the PB framework was revised in 2015, extending the planetary freshwater boundary with a set of basin-level boundaries inferred from environmental water flow assumptions. Yet, no new evidence was presented, either with respect to the ability of those basin-level boundaries to reflect the risk of regional regime shifts or with respect to a potential mechanism linking river basins to the planetary scale. So while the idea of a planetary boundary on freshwater use appears intriguing, the line of arguments presented so far remains speculative and implicatory. As long as Earth system science does not present compelling evidence, the exercise of assigning actual numbers to such a boundary is arbitrary, premature, and misleading. Taken as a basis for water-related policy and management decisions, though, the idea transforms from misleading to dangerous, as it implies that we can globally offset water-related environmental impacts. A planetary boundary on freshwater use should thus be disapproved and actively refuted by the hydrological and water resources community.}, language = {en} } @phdthesis{Korzeniowska2017, author = {Korzeniowska, Karolina}, title = {Object-based image analysis for detecting landforms diagnostic of natural hazards}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-402240}, school = {Universit{\"a}t Potsdam}, pages = {XV, 139}, year = {2017}, abstract = {Natural and potentially hazardous events occur on the Earth's surface every day. The most destructive of these processes must be monitored, because they may cause loss of lives, infrastructure, and natural resources, or have a negative effect on the environment. A variety of remote sensing technologies allow the recoding of data to detect these processes in the first place, partly based on the diagnostic landforms that they form. To perform this effectively, automatic methods are desirable. Universal detection of natural hazards is challenging due to their differences in spatial impacts, timing and longevity of consequences, and the spatial resolution of remote-sensing data. Previous studies have reported that topographic metrics such as roughness, which can be captured from digital elevation data, can reveal landforms diagnostic of natural hazards, such as gullies, dunes, lava fields, landslides and snow avalanches, as these landforms tend to be more heterogeneous than the surrounding landscape. A single roughness metric is often limited in such detections; however, a more complex approach that exploits the spatial relation and the location of objects, such as object-based image analysis (OBIA), is desirable. In this thesis, I propose a topographic roughness measure derived from an airborne laser scanning (ALS) digital terrain model (DTM) and discuss its performance in detecting landforms principally diagnostic of natural hazards. I further develop OBIA-based algorithms for the detection of snow avalanches using near-infrared (NIR) aerial images, and the size (changes) of mountain lakes using LANDSAT satellite images. I quantitatively test and document how the level of difficulty in detecting these very challenging landforms depends on the input data resolution, the derivatives that could be evaluated from images and DTMs, the size, shape and complexity of landforms, and the capabilities of obtaining the information in the data. I demonstrate that surface roughness is a promising metric for detecting different landforms in diverse environments, and that OBIA assists significantly in detecting parts of lakes and snow avalanches that may not be correctly assigned by applying only the thresholding of spectral properties of data and their derivatives. The curvature-based surface roughness parameter allows the detection of gullies, dunes, lava fields and landslides with a user's accuracy of 0.63, 0.21, 0.53, and 0.45, respectively. The OBIA algorithms for detecting lakes and snow avalanches obtained user's accuracy of 0.98, and 0.78, respectively. Most of the analysed landforms constituted only a small part of the entire dataset, and therefore the user's accuracy is the most appropriate performance measure that should be given in a such classification, because it tells how many automatically-extracted pixels in fact represent the object that one wants to classify, and its calculation does not take the second (background) class into account. One advantage of the proposed roughness parameter is that it allows the extraction of the heterogeneity of the surface without the need for data detrending. The OBIA approach is novel in that it allows the classification of lakes regardless of the physical state of their water, and also allows the separation of frozen lakes from glaciers that have very similar water indices used in purely optical remote sensing applications. The algorithm proposed for snow avalanches allows the detection of release zones, tracks, and deposition zones by verifying the snow heterogeneity based on a roughness metric evaluated from a water index, and by analysing the local relation of segments with their neighbouring objects. This algorithm contains few steps, which allows for the simultaneous classification of avalanches that occur on diverse mountain slopes and differ in size and shape. This thesis contributes to natural hazard research as it provides automatic solutions to tracking six different landforms that are diagnostic of natural hazards over large regions. This is a step toward delineating areas susceptible to the processes producing these landforms and the improvement of hazard maps.}, language = {en} } @phdthesis{Wieczorek2017, author = {Wieczorek, Mareike}, title = {Stand structure patterns in the Siberian treeline under climate change}, school = {Universit{\"a}t Potsdam}, pages = {140}, year = {2017}, language = {en} } @masterthesis{Lehmann2017, type = {Bachelor Thesis}, author = {Lehmann, Lukas}, title = {Performance Test von Phasenpickern}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-401993}, school = {Universit{\"a}t Potsdam}, pages = {I, 40, XXXIX}, year = {2017}, abstract = {Die genauen Einsatzzeiten seismischer P-Phasen von Erdbeben werden in SeisComP3 und anderen Auswerteprogrammen standardm{\"a}ßig und in Echtzeit automatisch bestimmt. S-Phasen stellen dagegen eine weit gr{\"o}ßere Herausforderung dar. Nur mit genauen Picks der P- bzw. S-Phasen k{\"o}nnen die Erdbebenlokationen korrekt und stabil bestimmt werden. Darum besteht erhebliches Interesse, diese mit hoher Genauigkeit zu bestimmen. Das Ziel der vorliegenden Bachelorarbeit war es, vier verschiedene, bereits vorhandene S-Phasenpicker auf ausgew{\"a}hlte Parameter optimal zu konfigurieren, auf Testdaten anzuwenden und deren Leistungsf{\"a}higkeit objektiv zu bewerten. Dazu wurden ein S-Picker (S-L2) aus dem OpenSource SeisComp3-Programmpaket, zwei S-Picker (S-AIC, S-AIC-V) als kommerzielles Modul der Firma gempa GmbH f{\"u}r SeisComP3 und ein S-Picker (Frequenzband) aus dem OpenSource PhasePaPy-Paket ausgew{\"a}hlt. Die Bewertung erfolgte durch Vergleich automatischer Picks mit manuell bestimmten Einsatzzeiten. Alle vier Picker wurden separat konfiguriert und auf drei verschiedene Datens{\"a}tze von Erdbeben in N-Chile und im Vogtland, Deutschland, angewandt. Dazu wurden regional bzw. lokal typische Erdbeben zuf{\"a}llig ausgew{\"a}hlt und die P- und S-Phasen manuell bestimmt. Mit den zu testenden S-Pickeralgorithmen wurden dieselben Daten durchsucht und die Picks automatisch bestimmt. Die Konfigurationen der Picker wurden gleichzeitig automatisch und objektiv durch iterative Anpassung optimiert. Ein neu erstelltes Bewertungssystem vergleicht die manuellen und die automatisch gefundenen S-Picks anhand von definierten Qualit{\"a}tsfaktoren. Die Qualit{\"a}tsfaktoren sind: der Mittelwert und die Standardabweichung der zeitlichen Differenzen zwischen den S-Picks, die Anzahl an {\"u}bereinstimmenden S-Picks, die Prozentangaben {\"u}ber m{\"o}gliche S-Picks und die ben{\"o}tigt Rechenzeit. Die objektive Bewertung erfolgte anhand eines Scores. Der Scorewert ergibt sich aus der gewichteten Summe folgender normierter Qualit{\"a}tsfaktoren: Standardabweichung (20\%), Mittelwert (20\%) und Prozentangabe {\"u}ber m{\"o}gliche S-Picks (60\%). Konfigurationen mit hohem Score werden bevorzugt. Die bevorzugten Konfigurationen der verschiedenen Picker wurden miteinander verglichen, um den am besten geeigneten S-Pickeralgorithmus zu bestimmen. Allgemein zeigt sich, dass der S-AIC Picker f{\"u}r jeden der drei Datens{\"a}tze die h{\"o}chsten Scores und damit die besten Ergebnisse liefert. Dabei wurde f{\"u}r jeden Datensatz ein andere Konfiguration der Parameter des S-AIC Pickers als die am besten geeignete bezeichnet. Daher ist f{\"u}r jede Erdbebenregion eine andere Konfigurationen erforderlich, um optimale Ergebnisse mit diesem S-Picker zu bekommen.}, language = {de} } @misc{ToetzkeKardjilovMankeetal.2017, author = {T{\"o}tzke, Christian and Kardjilov, Nikolay and Manke, Ingo and Oswald, Sascha}, title = {Capturing 3D Water Flow in Rooted Soil by Ultra-fast Neutron Tomography}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-402237}, pages = {9}, year = {2017}, abstract = {Water infiltration in soil is not only affected by the inherent heterogeneities of soil, but even more by the interaction with plant roots and their water uptake. Neutron tomography is a unique non-invasive 3D tool to visualize plant root systems together with the soil water distribution in situ. So far, acquisition times in the range of hours have been the major limitation for imaging 3D water dynamics. Implementing an alternative acquisition procedure we boosted the speed of acquisition capturing an entire tomogram within 10 s. This allows, for the first time, tracking of a water front ascending in a rooted soil column upon infiltration of deuterated water time-resolved in 3D. Image quality and resolution could be sustained to a level allowing for capturing the root system in high detail. Good signal-to-noise ratio and contrast were the key to visualize dynamic changes in water content and to localize the root uptake. We demonstrated the ability of ultra-fast tomography to quantitatively image quick changes of water content in the rhizosphere and outlined the value of such imaging data for 3D water uptake modelling. The presented method paves the way for time-resolved studies of various 3D flow and transport phenomena in porous systems}, language = {en} } @article{ToetzkeKardjilovMankeetal.2017, author = {T{\"o}tzke, Christian and Kardjilov, Nikolay and Manke, Ingo and Oswald, Sascha}, title = {Capturing 3D Water Flow in Rooted Soil by Ultra-fast Neutron Tomography}, series = {Scientific reports}, volume = {7}, journal = {Scientific reports}, publisher = {Macmillan Publishers Limited}, address = {London}, issn = {2045-2322}, doi = {10.1038/s41598-017-06046-w}, year = {2017}, abstract = {Water infiltration in soil is not only affected by the inherent heterogeneities of soil, but even more by the interaction with plant roots and their water uptake. Neutron tomography is a unique non-invasive 3D tool to visualize plant root systems together with the soil water distribution in situ. So far, acquisition times in the range of hours have been the major limitation for imaging 3D water dynamics. Implementing an alternative acquisition procedure we boosted the speed of acquisition capturing an entire tomogram within 10 s. This allows, for the first time, tracking of a water front ascending in a rooted soil column upon infiltration of deuterated water time-resolved in 3D. Image quality and resolution could be sustained to a level allowing for capturing the root system in high detail. Good signal-to-noise ratio and contrast were the key to visualize dynamic changes in water content and to localize the root uptake. We demonstrated the ability of ultra-fast tomography to quantitatively image quick changes of water content in the rhizosphere and outlined the value of such imaging data for 3D water uptake modelling. The presented method paves the way for time-resolved studies of various 3D flow and transport phenomena in porous systems.}, language = {en} } @phdthesis{Hendriyana2017, author = {Hendriyana, Andri}, title = {Detection and Kirchhoff-type migration of seismic events by use of a new characteristic function}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-398879}, school = {Universit{\"a}t Potsdam}, pages = {v, 139}, year = {2017}, abstract = {The classical method of seismic event localization is based on the picking of body wave arrivals, ray tracing and inversion of travel time data. Travel time picks with small uncertainties are required to produce reliable and accurate results with this kind of source localization. Hence recordings, with a low Signal-to-Noise Ratio (SNR) cannot be used in a travel time based inversion. Low SNR can be related with weak signals from distant and/or low magnitude sources as well as with a high level of ambient noise. Diffraction stacking is considered as an alternative seismic event localization method that enables also the processing of low SNR recordings by mean of stacking the amplitudes of seismograms along a travel time function. The location of seismic event and its origin time are determined based on the highest stacked amplitudes (coherency) of the image function. The method promotes an automatic processing since it does not need travel time picks as input data. However, applying diffraction stacking may require longer computation times if only limited computer resources are used. Furthermore, a simple diffraction stacking of recorded amplitudes could possibly fail to locate the seismic sources if the focal mechanism leads to complex radiation patterns which typically holds for both natural and induced seismicity. In my PhD project, I have developed a new work flow for the localization of seismic events which is based on a diffraction stacking approach. A parallelized code was implemented for the calculation of travel time tables and for the determination of an image function to reduce computation time. In order to address the effects from complex source radiation patterns, I also suggest to compute diffraction stacking from a characteristic function (CF) instead of stacking the original wave form data. A new CF, which is called in the following mAIC (modified from Akaike Information Criterion) is proposed. I demonstrate that, the performance of the mAIC does not depend on the chosen length of the analyzed time window and that both P- and S-wave onsets can be detected accurately. To avoid cross-talk between P- and S-waves due to inaccurate velocity models, I separate the P- and S-waves from the mAIC function by making use of polarization attributes. Then, eventually the final image function is represented by the largest eigenvalue as a result of the covariance analysis between P- and S-image functions. Before applying diffraction stacking, I also apply seismogram denoising by using Otsu thresholding in the time-frequency domain. Results from synthetic experiments show that the proposed diffraction stacking provides reliable results even from seismograms with low SNR=1. Tests with different presentations of the synthetic seismograms (displacement, velocity, and acceleration) shown that, acceleration seismograms deliver better results in case of high SNR, whereas displacement seismograms provide more accurate results in case of low SNR recordings. In another test, different measures (maximum amplitude, other statistical parameters) were used to determine the source location in the final image function. I found that the statistical approach is the preferred method particularly for low SNR. The work flow of my diffraction stacking method was finally applied to local earthquake data from Sumatra, Indonesia. Recordings from a temporary network of 42 stations deployed for 9 months around the Tarutung pull-apart Basin were analyzed. The seismic event locations resulting from the diffraction stacking method align along a segment of the Sumatran Fault. A more complex distribution of seismicity is imaged within and around the Tarutung Basin. Two lineaments striking N-S were found in the middle of the Tarutung Basin which support independent results from structural geology. These features are interpreted as opening fractures due to local extension. A cluster of seismic events repeatedly occurred in short time which might be related to fluid drainage since two hot springs are observed at the surface near to this cluster.}, language = {en} } @misc{MielkeRogassBoescheetal.2017, author = {Mielke, Christian and Rogass, Christian and Boesche, Nina and Segl, Karl and Altenberger, Uwe}, title = {EnGeoMAP 2.0}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-400650}, pages = {26}, year = {2017}, abstract = {Algorithms for a rapid analysis of hyperspectral data are becoming more and more important with planned next generation spaceborne hyperspectral missions such as the Environmental Mapping and Analysis Program (EnMAP) and the Japanese Hyperspectral Imager Suite (HISUI), together with an ever growing pool of hyperspectral airborne data. The here presented EnGeoMAP 2.0 algorithm is an automated system for material characterization from imaging spectroscopy data, which builds on the theoretical framework of the Tetracorder and MICA (Material Identification and Characterization Algorithm) of the United States Geological Survey and of EnGeoMAP 1.0 from 2013. EnGeoMAP 2.0 includes automated absorption feature extraction, spatio-spectral gradient calculation and mineral anomaly detection. The usage of EnGeoMAP 2.0 is demonstrated at the mineral deposit sites of Rodalquilar (SE-Spain) and Haib River (S-Namibia) using HyMAP and simulated EnMAP data. Results from Hyperion data are presented as supplementary information.}, language = {en} } @misc{KormannBronstertFranckeetal.2017, author = {Kormann, Christoph and Bronstert, Axel and Francke, Till and Recknagel, Thomas and Gr{\"a}ff, Thomas}, title = {Model-Based attribution of high-resolution streamflow trends in two alpine basins of Western Austria}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-400641}, pages = {21}, year = {2017}, abstract = {Several trend studies have shown that hydrological conditions are changing considerably in the Alpine region. However, the reasons for these changes are only partially understood and trend analyses alone are not able to shed much light. Hydrological modelling is one possible way to identify the trend drivers, i.e., to attribute the detected streamflow trends, given that the model captures all important processes causing the trends. We modelled the hydrological conditions for two alpine catchments in western Austria (a large, mostly lower-altitude catchment with wide valley plains and a nested high-altitude, glaciated headwater catchment) with the distributed, physically-oriented WaSiM-ETH model, which includes a dynamical glacier module. The model was calibrated in a transient mode, i.e., not only on several standard goodness measures and glacier extents, but also in such a way that the simulated streamflow trends fit with the observed ones during the investigation period 1980 to 2007. With this approach, it was possible to separate streamflow components, identify the trends of flow components, and study their relation to trends in atmospheric variables. In addition to trends in annual averages, highly resolved trends for each Julian day were derived, since they proved powerful in an earlier, data-based attribution study. We were able to show that annual and highly resolved trends can be modelled sufficiently well. The results provide a holistic, year-round picture of the drivers of alpine streamflow changes: Higher-altitude catchments are strongly affected by earlier firn melt and snowmelt in spring and increased ice melt throughout the ablation season. Changes in lower-altitude areas are mostly caused by earlier and lower snowmelt volumes. All highly resolved trends in streamflow and its components show an explicit similarity to the local temperature trends. Finally, results indicate that evapotranspiration has been increasing in the lower altitudes during the study period.}, language = {en} }