550 Geowissenschaften
Filtern
Erscheinungsjahr
Dokumenttyp
- Wissenschaftlicher Artikel (888)
- Dissertation (194)
- Beitrag zu einer (nichtwissenschaftlichen) Zeitung oder Zeitschrift (32)
- Buch (Monographie) (26)
- Arbeitspapier (22)
- Ausgabe (Heft) zu einer Zeitschrift (20)
- Konferenzveröffentlichung (18)
- Teil eines Buches (Kapitel) (9)
- Diplomarbeit (8)
- diplomthesis (7)
- Sonstiges (5)
- Bericht (5)
- Masterarbeit (4)
- Rezension (4)
- Periodikum (3)
- Bachelorarbeit (2)
- Habilitation (2)
- Preprint (2)
Sprache
- Englisch (832)
- Deutsch (394)
- Französisch (17)
- Italienisch (2)
- Latein (2)
- Mehrsprachig (2)
- dut (1)
- mis (1)
Schlagworte
- climate change (11)
- Climate change (7)
- Klima (7)
- Klimaänderung (7)
- Modellierung (7)
- COSMO-CLM (6)
- Klimawandel (6)
- precipitation (6)
- Atmospheric chemistry (5)
- Deutschland (5)
Institut
- Geowissenschaften (775)
- Geowissenschaften / Geographie (135)
- Biodiversität und Klima Forschungszentrum (BiK-F) (61)
- Geographie (61)
- Senckenbergische Naturforschende Gesellschaft (54)
- Präsidium (44)
- Extern (28)
- Biowissenschaften (22)
- Institut für Ökologie, Evolution und Diversität (8)
- Physik (8)
MIPAS-Envisat is a satellite-borne sensor which measured vertical profiles of a wide range of trace gases from 2002 to 2012 using IR emission spectroscopy. We present geophysical validation of the MIPAS-Envisat operational retrieval (version 6.0) of N2O, CH4, CFC-12, and CFC-11 by the European Space Agency (ESA). The geophysical validation data are derived from measurements of samples collected by a cryogenic whole air sampler flown to altitudes of up to 34 km by means of large scientific balloons. In order to increase the number of coincidences between the satellite and the balloon observations, we applied a trajectory matching technique. The results are presented for different time periods due to a change in the spectroscopic resolution of MIPAS in early 2005. Retrieval results for N2O, CH4, and CFC-12 show partly good agreement for some altitude regions, which differs for the periods with different spectroscopic resolution. The more recent low spectroscopic resolution data above 20 km altitude show agreement with the combined uncertainties, while there is a tendency of the earlier high spectral resolution data set to underestimate these species above 25 km. The earlier high spectral resolution data show a significant overestimation of the mixing ratios for N2O, CH4, and CFC-12 below 20 km. These differences need to be considered when using these data. The CFC-11 results from the operation retrieval version 6.0 cannot be recommended for scientific studies due to a systematic overestimation of the CFC-11 mixing ratios at all altitudes.
MIPAS-Envisat is a satellite-borne sensor which measured vertical profiles of a wide range of trace gases from 2002 to 2012 using IR emission spectroscopy. We present geophysical validation of the MIPAS-Envisat operational retrieval (version 6.0) of N2O, CH4, CFC-12, and CFC-11 by the European Space Agency (ESA). The geophysical validation data are derived from measurements of samples collected by a cryogenic whole air sampler flown to altitudes of up to 34 km by means of large scientific balloons. In order to increase the number of coincidences between the satellite and the balloon observations, we applied a trajectory matching technique. The results are presented for different time periods due to a change in the spectroscopic resolution of MIPAS in early 2005. Retrieval results for N2O, CH4, and CFC-12 show partly good agreement for some altitude regions, which differs for the periods with different spectroscopic resolution. The more recent low spectroscopic resolution data above 20 km altitude show agreement with the combined uncertainties, while there is a tendency of the earlier high spectral resolution data set to underestimate these species above 25 km. The earlier high spectral resolution data show a significant overestimation of the mixing ratios for N2O, CH4, and CFC-12 below 20 km. These differences need to be considered when using these data. The CFC-11 results from the operation retrieval version 6.0 cannot be recommended for scientific studies due to a systematic overestimation of the CFC-11 mixing ratios at all altitudes.
Chlorine and bromine atoms lead to catalytic depletion of ozone in the stratosphere. Therefore the use and production of ozone-depleting substances (ODSs) containing chlorine and bromine is regulated by the Montreal Protocol to protect the ozone layer. Equivalent effective stratospheric chlorine (EESC) has been adopted as an appropriate metric to describe the combined effects of chlorine and bromine released from halocarbons on stratospheric ozone. Here we revisit the concept of calculating EESC. We derive a refined formulation of EESC based on an advanced concept of ODS propagation into the stratosphere and reactive halogen release. A new transit time distribution is introduced in which the age spectrum for an inert tracer is weighted with the release function for inorganic halogen from the source gases. This distribution is termed the release time distribution. We show that a much better agreement with inorganic halogen loading from the chemistry transport model TOMCAT is achieved compared with using the current formulation. The refined formulation shows EESC levels in the year 1980 for the mid-latitude lower stratosphere, which are significantly lower than previously calculated. The year 1980 is commonly used as a benchmark to which EESC must return in order to reach significant progress towards halogen and ozone recovery. Assuming that – under otherwise unchanged conditions – the EESC value must return to the same level in order for ozone to fully recover, we show that it will take more than 10 years longer than estimated in this region of the stratosphere with the current method for calculation of EESC. We also present a range of sensitivity studies to investigate the effect of changes and uncertainties in the fractional release factors and in the assumptions on the shape of the release time distributions. We further discuss the value of EESC as a proxy for future evolution of inorganic halogen loading under changing atmospheric dynamics using simulations from the EMAC model. We show that while the expected changes in stratospheric transport lead to significant differences between EESC and modelled inorganic halogen loading at constant mean age, EESC is a reasonable proxy for modelled inorganic halogen on a constant pressure level.
Chlorine and bromine atoms can lead to catalytic destruction of ozone in the stratosphere. Therefore the use and production of ozone depleting substances (ODS) containing chlorine and bromine is regulated by the Montreal Protocol to protect the ozone layer. Equivalent Effective Stratospheric Chlorine (EESC) has been adapted as an appropriate metric to describe the combined effects of chlorine and bromine released from halocarbons on stratospheric ozone. Here we revisit the concept of calculating EESC. We derive a new formulation of EESC based on an advanced concept of ODS propagation into the stratosphere and reactive halogen release. A new transit time distribution is introduced in which the age spectrum for an inert tracer is weighted with the release function for inorganic halogen from the source gases. This distribution is termed the “release time distribution”. The improved formulation shows that EESC levels in the year 1980 for the mid latitude lower stratosphere were significantly lower than previously calculated. 1980 marks the year commonly defined as the onset of anthropogenic ozone depletion in the stratosphere. Assuming that the EESC value must return to the same level in order for ozone to fully recover, we show that it will take more than 10 years longer than currently assumed in this region of the stratosphere. Based on the improved formulation, EESC level at mid-latitudes will reach this landmark only in 2060. We also present a range of sensitivity studies to investigate the effect of changes and uncertainties in the fractional release factors and in the assumptions on the shape of the release time distributions. We conclude that, under the assumptions that all other atmospheric parameters like stratospheric dynamics and chemistry are unchanged, the recovery of mid latitude stratospheric ozone would be expected to be delayed by about a 10 years, in a similar way as EESC.
During SPURT (Spurenstofftransport in der Tropopausenregion, trace gas transport in the tropopause region) we performed measurements of a wide range of trace gases with different lifetimes and sink/source characteristics in the northern hemispheric upper troposphere (UT) and lowermost stratosphere (LMS). A large number of in-situ instruments were deployed on board a Learjet 35A, flying at altitudes up to 13.7 km, at times reaching to nearly 380 K potential temperature. Eight measurement campaigns (consisting of a total of 36 flights), distributed over all seasons and typically covering latitudes between 35° N and 75° N in the European longitude sector (10° W–20° E), were performed. Here we present an overview of the project, describing the instrumentation, the encountered meteorological situations during the campaigns and the data set available from SPURT. Measurements were obtained for N2O, CH4, CO, CO2, CFC12, H2, SF6, NO, NOy, O3 and H2O. We illustrate the strength of this new data set by showing mean distributions of the mixing ratios of selected trace gases, using a potential temperature – equivalent latitude coordinate system. The observations reveal that the LMS is most stratospheric in character during spring, with the highest mixing ratios of O3 and NOy and the lowest mixing ratios of N2O and SF6. The lowest mixing ratios of NOy and O3 are observed during autumn, together with the highest mixing ratios of N2O and SF6 indicating a strong tropospheric influence. For H2O, however, the maximum concentrations in the LMS are found during summer, suggesting unique (temperature- and convection-controlled) conditions for this molecule during transport across the tropopause. The SPURT data set is presently the most accurate and complete data set for many trace species in the LMS, and its main value is the simultaneous measurement of a suite of trace gases having different lifetimes and physical-chemical histories. It is thus very well suited for studies of atmospheric transport, for model validation, and for investigations of seasonal changes in the UT/LMS, as demonstrated in accompanying and elsewhere published studies.
During SPURT (Spurenstofftransport in der Tropopausenregion, trace gas transport in the tropopause region) we performed measurements of a wide range of trace gases with different lifetimes and sink/source characteristics in the northern hemispheric upper troposphere (UT) and lowermost stratosphere (LMS). A large number of in-situ instruments were deployed on board a Learjet 35A, flying at altitudes up to 13.7 km, at times reaching to nearly 380 K potential temperature. Eight measurement campaigns (consisting of a total of 36 flights), distributed over all seasons and typically covering latitudes between 35° N and 75° N in the European longitude sector (10° W–20° E), were performed. Here we present an overview of the project, describing the instrumentation, the encountered meteorological situations during the campaigns and the data set available from SPURT. Measurements were obtained for N2O, CH4, CO, CO2, CFC12, H2, SF6, NO, NOy, O3 and H2O. We illustrate the strength of this new data set by showing mean distributions of the mixing ratios of selected trace gases, using a potential temperature – equivalent latitude coordinate system. The observations reveal that the LMS is most stratospheric in character during spring, with the highest mixing ratios of O3 and NOy and the lowest mixing ratios of N2O and SF6. The lowest mixing ratios of NOy and O3 are observed during autumn, together with the highest mixing ratios of N2O and SF6 indicating a strong tropospheric influence. For H2O, however, the maximum concentrations in the LMS are found during summer, suggesting unique (temperature- and convection-controlled) conditions for this molecule during transport across the tropopause. The SPURT data set is presently the most accurate and complete data set for many trace species in the LMS, and its main value is the simultaneous measurement of a suite of trace gases having different lifetimes and physical-chemical histories. It is thus very well suited for studies of atmospheric transport, for model validation, and for investigations of seasonal changes in the UT/LMS, as demonstrated in accompanying and elsewhere published studies.
Die Freisetzung von Fluorchlorkohlenwasserstoffen (FCKW) in die Atmosphäre ist seit Inkrafttreten des Montreal-Protokolls zum Schutz der Ozonschicht im Jahr 1987 reglementiert. Aber die ozonzerstörenden Gase sind äußerst langlebig. Sie können erst in der Stratosphäre, also in Höhen oberhalb von etwa zehn Kilometern, durch kurzwelliges, energiereiches Sonnenlicht gespalten werden. Messungen der FCKW und ihrer Ersatzstoffe am Institut für Atmosphäre und Umwelt erlauben es, die Lebenszeiten dieser Substanzen zu bestimmen und damit auch ihr Potenzial, die Ozonschicht zu schädigen und zur Klimaerwärmung beizutragen. Sie stellen einen wichtigen Beitrag zur Klimaforschung dar.
One possible approach to study systematically the influence of the deformation regime on the geometry of geological structures like folds and boudins is analogue modelling. For a complete understanding of the resulting structures, consideration of the third dimension is required. This PhD study deals with scaled analogue modelling under constriction and plane-strain conditions to improve our knowledge of folding and boudinage of lower crustal rocks in space and time. Plasticine is an appropriate analogue material for rocks in the lower crust. Therefore, this material was used for the experiments. The macroscopic behaviour of most types of plasticine is quite similar to rocks undergoing strain-rate softening and strain hardening regardless of the different microscopic aspects of deformation. Therefore, if one is aware that the stress exponent and viscosity increase with increasing strain, the original plasticine types used with stress exponents ranging from 5.8 to 8.0 are adequate for modelling geologic structures. The same holds for plasticine/oil mixtures. Thus, plasticine and plasticine/oil mixtures can be used to model the viscous flow of different rock types in the lower crust. If climb-accommodated dislocation creep and associated steady-state flow is assumed for the natural rocks, the plasticine/oil mixtures should be used, which flow under steady-state conditions. Three different experimental studies of plane-strain coaxial deformation of stiff layers, with viscosity η2 and stress exponent n2, embedded in a weak matrix, with viscosity η1 and stress exponent n1, have been carried out. The undeformed samples (matrix plus layer) were cubes with an edge length of 12 cm. All experimental runs have been carried out at T = 25 ± 1°C and varying strain rates ė, ranging from 7.9 x 10 high -6 s high -1 to 1.7 x 10 high -2 s high -1, until a finite longitudinal strain of 30% – 40% was achieved. The first experimental study improved the understanding about the evolution of folds and boudins when the layer is oriented perpendicular to the Y-axis of the finite strain ellipsoid. The rock analogues used were Beck’s green plasticine (matrix) and Beck’s black plasticine (competent layer), both of which are strain-rate softening modelling materials with stress exponent n = ca. 8. The effective viscosity η of the matrix plasticine was changed by adding different amounts of oil to the original plasticine. At a strain rate ė of 10 high -3 s high -1 and a finite strain e of 10%, the effective viscosity of the matrix ranges from 1.2 x 10 high 6 to 7.2 x 10 high 6 Pa s. The effective viscosity of the competent layer has been determined as 4.2 x 10 high 7 Pa s. If the viscosity ratio is large (> ca. 20) and the initial thickness of the competent layer is small, both folds and boudins develop simultaneously. Although the growth rate of the folds seems to be higher than the growth rate of the boudins, the wavelength of both structures is approximately the same as is suggested by analytical solutions. A further unexpected, but characteristic, aspect of the deformed competent layer is a significant increase in thickness, which can be used to distinguish plane-strain folds and boudins from constrictional folds and boudins. In the second experimental study, the impact of varying strain rates on growing folds and boudins under plane strain have been investigated. The strain rates used range from 7.9 x 10 high -6 s high -1 to 1.7 x 10 high -2 s high -1. The stiff layer and matrix consist of non-linear viscous Kolb grey and Beck’s green plasticine, respectively, both of which are strain-rate softening modelling materials with power law exponents (n) and apparent viscosities (η) ranging from 6.5 to 7.9 and 8.5 x 10 high 6 to 7.2 x 10 high 6 Pa s, respectively. The effective viscosity (η) of the matrix plasticine was partly modified by adding oil to the original plasticine. At the strain rates used in the experiments the viscosity ratio between layer and matrix ranges between 3 and 10. Different runs have been carried out where the layer was oriented perpendicular to the principal strain axes (X>Y>Z). The results suggest a considerable influence of the strain rate on the geometry of the deformed stiff layer including its thickness. This holds for every type of layer orientation (S ┴ X, S ┴ Y, S ┴ Z). If the stiff layer is oriented perpendicular to the short axis Z of the finite strain ellipsoid, the number of the resulting boudins and the thickness of the stiff layer increase, whereas the length of boudins decreases with increasing strain rate. If the stiff layer is oriented perpendicular to the long axis, X, of the finite strain ellipsoid, enlargement of the strain rate results in increasing wavelength of folds, whereas the number of folds and the degree of thickening of the stiff layer decreased. If the stiff layer is oriented perpendicular to the intermediate Y-axis of the finite strain ellipsoid enlargement of the strain rate results in a decreasing number of boudins and folds associated with increasing wavelengths of both structures. The wavelength of folds is approximately half of the boudins wavelength. This is true for the case where folds and boudins develop simultaneously (S ┴ Y) and for cases where both structures develop independently (folds at S ┴ X and boudins at S ┴ Z). In the third experimental study, scaled analogue experiments have been carried out to demonstrate the growth of plane-strain folds and boudins through space and time. Previous 3D-studies are based only on finite deformation structures. Their results can therefore not be used to prove if both structures grew simultaneously or in sequence. Plane strain acted on a single stiff layer that was embedded in a weak matrix, with the layer oriented perpendicular to the intermediate Y-axis of the finite strain ellipsoid. Two different experimental runs have been carried out using computer tomography (CT) to analyse the results. The first run was carried out without interruption. During the second run, the deformation was stopped in each case at longitudinal strain increments of 10%. Every experiment was carried out at a temperature T of 25°C and a strain rate, ė, of ca. 4 x 10 high -3 s high -1 until a finite longitudinal strain of 40% was achieved with a viscosity contrast m of 18.6 between the non-linear viscous layer (Kolb brown plasticine) and the matrix (Beck’s green plasticine with 150 ml oil kg high -1). The apparent viscosity, η, and the stress exponent, n, for the layer at a strain rate ė = ca. 10 high -3 s high -1 and a finite strain e = 10% are 2.23 x 10 high 7 Pa s and n = 5.8 and for the matrix 1.2 x 10 high 6 Pa s and 10.5. These new data that result from incremental analogue modelling corroborate previous suggestions that folds and boudins are coeval structures in cases of plane-strain coaxial deformation with the stiff layer oriented perpendicular to the intermediate Y-axis of the finite strain ellipsoid. They will be of interest for all workers who are dealing with plane-strain boudins and folds, where the fold axes are parallel to the major axis (X) of the finite strain ellipsoid. As has been demonstrated by the first experimental study, coeval folding and boudinage under plane strain, with S ┴ Y, are associated with a significant increase in the thickness of the competent layer. The latter phenomenon does not occur in other cases of simultaneous folding and boudinage, such as bulk pure constriction. To study the impact of layer thickness on the geometry of folds and boudins under pure constriction, we carried out additional experiments using different types of plasticine for a stiff layer and a weaker matrix to model folding and boudinaging under pure constriction, with the initially planar layer oriented parallel to the Xaxis of the finite strain ellipsoid. The stiff layer and matrix consist of non-linear viscous Kolb brown and Beck’s green plasticine, respectively, both of which are strain-rate softening modelling materials. Six runs have been carried out using thicknesses of the stiff layer of 1, 2, 4, 6, 8 and 10 ± 0.2 mm. All experimental runs were carried out at a temperature T of 30 ± 2°C and a strain rate, ė, of ca. 1.1 x 10 high -4 s high -1 until a finite longitudinal strain of 40% was achieved with a viscosity contrast m of 3.1 between the stiff layer (Kolb brown plasticine) and the matrix (Beck’s green plasticine). The apparent viscosity, η, and the stress exponent, n, for the layer at a strain rate ė = ca. 10 high -3 s high -1 and a finite strain e = 10% are 2.23 x 10 high 7 Pa s and n = 5.8 and for the matrix 7.2 x 10 high 6 Pa s and 7.9. Our results suggest a considerable influence of the initial thickness of the stiff layer on the geometry of the deformed stiff layer. There is no evidence for folding in XY=XZ-sections if the initial thickness of the competent layer is larger than ca. 8 mm. If the initial thickness of the competent layer is set at ca. 10 ± 0.2 mm, both folds and boudins develop simultaneously. However, the growth rate of the boudins seems to be higher than the growth rate of the folds. A further expected, but characteristic, aspect of the deformed competent layer is no change in thickness of the competent layer, which can be used to distinguish plane-strain folds and boudins from constrictional folds and boudins. The model results are important for the analysis and interpretation of deformation structures in rheologically stratified rocks undergoing dislocation creep under bulk constriction. Tectonic settings where constrictional folds and boudins may develop simultaneously are stems of salt diapirs, subduction zones or thermal plumes. To make (paleo) viscosimetric statements possible, the rheological data of the different plasticine types were related to the geometrical data. When comparing the normalized dominant wavelength Wd obtained from the deformed layer of the models with the theoretical dominant wavelength (Ld) calculated using the Smith equation (1977, 1979), the latter probably also holds when folding and boudinage develop simultaneously (S ┴ Y) and when boudins develop independently (S ┴ Z), but can obviously not be applied at very low viscosity ratios as is indicated by the low-strain-rate experiments.
Die METEOR-Fahrt 71 umfasst 3 biologisch und biogeochemisch orientierte Fahrtabschnitte mit insgesamt 50 Schiffstagen im östlichen Mittelmeer und hat folgende Ziele: Der Abschnitt METEOR 71-1 dient der physikalischen, biogeochemischen und biologischen Probengewinnung im Bereich der Anaximander Mountains. Es gibt nur einige wenige Seeberge im östlichen Mittelmeeres, die weitgehend isoliert vom übrigen Ozean sind und in einer Region liegen, die sich durch ein im Vergleich zum Weltozean sehr warmes Tiefenwasser von rund 14 °C auszeichnet. Hauptziel der Untersuchungen an einem Gipfel der Anaximander Mountains ist die Beantwortung der Frage, ob sich ein Seeberg-Ökosystem in einer oligotrophen Region mit warmen Tiefenwasser in Bezug auf seinen Einfluß auf das umgebende Strömungs- und Nährstoffregime, die Produktivität und Verteilung der Nahrungsketten, sowie in Bezug auf die Größe der „Sphere of interference“, das heißt dem Einflußbereich des Seamounts auf den umgebenden Wasserkörper, ähnlich verhält wie entsprechende Erhebungen im Nordostatlantik. Die Expedition METEOR 71-2 beschäftigt sich mit der Biodiversität in der Tiefsee des östlichen Mittelmeeres und ihren Steuerungsfaktoren (Tiefe, Küstenabstand, Nahrungsverfügbarkeit). Zum einen geht es um eine möglichst vollständige Erfassung der Artenzusammensetzung in zwei Referenzregionen durch Vielfachbeprobung an der selben Stelle, zum anderen um die Unterschiede des Arteninventars und des Artenreichtums in Abhängigkeit von der Tiefe und vom Küstenabstand. Die Arbeitsgebiete von jeweils 17 sm x 5 sm sind das Ierapetra-Becken südlich Kreta. (> 4000m Tiefe) und ein Gebiet der gleichen Größe weiter südlich (2800 m Tiefe doppelter Abstand zur Küste).Die Untersuchungen berücksichtigen alle Grössenklassen des Benthos (Mega-, Macro-, Meiound Nanofauna), um Gemeinsamkeiten und Unterschiede in der Abhängigkeit der Biodiversität von Ökofaktoren zu erkennen. Damit sollen die Struktur und die Funktion der Lebensgemeinschaften am äußerst oligotrophen Tiefseeboden des levantinischen Beckens besser und detaillierter verstanden werden. Arbeiten der Expedition METEOR 71-3 zielen auf die Klärung der Frage, ob im heutigen Mittelmeer Phosphatverlust und unvollständige Nitratnutzung, oder Stickstoff-Fixierung im ultraoligotrophen östlichen Mittelmeer für isotopisch abgereicherte d15N Signaturen von Sedimenten und Schwebstoffen verantwortlich sind. Ein Nebenziel ist die Gewinnung zusätzlicher Oberflächensedimente, um die Datenbasis für Eichungen des UK´37-Index und Abschätzung der Nährstoffakkumulationsraten in Sedimenten im Mittelmeers zu verbessern. Dazu werden auf Schnitten durch das östliche Mittelmeer Nährstoffprofile beprobt, Proben für Messungen der 15N/14N-Verhältnisse in Nitrat, gelöstem organischem Stickstoff, in Sinkstoffen und Oberflächensedimenten gewonnen, Untersuchungen des Phytoplanktons sowie Messungen von N2-Fixierungsraten durchgeführt. Weiter werden molekulare Techniken eingesetzt, um das Vorhandensein und die Transkription der nifH-Gene für das Nitrogenase-Enzym diazotropher Organismen zu überprüfen. Die Methoden zielen auf das nifHGen und seine Transkripte und geben Aufschluss über das Potential für Stickstofffixierung. Die Ergebnisse werden zeigen, ob das Gen aktiv in der Plankton-Gemeinschaft transkribiert wird. Ferne wird mit der DNA Sequenzanalyse neben der Anwesenheit auch die Diversität der diazotrophen Organismen etabliert. Schließlich wird im Verlauf der Fahrt an einer Station im Rhodos-Becken eine Sedimentfalle ausgebracht.
We present the first 3-D model of seismic P and S velocities in the crust and uppermost mantle beneath the Gulf of Aqaba and surrounding areas based on the results of passive travel time tomography. The tomographic inversion was performed based on travel time data from ∼ 9000 regional earthquakes provided by the Egyptian National Seismological Network (ENSN), and this was complemented with data from the International Seismological Centre (ISC). The resulting P and S velocity patterns were generally consistent with each other at all depths. Beneath the northern part of the Red Sea, we observed a strong high-velocity anomaly with abrupt limits that coincide with the coastal lines. This finding may indicate the oceanic nature of the crust in the Red Sea, and it does not support the concept of gradual stretching of the continental crust. According to our results, in the middle and lower crust, the seismic anomalies beneath the Gulf of Aqaba seem to delineate a sinistral shift (∼ 100 km) in the opposite flanks of the fault zone, which is consistent with other estimates of the left-lateral displacement in the southern part of the Dead Sea Transform fault. However, no displacement structures were visible in the uppermost lithospheric mantle.
Inappropriate land management leads to soil loss with destruction of the land’s resource and sediment input into the receiving river. Part of the sediment budget of a catchment is the estimation of soil loss. In the Ruzizi catchment in the Eastern Democratic Republic of the Congo (DRC), only limited research has been conducted on soil loss mainly dealing with local observations on geomorphological forms or river load measurements; a regional quantification of soil loss is missing so far. Such quantifications can be calculated using the Universal Soil Loss Equation (USLE). It is composed of four factors: precipitation (R), soil (K), topography (LS), and vegetation cover (C). The factors can be calculated in different ways according to the characteristics of the study area. In this paper, different approaches for calculating the single factors are reviewed and validated with field work in two sub-catchments of Ruzizi River supplying the water for the reservoirs of Ruzizi I and II hydroelectric dams. It became obvious that the (R)USLE model provides the best results with revised R and LS factors. C factor calculations required to conduct a supervised classification using the Maximum Likelihood Procedure. Different C factor values were assigned to the land cover classes. The calculations resulted in a soil loss rate for the predominantly occurring Ferralsols and Leptosols of around 576 kt/yr in both catchments, when 2016 landcover and precipitation are used. This represents an area-normalized value of 40.4 t/ha/yr for Ruzizi I and 50.5 t/ha/yr for Ruzizi II due to different landcover in the two sub-catchments. The mean value for the whole study area is 47.8 t/ha/yr or even 27.1 t/ha/yr when considering land management techniques like terracing on the slopes (P factor). This work has shown that the (R)USLE model can serve as an easy to handle tool for soil loss quantification when comprehensive field work results are sparse. The model can be implemented in Geographic Information Systems (GIS) with free data; hence, a validation is crucial. It becomes apparent that the use of high resolution Sentinel 2a MSI data as the basis for C factor calculations is an appropriate method for considering heterogeneous Land Use Land Cover (LULC) patterns. To transfer the approach to other regions, the calculation of factor R needs to be modified
Durch die vorliegende Arbeit wird die Genese von Nyong- und Ntem-Einzugsgebiet seit der Öffnung des Südatlantiks unter Berücksichtigung neotektonischer Vorgänge nachgezeichnet. Die Ergebnisse unterstützen die Identifikation geeigneter Sedimentfallen als Proxydatenarchive zur Paläoumweltrekonstruktion. Mithilfe von Fernerkundung und Geländearbeit wird der Formenschatz in den Einzugsgebieten hinsichtlich ihrer Morphogenese untersucht. Vier Formengesellschaften werden unterschieden: (1) Rumpfflächen und Inselberge, (2) ‚demi-oranges’ und ‚bas-fonds’, (3) anastomosierender Flusslauf und (4) Rumpfstufe mit Inselgebirge und Kerbtälern. Sie werden morphodynamisch-genetisch interpretiert. (1) Ein Pisolithhorizont unter einer hillwash-Decke wird als Ferricretresiduum einer Paläooberfläche gedeutet und als Ergebnis der Pedimentierung gewertet. Die Morphogenese eines Inselbergs ergänzt die Diskussion zur Einrumpfung. Die Entwicklung zweier Altarme zeigt einen dritten Prozess, der vermutlich LGM-zeitlich die Region veränderte. Die Kuppe eines Inselbergs gibt ein ehemaliges Flächenniveau wieder. Durch die rückschreitende Verlagerung einer Stufe wurde er herauspräpariert. (2) In den oberen Einzugsgebieten liegen zwischen polykonvexen Hügeln breite Auen. Es wird angenommen, dass sich der Formenschatz durch Lateralerosion nach einer initialen Eintiefung gebildet hat. Flussanzapfungen reduzieren das obere Einzugsgebiet des Nyong. Eine Klassifikation in drei Klassen ist anhand der Überformung der Anzapfungen möglich: Die erste ist durch eine Talwasserscheide und Anzapfungsknie definiert. Bei der zweiten ist das Erscheinungsbild überprägt, die Orientierung zum ehemaligen Vorfluter ist jedoch eindeutig zu erkennen. Die dritte Klasse lässt nur noch aufgrund der Flussbettphysiognomie eine Anzapfung vermuten. (3) Im Ntem-Binnendelta wurden weitflächig Schotter und Gesteinsbruchstücke abgelagert und durch Mangan- und Eisenoxid zu einem Fanglomerat ausgehärtet. Das Gewässernetz bildet die geologischen Strukturen ab. Es wird angenommen, dass sich das Binnendelta primär durch eine gestaffelte Abschiebung entlang E-W verlaufender Brüche gebildet hat. Die Sedimentfallen wurden vom Ntem mit spätpleistozänen bis holozänen Sedimenten verfüllt. Ein ursprünglich flächenhaft ausgebildetes Ferricret wurde durch E-W verlaufende Brüche unterteilt. (4) Unterhalb des Binnendeltas überwindet der Ntem in einem Kerbtal entlang einer NNE-SSW-Struktur mit zwei linearen Störungen die Rumpfstufe. Es erinnert an einen Graben mit zwei Transformstörungen. Entlang des Tals wurden weitflächig Gesteinsbruchstücke und Schotter abgelagert, die zu einem Fanglomerat aushärteten. Gesteinsschnitte geben verschiedene Prozesse wieder, die die Bildung des Kerbtals als Graben belegen. Ergänzend wird eine Lineamentanalyse durchgeführt. Es werden vier Cluster herausgearbeitet, die die linearen Einheiten primär der panafrikanischen Orogenese zuordnen. Archaische Strukturen konnten nicht eindeutig zugewiesen werden. In der Synthese wird versucht, die Einzelergebnisse auf die Fläche zu extrapolieren. Die Arbeit bietet einen breiten Einblick in die tropische Geomorphologie mit der genetischen Diskussion unterschiedlicher Formengesellschaften. Es werden primär die strukturellen Richtungen N-S, E-W und NE-SW hervorgehoben, entlang derer eine neotektonische Remobilisation stattfand. Hebungen, die sich seit dem Miozän verstärkt haben, sind Auslöser für geomorphologische Modifikationen und Extensionsbrüche. Die Nähe zur aktiven Cameroon Volcanic Line und die Kompression des Kongokratons durch Riftprozesse lösen die tektonischen Ereignisse aus. Die wiederholte tektonische Erneuerung durch Hebungen des zentralafrikanischen Hinterlands führte zu einer Umgestaltung des Drainagenetzes.
The Late Tertiary to Quaternary evolution of the Ntem interior delta in SW Cameroon shall be modelled. A step fault was formed along neotectonically remobilized Precambrian structures. Uncalibrated 14C-datations in this ‘sediment trap’ show Pleistocene to Holocene ages. Both within and below the interior delta pebbles and clasts which are cemented in an iron and manganese matrix were found. These ‘fanglomerates’ are used to discuss different processes of the younger evolution also concerning climatic fluctuations in the study area.
Beim Clusterprojekt ELEMENTS von Goethe-Universität, TU Darmstadt, Universität Gießen und GSI Helmholtzzentrum für Schwerionenforschung arbeiten Theorie und Experiment Hand in Hand, um die Struktur der Materie unter extremen Bedingungen zu verstehen. So wird ersichtlich, warum etwa Kollisionen von Neutronensternen viele der schweren Elemente auf unserem Planeten geliefert haben.
Questions: Habitat islands are often characterized by the presence of more or less sharp boundaries to adjacent matrix habitats. However, knowledge on boundaries of natural habitat islands is scarce, especially regarding patterns of beta diversity and its two underlying components: species turnover and nestedness. We therefore aim to quantify the effects of fine-scaled and sharp boundaries of quartz islands (quartz gravel-covered soils) on the different components of plant beta diversity and how they are linked to different soil environmental drivers. Location: Knersvlakte, Western Cape, South Africa. Methods: We sampled plant species richness in 56 fine-scale transects of 6 m × 1 m plots across eight different boundary types (four quartz island to matrix, four between habitats on quartz islands). Soil depth and chemistry (pH, electrical conductivity) were analyzed for each 1 m2 plot. Differences in the two beta diversity components (turnover and nestedness) for each boundary type were tested by t tests. We used linear models to test relationships between species and environmental dissimilarity. Results: All boundary types showed high beta diversity. Species turnover was the prevailing component for six boundary types, the nestedness component was only important for two boundary types. We found a significant linear increase of species dissimilarity with increasing dissimilarity in soil pH and distinct plant communities for the habitat types, but no significant increase for electrical conductivity or soil depth. Conclusions: The spatial distinctiveness of the quartz islands leads to sharp boundaries, which result in high beta diversity, mainly through species turnover. This reflects the high levels of diversification and adaptation of the local plant communities. Nestedness occurred at two boundaries to the matrix, indicating that the latter does not necessarily represent an impermeable boundary for all species of the respective ecosystem. Studying diversity patterns across boundaries contributes to the question of applicability of island biogeography theory to habitat islands.
Positive plant–plant interactions are thought to drive vegetation patterns in harsh environments, such as semi-arid areas. According to the stress-gradient hypothesis (SGH), the role of positive interactions between species (facilitation) is expected to increase with harshness, predicting associated variation in species composition along environmental gradients. However, the relation between stress and facilitation along environmental gradients is debated. Furthermore, differentiating facilitative interactions from other underlying mechanisms, such as microtopographic heterogeneity, is not trivial. We analysed the spatial co-occurrence relationships of vascular plant species that form patchy vegetation in arid lapilli fields (tephra) from recent volcanic eruptions on La Palma, Canary Islands. Assuming a harshness gradient negatively correlated with elevation because the lower elevations are more arid and water availability is considered the most limiting resource, and that an outcome of facilitation is plants co-occurring in the same patch, from the SGH we expected a greater degree of co-occurrence at lower elevation. We tested this at both the species and the individual plant level. We analysed the species composition of 1277 shrubby vegetation patches at 64 different sampling points, ranging from the coast to around 700 m a.s.l. Patch morphology and microtopographic heterogeneity variables were also measured, to account for their potential effects on the species composition of patches. We used generalized linear models and generalized mixed-effects models to analyse species richness, number of individuals in patches and percentage of patches with positive co-occurrences, and a pairwise co-occurrence analysis combined with a graphical network analysis to reveal positive links between 13 of the species. We found that the percentage of patches with positive co-occurrences increased at higher elevations, in contrast to the predictions of the SGH, but in accordance with a refined stress-gradient hypothesis for arid sites, in which characteristics of the interacting species are incorporated.
Selbstbedienung im Museum
(1974)
Es wird kurz über die Geschichte des Museums berichtet, das als Abteilung im "Städtischen Museum Osnabrück" 1890 seinen Anfang nahm. 1963 konnte die "Schlikkersche Villa" bezogen werden, und 1971 wurde die Abteilung zum selbständigen "Naturwissenschaftlichen Museum". Die weitere Entwicklung bis zum Tag der Eröffnung wird dargestellt und Angaben zum Gebäude und zum Personal bestand gemacht. Die Ansprachen anläßlich der Eröffnungsfeier werden wiedergegeben und die wesentlichen Schwerpunkte der Ausstellung beschrieben.
Binary nucleation of sulphuric acid-water particles is expected to be an important process in the free troposphere at low temperatures. SAWNUC (Sulphuric Acid Water Nucleation) is a model of binary nucleation that is based on laboratory measurements of the binding energies of sulphuric acid and water in charged and neutral clusters. Predictions of SAWNUC are compared for the first time comprehensively with experimental binary nucleation data from the CLOUD chamber at European Organization for Nuclear Research. The experimental measurements span a temperature range of 208–292 K, sulphuric acid concentrations from 1·106 to 1·109 cm−3, and distinguish between ion-induced and neutral nucleation. Good agreement, within a factor of 5, is found between the experimental and modeled formation rates for ion-induced nucleation at 278 K and below and for neutral nucleation at 208 and 223 K. Differences at warm temperatures are attributed to ammonia contamination which was indicated by the presence of ammonia-sulphuric acid clusters, detected by an Atmospheric Pressure Interface Time of Flight (APi-TOF) mass spectrometer. APi-TOF measurements of the sulphuric acid ion cluster distributions (math formula with i = 0, 1, ..., 10) show qualitative agreement with the SAWNUC ion cluster distributions. Remaining differences between the measured and modeled distributions are most likely due to fragmentation in the APi-TOF. The CLOUD results are in good agreement with previously measured cluster binding energies and show the SAWNUC model to be a good representation of ion-induced and neutral binary nucleation of sulphuric acid-water clusters in the middle and upper troposphere.
The SAWNUC microphysical aerosol nucleation model is used to study the effect of reactor walls on the interpretation of nucleation experiments with respect to nucleation theory. This work shows that loss processes, such as wall losses, influence the interpretation of nucleation experiments, especially at low growth rates and short lifetime of freshly nucleated particles. In these cases the power dependency of the formation rates, determined at a certain particle size, with respect to H2SO4 does not correspond to the approximate number of H2SO4 molecules in the critical cluster as expected by the first nucleation theorem. Observed ∂log(J)/∂log([H2SO4]) therefore can vary widely for identical nucleation conditions but different sink terms.
The SAWNUC (Sulphuric Acid Water NUCleation) microphysical aerosol nucleation model is used to study the effect of reactor walls on the interpretation of nucleation experiments with respect to nucleation theory. This work shows that loss processes, such as wall losses, influence the interpretation of nucleation experiments, especially at low growth rates and short lifetimes of freshly nucleated particles. In these cases the power dependency of the formation rates, determined at a certain particle size, with respect to H2SO4 does not correspond to the approximate number of H2SO4 molecules in the critical cluster as expected by the first nucleation theorem. Observed ∂log(J)/∂log([H2SO4]) therefore can vary widely for identical nucleation conditions but different sink terms.
Profiles of CFC-11 (CCl3F) and CFC-12 (CCl2F2) of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) aboard the European satellite Envisat have been retrieved from versions MIPAS/4.61 to MIPAS/4.62 and MIPAS/5.02 to MIPAS/5.06 level-1b data using the scientific level-2 processor run by Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research (IMK) and Consejo Superior de Investigaciones Científicas (CSIC), Instituto de Astrofísica de Andalucía (IAA). These profiles have been compared to measurements taken by the balloon-borne cryosampler, Mark IV (MkIV) and MIPAS-Balloon (MIPAS-B), the airborne MIPAS-STRatospheric aircraft (MIPAS-STR), the satellite-borne Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) and the High Resolution Dynamic Limb Sounder (HIRDLS), as well as the ground-based Halocarbon and other Atmospheric Trace Species (HATS) network for the reduced spectral resolution period (RR: January 2005–April 2012) of MIPAS. ACE-FTS, MkIV and HATS also provide measurements during the high spectral resolution period (full resolution, FR: July 2002–March 2004) and were used to validate MIPAS CFC-11 and CFC-12 products during that time, as well as profiles from the Improved Limb Atmospheric Spectrometer, ILAS-II. In general, we find that MIPAS shows slightly higher values for CFC-11 at the lower end of the profiles (below ∼ 15 km) and in a comparison of HATS ground-based data and MIPAS measurements at 3 km below the tropopause. Differences range from approximately 10 to 50 pptv ( ∼ 5–20 %) during the RR period. In general, differences are slightly smaller for the FR period. An indication of a slight high bias at the lower end of the profile exists for CFC-12 as well, but this bias is far less pronounced than for CFC-11 and is not as obvious in the relative differences between MIPAS and any of the comparison instruments. Differences at the lower end of the profile (below ∼ 15 km) and in the comparison of HATS and MIPAS measurements taken at 3 km below the tropopause mainly stay within 10–50 pptv (corresponding to ∼ 2–10 % for CFC-12) for the RR and the FR period. Between ∼ 15 and 30 km, most comparisons agree within 10–20 pptv (10–20 %), apart from ILAS-II, which shows large differences above ∼ 17 km. Overall, relative differences are usually smaller for CFC-12 than for CFC-11. For both species – CFC-11 and CFC-12 – we find that differences at the lower end of the profile tend to be larger at higher latitudes than in tropical and subtropical regions. In addition, MIPAS profiles have a maximum in their mixing ratio around the tropopause, which is most obvious in tropical mean profiles. Comparisons of the standard deviation in a quiescent atmosphere (polar summer) show that only the CFC-12 FR error budget can fully explain the observed variability, while for the other products (CFC-11 FR and RR and CFC-12 RR) only two-thirds to three-quarters can be explained. Investigations regarding the temporal stability show very small negative drifts in MIPAS CFC-11 measurements. These instrument drifts vary between ∼ 1 and 3 % decade−1. For CFC-12, the drifts are also negative and close to zero up to ∼ 30 km. Above that altitude, larger drifts of up to ∼ 50 % decade−1 appear which are negative up to ∼ 35 km and positive, but of a similar magnitude, above.
Profiles of CFC-11 (CCl3F) and CFC-12 (CCl2F2) of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) aboard the European satellite Envisat have been retrieved from versions MIPAS/4.61 to MIPAS/4.62 and MIPAS/5.02 to MIPAS/5.06 level-1b data using the scientific level-2 processor run by Karlsruhe Institute of Technology (KIT), Institute of Meteorology and Climate Research (IMK) and Consejo Superior de Investigaciones Científicas (CSIC), Instituto de Astrofísica de Andalucía (IAA). These profiles have been compared to measurements taken by the balloon-borne cryosampler, Mark IV (MkIV) and MIPAS-Balloon (MIPAS-B), the airborne MIPAS-STRatospheric aircraft (MIPAS-STR), the satellite-borne Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) and the High Resolution Dynamic Limb Sounder (HIRDLS), as well as the ground-based Halocarbon and other Atmospheric Trace Species (HATS) network for the reduced spectral resolution period (RR: January 2005–April 2012) of MIPAS. ACE-FTS, MkIV and HATS also provide measurements during the high spectral resolution period (full resolution, FR: July 2002–March 2004) and were used to validate MIPAS CFC-11 and CFC-12 products during that time, as well as profiles from the Improved Limb Atmospheric Spectrometer, ILAS-II. In general, we find that MIPAS shows slightly higher values for CFC-11 at the lower end of the profiles (below ∼ 15 km) and in a comparison of HATS ground-based data and MIPAS measurements at 3 km below the tropopause. Differences range from approximately 10 to 50 pptv ( ∼ 5–20 %) during the RR period. In general, differences are slightly smaller for the FR period. An indication of a slight high bias at the lower end of the profile exists for CFC-12 as well, but this bias is far less pronounced than for CFC-11 and is not as obvious in the relative differences between MIPAS and any of the comparison instruments. Differences at the lower end of the profile (below ∼ 15 km) and in the comparison of HATS and MIPAS measurements taken at 3 km below the tropopause mainly stay within 10–50 pptv (corresponding to ∼ 2–10 % for CFC-12) for the RR and the FR period. Between ∼ 15 and 30 km, most comparisons agree within 10–20 pptv (10–20 %), apart from ILAS-II, which shows large differences above ∼ 17 km. Overall, relative differences are usually smaller for CFC-12 than for CFC-11. For both species – CFC-11 and CFC-12 – we find that differences at the lower end of the profile tend to be larger at higher latitudes than in tropical and subtropical regions. In addition, MIPAS profiles have a maximum in their mixing ratio around the tropopause, which is most obvious in tropical mean profiles. Comparisons of the standard deviation in a quiescent atmosphere (polar summer) show that only the CFC-12 FR error budget can fully explain the observed variability, while for the other products (CFC-11 FR and RR and CFC-12 RR) only two-thirds to three-quarters can be explained. Investigations regarding the temporal stability show very small negative drifts in MIPAS CFC-11 measurements. These instrument drifts vary between ∼ 1 and 3 % decade−1. For CFC-12, the drifts are also negative and close to zero up to ∼ 30 km. Above that altitude, larger drifts of up to ∼ 50 % decade−1 appear which are negative up to ∼ 35 km and positive, but of a similar magnitude, above.
U–Pb age spectra of detrital zircons related to the East European Platform could be traced in paragneiss through the whole Mid-German-Crystalline Zone (Variscides, Central Europe) from the Odenwald via the Spessart to the Ruhla crystalline forming an exotic unit between Armorica and Laurussia. The depositional ages of the paragneiss are defined by the youngest age of the detrital zircons and the oldest intrusion ages as Ordovician to Silurian. The Ediacaran dominated age spectrum of detrital zircons from the paragneiss of the East Odenwald suggests the latter to be derived from the shelf of the East European Platform (Baltica), which was influenced by the 1.5 Ga old detritus delivered from a giant intrusion (Mazury granitoid, Poland). The detrital zircon age spectrum of the lower Palaeozoic paragneiss of the East Odenwald and sandstone of the northern Holy Cross Mountains are identical. The pure Sveconorwegian spectrum of the lower Palaeozoic quartzite from the Spessart, (Kirchner and Albert Int J Earth Sci 2020) and the Ruhla (Zeh and Gerdes Gondwana Res 17:254–263, 2010) could be sourced from Bornholm and southern Sweden. A U–Pb age spectrum with 88% Palaeozoic detrital zircons from a volcano-sedimentary rock of the East Odenwald is interpreted to be derived from a Silurian magmatic arc (46%), which was probably generated during the drift of the Mid-German-Crystalline Zone micro-continent to the south. A tentative plate tectonic model of Mid-German-Crystalline Zone is presented taking into account (a) the East European Platform related age spectra of the detrital zircons (b) the Ordovician to Silurian depositional age of the metasediments (c) the Silurian and Early Devonian intrusion age of the plutonic and volcanic rocks and (d) the U–Pb ages of the Middle Devonian high-grade metamorphism. The East European Platform-related part of the Mid-German-Crystalline Zone is interpreted as a micro-continent, which drifted through the Rheic Ocean to the south and collided with the Saxothuringian (Armorican Terrane Assemblage) during the Early Devonian. Such large-scale tectonic transport from the northern continent to the southern continent is also known from the SW Iberia, where Laurussia-related metasediments of the Rheic suture zone are explained by a large scale tectonic escape (Braid et al. J Geol Soc Lond 168:383–392, 2011).
U–Pb age spectra of detrital zircons related to the East European Platform could be traced in paragneiss through the whole Mid-German-Crystalline Zone (Variscides, Central Europe) from the Odenwald via the Spessart to the Ruhla crystalline forming an exotic unit between Armorica and Laurussia. The depositional ages of the paragneiss are defined by the youngest age of the detrital zircons and the oldest intrusion ages as Ordovician to Silurian. The Ediacaran dominated age spectrum of detrital zircons from the paragneiss of the East Odenwald suggests the latter to be derived from the shelf of the East European Platform (Baltica), which was influenced by the 1.5 Ga old detritus delivered from a giant intrusion (Mazury granitoid, Poland). The detrital zircon age spectrum of the lower Palaeozoic paragneiss of the East Odenwald and sandstone of the northern Holy Cross Mountains are identical. The pure Sveconorwegian spectrum of the lower Palaeozoic quartzite from the Spessart, (Kirchner and Albert Int J Earth Sci 2020) and the Ruhla (Zeh and Gerdes Gondwana Res 17:254–263, 2010) could be sourced from Bornholm and southern Sweden. A U–Pb age spectrum with 88% Palaeozoic detrital zircons from a volcano-sedimentary rock of the East Odenwald is interpreted to be derived from a Silurian magmatic arc (46%), which was probably generated during the drift of the Mid-German-Crystalline Zone micro-continent to the south. A tentative plate tectonic model of Mid-German-Crystalline Zone is presented taking into account (a) the East European Platform related age spectra of the detrital zircons (b) the Ordovician to Silurian depositional age of the metasediments (c) the Silurian and Early Devonian intrusion age of the plutonic and volcanic rocks and (d) the U–Pb ages of the Middle Devonian high-grade metamorphism. The East European Platform-related part of the Mid-German-Crystalline Zone is interpreted as a micro-continent, which drifted through the Rheic Ocean to the south and collided with the Saxothuringian (Armorican Terrane Assemblage) during the Early Devonian. Such large-scale tectonic transport from the northern continent to the southern continent is also known from the SW Iberia, where Laurussia-related metasediments of the Rheic suture zone are explained by a large scale tectonic escape (Braid et al. J Geol Soc Lond 168:383–392, 2011).
River flow regimes, including long-term average flows, seasonality, low flows, high flows and other types of flow variability, play an important role for freshwater ecosystems. Thus, climate change affects freshwater ecosystems not only by increased temperatures but also by altered river flow regimes. However, with one exception, transferable quantitative relations between flow alterations and ecological responses have not yet been derived. While discharge decreases are generally considered to be detrimental for ecosystems, the effect of future discharge increases is unclear. As a first step towards a global-scale analysis of climate change impacts on freshwater ecosystems, we quantified the impact of climate change on five ecologically relevant river flow indicators, using the global water model WaterGAP 2.1g to simulate monthly time series of river discharge with a spatial resolution of 0.5 degrees. Four climate change scenarios based on two global climate models and two greenhouse gas emissions scenarios were evaluated. We compared the impact of climate change by the 2050s to the impact of water withdrawals and dams on natural flow regimes that had occurred by 2002. Climate change was computed to alter seasonal flow regimes significantly (i.e. by more than 10%) on 90% of the global land area (excluding Greenland and Antarctica), as compared to only one quarter of the land area that had suffered from significant seasonal flow regime alterations due to dams and water withdrawals. Due to climate change, the timing of the maximum mean monthly river discharge will be shifted by at least one month on one third on the global land area, more often towards earlier months (mainly due to earlier snowmelt). Dams and withdrawals had caused comparable shifts on less than 5% of the land area only. Long-term average annual river discharge is predicted to significantly increase on one half of the land area, and to significantly decrease on one quarter. Dams and withdrawals had led to significant decreases on one sixth of the land area, and nowhere to increases. Thus, by the 2050s, climate change may have impacted ecologically relevant river flow characteristics more strongly than dams and water withdrawals have up to now. The only exception refers to the decrease of the statistical low flow Q90, with significant decreases both by past water withdrawals and future climate change on one quarter of the land area. However, dam impacts are likely underestimated by our study. Considering long-term average river discharge, only a few regions, including Spain, Italy, Iraq, Southern India, Western China, the Australian Murray Darling Basin and the High Plains Aquifer in the USA, all of them with extensive irrigation, are expected to be less affected by climate change than by past anthropogenic flow alterations. In some of these regions, climate change will exacerbate the discharge reductions, while in others climate change provides opportunities for reducing past reductions. Emissions scenario B2 leads to only slightly reduced alterations of river flow regimes as compared to scenario A2 even though emissions are much smaller. The differences in alterations resulting from the two applied climate models are larger than those resulting from the two emissions scenarios. Based on general knowledge about ecosystem responses to flow alterations and data related to flow alterations by dams and water withdrawals, we expect that the computed climate change induced river flow alterations will impact freshwater ecosystems more strongly than past anthropogenic alterations.
River flow regimes, including long-term average flows, seasonality, low flows, high flows and other types of flow variability, play an important role for freshwater ecosystems. Thus, climate change affects freshwater ecosystems not only by increased temperatures but also by altered river flow regimes. However, with one exception, transferable quantitative relations between flow alterations and ecosystem responses have not yet been derived. While discharge decreases are generally considered to be detrimental for ecosystems, the effect of future discharge increases is unclear. As a first step towards a global-scale analysis of climate change impacts on freshwater ecosystems, we quantified the impact of climate change on five ecologically relevant river flow indicators, using the global water model WaterGAP 2.1g to simulate monthly time series of river discharge with a spatial resolution of 0.5 degrees. Four climate change scenarios based on two global climate modelsand two greenhouse gas emissions scenarios were evaluated.
We compared the impact of climate change by the 2050s to the impact of water withdrawals and dams on natural flow regimes that had occurred by 2002. Climate change was computed to alter seasonal flow regimes significantly (i.e. by more than 10%) on 90% of the global land area (excluding Greenland and Antarctica), as compared to only one quarter of the land area that had suffered from significant seasonal flow regime alterations due to dams and water withdrawals. Due to climate change, the timing of the maximum mean monthly river discharge will be shifted by at least one month on one third on the global land area, more often towards earlier months (mainly due to earlier snowmelt). Dams and withdrawals had caused comparable shifts on less than 5% of the land area only. Long-term average annual river discharge is predicted to significantly increase on one half of the land area, and to significantly decrease on one quarter. Dams and withdrawals had led to significant decreases on one sixth of the land area, and nowhere to increases.
Thus, by the 2050s, climate change will have impacted ecologically relevant river flow characteristics much more strongly than dams and water withdrawals have up to now. The only exception refers to the decrease of the statistical low flow Q90, with significant decreases both by past water withdrawals and future climate change on one quarter of the land area. Considering long-term average river discharge, only a few regions, including Spain, Italy, Iraq, Southern India, Western China, the Australian Murray Darling Basin and the High Plains Aquifer in the USA, all of them with extensive irrigation, are expected to be less affected by climate change than by past anthropogenic flow alterations. In some of these regions, climate change will exacerbate the discharge reduction. Emissions scenario B2 leads to only slightly reduced alterations of river flow regimes as compared to scenario A2 even though emissions are much smaller. The differences in alterations resulting from the two applied climate models are larger than those resulting from the two emissions scenarios. Based on general knowledge about ecosystem responses to flow alterations and data related to flow alterations by dams and water withdrawals, we expect that the computed climate change induced river flow alterations will impact freshwater ecosystems more strongly than past anthropogenic alterations.
Wetlands such as bogs, swamps, or freshwater marshes are hotspots of biodiversity. For 5.1 million km2 of inland wetlands, the dynamics of area and water storage, which strongly impact biodiversity and ecosystem services, were simulated using the global hydrological model WaterGAP. For the first time, the impacts of both human water use and man‐made reservoirs (WUR) and future climate change (CC) on wetlands around the globe were quantified. WUR impacts are concentrated in arid/semiarid regions, where WUR decreased mean wetland water storage by more than 5% on 8.2% of the mean wetland area during 1986–2005 (Am), with highest decreases in groundwater depletion area. Using output of three climate models, CC impacts on wetlands were quantified, distinguishing unavoidable impacts [i.e., at 2 °C global warming (GW)] from avoidable impacts (difference between 3 °C and 2 °C impacts). Even unavoidable CC impacts are projected to be much larger than WUR impacts, also in arid/semiarid regions. On most wetland area with reliable estimates, avoidable CC impacts are more than twice as large as unavoidable impacts. In case of 2 °C GW, half of Am is estimated to be unaffected by mean storage changes of more than 5%, but only one third in case of 3 °C GW. Temporal variability of water storage will increase for most wetlands. Wetlands in dry regions will be affected the most, particularly by water storage decreases in the dry season. Different from wealthier countries, low‐income countries will dominantly suffer from a decrease in wetland water storage due to CC.
The Earth's future depends on how we manage the manifold risks of climate change (CC). It is state-of-the-art to assume that risk reduction requires participatory management involving a broad range of stakeholders and scientists. However, there is still little knowledge about the optimal design of participatory climate change risk management processes (PRMPs), in particular with respect to considering the multitude of substantial uncertainties that are relevant for PRMPs. To support the many local to regional PRMPs that are necessary for a successful global-scale reduction of CC risks, we present a roadmap for designing such transdisciplinary knowledge integration processes. The roadmap suggests ways in which uncertainties can be comprehensively addressed within a PRMP. We discuss the concept of CC risks and their management and propose an uncertainty framework that distinguishes epistemic, ontological, and linguistic uncertainty as well as ambiguity. Uncertainties relevant for CC risk management are identified. Communicative and modeling methods that support social learning as well as the development of risk management strategies are proposed for each of six phases of a PRMP. Finally, we recommend how to evaluate PRMPs as such evaluations and their publication are paramount for achieving a reduction of CC risks.
Groundwater recharge is the major limiting factor for the sustainable use of groundwater. To support water management in a globalized world, it is necessary to estimate, in a spatially resolved way, global-scale groundwater recharge. In this report, improved model estimates of diffuse groundwater recharge at the global-scale, with a spatial resolution of 0.5° by 0.5°, are presented. They are based on calculations of the global hydrological model WGHM (WaterGAP Global Hydrology Model) which, for semi-arid and arid areas of the globe, was tuned against independent point estimates of diffuse groundwater recharge. This has led to a decrease of estimated groundwater recharge under semi-arid and arid conditions as compared to the model results before tuning, and the new estimates are more similar to country level data on groundwater recharge. Using the improved model, the impact of climate change on groundwater recharge was simulated, applying two greenhouse gas emissions scenarios as interpreted by two different climate models.
Global-scale information on natural river flows and anthropogenic river flow alterations is required to identify areas where aqueous ecosystems are expected to be strongly degraded. Such information can support the identification of environmental flow guidelines and a sustainable water management that balances the water demands of humans and ecosystems. This study presents the first global assessment of the anthropogenic alteration of river flow regimes, in particular of flow variability, by water withdrawals and dams/reservoirs. Six ecologically relevant flow indicators were quantified using an improved version of the global water model WaterGAP. WaterGAP simulated, with a spatial resolution of 0.5 degree, river discharge as affected by human water withdrawals and dams around the year 2000, as well as naturalized discharge without this type of human interference. Compared to naturalized conditions, long-term average global discharge into oceans and internal sinks has decreased by 2.7% due to water withdrawals, and by 0.8% due to dams. Mainly due to irrigation, long-term average river discharge and statistical low flow Q90 (monthly river discharge that is exceeded in 9 out of 10 months) have decreased by more than 10% on one sixth and one quarter of the global land area (excluding Antarctica and Greenland), respectively. Q90 has increased significantly on only 5% of the land area, downstream of reservoirs. Due to both water withdrawals and reservoirs, seasonal flow amplitude has decreased significantly on one sixth of the land area, while interannual variability has increased on one quarter of the land area mainly due to irrigation. It has decreased on only 8% of the land area, in areas downstream of reservoirs where consumptive water use is low. The impact of reservoirs is likely underestimated by our study as small reservoirs are not taken into account. Areas most affected by anthropogenic river flow alterations are the Western and Central USA, Mexico, the western coast of South America, the Mediterranean rim, Southern Africa, the semi-arid and arid countries of the Near East and Western Asia, Pakistan and India, Northern China and the Australian Murray-Darling Basin, as well as some Arctic rivers. Due to a large number of uncertainties related e.g. to the estimation of water use and reservoir operation rules, the analysis is expected to provide only first estimates of river flow alterations that should be refined in the future.
Global-scale information on natural river flows and anthropogenic river flow alterations is required to identify areas where aqueous ecosystems are expected to be strongly degraded. Such information can support the identification of environmental flow guidelines and a sustainable water management that balances the water demands of humans and ecosystems. This study presents the first global assessment of the anthropogenic alteration of river flow regimes by water withdrawals and dams, focusing in particular on the change of flow variability. Six ecologically relevant flow indicators were quantified using an improved version of the global water model WaterGAP. WaterGAP simulated, with a spatial resolution of 0.5 degree, river discharge as affected by human water withdrawals and dams, as well as naturalized discharge without this type of human interference. Mainly due to irrigation, long-term average river discharge and statistical low flow Q90 (monthly river discharge that is exceeded in 9 out of 10 months) have decreased by more than 10% on one sixth and one quarter of the global land area (excluding Antarctica and Greenland), respectively. Q90 has increased significantly on only 5% of the land area, downstream of reservoirs. Due to both water withdrawals and dams, seasonal flow amplitude has decreased significantly on one sixth of the land area, while interannual variability has increased on one quarter of the land area mainly due to irrigation. It has decreased on only 8% of the land area, in areas with little consumptive water use that are downstream of dams. Areas most affected by anthropogenic river flow alterations are the western and central USA, Mexico, the western coast of South America, the Mediterranean rim, Southern Africa, the semi-arid and arid countries of the Near East and Western Asia, Pakistan and India, Northern China and the Australian Murray-Darling Basin, as well as some Arctic rivers. Due to a large number of uncertainties related e.g. to the estimation of water use and reservoir operation rules, the analysis is expected to provide only first estimates of river flow alterations that should be refined in the future.
Long-term average groundwater recharge, which is equivalent to renewable groundwater resources, is the major limiting factor for the sustainable use of groundwater. Compared to surface water resources, groundwater resources are more protected from pollution, and their use is less restricted by seasonal and inter-annual flow variations. To support water management in a globalized world, it is necessary to estimate groundwater recharge at the global scale. Here, we present a best estimate of global-scale long-term average diffuse groundwater recharge (i.e. renewable groundwater resources) that has been calculated by the most recent version of the WaterGAP Global Hydrology Model WGHM (spatial resolution of 0.5° by 0.5°, daily time steps). The estimate was obtained using two state-of-the-art global data sets of gridded observed precipitation that we corrected for measurement errors, which also allowed to quantify the uncertainty due to these equally uncertain data sets. The standard WGHM groundwater recharge algorithm was modified for semi-arid and arid regions, based on independent estimates of diffuse groundwater recharge, which lead to an unbiased estimation of groundwater recharge in these regions. WGHM was tuned against observed long-term average river discharge at 1235 gauging stations by adjusting, individually for each basin, the partitioning of precipitation into evapotranspiration and total runoff. We estimate that global groundwater recharge was 12 666 km3/yr for the climate normal 1961–1990, i.e. 32% of total renewable water resources. In semi-arid and arid regions, mountainous regions, permafrost regions and in the Asian Monsoon region, groundwater recharge accounts for a lower fraction of total runoff, which makes these regions particularly vulnerable to seasonal and inter-annual precipitation variability and water pollution. Average per-capita renewable groundwater resources of countries vary between 8 m3/(capita yr) for Egypt to more than 1 million m3/(capita yr) for the Falkland Islands, the global average in the year 2000 being 2091 m3/(capita yr). Regarding the uncertainty of estimated groundwater resources due to the two precipitation data sets, deviation from the mean is 1.1% for the global value, and less than 1% for 50 out of the 165 countries considered, between 1 and 5% for 62, between 5 and 20% for 43 and between 20 and 80% for 10 countries. Deviations at the grid scale can be much larger, ranging between 0 and 186 mm/yr.
Long-term average groundwater recharge, which is equivalent to renewable groundwater resources, is the major limiting factor for the sustainable use of groundwater. Compared to surface water resources, groundwater resources are more protected from pollution, and their use is less restricted by seasonal and inter-annual flow variations. To support water management in a globalized world, it is necessary to estimate groundwater recharge at the global scale. Here, we present a best estimate of global-scale long-term average diffuse groundwater recharge (i.e. renewable groundwater resources) that has been calculated by the most recent version of the WaterGAP Global Hydrology Model WGHM (spatial resolution of 0.5° by 0.5°, daily time steps). The estimate was obtained using two state-of-the art global data sets of gridded observed precipitation that we corrected for measurement errors, which also allowed to quantify the uncertainty due to these equally uncertain data sets. The standard WGHM groundwater recharge algorithm was modified for semi-arid and arid regions, based on 15 independent estimates of diffuse groundwater recharge, which lead to an unbiased estimation of groundwater recharge in these regions. WGHM was tuned against observed long-term average river discharge at 1235 gauging stations by adjusting, individually for each basin, the partitioning of precipitation into evapotranspiration and total runoff. We estimate that global groundwater recharge was 12 666 km3/yr for the climate nor20 mal 1961–1990, i.e. 32% of total renewable water resources. In semi-arid and arid regions, mountainous regions, permafrost regions and in the Asian Monsoon region, groundwater recharge accounts for a lower fraction of total runoff, which makes these regions particularly vulnerable to seasonal and inter-annual precipitation variability and water pollution. Average per-capita renewable groundwater resources of countries vary 25 between 8m3/(capita yr) for Egypt to more than 1 million m3/(capita yr) for the Falkland Islands, the global average in the year 2000 being 2091m3/(capita yr). Regarding the uncertainty of estimated groundwater resources due to the two precipitation data sets, deviation from the mean is less than 1% for 50 out of the 165 countries considered, between 1 and 5% for 62, between 5 and 20% for 43 and between 20 and 80% for 10 countries. Deviations at the grid scale can be much larger, ranging between 0 and 186 mm/yr.
Quantification of spatially and temporally resolved water flows and water storage variations for all land areas of the globe is required to assess water resources, water scarcity and flood hazards, and to understand the Earth system. This quantification is done with the help of global hydrological models (GHMs). What are the challenges and prospects in the development and application of GHMs? Seven important challenges are presented. (1) Data scarcity makes quantification of human water use difficult even though significant progress has been achieved in the last decade. (2) Uncertainty of meteorological input data strongly affects model outputs. (3) The reaction of vegetation to changing climate and CO2 concentrations is uncertain and not taken into account in most GHMs that serve to estimate climate change impacts. (4) Reasons for discrepant responses of GHMs to changing climate have yet to be identified. (5) More accurate estimates of monthly time series of water availability and use are needed to provide good indicators of water scarcity. (6) Integration of gradient-based groundwater modelling into GHMs is necessary for a better simulation of groundwater–surface water interactions and capillary rise. (7) Detection and attribution of human interference with freshwater systems by using GHMs are constrained by data of insufficient quality but also GHM uncertainty itself. Regarding prospects for progress, we propose to decrease the uncertainty of GHM output by making better use of in situ and remotely sensed observations of output variables such as river discharge or total water storage variations by multi-criteria validation, calibration or data assimilation. Finally, we present an initiative that works towards the vision of hyperresolution global hydrological modelling where GHM outputs would be provided at a 1-km resolution with reasonable accuracy.
Large-scale hydrological modelling has become increasingly wide-spread during the last decade. An annual workshop series on large-scale hydrological modelling has provided, since 1997, a forum to the German-speaking community for discussing recent developments and achievements in this research area. In this paper we present the findings from the 2007 workshop which focused on advances and visions in large-scale hydrological modelling. We identify the state of the art, difficulties and research perspectives with respect to the themes "sensitivity of model results", "integrated modelling" and "coupling of processes in hydrosphere, atmosphere and biosphere". Some achievements in large-scale hydrological modelling during the last ten years are presented together with a selection of remaining challenges for the future.
Wasser weltweit : wie groß sind die globalen Süßwasserressourcen, und wie nutzt sie der Mensch?
(2008)
Ohne Wasser kein Leben – die ersten organischen Moleküle entwickelten sich im Wasser, aus Wasser plus Kohlenstoff und Stickstoff, und auch heute brauchen Pflanzen, Tiere und Menschen viel Wasser, um zu überleben. Die Erde ist der einzige Planet mit flüssigem Wasser und der einzige Planet, auf dem es Leben gibt, zumindest in unserem Sonnensystem. Zwei Umstände bewirken gemeinsam, dass nur die Erde die richtige Temperatur für flüssiges Wasser an ihrer Oberfl äche hat: ihr Abstand zur Sonne und ihre Masse. Aufgrund ihrer ausreichend großen Masse kann sie eine Atmosphäre halten, die die mittlere Oberflächentemperatur von –18 °C auf +15 °C erhöht. Nur daher konnte sich im Frühstadium der Erdentstehung das Wasser, das in großen Mengen aus dem Erdinnern ausgaste, an der Oberfläche als flüssiges Wasser in den Ozeanen sammeln.
Die vorliegende Arbeit wurde im Rahmen des Forschungsprojekts „Integrierte Analyse von mobilen, organischen Fremdstoffen in Fließgewässern“ (INTAFERE) am Institut für Physische Geographie an der Goethe-Universität Frankfurt erstellt. In INTAFERE wurde das Gefährdungspotenzial von mobilen, organischen Fremdstoffen (MOF) für aquatische Ökosysteme und die natürlichen Wasserressourcen in integrierter und partizipativer Art und Weise untersucht. MOF sind chemische Substanzen, die in Alltagsprodukten enthalten sind und durch unterschiedliche Eintragsfade in unbekannten Mengen in Oberflächengewässer eingetragen werden. Problematisch sind aus Umweltgesichtspunkten ihre Eigenschaften: sie besitzen im Wasser eine hohe Mobilität und sind schwer abbaubar. Dies führt zu einer Persistenz über lange Zeiträume. Für einige dieser Substanzen wurde zudem gezeigt, dass sie in sehr geringen Konzentrationen biologisch aktiv sind und für aquatische Ökosysteme eine Gefahr darstellen. In INTAFERE wurden drei zentrale Ziele verfolgt: Charakterisierung des Problemfeldes MOF, Erzeugung von praxisrelevantem Wissen für das Management von MOF und Entwicklung einer Softwareanwendung, die gesellschaftliche Aushandlungsprozesse durch eine transparente Darstellung der Wirkungszusammenhänge im Problemfeld unterstützt. Um einen Beitrag für die Erfüllung der Ziele zu leisten, war es die Aufgabe der Verfasserin, eine Akteursanalyse und -modellierung durchzuführen sowie Zukunftsszenarien im Bereich der MOF zu entwickeln. Dafür existierte keine adäquate Methodik, daher verfolgt die Dissertation zum einen die Entwicklung einer Methodik und zum anderen deren Anwendung im Kontext des Projektes INTAFERE. Da im Forschungsprozess die Durchführung von Analysen, die wissenschaftliche und gesellschaftliche Sichtweise der Problematik sowie die Erarbeitung von praktischen Lösungen im Mittelpunkt standen, wurde eine transdisziplinäre Herangehensweise gewählt. Ziel war es, eine Methodik zu entwerfen, die sowohl eine Entwicklung von Szenarien als auch eine Modellierung von Handlungsentscheidungen umfasst. Eine Modellierung und Visualisierung von Handlungsentscheidungen ist notwendig, um Strategien für ein Umweltproblem für verschiedene Szenarien zu ermitteln, und damit einen Lernprozess der Stakeholder zu initiieren. Dies wurde mit der transdisziplinären Methode „Akteursbasierte Modellierung“ umgesetzt. Hierbei wurden insbesondere Aspekte der Problemwahrnehmung von Akteuren und deren Darstellung, der partizipativen Szenarienentwicklung sowie der semi-quantitativen Modellierung von Handlungsentscheidungen berücksichtigt. Die Verfasserin hat mit der semi-quantitativen akteursbasierten Modellierung eine Methode erarbeitet und getestet, die bisher unverbundene Komponenten (wie die Software Dynamic Actor Network Analysis (DANA) und die Szenarienentwicklung) zusammenführt. Um Handlungsentscheidungen unter verschiedenen Szenarien zu modellieren hat die Autorin eine sequentielle Modellierung entwickelt, die mit der Software DANA durchgeführt werden kann. Die dafür notwendige Weiterentwicklung von DANA wurde von Dr. Pieter Bots (TU Delft) umgesetzt. Die akteursbasierte Modellierung läuft in drei methodischen Schritten ab: 1. Modellierung von Akteurs-Sichtweisen in Form von Wahrnehmungsgraphen und deren Analyse, aufbauend auf Ergebnissen von qualitativen, leitfaden-gestützten Expertengesprächen (= Akteursmodellierung), 2. partizipative Szenarienentwicklung mit den Akteuren und 3. Zusammenführung der Ergebnisse der Akteursmodellierung und der Szenarienentwicklung und darauf aufbauend eine sequentielle Modellierung von Handlungsentscheidungen und deren Auswirkungen auf Schlüsselfaktoren. Im Zuge der Anwendung auf das Problemfeld der MOF wurde für folgende Akteure jeweils ein Wahrnehmungsgraph modelliert: Obere Wasserbehörde, Umweltbundesamt, Umwelt- und Verbraucherschutzorganisationen, Wasserversorger sowie für die Hersteller von verschiedenen MOF, weiterhin für die European Flame Retardants Association und die Weiterverarbeitende Industrie. Das Ergebnis der Szenarienentwicklung waren vier Szenarien: ein Gesundheitsszenario, unter der Annahme von hohen lokalen Umweltstandards durch nachhaltigkeitsorientierte KonsumentInnen, ein Umweltszenario, in dem eine starke Regulierung und nachhaltigkeitsorientierter Konsum Hand in Hand gehen, ein Globalisierungsszenario, in dem Wirtschaftsmacht und preisbewusste KonsumentInnen statt staatliche Regulierung vorherrschen und ein Technikszenario, unter der Annahme, dass Kläranlagen, bedingt durch eine starke Regulierung, aufgerüstet werden. Bei der Modellierung von Handlungsentscheidungen wurden die Wahrnehmungsgraphen und die vier Szenarien miteinander verknüpft. Pro Substanz wurde ein Modell entwickelt, welches die wichtigsten Systemkomponenten in einer angemessenen Komplexität umfasst und die von den Akteuren gemeinsam getragene Einschätzung der Wirkungsbeziehungen darstellt. Insgesamt wurden 16 Modelle entwickelt. Basierend auf den simulierten Akteurshandlungen wurden relativen Veränderungen der Schlüsselfaktoren Produktion, Import und Leistungsfähigkeit der Kläranlagen für die vier genannten Szenarien berechnet. In Zusammenarbeit mit Pieter Bots konnten algorithmische Beiträge zur Analyse- und Modellierungssoftware DANA getestet und verbessert werden. Da keine vollständige und zugleich leicht verständliche Einführung zu DANA vorlag, wurde für Nutzer im Rahmen dieser Dissertation eine Anleitung verfasst, die die Modellierung von Wahrnehmungsgraphen und deren Analyse sowie alle Schritte der akteursbasierten Modellierung mit DANA erläutert.
Die vorliegende Arbeit wurde im Rahmen des Forschungsprojekts „Integrierte Analyse von mobilen, organischen Fremdstoffen in Fließgewässern“ (INTAFERE) am Institut für Physische Geographie an der Goethe-Universität Frankfurt erstellt. In INTAFERE wurde das Gefährdungspotenzial von mobilen, organischen Fremdstoffen (MOF) für aquatische Ökosysteme und die natürlichen Wasserressourcen in integrierter und partizipativer Art und Weise untersucht. MOF sind chemische Substanzen, die in Alltagsprodukten enthalten sind und durch unterschiedliche Eintragsfade in unbekannten Mengen in Oberflächengewässer eingetragen werden. Problematisch sind aus Umweltgesichtspunkten ihre Eigenschaften: sie besitzen im Wasser eine hohe Mobilität und sind schwer abbaubar. Dies führt zu einer Persistenz über lange Zeiträume. Für einige dieser Substanzen wurde zudem gezeigt, dass sie in sehr geringen Konzentrationen biologisch aktiv sind und für aquatische Ökosysteme eine Gefahr darstellen. In INTAFERE wurden drei zentrale Ziele verfolgt: Charakterisierung des Problemfeldes MOF, Erzeugung von praxisrelevantem Wissen für das Management von MOF und Entwicklung einer Softwareanwendung, die gesellschaftliche Aushandlungsprozesse durch eine transparente Darstellung der Wirkungszusammenhänge im Problemfeld unterstützt. Um einen Beitrag für die Erfüllung der Ziele zu leisten, war es die Aufgabe der Verfasserin, eine Akteursanalyse und -modellierung durchzuführen sowie Zukunftsszenarien im Bereich der MOF zu entwickeln. Dafür existierte keine adäquate Methodik, daher verfolgt die Dissertation zum einen die Entwicklung einer Methodik und zum anderen deren Anwendung im Kontext des Projektes INTAFERE. Da im Forschungsprozess die Durchführung von Analysen, die wissenschaftliche und gesellschaftliche Sichtweise der Problematik sowie die Erarbeitung von praktischen Lösungen im Mittelpunkt standen, wurde eine transdisziplinäre Herangehensweise gewählt. Ziel war es, eine Methodik zu entwerfen, die sowohl eine Entwicklung von Szenarien als auch eine Modellierung von Handlungsentscheidungen umfasst. Eine Modellierung und Visualisierung von Handlungsentscheidungen ist notwendig, um Strategien für ein Umweltproblem für verschiedene Szenarien zu ermitteln, und damit einen Lernprozess der Stakeholder zu initiieren. Dies wurde mit der transdisziplinären Methode „Akteursbasierte Modellierung“ umgesetzt. Hierbei wurden insbesondere Aspekte der Problemwahrnehmung von Akteuren und deren Darstellung, der partizipativen Szenarienentwicklung sowie der semi-quantitativen Modellierung von Handlungsentscheidungen berücksichtigt. Die Verfasserin hat mit der semi-quantitativen akteursbasierten Modellierung eine Methode erarbeitet und getestet, die bisher unverbundene Komponenten (wie die Software Dynamic Actor Network Analysis (DANA) und die Szenarienentwicklung) zusammenführt. Um Handlungsentscheidungen unter verschiedenen Szenarien zu modellieren hat die Autorin eine sequentielle Modellierung entwickelt, die mit der Software DANA durchgeführt werden kann. Die dafür notwendige Weiterentwicklung von DANA wurde von Dr. Pieter Bots (TU Delft) umgesetzt. Die akteursbasierte Modellierung läuft in drei methodischen Schritten ab: 1. Modellierung von Akteurs-Sichtweisen in Form von Wahrnehmungsgraphen und deren Analyse, aufbauend auf Ergebnissen von qualitativen, leitfaden-gestützten Expertengesprächen (= Akteursmodellierung), 2. partizipative Szenarienentwicklung mit den Akteuren und 3. Zusammenführung der Ergebnisse der Akteursmodellierung und der Szenarienentwicklung und darauf aufbauend eine sequentielle Modellierung von Handlungsentscheidungen und deren Auswirkungen auf Schlüsselfaktoren. Im Zuge der Anwendung auf das Problemfeld der MOF wurde für folgende Akteure jeweils ein Wahrnehmungsgraph modelliert: Obere Wasserbehörde, Umweltbundesamt, Umwelt- und Verbraucherschutzorganisationen, Wasserversorger sowie für die Hersteller von verschiedenen MOF, weiterhin für die European Flame Retardants Association und die Weiterverarbeitende Industrie. Das Ergebnis der Szenarienentwicklung waren vier Szenarien: ein Gesundheitsszenario, unter der Annahme von hohen lokalen Umweltstandards durch nachhaltigkeitsorientierte KonsumentInnen, ein Umweltszenario, in dem eine starke Regulierung und nachhaltigkeitsorientierter Konsum Hand in Hand gehen, ein Globalisierungsszenario, in dem Wirtschaftsmacht und preisbewusste KonsumentInnen statt staatliche Regulierung vorherrschen und ein Technikszenario, unter der Annahme, dass Kläranlagen, bedingt durch eine starke Regulierung, aufgerüstet werden. Bei der Modellierung von Handlungsentscheidungen wurden die Wahrnehmungsgraphen und die vier Szenarien miteinander verknüpft. Pro Substanz wurde ein Modell entwickelt, welches die wichtigsten Systemkomponenten in einer angemessenen Komplexität umfasst und die von den Akteuren gemeinsam getragene Einschätzung der Wirkungsbeziehungen darstellt. Insgesamt wurden 16 Modelle entwickelt. Basierend auf den simulierten Akteurshandlungen wurden relativen Veränderungen der Schlüsselfaktoren Produktion, Import und Leistungsfähigkeit der Kläranlagen für die vier genannten Szenarien berechnet. In Zusammenarbeit mit Pieter Bots konnten algorithmische Beiträge zur Analyse- und Modellierungssoftware DANA getestet und verbessert werden. Da keine vollständige und zugleich leicht verständliche Einführung zu DANA vorlag, wurde für Nutzer im Rahmen dieser Dissertation eine Anleitung verfasst, die die Modellierung von Wahrnehmungsgraphen und deren Analyse sowie alle Schritte der akteursbasierten Modellierung mit DANA erläutert.
The present work was devised to address the systematic analysis of samples from a range of Roman non-ferrous metal artefacts from different archaeological contexts and sites in the Roman provinces of Germania Superior. One of the focal points of this study is the provenancing of different lead objects from five important Roman settlements between 15 BC and the beginning of fourth century AD. For this purpose, measurements were made on lead and copper ore samples from the Siegerland, Eifel, Hunsrück and Lahn-Dill area in Germany and supplemented with data from the literature to create a data bank of lead isotope ratios of European deposits. Compositional analysis of lead objects by Electron Microprobe analysis showed that Romans were able to purify lead from ore up to 99%. Multi-Collector Inductively Coupled Plasma Mass-Spectrometry was used to determine the source of lead, which played an important role in nearly all aspects of Roman life. Lead isotope ratios were measured for ore samples from German deposits from the eastern side of the Rhine (Siegerland, Lahn-Dill, Ems) and the western side of the Rhine (Eifel, Hunsrück), which contained enough ore reserves to answer the increasing local demand and are believed to have been mined during the Roman period. This data together with those from Mediterranean ore deposits from the literature was used to establish a data bank. The Mediterranean ore deposits range from Cambrian (high 207Pb/206Pb) to tertiary (lower 207Pb/206Pb) values. In particular, the Cypriot deposits are younger, while the Spanish deposits fall either with the younger Sardic ores or close to the older Cypriot ores. The lead isotope ratios of most German ore deposits fall in between the 208Pb/206Pb vs. 207Pb/206Pb ratios of Sardinia and Cyprus, where the lead isotope signature of ore deposits from France and Britain are also found. Over 240 lead objects were measured from Wallendorf (second century BC to first century AD) Dangstetten (15-8 BC), Waldgirmes (AD 1-10), Mainz (AD 1-300), Martberg (first to fourth centuries AD) & Trier (third to fourth centuries AD). Comparing the lead isotope ratios of lead objects and those from German ores shows that the source of over 85 percent of objects are Eifel ore deposits, but the Roman’s had also imported lead from the Southern Massif Central and from Great Britain. A further topic of this work was the systematic study of the variation of copper isotope ratios in different copper minerals and the mechanisms, which controls copper isotope fractionation in ores deposits. For this purpose, copper isotope analyses were made by Multi-Collector Inductively Coupled Plasma Mass-Spectrometry from a series of hydrothermal copper sulphides and their alteration products. Copper and lead isotope ratios were measured in coexisting phases of chalcopyrite and malachite and also coexisting malachite and azurite. No significant fractionation was observed in malachite-azurite phases, but in chalcopyrite-malachite coexisting phases, malachite always shows a positive fractionation to heavier isotope values. Zhu et al. and Larson et al. showed that isotopic variations in copper principally reflect mass fractionation in response to low temperature processes rather than source heterogeneity. The low temperature ore formation processes are mostly represented by weathering of primary sulphide ores to produce secondary carbonate phases and therefore are usually observed on the surface of ore deposits, which were probably removed during the early Bronze Age. Using this concept, copper isotope ratios were measured in some Early Bronze Age copper alloys and Roman copper alloys. However, no large copper isotope fractionation has been observed. Lead and copper isotope ratios were measured on samples from the Kupferschiefer. Two profiles were investigated; 1) Sangerhausen, which was not directly influenced by the oxidizing brines of Rote Fäule and 2) Oberkatz, where both Rote Fäule-controlled and structure-controlled mineralization were observed. Results from maturation studies of organic matter suggest the maximum temperature affecting the Kupferschiefer did not exceed 130°C. delta-65-Cu ranges between -0.78-+0.58‰, shows a positive correlation with copper concentration. Maximum temperature in the Kupferschiefer profile from Oberkatz is supposed to be around 150°C. delta-65Cu in this profile ranges between -0.71-+0.68‰. The pattern of copper isotope fractionation and copper concentration is same as the for profile of Sangerhausen. Origina lead isotope ratios are strongly overprinted by high concentrations of uranium in bottom of both profiles causing more radiogenic lead.
During a 4-week run in October–November 2006, a pilot experiment was performed at the CERN Proton Synchrotron in preparation for the CLOUD1 experiment, whose aim is to study the possible influence of cosmic rays on clouds. The purpose of the pilot experiment was firstly to carry out exploratory measurements of the effect of ionising particle radiation on aerosol formation from trace H2SO4 vapour and secondly to provide technical input for the CLOUD design. A total of 44 nucleation bursts were produced and recorded, with formation rates of particles above the 3 nm detection threshold of between 0.1 and 100 cm−3s−1, and growth rates between 2 and 37 nm h−1. The corresponding H2SO4 concentrations were typically around 106 cm−3 or less. The experimentally-measured formation rates and H2SO4 concentrations are comparable to those found in the atmosphere, supporting the idea that sulphuric acid is involved in the nucleation of atmospheric aerosols. However, sulphuric acid alone is not able to explain the observed rapid growth rates, which suggests the presence of additional trace vapours in the aerosol chamber, whose identity is unknown. By analysing the charged fraction, a few of the aerosol bursts appear to have a contribution from ion-induced nucleation and ion-ion recombination to form neutral clusters. Some indications were also found for the accelerator beam timing and intensity to influence the aerosol particle formation rate at the highest experimental SO2 concentrations of 6 ppb, although none was found at lower concentrations. Overall, the exploratory measurements provide suggestive evidence for ion-induced nucleation or ion-ion recombination as sources of aerosol particles. However in order to quantify the conditions under which ion processes become significant, improvements are needed in controlling the experimental variables and in the reproducibility of the experiments. Finally, concerning technical aspects, the most important lessons for the CLOUD design include the stringent requirement of internal cleanliness of the aerosol chamber, as well as maintenance of extremely stable temperatures (variations below 0.1°C).
During a 4-week run in October–November 2006, a pilot experiment was performed at the CERN Proton Synchrotron in preparation for the Cosmics Leaving OUtdoor Droplets (CLOUD) experiment, whose aim is to study the possible influence of cosmic rays on clouds. The purpose of the pilot experiment was firstly to carry out exploratory measurements of the effect of ionising particle radiation on aerosol formation from trace H2SO4 vapour and secondly to provide technical input for the CLOUD design. A total of 44 nucleation bursts were produced and recorded, with formation rates of particles above the 3 nm detection threshold of between 0.1 and 100 cm -3 s -1, and growth rates between 2 and 37 nm h -1. The corresponding H2O concentrations were typically around 106 cm -3 or less. The experimentally-measured formation rates and htwosofour concentrations are comparable to those found in the atmosphere, supporting the idea that sulphuric acid is involved in the nucleation of atmospheric aerosols. However, sulphuric acid alone is not able to explain the observed rapid growth rates, which suggests the presence of additional trace vapours in the aerosol chamber, whose identity is unknown. By analysing the charged fraction, a few of the aerosol bursts appear to have a contribution from ion-induced nucleation and ion-ion recombination to form neutral clusters. Some indications were also found for the accelerator beam timing and intensity to influence the aerosol particle formation rate at the highest experimental SO2 concentrations of 6 ppb, although none was found at lower concentrations. Overall, the exploratory measurements provide suggestive evidence for ion-induced nucleation or ion-ion recombination as sources of aerosol particles. However in order to quantify the conditions under which ion processes become significant, improvements are needed in controlling the experimental variables and in the reproducibility of the experiments. Finally, concerning technical aspects, the most important lessons for the CLOUD design include the stringent requirement of internal cleanliness of the aerosol chamber, as well as maintenance of extremely stable temperatures (variations below 0.1 °C)
A hygroscopicity tandem differential mobility analyzer (HTDMA) was used to measure the water uptake (hygroscopicity) of secondary organic aerosol (SOA) formed during the chemical and photochemical oxidation of several organic precursors in a smog chamber. Electron ionization mass spectra of the non-refractory submicron aerosol were simultaneously determined with an aerosol mass spectrometer (AMS), and correlations between the two different signals were investigated. SOA hygroscopicity was found to strongly correlate with the relative abundance of the ion signal m/z 44 expressed as a fraction of total organic signal (f44). m/z 44 is due mostly to the ion fragment CO2+ for all types of SOA systems studied, and has been previously shown to strongly correlate with organic O/C for ambient and chamber OA. The analysis was also performed on ambient OA from two field experiments at the remote site Jungfraujoch, and the megacity Mexico City, where similar results were found. A simple empirical linear relation between the hygroscopicity of OA at subsaturated RH, as given by the hygroscopic growth factor (GF) or "ϰorg" parameter, and f44 was determined and is given by ϰorg = 2.2 × f44 − 0.13. This approximation can be further verified and refined as the database for AMS and HTDMA measurements is constantly being expanded around the world. The use of this approximation could introduce an important simplification in the parameterization of hygroscopicity of OA in atmospheric models, since f44 is correlated with the photochemical age of an air mass.
A hygroscopicity tandem differential mobility analyzer (HTDMA) was used to measure the water uptake (hygroscopicity) of secondary organic aerosol (SOA) formed during the chemical and photochemical oxidation of several organic precursors in a smog chamber. Electron ionization mass spectra of the non-refractory submicron aerosol were simultaneously determined with an aerosol mass spectrometer (AMS), and correlations between the two different signals were investigated. SOA hygroscopicity was found to strongly correlate with the relative abundance of the ion signal m/z 44 expressed as a fraction of total organic signal (f44). m/z 44 is due mostly to the ion fragment CO2+ for all types of SOA systems studied, and has been previously shown to strongly correlate with organic O/C for ambient and chamber OA. The analysis was also performed on ambient OA from two field experiments at the remote site Jungfraujoch, and the megacity Mexico City, where similar results were found. A simple empirical linear relation between the hygroscopicity of OA at subsaturated RH, as given by the hygroscopic growth factor (GF) or "κorg" parameter, and f44 was determined and is given by κorg=2.2×f44−0.13. This approximation can be further verified and refined as the database for AMS and HTDMA measurements is constantly being expanded around the world. The use of this approximation could introduce an important simplification in the parameterization of hygroscopicity of OA in atmospheric models, since f44 is correlated with the photochemical age of an air mass.
Sur les îles du Grand Océan
(1832)
L'Astrolabe a Vanikoro
(1829)
Extensive black shale deposits formed in the Early Cretaceous South Atlantic, supporting the notion that this emerging ocean basin was a globally important site of organic carbon burial. The magnitude of organic carbon burial in marine basins is known to be controlled by various tectonic, oceanographic, hydrological, and climatic processes acting on different temporal and spatial scales, the nature and relative importance of which are poorly understood for the young South Atlantic. Here we present new bulk and molecular geochemical data from an Aptian–Albian sediment record recovered from the deep Cape Basin at Deep Sea Drilling Project (DSDP) Site 361, which we combine with general circulation model results to identify driving mechanisms of organic carbon burial. A multimillion-year decrease (i.e., Early Aptian–Albian) in organic carbon burial, reflected in a lithological succession of black shale, gray shale, and red beds, was caused by increasing bottom water oxygenation due to abating hydrographic restriction via South Atlantic–Southern Ocean gateways. These results emphasize basin evolution and ocean gateway development as a decisive primary control on enhanced organic carbon preservation in the Cape Basin at geological timescales (> 1 Myr). The Early Aptian black shale sequence comprises alternations of shales with high (> 6 %) and relatively low (∼ 3.5 %) organic carbon content of marine sources, the former being deposited during the global Oceanic Anoxic Event (OAE) 1a, as well as during repetitive intervals before and after OAE 1a. In all cases, these short-term intervals of enhanced organic carbon burial coincided with strong influxes of sediments derived from the proximal African continent, indicating closely coupled climate–land–ocean interactions. Supported by our model results, we show that fluctuations in weathering-derived nutrient input from the southern African continent, linked to changes in orbitally driven humidity and aridity, were the underlying drivers of repetitive episodes of enhanced organic carbon burial in the deep Cape Basin. These results suggest that deep marine environments of emerging ocean basins responded sensitively and directly to short-term fluctuations in riverine nutrient fluxes. We explain this relationship using the lack of wide and mature continental shelf seas that could have acted as a barrier or filter for nutrient transfer from the continent into the deep ocean.
Extensive black shale deposits formed in the Early Cretaceous South Atlantic, supporting the notion that this emerging ocean basin was a globally important site of organic carbon burial. The magnitude of organic carbon burial in marine basins is known to be controlled by various tectonic, oceanographic, hydrological, and climatic processes acting on different temporal and spatial scales, the nature and relative importance of which are poorly understood for the young South Atlantic. Here we present new bulk and molecular geochemical data from an Aptian–Albian sediment record recovered from the deep Cape Basin at Deep Sea Drilling Project (DSDP) Site 361, which we combine with general circulation model results to identify driving mechanisms of organic carbon burial. A multi-million year decrease (i.e. Early Aptian–Albian) in organic carbon burial, reflected in a lithological succession of black shale, gray shale, and red beds, was caused by increasing bottom water oxygenation due to abating tectonic restriction via South Atlantic-Southern Ocean gateways. These results emphasize basin evolution and ocean gateway development as a decisive primary control on enhanced organic carbon preservation in the Cape Basin at geological time scales (>1 Myr). The Early Aptian black shale sequence comprises alternations of shales with high (>5%) and relatively low (~3%) organic carbon content of marine sources, the former being deposited during the global Oceanic Anoxic Event (OAE) 1a, as well as during repetitive events before and after OAE 1a. In all cases, these short-term events of enhanced organic carbon burial coincided with strong influxes of sediments derived from the proximal African continent, indicating closely coupled climate–land–ocean interactions. Supported by our model results, we propose that fluctuations in weathering-derived nutrient input from the southern African continent, linked to fluctuations in pCO2 and/or orbitally driven humidity/aridity, were the underlying drivers of short-term organic carbon burial in the deep Cape Basin. These results suggest that deep marine environments of emerging ocean basins responded sensitively and directly to short term fluctuations in riverine nutrient fluxes. We explain this relationship by the lack of wide and mature continental shelf seas that could have acted as a barrier or filter for nutrient transfer from the continent into the deep ocean.
Im Mai 1885 erschien im zweiten Jahrgang der Meteorologischen Zeitschrift eine Abhandlung von Dr. H. Meyer in Göttingen, betitelt "Über den jährlichen Gang der Luftfeuchtigkeit in Norddeutschland". In dieser Arbeit, welcher die Beobachtungen von 27 Stationen zu Grunde liegen, beschränkt sich jedoch der Verfasser auf die Bestimmung des jährlichen Ganges der Luftfeuchtigkeit. Außerdem legte er derselben verschieden lange und verschieden zeitige Beobachtungsreihen zu Grunde, wodurch naturgemäß die strenge Vergleichbarkeit sehr beeinträchtigt wurde.
Herr Prof. Dr. Kremser, Abteilungsvorstand im Kgl. Pr. Meteorologischen Institut in Berlin - dem auch' an dieser Stelle für sein überaus liebenswürdiges Entgegenkommen mir gegenüber mein herzlichster Dank ausgesprochen sein möge - machte mich darauf aufmerksam, dass es eine sehr wünschenswerte und dankbare Arbeit sein würde, auf Grund eines einheitlichen Zeitraumes die Luftfeuchtigkeit Norddeutschlands allseitig und mehr ins einzelne eingehend zu behandeln.
Vorliegende Arbeit wird sich somit von der Meyer'schen Abhandlung wesentlich dadurch unterscheiden, dass derselben zunächst lauter gleich lange und gleichzeitige Beobachtungsreihen zu Grunde liegen; dass in derselben ferner nicht allein auf die Tagesmittel, sondern auch auf die Terminmittel eingegangen worden ist, und endlich noch eine Reihe weiterer Untersuchungen angeknüpft wurde.
In this study we investigate the scaling of precipitation extremes with temperature in the Mediterranean region by assessing against observations the present day and future regional climate simulations performed in the frame of the HyMeX and MED-CORDEX programs. Over the 1979–2008 period, despite differences in quantitative precipitation simulation across the various models, the change in precipitation extremes with respect to temperature is robust and consistent. The spatial variability of the temperature–precipitation extremes relationship displays a hook shape across the Mediterranean, with negative slope at high temperatures and a slope following Clausius–Clapeyron (CC)-scaling at low temperatures. The temperature at which the slope of the temperature–precipitation extreme relation sharply changes (or temperature break), ranges from about 20 °C in the western Mediterranean to <10 °C in Greece. In addition, this slope is always negative in the arid regions of the Mediterranean. The scaling of the simulated precipitation extremes is insensitive to ocean–atmosphere coupling, while it depends very weakly on the resolution at high temperatures for short precipitation accumulation times. In future climate scenario simulations covering the 2070–2100 period, the temperature break shifts to higher temperatures by a value which is on average the mean regional temperature change due to global warming. The slope of the simulated future temperature–precipitation extremes relationship is close to CC-scaling at temperatures below the temperature break, while at high temperatures, the negative slope is close, but somewhat flatter or steeper, than in the current climate depending on the model. Overall, models predict more intense precipitation extremes in the future. Adjusting the temperature–precipitation extremes relationship in the present climate using the CC law and the temperature shift in the future allows the recovery of the temperature–precipitation extremes relationship in the future climate. This implies negligible regional changes of relative humidity in the future despite the large warming and drying over the Mediterranean. This suggests that the Mediterranean Sea is the primary source of moisture which counteracts the drying and warming impacts on relative humidity in parts of the Mediterranean region.
Paläozoische Notizen
(1907)
Unter diesem Titel sollen kleinere Beobachtungen an paläozoischen Fossilien beschrieben werden. Hauptsächlich werden es Stücke des Senckenbergischen Museums sein, jedoch sollen auch Exemplare anderer Sammlungen gelegentlich in Betracht gezogen werden. Die ersten vier der hier beschriebenen Versteinerungen stammen aus den Oberkoblenzschichten von Prüm in der Eifel, wo der Verfasser im Sommer 1905 größere Aufsammlungen machen konnte.
With the Earth system being about to leave Holocene conditions and thus the known safe operating space for humanity, frameworks such as the Planetary Boundaries (PBs) and the Sustainable Development Goals (SDGs) provide quantitative metrics to guide sustainability transformations. In order to strive, not only for compliance with the PBs but also for societal well-being, some approaches attempt to combine both PBs and SDGs within a single assessment. We focus on two prominent examples, the “Doughnut” by Kate Raworth and the #SDGinPB project of the 2018 report to the Club of Rome, which are not only aimed at public outreach, but also at guiding policy-making. To meet these objectives, the approaches should possess a certain accuracy in determining the progress in achieving the SDGs and in complying with the PBs. We evaluate, by using a multi-indicator approach for comparison, whether both approaches’ limited set of indicators can still represent the SDGs’ complexity. This comparative approach estimates the progress in achieving SDGs, especially in the Global North, to be significantly lower. Based on these results and against the approaches’ purposes, we discuss their simplifications and at which point the results are no longer reliable. We conclude that global assessments can be an important factor in initiating transformative processes by stimulating public discourse, but that the actual implementation of these would require approaches with greater recognition of local particularities.
Die Montagne Noire am Südrand des französischen Zentralmassivs gehört in das Vorland der französischen Varisziden. Es handelt sich um einen metamorphen Kemkomplex mit einem Kern ("Axialzone") aus Graniten sowie teilweise migmatisierten Ortho- und Paragesteinen. Die Axialzone wird im Norden ("Nordflügel") und Süden ("Südflügel") von paläozoischen Sedimenten umrahmt. Der Nordflügel wird in die "westlichen Monts de Lacaune" (im Westen) und die "Nördliche Schuppenzone" (im Osten) unterteilt und besteht aus Gesteinen mit kambrischem bis silurischem Alter. Der Südflügel wird von einem Stapel aus mehreren Deckeneinheiten aufgebaut, deren stratigraphisches Alter vom Kambrium bis ins Karbon reicht. Die Deckeneinheiten heißen (von oben nach unten im Stapel): Pardailhan-Decke, Minervois-Decke, Mont Peyroux-Decke, Faugeres-Decke und Parautochthon. Die Montagne Noire repräsentiert den seltenen Fall eines "heißen" metamorphen Kernkomplexes, ist aber auch ein ideales Gebiet für vergleichende methodische Studien der sehr niedriggradigen Metamorphose: unterschiedliche Gesteinstypen (Sand- und Siltsteine, Tonschiefer, verschiedene Karbonate) lassen sich quer zur Metamorphosezonierung vom Bereich der Diagenese bis in die Grünschieferfazies verfolgen. In der vorliegenden Arbeit wurde die tektono-metamorphe Entwicklung der niedriggradigen paläozoischen Sedimente untersucht. Dazu wurde eine flächenhafte Studie der Schichtsilikatentwicklung in den Peliten durchgeführt. Es wurden folgende Methoden angewandt: Kubier Index ("Illitkristallinität"), Arkai-Index ("Chloritkristallinität"), "bo-Index" (zur Bestimmung des geothermischen Gradienten), Polytypie-Untersuchungen, sowie an ausgesuchten Proben Mikrosondenanalytik und Röntgenfluoreszenzanalyse. Femer wurden von K. Wemmer (Göttingen) an einigen Proben K-Ar-Datierungen der Feinfraktionen (<2 mikro m und <0,2 mikro m) durchgeführt, um die Entwicklung auch zeitlich zu erfassen. Die petrologischen und geochronologische Daten wurden zur Deformation in Bezug gesetzt. Dabei wurden sowohl Literaturdaten als auch eigene strukturgeologische Befunde verwendet. Es konnten drei tektono-metamorphe Hauptphasen nachgewiesen werden: Die erste Phase (D1 entspricht dem variszischen Deckenbau. Dabei wurde eine M1-Metamorphose angelegt, die durch den bo-Index als Mitteldruck-Metamorphose charakterisiert werden kann. Das Strukturinventar belegt einen etwa südgerichteten tektonischen Transport während D1. Diese Phase ist in der Nördlichen Schuppenzone sowie im W-Teil der Pardailhan-Decke erhalten. Das Alter dieser Phase konnte in kambro-ordovizischen Gesteinen mit der K-Ar-Methode auf 340 bis 330 Ma datiert werden. Diese Alter zeigen eine gute Übereinstimmung mit Ar/Ar-Datierungen aus den im N angrenzenden grünschieferfaziellen Decken des Albigeois. In den tieferen Decken des Südflügels, die ursprünglich weiter im Süden gelegen haben, kann die D1-Deformation erst nach Ende der Flyschsedimentation an der Grenze Vise/Namur (<320 Ma) stattgefunden haben. Die zweite Phase (D2) entspricht dem Aufstieg des metamorphen Kemkomplexes. Im Kontakt mit dem aufsteigenden, heißen Kern ist der größere Teil der paläozoischen Hüllschichten kinematisch und thermisch geprägt wurden. Dabei sind Strukturen und Mineralbestand von D1 und M1 ganz oder teilweise gelöscht worden. Die Extensions-bedingte penetrative S2-Schieferung ist im größten Teil des Südflügels das dominante Flächensystem: dies gilt für das Parautochthon, die gesamte Faugeres-Decke. den westlichen Teil der Mont Peyroux-Decke, den östlichen Teil der Pardailhan- Decke und wahrscheinlich auch die Minervois-Decke. Der Grad der Mz-Metamorphose, die auch in den westlichen Monts de Lacaune (Nordflügel) die prägende Metamorphose ist, nimmt generell mit zunehmender Entfernung von der Axialzone ab. Der bo-Index belegt Niederdruck-metamorphe Bedingungen. K-Ar-Datierungen aus verschiedenen Decken des Südflügels ergeben für D2/M2 Werte zwischen 310 und 300 Ma. Dieses Altersspektrum entspricht Ar/Ar-Datierungen (etwa 311 bis 303 Ma; synkinematischer Biotit und Muskovit; Maluski et al.1991) aus Scherzonen am S-Rand der Axialzone, die während der Exhumierung angelegt wurden. Die K-Ar-Alter der paläozoischen Decken passen auch sehr gut zu U/Pb-Altem aus Paragneisen (308 Ma, Monazit; Gebauer et al. 1988), Graniten (308 Ma, Monazit) und migmatischen Gneisen (313 Ma; beide Krause et al. 2004) der Axialzone, die eine starke thermische Aktivität zu dieser Zeit belegen. Das dritte metamorphe Ereignis (M3) ist unter Anderem im Stephanbecken von Graissessac, nachgewiesen, das im Zuge der Extensionstektonik (D2) am ENE-Ende der Axialzone entstanden ist. Nach dem bisherigen Kenntnisstand ist diese Metamorphose statisch. Der bo-Index belegt - wie auch bei M2 - eine LP-Metamorphose. Sie wurde vermutlich durch magmatische Instrusionen hervorgerufen. M3 muss jünger sein als das U-Pb-Alter eines Tuffes im tiefen Teil der Stefan-Abfolge (c. 295 Ma). Dazu passen Rb-Sr Mineralisochronen von 292 bis 277 Ma aus zwei benachbarten Granitplutonen. Ähnliche Alter treten auch in Pegmatiten der Axialzone auf. Nicht alle der untersuchten Bereiche können eindeutig einer der drei tektono-metamorphen Hauptphasen zugeordnet werden (St. Gervais-Einheit im NE der Axialzone, östlicher Teil der Mont Peyroux-Decke). Dies liegt vielfach an einer unzureichenden strukturgeologischen Datenlage. Teilweise haben aber auch Alterationsprozesse stattgefunden, welche die K-Ar-Alter verjüngt haben, oder der regionale Metamorphosegrad ist sehr niedrig. Schließlich ist in schwach anchimetamorphen oder nur diagenetisch beeinflussten Gesteinen die bo-Index-Methode nicht anwendbar. Insgesamt bestätigen die regionalen Untersuchungen das Bild eines heißen Gneiskerns, der während seines Extensions-bedingten Aufstieges seine Hüllschichten syntektonisch aufheizt. Zusätzlich zur geodynamischen Fragestellung wurden in dieser Arbeit auch methodische Aspekte verfolgt. Der Schwerpunkt lag hierbei auf der Untersuchung der K-Na-Verteilung in den Illiten bzw. Muskoviten. Es hat sich gezeigt, dass einige Proben Paragonit und/oder K/Na-Illit rührten. Diese Minerale stören die Bestimmung der Illitkristallinität im Röntgendiffraktogramm, da sich ihre Peaks mit denen des Illit überlagern. Es wurden daher verschiedene "Peak-Fittings" durchgeführt, bei denen sich zum einen zeigte, dass der 10 A-Peak besser für das Fitting von Illit und diskretem Paragonit geeignet ist als der 5 A-Peak. Es wurde zudem festgestellt, dass es nur schwer oder gar nicht möglich ist, Illit und eine K/Na-Phase mit einer zufriedenstellenden Qualität zu fitten. da die Peakmaxima zu nahe beieinander liegen. Eine Mikrosondenanalyse (teilweise auch Mikrosonden- Mapping) der betreffenden Proben zeigte, wie unterschiedlich die K-Na-Verteilung in den Illiten im anchimetamorphen Bereich sein kann. Es wurden diskrete Mineralphasen, eine domänenartige Verteilung und auch relativ homogene Mischkristalle beobachtet.
Pollen-based climate reconstructions were performed on two high-resolution pollen marines cores from the Alboran and Aegean Seas in order to unravel the climatic variability in the coastal settings of the Mediterranean region between 15 000 and 4000 years BP (the Lateglacial, and early to mid-Holocene). The quantitative climate reconstructions for the Alboran and Aegean Sea records focus mainly on the reconstruction of the seasonality changes (temperatures and precipitation), a crucial parameter in the Mediterranean region. This study is based on a multi-method approach comprising 3 methods: the Modern Analogues Technique (MAT), the recent Non-Metric Multidimensional Scaling/Generalized Additive Model method (NMDS/GAM) and Partial Least Squares regression (PLS). The climate signal inferred from this comparative approach confirms that cold and dry conditions prevailed in the Mediterranean region during the Oldest and Younger Dryas periods, while temperate conditions prevailed during the Bølling/Allerød and the Holocene. Our records suggest a West/East gradient of decreasing precipitation across the Mediterranean region during the cooler Late-glacial and early Holocene periods, similar to present-day conditions. Winter precipitation was highest during warm intervals and lowest during cooling phases. Several short-lived cool intervals (i.e. Older Dryas, another oscillation after this one (GI-1c2), Gerzensee/Preboreal Oscillations, 8.2 ka event, Bond events) connected to the North Atlantic climate system are documented in the Alboran and Aegean Sea records indicating that the climate oscillations associated with the successive steps of the deglaciation in the North Atlantic area occurred in both the western and eastern Mediterranean regions. This observation confirms the presence of strong climatic linkages between the North Atlantic and Mediterranean regions.
Pollen-based climate reconstructions were performed on two high-resolution pollen – marines cores from the Alboran and Aegean Seas in order to unravel the climatic variability in the coastal settings of the Mediterranean region between 15 000 and 4000 cal yrs BP (the Lateglacial, and early to mid-Holocene). The quantitative climate reconstructions for the Alboran and Aegean Sea records focus mainly on the reconstruction of the seasonality changes (temperatures and precipitation), a crucial parameter in the Mediterranean region. This study is based on a multi-method approach comprising 3 methods: the Modern Analogues Technique (MAT), the recent Non-Metric Multidimensional Scaling/Generalized Additive Model method (NMDS/GAM) and Partial Least Squares regression (PLS). The climate signal inferred from this comparative approach confirms that cold and dry conditions prevailed in the Mediterranean region during the Heinrich event 1 and Younger Dryas periods, while temperate conditions prevailed during the Bølling/Allerød and the Holocene. Our records suggest a West/East gradient of decreasing precipitation across the Mediterranean region during the cooler Late-glacial and early Holocene periods, similar to present-day conditions. Winter precipitation was highest during warm intervals and lowest during cooling phases. Several short-lived cool intervals (i.e., Older Dryas, another oscillation after this one (GI-1c2), Gerzensee/Preboreal Oscillations, 8.2 ka event, Bond events) connected to the North Atlantic climate system are documented in the Alboran and Aegean Sea records indicating that the climate oscillations associated with the successive steps of the deglaciation in the North Atlantic area occurred in both the western and eastern Mediterranean regions. This observation confirms the presence of strong climatic linkages between the North Atlantic and Mediterranean regions.
Balloon-borne stratospheric BrO measurements: comparison with Envisat/SCIAMACHY BrO limb profiles
(2006)
For the first time, results of all four existing stratospheric BrO profiling instruments, are presented and compared with reference to the SLIMCAT 3-dimensional chemical transport model (3-D CTM). Model calculations are used to infer a BrO profile validation set, measured by 3 different balloon sensors, for the new Envisat/SCIAMACHY (ENVIronment SATellite/SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) satellite instrument. The balloon observations include (a) balloon-borne in situ resonance fluorescence detection of BrO, (b) balloon-borne solar occultation DOAS measurements (Differential Optical Absorption Spectroscopy) of BrO in the UV, and (c) BrO profiling from the solar occultation SAOZ (Systeme d'Analyse par Observation Zenithale) balloon instrument. Since stratospheric BrO is subject to considerable diurnal variation and none of the measurements are performed close enough in time and space for a direct comparison, all balloon observations are considered with reference to outputs from the 3-D CTM. The referencing is performed by forward and backward air mass trajectory calculations to match the balloon with the satellite observations. The diurnal variation of BrO is considered by 1-D photochemical model calculation along the trajectories. The 1-D photochemical model is initialised with output data of the 3-D model with additional constraints on the vertical transport, the total amount and photochemistry of stratospheric bromine as given by the various balloon observations. Total [Bry]=(20.1±2.8)pptv obtained from DOAS BrO observations at mid-latitudes in 2003, serves as an upper limit of the comparison. Most of the balloon observations agree with the photochemical model predictions within their given error estimates. First retrieval exercises of BrO limb profiling from the SCIAMACHY satellite instrument agree to <±50% with the photochemically-corrected balloon observations, and tend to show less agreement below 20 km.
Balloon-borne stratospheric BrO measurements : comparison with Envisat/SCIAMACHY BrO limb profiles
(2005)
For the first time, results of all four existing stratospheric BrO profiling instruments, are presented and compared with reference to the SLIMCAT 3-dimensional chemical transport model (3-D CTM). Model calculations are used to infer a BrO profile validation set, measured by 3 different balloon sensors, for the new Envisat/SCIAMACHY (ENVIronment SATellite/SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) satellite instrument. The balloon observations include (a) balloon-borne in situ resonance fluorescence detection of BrO, (b) balloon-borne solar occultation DOAS measurements (Differential Optical Absorption Spectroscopy) of BrO in the UV, and (c) BrO profiling from the solar occultation SAOZ (Systeme d'Analyse par Observation Zenithale) balloon instrument. Since stratospheric BrO is subject to considerable diurnal variation and none of the measurements are performed close enough in time and space for a direct comparison, all balloon observations are considered with reference to outputs from the 3-D CTM. The referencing is performed by forward and backward air mass trajectory calculations to match the balloon with the satellite observations. The diurnal variation of BrO is considered by 1-D photochemical model calculation along the trajectories. The 1-D photochemical model is initialised with output data of the 3-D model with additional constraints on the vertical transport, the total amount and photochemistry of stratospheric bromine as given by the various balloon observations. Total [Bry]=(20.1±2.8)pptv obtained from DOAS BrO observations at mid-latitudes in 2003, serves as an upper limit of the comparison. Most of the balloon observations agree with the photochemical model predictions within their given error estimates. First retrieval exercises of BrO limb profiling from the SCIAMACHY satellite instrument agree to <±50% with the photochemically-corrected balloon observations, and tend to show less agreement below 20 km.
Motions on planetary spatial scales in the atmosphere are governed by the planetary geostrophic equations. However, little attention has been paid to the interaction between the baroclinic and barotropic flows within the planetary geostrophic scaling. This is the focus of the present study, which utilizes planetary geostrophic equations for a Boussinesq fluid supplemented by a novel evolution equation for the barotropic flow. The latter is affected by meridional momentum flux due to baroclinic flow and drag by the surface wind. The barotropic wind, on the other hand, affects the baroclinic flow through buoyancy advection. Via a relaxation towards a prescribed buoyancy profile the model produces realistic major features of the zonally symmetric wind and temperature fields. We show that there is considerable cancellation between the barotropic and the baroclinic surface zonal mean zonal winds. Linear and nonlinear model responses to steady diabatic zonally asymmetric forcing are investigated, and the arising stationary waves are interpreted in terms of analytical solutions. We also study the problem of baroclinic instability on the sphere within the present model.
In partially molten regions inside the earth melt buoyancy may trigger upwelling of both solid and fluid phases, i.e. diapirism. If the melt is allowed to move separately with respect to the matrix, melt perturbations may evolve into solitary porosity waves. While diapirs may form on a wide range of scales, porosity waves are restricted to sizes of a few times the compaction length. Thus, the size of a partially molten perturbation controls whether a diapir or a porosity wave will emerge. We study the transition from diapiric rise to solitary porosity waves by solving the two-phase flow equations of conservation of mass and momentum in 2D with porosity dependent matrix viscosity. We systematically vary the initial size of a porosity perturbation from 1 to 100 times the compaction length. If the perturbation is much larger than a regular solitary wave, its Stokes velocity is large and therefore faster than the segregating melt. Consequently, the fluid is not able to form a porosity wave and a diapir emerges. For small perturbations solitary waves emerge, either with a positive or negative vertical matrix velocity inside. In between the diapir and solitary wave regimes we observe a third regime of solitary wave induced focusing of melt. In these cases, diapirism is dominant but the fluid is still fast enough to locally build up small solitary waves which rise slightly faster than the diapir and form finger like structures at the front of the diapir. In our numerical simulations the width of these fingers is controlled by the compaction length or the grid size, whichever is larger. In cases where the compaction length becomes similar to or smaller than the grid size the finger-like leading solitary porosity waves are no more properly resolved, and too big and too fast waves may be the result. Therefore, one should be careful in large scale two-phase flow modelling with melt focusing especially when compaction length and grid size are of similar order.
In partially molten regions inside the Earth, melt buoyancy may trigger upwelling of both solid and fluid phases, i.e., diapirism. If the melt is allowed to move separately with respect to the matrix, melt perturbations may evolve into solitary porosity waves. While diapirs may form on a wide range of scales, porosity waves are restricted to sizes of a few times the compaction length. Thus, the size of a partially molten perturbation in terms of compaction length controls whether material is dominantly transported by porosity waves or by diapirism. We study the transition from diapiric rise to solitary porosity waves by solving the two-phase flow equations of conservation of mass and momentum in 2D with porosity-dependent matrix viscosity. We systematically vary the initial size of a porosity perturbation from 1.8 to 120 times the compaction length. If the perturbation is of the order of a few compaction lengths, a single solitary wave will emerge, either with a positive or negative vertical matrix flux. If melt is not allowed to move separately to the matrix a diapir will emerge. In between these end members we observe a regime where the partially molten perturbation will split up into numerous solitary waves, whose phase velocity is so low compared to the Stokes velocity that the whole swarm of waves will ascend jointly as a diapir, just slowly elongating due to a higher amplitude main solitary wave. Only if the melt is not allowed to move separately to the matrix will no solitary waves build up, but as soon as two-phase flow is enabled solitary waves will eventually emerge. The required time to build them up increases nonlinearly with the perturbation radius in terms of compaction length and might be too long to allow for them in nature in many cases.
Melting inside earth is a common phenomenon and can be observed in many different regions where melt travels through the mantle and crust to eventually reach the surface where it crystallizes to build large volcanic provinces, whole stratigraphic layers of flood basalts, or even the oceanic crust. Often, melt reaching the surface is a good source of information. It can be used to achieve a better understanding about processes taking place in deeper regions inside the mantle and it is therefore essential to fundamentally understand melting and melt percolation processes. In order to achieve a deeper understanding, the aim of this thesis is to investigate processes that are connected to melting by using numerical models.
The physical model used is a so called two-phase flow model which describes the ability of melt to percolate through a viscously deforming, partially molten matrix. A famous feature of two-phase flow are solitary porosity waves, which are waves of locally higher porosity ascending through a partially molten background, keeping its shape constant, driven by decompaction and compaction of the solid matrix in front and behind the wave.
The viscosity law for shear- and volume viscosity was strongly simplified in most previous studies that modeled solitary waves. Often the porosity dependency is underestimated or its influence on the volume viscosity is even neglected, leading to too high viscosities. In this work more realistic laws are used that strongly decrease for small melt fractions. Those laws are incorporated into a 2D Finite Difference mantle convection code with two-phase flow to study the ascent of solitary porosity waves.
The model results show that an initial Gaussian-shaped wave rapidly evolves into a solitary wave with a certain amplitude, traveling upwards with constant velocity. Even though strongly weaker viscosities are used, the effect on dispersion curves and wave shape are only minor as long as the background porosity is rather small. The results are still in agreement to semi-analytical solutions which neglect shear stresses in the melt segregation equation. Higher background porosities and wave amplitudes lead to significant decrease in phase velocity and wave width, as the viscosity is strongly effected. However, the models show that solitary waves are still a possible mechanism for more realistic matrix viscosities.
While the ascending of porosity waves are mostly described by the movement of fluid melt, partially molten regions inside Earth trigger upwelling of both, solid and fluid phases, which can be called diapirism. While diapirs can have a wide variety of wavelengths, porosity waves are restricted to a few times the compaction length. The size of a melt perturbation in terms of compaction length therefore describes whether material is transported by diapirism or porosity waves. In this thesis we study the transition from diapiric rise to solitary porosity waves by systematically changing the size of a porosity perturbation from 1.8 to 120 times the compaction length. In case of a perturbation of the size of a few times the compaction length a single porosity wave will emerge, either with a positive or negative vertical matrix flux and if melt is not allowed to move relative to the matrix a diapir will emerge. In between these physical end members a regime can be observed where the partially molten perturbation will split up into numerous solitary waves, whose phase velocity is low compared to the Stokes velocity and the swarm of solitary waves will ascend jointly as a diapir, slowly elongating due to a higher amplitude main solitary wave.
Solitary waves will always emerge from a melt perturbation as long as two-phase flow is enabled, but the time for a solitary wave to emerge increases non-linearly with the perturbation radius in terms of compaction length. In nature, in many cases this time might be too long for solitary waves to emerge.
Another important feature when it comes to two-phase flow is the transport of trace elements in melt. Incompatible elements prefer to go into the melt, which eventually enriches the area where it crystallizes again. In order to model this redistribution, the code FDCON was extended to allow for fully consistent transport of elements in melt, including melting, freezing and re-equilibration with time. A 2D model, a simple representation of a volcanic back arc, is set up to investigate the behavior of trace elements. The influence of retention number and re-equilibration time is examined. Lava-lamp like convection can be observed in the lower part of the model, producing melt, that eventually leads to enrichment in trace elements in the upper high-viscous layer. The total enrichment in this layer approaches an asymptotic value and a 0D model is introduced to recreate this behavior.
Projections from coarse-grid global circulation models are not suitable for regional estimates of water balance or trends of extreme precipitation and temperature, especially not in complex terrain. Thus, downscaling of global to regionally resolved projections is necessary to provide input to integrated water resources management approaches for river basins like the Upper Danube River Basin (UDRB) and the Upper Brahmaputra River Basin (UBRB).
This paper discusses the application of the regional climate model COSMO-CLM as a dynamical downscaling tool. To provide accurate data the COSMO-CLM model output was post-processed by statistical means. This downscaling chain performs well in the baseline period 1971 to 2000. However, COSMO-CLM performs better in the UDRB than in the UBRB because of a longer application experience and a less complex climate in Europe.
Different climate change scenarios were downscaled for the time period 1960–2100. The projections show an increase of temperature in both basins and for all seasons. The values are generally higher in the UBRB with the highest values occurring in the region of the Tibetan Plateau. Annual precipitation shows no substantial change. However, seasonal amounts show clear trends, for instance an increasing amount of spring precipitation in the UDRB. Again, the largest trends for different precipitation statistics are projected in the region of the Tibetan Plateau. Here, the projections show up to 50% longer dry periods in the months June to September with a simultaneous increase of about 10% for the maximum amount of precipitation on five consecutive days. For the Assam region in India, the projections also show an increase of 25% in the number of consecutive dry days during the monsoon season leading to prolonged monsoon breaks.
Das Ziel dieser Studie ist es, die Möglichkeiten und Grenzen von hochauflösenden Klimaprojektionen in orographisch beeinflussten Gebieten an den Beispielen der europäischen Alpen und des Himalajas zu prüfen. Insbesondere wird die Fragestellung untersucht, ob beobachtete regionale Muster in den höher aufgelösten Daten besser wiedergegeben werden als in den antreibenden großskaligen Daten. Dazu werden regionale Klimasimulationen des COSMO-CLM Modells und Daten von zwei statistischen Regionalisierungsmethoden mit ERA40 Reanalysen sowie Daten des globalen Atmosphäre-Ozean Modells ECHAM5/MPIOM für verschiedene Parameter des Klimasystems verglichen. Ein Vergleich mit den Reanalysen anhand täglicher Niederschlagsstatistiken ergibt, dass die COSMO-CLM Niederschlagsdaten auf der 0.5° Skala vergleichbar sind mit ERA40 Niederschlägen und mit statistisch regionalisierten ERA40 Niederschlägen. Eine zusätzliche Fehlerkorrektur der COSMO-CLM Niederschläge liefert gute Ergebnisse. Dabei sind jedoch etwa 500 Regentage notwendig, um eine robuste Fehlerabschätzung zu gewährleisten. Für das südasiatische Gebiet ist eine realistische Wiedergabe des indischen Sommermonsuns (ISM) in den Modellen von hoher Relevanz. Betrachtet man nur die Mittelwerte und zeitlichen Variabilitäten von verschiedenen Indizes des ISM, so liefert das COSMO-CLM keinen Mehrwert im Vergleich zu den antreibenden Daten. Allerdings werden die räumlichen Strukturen von Niederschlag und vertikaler Windscherung, sowie die zeitliche Korrelation der modellierten Indizes gegenüber dem ECHAM5/MPIOM Modell verbessert. Die durchgeführten COSMO-CLM Projektionen für die Jahre 1960 bis 2100 zeigen negative Trends des ISM für die SRES Szenarien A2, A1B und B1. Die negativsten Trends sind dabei im Szenario A2 zu finden, gefolgt von A1B und B1. Fast keine Trends zeigen sich im commitment Szenario. Trotz großen zeitlichen Variabilitäten sind die Abnahmen in Niederschlagsmengen, ausgehender langwelliger Strahlung und Windscherung statistisch signifikant in großen Regionen des Simulationsgebietes. Für Nordwest-Indien weisen die Projektionen teilweise einen Rückgang der Monsunniederschläge von über 70% in 100 Jahren auf. Der Rückgang der Windscherung ist hauptsächlich auf Veränderungen in der oberen Troposphäre bei 200 hPa zurück zu führen. Während in den COSMO-CLM Projektionen alle Indizes des ISM synchrone Negativtrends aufweisen, sind die Trends für den Monsunregen über Indien im globalen ECHAM5/MPIOM Model positiv. Gemäß den Definitionen der verschiedenen Indizes, sind jedoch synchrone Trends wahrscheinlicher und das COSMO-CLM liefert zu den globalen ISM Projektionen ebenfalls einen Mehrwert. Insgesamt zeigen die Ergebnisse dieser Studie, dass das COSMO-CLM wertvolle regionale Zusatzinformationen zu den globalen Modellen in den beiden untersuchten Regionen liefert. Für die Einzugsgebiete der oberen Donau und des oberen Brahmaputra liefern die COSMO-CLM Projektionen einen signifikanten Anstieg der Temperatur für alle Jahreszeiten der Jahre 1960 bis 2100. Die Werte sind generell höher im Brahmaputragebiet, mit den größten Trends in der Region des tibetanischen Plateaus. Im Niederschlag zeigen die saisonalen Anteile ebenfalls klare Trends, beispielsweise eine Zunahme des Frühjahrsniederschlags im Einzugsgebiet der oberen Donau. Die größten Trends werden wiederum in der Region des tibetanischen Plateaus projiziert mit einem Anstieg von bis zu 50% in der Länge der Trockenperioden zwischen Juni und September und einem gleichzeitigen Anstieg von etwa 10% für die maximale Niederschlagsmenge an fünf aufeinander folgenden Tagen. Für die Region Assam in Indien, zeigen die Projektionen zudem eine Zunahme von 25% in der Anzahl der aufeinander folgenden trockenen Tage während der Monsunzeit
The CLOUD (Cosmics Leaving OUtdoor Droplets) experiment at CERN is studying the nucleation and growth of aerosol particles under atmospheric conditions, and their activation into cloud droplets. A key feature of the CLOUD experiment is precise control of the experimental parameters. Temperature uniformity and stability in the chamber are important since many of the processes under study are sensitive to temperature and also to contaminants that can be released from the stainless steel walls by upward temperature fluctuations. The air enclosed within the 3 m CLOUD chamber is equipped with several arrays (strings) of high precision, fast-response thermometers to measure its temperature. Here we present a study of the air temperature uniformity inside the CLOUD chamber under various experimental conditions. Measurements were performed under calibration conditions and run conditions, which are distinguished by the flow rate of fresh air and trace gases entering the chamber: 20 l/min and up to 210 l/min, respectively. During steady-state calibration runs between −70 °C and +20 °C, the air temperature uniformity is better than +/−0.06 °C in the radial direction and +/−0.1 °C in the vertical direction. Larger non-uniformities are present during experimental runs, depending on the temperature control of the make-up air and trace gases (since some trace gases require elevated temperatures until injection into the chamber). The temperature stability is a few times 0.01 °C over periods of several hours during either calibration or steady-state run conditions. During rapid adiabatic expansions to activate cloud droplets and ice particles, the chamber walls are up to 10 °C warmer than the enclosed air. This results in larger non-uniformities while the air returns to its equilibrium temperature with time constant of about 200 s.
In this study, we construct a new monthly zonal mean carbon dioxide (CO2) distribution from the upper troposphere to the stratosphere over the 2000–2010 time period. This reconstructed CO2 product is based on a Lagrangian backward trajectory model driven by ERA-Interim reanalysis meteorology and tropospheric CO2 measurements. Comparisons of our CO2 product to extratropical in situ measurements from aircraft transects and balloon profiles show remarkably good agreement. The main features of the CO2 distribution include (1) relatively large mixing ratios in the tropical stratosphere; (2) seasonal variability in the extratropics, with relatively high mixing ratios in the summer and autumn hemisphere in the 15–20 km altitude layer; and (3) decreasing mixing ratios with increasing altitude from the upper troposphere to the middle stratosphere ( ∼ 35 km). These features are consistent with expected variability due to the transport of long-lived trace gases by the stratospheric Brewer–Dobson circulation. The method used here to construct this CO2 product is unique from other modelling efforts and should be useful for model and satellite validation in the upper troposphere and stratosphere as a prior for inversion modelling and to analyse features of stratosphere–troposphere exchange as well as the stratospheric circulation and its variability.
In this study, we aim to reconstruct a relevant and new database of monthly zonal mean distribution of carbon dioxide (CO2) at global scale extending from the upper-troposphere (UT) to stratosphere (S). This product can be used for model and satellite validation in the UT/S, as a prior for inversion modelling and mainly to analyse a plausible feature of the stratospherictropospheric exchange as well as the stratospheric circulation and its variability. To do so, we investigate the ability of a Lagrangian trajectory model guided by ERA-Interim reanalysis to construct the CO2 abundance in the UT/S. From 10 year backward trajectories and tropospheric observations of CO2, we reconstruct upper-tropospheric and stratospheric CO2 over the period 2000–2010. The inter-comparisons of the reconstructed CO2 with mid-latitude vertical profiles measured by balloon samples as well as quasi-horizontal air samples from ER-2 aircraft during SOLVE and CONTRAIL campaigns exhibit a remarkable agreement. That demonstrates the potential of Lagrangian model to reconstruct CO2 in the UT/S. The zonal mean distribution exhibits relatively large CO2 in the tropical stratosphere due to the seasonal variation of the tropical upwelling of Brewer-Dobson circulation. During winter and spring, the tropical pipe is relatively isolated but is less confined during summer and autumn so that high CO2 values are more readily transported out of the tropics to the mid- and high latitude stratosphere. The shape of the vertical profiles suggests that relatively high CO2 above 20 km altitude mainly enter the stratosphere through tropical upwelling. CO2 mixing ratio is relatively low in the polar and tropical regions above 25 km. On average the CO2 mixing ratio decreases with altitude by 6-8 ppmv from the UT to stratosphere (e.g. up to 35 km) and is nearly constant with altitude.
Remote sensing data are essential for monitoring the Earth’s surface waters, especially since the amount of publicly available in-situ data is declining. Satellite altimetry provides valuable information on the water levels and variations of lakes, reservoirs and rivers. In combination with satellite imagery, the derived time series allow the monitoring of lake storage changes and river discharge. However, satellite altimetry is limited in terms of its spatial resolution due to its measurement geometry, only providing information in the nadir direction beneath the satellite’s orbit. In a case study in the Mississippi River Basin (MRB), this study investigates the potential and limitations of past and current satellite missions for the monitoring of basin-wide storage changes. For that purpose, an automated target detection is developed and the extracted lake surfaces are merged with the satellites’ tracks. This reveals that the current altimeter configuration misses about 80% of all lakes larger than 0.1 km2 in the MRB and 20% of lakes larger than 10 km2, corresponding to 30% and 7% of the total water area, respectively. Past altimetry configurations perform even more poorly. From the larger water bodies represented by a global hydrology model, at least 91% of targets and 98% of storage changes are captured by the current altimeter configuration. This will improve significantly with the launch of the planned Surface Water and Ocean Topography (SWOT) mission.
The objective of the present doctoral thesis was to investigate the occurrence, distribution, and behaviour of six hydrophilic ethers: ethyl tert-butyl ether (ETBE), 1,4-dioxane, ethylene glycol dimethyl ether (monoglyme), diethylene glycol dimethyl ether (diglyme), triethylene glycol dimethyl ether (triglyme), and tetraethylene glycol dimethyl ether (tetraglyme) in surface-, waste-, ground- and drinking water samples. Solid phase extraction and gas chromatography/mass spectrometry were used to analyze the six hydrophilic ethers. Altogether more than 150 surface water samples, almost 100 of each groundwater and wastewater samples, and 10 raw and drinking water samples were analyzed during the research project.
Initially, the method was validated in order to simultaneously determine the analytes of interest in various aquatic environments. A solid phase extraction method that uses coconut charcoal (Resprep® activated coconut charcoal, Restek) or carbon molecular sieve material (SupelcleanTM Envi-CarbTM Plus, Supelco) for analyte absorption were found suitable for determination of ETBE, 1,4-dioxane, and glymes in surface-, drinking-, ground- and wastewater samples. Precision and accuracy of both methods was demonstrated for all analytes of interest. The recovery of target compounds from the ultrapure water spiked at 1.0 µg L−1 was between 86.8 % and 98.2 %, with relative standard deviation below 6 %. The samples spiked at 10.0 µg L−1 gave slightly higher recovery of 90.6 % to 112.2 % with a relative standard deviation below 3.4 % for each analyte. Detection and quantification limits in ultrapure water and surface waters were furthermore established. The limit of quantitation (LOQ) in ultrapure water ranged between 0.024 µg L−1 to 0.057 µg L−1 using Restek cartridges, and 0.030 µg L−1 to 0.069 µg L−1 using Supelco cartridges. In the surface water samples the calculated LOQ was 0.032 µg L−1 to 0.067µg L−1 using coconut charcoal material and 0.032 µg L−1 to 0.052 µg L−1 using the carbon molecular sieve material. Moreover, stability of the unpreserved and preserved water samples as well as the extracts was determined. Preservation of samples with sodium bisulfate (at 1 gram per Liter) resulted in much better stability of the ethers in water samples. Subsequently, 27 samples obtained from seven surface water bodies in Germany (Rivers Rhine, Lippe, Main, Oder, Rur, Schwarzbach and Wesel-Datteln Canal) were analyzed for the six hydrophilic ethers. ETBE was present in only two surface waters (Rhine River and Wesel-Datteln Canal) with concentrations close to the LOQ (up to 0.065 µg L−1). 1,4-Dioxane was detected in all of the water samples at concentrations reaching 1.93 µg L–1. Monoglyme was identified only in the Main and Rhine Rivers at the maximum concentration of 0.114 µg L–1 and 0.427 µg L–1, respectively. Very high concentrations (up to 1.73 µg L−1) of diglyme, triglyme, and tetraglyme were detected in the samples from the Oder River. These glymes were also detected in the Rhine River; however the concentrations did not exceed 0.200 µg L–1. Furthermore, tetraglyme was detected in the Main River at an average concentration of 0.409 µg L–1 (n = 6) and in one sample from the Rur River at 0.192 µg L–1.
Four sampling campaigns were conducted at the Oderbruch polder between October 2009 and May 2012, in order to study the behavior of the hydrophilic ethers and organophosphates during riverbank filtration and in the anoxic aquifer. Moreover the suitability of these target compounds was assessed for their use as groundwater organic tracers. At the time of each sampling campaign, concentrations of triglyme and tetraglyme in the Oder River were between 20–185 ng L–1 (n = 4) and 273¬–1576 ng L–1 (n = 4). Monoglyme, diglyme, and 1,4-dioxane were analyzed only during the two last sampling campaigns. At that time, the concentration of diglyme in Oder River was 65¬–94 ng L-1 (n = 2) and 1,4-dioxane 1610¬–3290 ng L–1 (n = 2). In the drainage ditch, following bank filtration, concentrations of ethers ranged between 1090 ng L–1 and 1467 ng L–1 for 1,4-dioxane, 23¬ng L–1 and 41 ng L–1 for diglyme, 37 ng L–1 and 149 ng L–1 for triglyme, and 496 ng L–1 and 1403 ng L–1 for tetraglyme. In the anoxic aquifer, 1,4-dioxane showed the greatest persistence during the groundwater passage. At the distance of 1150 m from the river and an estimated groundwater age of 41.9 years, a concentration above 200 ng L−1 was detected. A positive correlation was found for the inorganic tracer chloride (Cl−) with 1,4-dioxane and tetraglyme. Similarities in the behavior of Cl− and the organic compound suggested that 1,4-dioxane and tetraglyme are controlled by the same hydraulic process and therefore can be used as additional tracers to study the dynamics of the groundwater system. These results show that high concentrations of ethers are present in the surface water and are not removed during bank filtration processes. Moreover, the hydrophilic ethers persist in the anoxic aquifer and little or no degradation is expected, supporting, their possible application as organic tracers.
A separate sampling project was conducted for 1,4-dioxane that focused primarily on its fate in the aquatic environment. This study provided missing information on the extent of water pollution with 1,4-dioxane is Germany. Numerous waste-, surface-, ground- and drinking water samples were collected in order to determine the persistence of 1,4-dioxane in the aquatic environment. The occurrence of 1,4-dioxane was determined in wastewater samples from four municipal sewage treatment plants (STP). The influent and effluent samples were collected during weekly campaigns. The average influent concentrations in all four plants ranged from 262 ± 32 ng L−1 to 834 ± 480 ng L−1, whereas the average effluents concentrations were between 267 ± 35 ng L−1 and 62,260 ± 36,000 ng L−1. The source of increased 1,4-dioxane concentrations in one of the effluents was identified to originate from impurities in the methanol used in the postanoxic denitrification process. Spatial and temporal distribution of 1,4-dioxane in the river Main, Rhine, and Oder was also examined. Concentrations reaching 2,200 ng L−1 in the Oder River, and 860 ng L−1 in both Main and Rhine River were detected. The average load during the sampling was estimated to be 6.5 kg d−1 in the Main, 34.1 kg d−1 in the Oder, and 134.5 kg d−1 in the Rhine River. In all of the sampled rivers, concentrations of 1,4-dioxane increased with distance from the mouth of the river and were found to negatively correlate with the discharge of the river. In order to determine if 1,4-dioxane can reach drinking water supplies, samples from a Rhine River bank filtration site and potable water from two drinking water production facilities were analyzed for the presence of 1,4-dioxane in the raw water and finished potable water. The raw water (following bank filtration) contained 650 ng L−1 to 670 ng L−1 of 1,4-dioxane, whereas the concentration in the finished drinking water fell only to 600 ng L−1 and 490 ng L−1, respectively.
During the final project, investigations of the source identification of high glyme concentrations in the Oder River were carried out. During four sampling campaigns between January, 2012 and April, 2013, 50 samples from the Oder River in the Oderbruch region and Poland were collected. During the first two samplings in the Oderbruch polder, glymes were detected at concentration reaching 0.07 µg L-1 (diglyme), 0.54 µg L−1 (triglyme) and 1.73 µg L−1 (tetraglyme) in the Oder River. The extensive sampling campaign of the Oder River (about 500 km) in Poland helped to identify the area of possible glyme entry into the river. During that sampling the maximum concentrations of triglyme and tetraglyme were 0.46 µg L−1 and 2.21 µg L−1, respectively. A closer investigation of the identified area of pollution, helped to determine the possible sources of glymes in the Oder River. Hence, the final sampling focused on the Kaczawa River, a left tributary of the Oder River and Czarna Woda, a left tributary of Kaczawa River. Moreover, samples from an industrial wastewater treatment plant were collected. Samples from Czarna Woda stream and Kaczawa River contained even higher concentrations of diglyme, triglyme, and tetraglyme, reaching 5.18 µg L−1, 12.87 µg L−1 and 80.81 µg L−1, respectively. Finally, three water samples from a wastewater treatment plant receiving influents from a copper smelter were analyzed. Diglyme, triglyme, and tetraglyme were present at an average concentration of 569 µg L−1, 4300 µg L−1, and 65900 µg L−1, respectively in the wastewater. Further research helped to identify the source of the glymes in the wastewater. The gas desulfurization process – Solinox implemented in the nearby copper smelter uses glymes as physical absorption medium for sulfur dioxide.
Results of this doctoral research provide important information about the occurrence, distribution, and behavior of hydrophilic ethers: 1,4-dioxane, monoglyme, diglyme, triglyme, and tetraglyme in the aquatic environment. A method capable of analyzing a wide range of ether compounds: from a volatile ETBE to a high molecular weight tetraglyme was validated. 1,4-Dioxane and tetraglyme were found to be applicable as organic tracers, since they are not easily attenuated during bank filtration and the anoxic groundwater passage. The extent of water pollution with 1,4-dioxane was shown in waste-, surface-, ground-, and drinking waters. One source of extremely high concentrations of 1,4-dioxane in a municipal sewage treatment plant applying postanoxic denitrification was identified, however more information is needed on the entry of 1,4-dioxane into surface waters. Moreover, 1,4-dioxane was present in drinking water samples from river bank filtration, which demonstrates its persistence in the aquatic environment and its low degradation potential during bank filtration and subsequent water treatment. Furthermore, this was the first study that focused primarily on identifying sources of glymes in surface waters. Glymes find a widespread use in industrial sectors, hence establishing their origin in the surface water is difficult (as with 1,4-dioxane). In this work, a gas desulphurization process was identified to be a dominating source of glyme pollution in the Oder River.
[Nachruf auf] Carlos Ribeiro
(1883)
Comparing projections of future changes in runoff from hydrological and biome models in ISI-MIP
(2013)
Future changes in runoff can have important implications for water resources and flooding. In this study, runoff projections from ISI-MIP (Inter-sectoral Impact Model Intercomparison Project) simulations forced with HadGEM2-ES bias-corrected climate data under the Representative Concentration Pathway 8.5 have been analysed for differences between impact models. Projections of change from a baseline period (1981–2010) to the future (2070–2099) from 12 impacts models which contributed to the hydrological and biomes sectors of ISI-MIP were studied. The biome models differed from the hydrological models by the inclusion of CO2 impacts and most also included a dynamic vegetation distribution. The biome and hydrological models agreed on the sign of runoff change for most regions of the world. However, in West Africa, the hydrological models projected drying, and the biome models a moistening. The biome models tended to produce larger increases and smaller decreases in regionally averaged runoff than the hydrological models, although there is large inter-model spread. The timing of runoff change was similar, but there were differences in magnitude, particularly at peak runoff. The impact of vegetation distribution change was much smaller than the projected change over time, while elevated CO2 had an effect as large as the magnitude of change over time projected by some models in some regions. The effect of CO2 on runoff was not consistent across the models, with two models showing increases and two decreases. There was also more spread in projections from the runs with elevated CO2 than with constant CO2. The biome models which gave increased runoff from elevated CO2 were also those which differed most from the hydrological models. Spatially, regions with most difference between model types tended to be projected to have most effect from elevated CO2, and seasonal differences were also similar, so elevated CO2 can partly explain the differences between hydrological and biome model runoff change projections. Therefore, this shows that a range of impact models should be considered to give the full range of uncertainty in impacts studies.
Projections of future changes in runoff can have important implications for water resources and flooding. In this study, runoff projections from ISI-MIP (Inter-sectoral Impact Model Intercomparison Project) simulations forced with HadGEM2-ES bias-corrected climate data under the Representative Concentration Pathway 8.5 have been analysed. Projections of change from the baseline period (1981–2010) to the future (2070–2099) from a number of different ecosystems and hydrological models were studied. The differences between projections from the two types of model were looked at globally and regionally. Typically, across different regions the ecosystem models tended to project larger increases and smaller decreases in runoff than the hydrological models. However, the differences varied both regionally and seasonally. Sensitivity experiments were also used to investigate the contributions of varying CO2 and allowing vegetation distribution to evolve on projected changes in runoff. In two out of four models which had data available from CO2 sensitivity experiments, allowing CO2 to vary was found to increase runoff more than keeping CO2 constant, while in two models runoff decreased. This suggests more uncertainty in runoff responses to elevated CO2 than previously considered. As CO2 effects on evapotranspiration via stomatal conductance and leaf-area index are more commonly included in ecosystems models than in hydrological models, this may partially explain some of the difference between model types. Keeping the vegetation distribution static in JULES runs had much less effect on runoff projections than varying CO2, but this may be more pronounced if looked at over a longer timescale as vegetation changes may take longer to reach a new state.
Nach dem Reaktorunfall in Fukushima im März 2011 und dem darauf folgendem Beschluss in Deutschland, den Atomausstieg zu vollziehen, wird dort – sowohl auf nationaler, als auch auf regionaler Ebene – über eine alternative Energieversorgung diskutiert. Für die vorliegende Arbeit stellten sich die Fragen, wie die energiepolitische Ausgangssituation in Hessen aussieht und welche Potenziale erneuerbarer Energien in Hessen vorhanden sind. Mit einer Politikfeldanalyse wurde untersucht, welche Akteure am Ausbau erneuerbarer Energien beteiligt sind, wie diese interagieren, welche Instrumente zur Förderung erneuerbarer Energien in Hessen existieren und welche Erfolgsbedingungen und Restriktionen sich daraus ergeben. Ferner wurde anhand der jeweiligen Energiekonzepte die Frage verfolgt, welche Zukunftspotenziale für erneuerbare Energien die relevanten Akteure sehen und welche energiepolitischen Maßnahmen getroffen werden müssen, um den Ausbau zu forcieren. Bei einem Vergleich des Bundeslandes Hessen mit den Ländern Niedersachsen, Nordrhein-Westfalen und Sachsen-Anhalt wurde festgestellt, welche energiepolitischen Maßnahmen in diesen Bundesländern erfolgreich waren und auf Hessen übertragbar sind. Einerseits wurde aufgezeigt, dass Bemühungen den Ausbau erneuerbarer Energien zu forcieren erkennbar sind. Anderseits konnten ebenso die restriktiven Rahmenbedingungen dargestellt werden, die einen durchschlagenden Erfolg des Ausbaus erneuerbarer Energien bisher behindern. Die Untersuchung der Energiekonzepte hat ergeben, dass die Akteure die Zukunftspotenziale erneuerbarer Energien sehr unterschiedlich sehen und gewichten – sowohl was das zeitliche Ausbauziel als auch die Potenziale der jeweiligen erneuerbaren Energieträger betrifft.
Community trait assembly in highly diverse tropical rainforests is still poorly understood. Based on more than a decade of field measurements in a biodiversity hotspot of southern Ecuador, we implemented plant trait variation and improved soil organic matter dynamics in a widely used dynamic vegetation model (the Lund-Potsdam-Jena General Ecosystem Simulator, LPJ-GUESS) to explore the main drivers of community assembly along an elevational gradient. In the model used here (LPJ-GUESS-NTD, where NTD stands for nutrient-trait dynamics), each plant individual can possess different trait combinations, and the community trait composition emerges via ecological sorting. Further model developments include plant growth limitation by phosphorous (P) and mycorrhizal nutrient uptake. The new model version reproduced the main observed community trait shift and related vegetation processes along the elevational gradient, but only if nutrient limitations to plant growth were activated. In turn, when traits were fixed, low productivity communities emerged due to reduced nutrient-use efficiency. Mycorrhizal nutrient uptake, when deactivated, reduced net primary production (NPP) by 61–72% along the gradient. Our results strongly suggest that the elevational temperature gradient drives community assembly and ecosystem functioning indirectly through its effect on soil nutrient dynamics and vegetation traits. This illustrates the importance of considering these processes to yield realistic model predictions.
Climatology of morphology and cloud-radiative properties of marine low-level mixed-phase clouds
(2023)
Marine stratocumuli cover about 40 - 60% of the ocean surface. They self-organize into different morphological regimes. The two organized cellular regimes are called open and closed mesoscale-cellular convective (MCC) clouds. In mid-to-high latitudes, open and closed cells are the two most frequent types of MCC clouds. In particular, many MCC clouds consist of a mixture of vapor, liquid droplets, and ice particles, referred to as mixed-phase clouds (MPCs). Even for the same cloud fraction, the albedo of open cells is, on average, lower than that of closed MCC clouds. Cloud phase and morphology individually influence the cloud radiative effect. Thus, this thesis investigates the relationships between the cloud phase, MCC organization, cell size, and differences regarding the cloud-radiative effect.
This thesis focuses on space-borne retrievals to achieve extensive temporal and spatial coverage. The liDAR-raDAR (DARDAR) version 2 product collocates two active and one passive satellite: CloudSat, Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), and Moderate Resolution Imaging Spectroradiometer (MODIS). The cloud phase of DARDAR is vertically integrated to establish a single cloud phase at each data point. The MCC classification data set based on the liquid water path (LWP) of MODIS scenes is collocated with the DARDAR product to determine the MCC organization. Cell-size statistics of both MCC clouds are obtained using a marker-based image segmentation method on MODIS reflectance scenes. In addition, based on MODIS reflectance scenes, a convolutional neural network (CNN) is developed to classify open and closed MCC scenes to avoid missing mature MPCs with a low LWP.
The first part of this thesis explores the relationships between cloud phase, morphology, and cloud albedo in the Southern Ocean (SO). At a given cloud-top temperature (CTT), seasonal changes in the mixed-phase fraction, defined as the number of MPCs divided by the sum of MPC and supercooled liquid cloud (SLC) pixels, are stronger than the morphological changes. Therefore, external factors seem to influence these changes instead of morphology. The dependence of cloud phase on cloud-top height (CTH) is more substantial than on CTT in clouds with CTHs below 2.5 km. The previously observed acceleration of closed-to-open transition in MPCs, known as preconditioning, is not the primary driver of climatological cloud morphology statistics in the SO. The morphological differences in cloud albedo are more pronounced in SLCs than in MPCs. This change in albedo alters the cloud radiative effect in the SO by 21Wm−2 to 39Wm−2 depending onseason and cloud phase.
Open and closed MCC clouds exhibit larger equivalent cell diameters in the MPCs than in SLCs in austral summer, whereas, in austral winter, the SLCs are larger. The cell’s aspect ratio accounts for varying CTHs. Closed cells have smaller aspect ratios than open cells, so their cell diameter is smaller, independent of CTH. While the seasonal differences in closed cells are due to changes in CTH, the seasonal aspect ratio differences in open cells are mainly caused by MPCs. With increasing aspect ratios, the cloud albedo decreases in both open and closed MCC clouds, with the most substantial decrease in open MPCs clouds. This leads to cloud-radiative changes of 60 - 75Wm−2 in the SO, depending on cloud phase and aspect ratio.
The established CNN exhibits a good accuracy of 80.6%, with even higher accuracies in the Open (85.5%) and Closed (87.3%) categories. The global MCC climatology based on the CNN generally agrees well with previous MCC distributions. The most notable difference occurs in the Northern Hemisphere (NH) in boreal winter, with a higher occurrence frequency of closed and open MCC clouds. This might indicate missing MPCs in previous studies based on the LWP and some restricted to warm cloud scenes. Thus, the developed CNN seems to better represent the different morphologies in MPCs than in previous classifications.
In conclusion, this thesis shows that understanding the dependencies of cloud phase, cloud morphology, and cell size is important to enhance predictions of the cloud-radiative effect and thus, it is important to evaluate how cloud phase, cloud morphology, and cellsize change in a warming climate.
Ziel dieser Arbeit, die im Rahmen der Ice Nuclei Research Unit (INUIT) Forschergruppe erstellt wurde, war ursprünglich die saisonale und geographische Variabilität von bodennahen Eiskeimen zu untersuchen. Die Konzentrationen, Quellen und Zusammensetzung der Eisnuklei (ice nuclei, IN) sollte als Basis für Parametrisierungen dienen. Das Verständnis von Eiskeimen und deren Einfluss auf Wetter und Klima sind nur zum Teil bekannt und bedürfen daher noch weitgehender Forschung. Auch die Änderung der Eiskeimkonzentration mit der Zeit kann von Bedeutung sein, diese sollte durch die Fortführung einer Langzeitmessreihe untersucht werden. Durch Hinzuziehen von lokalen Parametern und Trajektorien sollten Proxies für die IN Konzentration ermittelt werden.
Im Rahmen dieser Arbeit taten sich jedoch Probleme am Messverfahren auf, weshalb die ursprünglichen Ziele in den Hintergrund gerieten und die Verbesserung und Neuaufnahme des Messverfahrens in den Vordergrund trat. Anhand von zielgerichteten Experimenten wurde ein Messfehler ermittelt, der durch die vorherige Fehlinterpretation von deliqueszierenden Partikeln und von Tröpfchen als vermeintliche Eiskristalle entstand. Dieser Fehler wurde charakterisiert und durch optische Analysen dessen Ursprung ermittelt. Datensätze, die durch diese hygroskopischen Partikel fehlerbehaftet waren, wurden korrigiert und reanalysiert. Ein in früheren Arbeiten am Taunus Observatorium/Kleiner Feldberg ermittelter Jahresgang in der Eiskeimkonzentration mit einem Maximum im Sommer und einem Minimum im Winter konnte bestätigt werden, die Absolutzahlen sind jedoch deutlich geringer als bisher angenommen. Lokale Parameter sowie Trajektorien wurden zur weiteren Analyse hinzugezogen.
Die Reevaluierung der Datensätze vom Taunus Observatorium führte zu keinem abschließenden Ergebnis. Ein allgemein gültiger Zusammenhang zwischen Eiskeimkonzentration und Parametern, welche das Staubvorkommen in der Atmosphäre quantifizieren (PM10 und Aerosol Optische Dicke), konnte nicht festgestellt werden. Da die Messungen bei relativ warmen Bedingungen (≥-18°C) durchgeführt wurden, Staub aber erst bei kälteren Temperaturen als effektiver Eiskeim gilt, ist dieses Ergebnis jedoch zu erwarten gewesen.
Auch die Luftmassenherkunft scheint keinen eindeutigen Einfluss zu haben. Betrachtungen der Bodenfeuchte lieferten signifikante Korrelationen, welche jedoch monatsabhängig positiv oder negativ ausfallen können. Im Frühling ist eine hohe Bodenfeuchte mit einer erhöhten Konzentration von IN in Verbindung zu bringen, im Sommer liegt bei niedriger Bodenfeuchte eine tendenziell höhere Eiskeimkonzentration vor. Die Windrichtung hat für die Eiskeimkonzentration einen Einfluss, wenn der Wind aus Südost zum Taunus Observatorium strömt. Anthropogenes Aerosol aus Frankfurt am Main hemmt hier vermutlich die Eisbildung, was zu einer signifikant niedrigeren mittleren Konzentration aus dieser Richtung führt.
Da das Messverfahren noch nicht in seinem vollen Potential genutzt wurde, wurde es um eine Analysemethode erweitert. Mittels Tröpfchengefrierexperimenten konnte ein weiterer Gefriermodus betrachtet werden. Nun deckt das hier genutzte Messverfahren drei der vier bekannten Gefriermoden ab. Anhand von Testsubstanzen wurde die Zuverlässigkeit der neu eingeführten Methode überprüft und nachgewiesen.
Erste Parallelproben der korrigierten Depositions- und Kondensationsgefriermessmethode und der neu eingeführten Immersionsgefriermessung wurden am Taunus Observatorium/Kleiner Feldberg genommen. Dabei wurde auch ein Staubereignis beprobt und detailliert ausgewertet. Zwischen lokalen Parametern und Eiskeimkonzentration fanden sich Zusammenhänge. Bei Messbedingungen <-20°C konnte ein signifikanter Zusammenhang zwischen PM10 und Eiskeimkonzentration im Immersions- und Kondensationsmodus gefunden werden. Der Depositionsgefriermodus blieb unauffällig. Zwischen Bodenfeuchte und IN-Konzentration konnten ebenfalls wie bei der Reevaluierung der alten Messdaten Signifikanzen festgestellt werden.
Die neu eingeführte Immersionsmessmethode und die korrigierte Methode zur Bestimmung von Depositions- und Kondensationsgefrierkernen liefern Messdaten, welche im Bereich anderer Eiskeimzähler liegen. Vergleiche mit Parametrisierungen zeigen, dass die Messwerte dem aktuellen Stand der Forschung entsprechen und davon ausgegangen werden kann, dass sie vertrauenswürdig und belastbar sind.
Beiträge zur spät- und postglazialen Fluß- und Landschaftsgeschichte im nördlichen Oberrheingraben
(2005)
Die spät- und postglaziale Fluß- und Landschaftsgeschichte im nördlichen Oberrheingraben ist durch einen mehrmaligen Wandel der fluvialen Geomorphodynamik gekennzeichnet. Im Rahmen dieser Studie waren unterschiedliche Entwicklungsphasen der Landschaft mit Hilfe verschiedener Methoden (14C-AMS, IR-OSL, Pollen- und Schwermineralanalysen) erstmals präziser zu datieren. Ab dem Spätglazial entwickelte der nördliche Oberrhein drei Mäandergenerationen. Die Entstehung der Älteren Mäandergeneration setzte vor dem Spät-Allerød ein und dauerte bis in das Atlantikum an, ehe im späten Atlantikum ein flußdynamischer Umbruch die Bildung der Mittleren Mäandergeneration einleitete. Damit begann eine Phase mit vorwiegend toniger Auensedimentation („Schwarze Tone“). Es ist nicht auszuschließen, daß dieses Geschehen teilweise durch die Effekte neolithischer Landnutzung beeinflußt war. Auch der Umbruch zur Jüngsten Mäandergeneration im Übergang vom Subboreal zum Subatlantikum war sicherlich nicht rein klimatisch gesteuert. Wahrscheinlich ist das nun wieder stärker furkativ geprägte Fließmuster und die einhergehende Vergröberung der Auenfazies auf die Überlagerung von natürlichen Abläufen mit anthropogenen Beeinflussungen zurückzuführen. Dafür spricht, daß die Landschaft während der Eisen- und der Römerzeit weitgehend entwaldet war. Die parallel dazu durchgeführten Untersuchungen am spätglazialen Bergstraßen-Neckar erlauben die zeitliche Trennung eines älteren Mäanderkurses, der in der Jüngeren Dryas verlandete, von einem jungdryaszeitlichen Verlauf. In der Paläorinne dieses jüngsten Laufes setzte im frühen Präboreal das Wachstum von Niedermootorfen ein. Das dokumentiert, daß der Bergstraßen-Neckar spätestens im beginnenden Holozän vollständig deaktiviert war. Die Abschnürung des Bergstraßenlaufes erfolgte vermutlich im Anschluß an die letzte würmzeitliche Flugsandphase, die nach schwermineralogischen und tephrostratigraphischen Befunden im Untersuchungsgebiet in die Jüngere Dryas zu stellen ist. Dabei wurde das auf der Oberen Niederterrasse existierende, endpleni- bis frühspätglaziale, zwischenzeitlich vom Bergstraßen-Neckar teilweise fluvial umgelagerte, ältere Dünenrelief überweht, während auf der Unteren Niederterrasse lokale Dünenvorkommen entstanden. Möglicherweise dauerte die Flugsandbildung örtlich bis in das früheste Präboreal an, bevor in den späteren Zeiten des Holozän ein anthropogen induziertes Aufleben der Flugsandaktivität zu beobachten ist.
This article presents a multiscale approach for detecting and monitoring soil erosion phenomena (i.e. gully erosion) in the agro-industrial area around the city of Taroudannt, Souss basin, Morocco. The study area is characterized as semi-arid with an annual average precipitation of 200 mm. Water scarcity, high population dynamics and changing land use towards huge areas of irrigation farming present numerous threats to sustainability. The agro-industry produces citrus fruits and vegetables in monocropping, mainly for the European market. Badland areas strongly affected by gully erosion border the agricultural areas as well as residential areas. To counteract the significant loss of land, land-leveling measures are attempted to create space for plantations and greenhouses. In order to develop sustainable approaches to limit gully growth the detection and monitoring of gully systems is fundamental. Specific gully sites are monitored with unmanned aerial vehicle (UAV) taking small-format aerial photographs (SFAP). This enables extremely high-resolution analysis (SFAP resolution: 2-10 cm) of the actual size of the gully channels as well as a detailed continued surveillance of their growth. Transferring the methodology on a larger scale using Quickbird satellite data (resolution: 60 cm) leads to the possibility of a large-scale analysis of the whole area around the city of Taroudannt (Area extent: ca. 350 km²). The results will then reveal possible relationships of gully growth and agro-industrial management and may even illustrate further interdependencies. The main objective is the identification of areas with high gully-erosion risk due to non-sustainable land use and the development of mitigation strategies for the study area.
This article presents an environmental remote sensing application using a UAV that is specifically aimed at reducing the data gap between field scale and satellite scale in soil erosion monitoring in Morocco. A fixed-wing aircraft type Sirius I (MAVinci, Germany) equipped with a digital system camera (Panasonic) is employed. UAV surveys are conducted over different study sites with varying extents and flying heights in order to provide both very high resolution site-specific data and lower-resolution overviews, thus fully exploiting the large potential of the chosen UAV for multi-scale mapping purposes. Depending on the scale and area coverage, two different approaches for georeferencing are used, based on high-precision GCPs or the UAV’s log file with exterior orientation values respectively. The photogrammetric image processing enables the creation of Digital Terrain Models (DTMs) and ortho-image mosaics with very high resolution on a sub-decimetre level. The created data products were used for quantifying gully and badland erosion in 2D and 3D as well as for the analysis of the surrounding areas and landscape development for larger extents.
This study reports and discusses new radiometric ages, petrographical and volcanological observations and whole rock geochemical data of the rocks of the Rudnik Mts. volcano-intrusive complex. The complex hosts a Pb-Zn-Ag deposit and belongs to the Serbo-Macedonian metallogenetic belt. Two distinct igneous events are distignuished. The first occurred >30 Ma and was mainly characterized by extrusive and shallow intrusive dacites and andesites and was unrelated to mineralization. The second igneous event occurred <23 Ma and was highly heterogeneous in terms of volcanic products and petrographic varieties, but with predominance of quartzlatites. The dacite-andesites (first event) and the quartzlatites (second event) are geochemically similar and display a calc-alkaline affinity and highly incompatible element enriched patterns on spider diagrams, but the younger quartzlatites are richer in K2O, Rb and Ba and poorer in Sr. This is taken as evidence that mixing between an ultrapotassic lamprophyre/lamproite magma and an acid calc-alkaline (dacite-like) magma was essential petrogenetic processes during the second event. The proposed simplified volcanological model suggests that this mixing was responsible for triggering strongly explosive volcanic activity as well as for providing conditions for active hydrothermal and mineralization processes. The observed link between a specific magmatic phase and ore deposit formation can be a general phennomenon in the Balkans, and must be addressed by further and more advanced studies.
Number concentrations of total and non-volatile aerosol particles with size diameters >0.01 µm as well as particle size distributions (0.4–23 µm diameter) were measured in situ in the Arctic lower stratosphere (10–20.5 km altitude). The measurements were obtained during the campaigns European Polar Stratospheric Cloud and Lee Wave Experiment (EUPLEX) and Envisat-Arctic-Validation (EAV). The campaigns were based in Kiruna, Sweden, and took place from January to March 2003. Measurements were conducted onboard the Russian high-altitude research aircraft Geophysica using the low-pressure Condensation Nucleus Counter COPAS (COndensation PArticle Counter System) and a modified FSSP 300 (Forward Scattering Spectrometer Probe). Around 18–20 km altitude typical total particle number concentrations nt range at 10–20 cm−3 (ambient conditions). Correlations with the trace gases nitrous oxide (N2O) and trichlorofluoromethane (CFC-11) are discussed. Inside the polar vortex the total number of particles >0.01 µm increases with potential temperature while N2O is decreasing which indicates a source of particles in the above polar stratosphere or mesosphere. A separate channel of the COPAS instrument measures the fraction of aerosol particles non-volatile at 250°C. Inside the polar vortex a much higher fraction of particles contained non-volatile residues than outside the vortex (~24% outside vortex). This is most likely due to a strongly increased fraction of meteoritic material in the particles which is transported downward from the mesosphere inside the polar vortex. The high fraction of non-volatile residual particles gives therefore experimental evidence for downward transport of mesospheric air inside the polar vortex. It is also shown that the fraction of non-volatile residual particles serves directly as a suitable experimental vortex tracer. Nanometer-sized meteoritic smoke particles may also serve as nuclei for the condensation of gaseous sulfuric acid and water in the polar vortex and these additional particles may be responsible for the increase in the observed particle concentration at low N2O. The number concentrations of particles >0.4 µm measured with the FSSP decrease markedly inside the polar vortex with increasing potential temperature, also a consequence of subsidence of air from higher altitudes inside the vortex. Another focus of the analysis was put on the particle measurements in the lowermost stratosphere. For the total particle density relatively high number concentrations of several hundred particles per cm3 at altitudes below ~14 km were observed in several flights. To investigate the origin of these high number concentrations we conducted air mass trajectory calculations and compared the particle measurements with other trace gas observations. The high number concentrations of total particles in the lowermost stratosphere are probably caused by transport of originally tropospheric air from lower latitudes and are potentially influenced by recent particle nucleation.
Number concentrations of total and non-volatile aerosol particles with size diameters >0.01 μm as well as particle size distributions (0.4–23 μm diameter) were measured in situ in the Arctic lower stratosphere (10–20.5 km altitude). The measurements were obtained during the campaigns European Polar Stratospheric Cloud and Lee Wave Experiment (EUPLEX) and Envisat-Arctic-Validation (EAV). The campaigns were based in Kiruna, Sweden, and took place from January to March 2003. Measurements were conducted onboard the Russian high-altitude research aircraft Geophysica using the low-pressure Condensation Nucleus Counter COPAS (COndensation PArticle Counter System) and a modified FSSP 300 (Forward Scattering Spectrometer Probe). Around 18–20 km altitude typical total particle number concentrations nt range at 10–20 cm−3 (ambient conditions). Correlations with the trace gases nitrous oxide (N2O) and trichlorofluoromethane (CFC-11) are discussed. Inside the polar vortex the total number of particles >0.01 μm increases with potential temperature while N2O is decreasing which indicates a source of particles in the above polar stratosphere or mesosphere. A separate channel of the COPAS instrument measures the fraction of aerosol particles non-volatile at 250°C. Inside the polar vortex a much higher fraction of particles contained non-volatile residues than outside the vortex (~67% inside vortex, ~24% outside vortex). This is most likely due to a strongly increased fraction of meteoric material in the particles which is transported downward from the mesosphere inside the polar vortex. The high fraction of non-volatile residual particles gives therefore experimental evidence for downward transport of mesospheric air inside the polar vortex. It is also shown that the fraction of non-volatile residual particles serves directly as a suitable experimental vortex tracer. Nanometer-sized meteoric smoke particles may also serve as nuclei for the condensation of gaseous sulfuric acid and water in the polar vortex and these additional particles may be responsible for the increase in the observed particle concentration at low N2O. The number concentrations of particles >0.4 μm measured with the FSSP decrease markedly inside the polar vortex with increasing potential temperature, also a consequence of subsidence of air from higher altitudes inside the vortex. Another focus of the analysis was put on the particle measurements in the lowermost stratosphere. For the total particle density relatively high number concentrations of several hundred particles per cm3 at altitudes below ~14 km were observed in several flights. To investigate the origin of these high number concentrations we conducted air mass trajectory calculations and compared the particle measurements with other trace gas observations. The high number concentrations of total particles in the lowermost stratosphere are probably caused by transport of originally tropospheric air from lower latitudes and are potentially influenced by recent particle nucleation.
Wolken haben einen maßgeblichen Einfluss auf den Wasserhaushalt der Erde, das Wettergeschehen und das Klima. Sie wissenschaftlich zu beschreiben, ist schwierig – und das erschwert die Niederschlagsvorhersage ebenso wie die Klimamodellierung. Wichtig für die Entstehung von Regen in unseren Breiten sind Eispartikel. Sie machen einen großen Teil der Wolken aus. Doch wie bilden sie sich, und warum sind sie für viele physikalische Prozesse in den Wolken unentbehrlich? Und schließlich: Wirkt sich menschliches Handeln auf die Wolken aus?
Two types of particles exist in the atmosphere, primary and secondary particles. While primary particles such as soot, mineral dust, sea salt particles or pollen are introduced directly as particles into the atmosphere, secondary particles are formed in the atmosphere by condensation of gases. The formation of such new aerosol particles takes place frequently and at a broad variety of atmospheric conditions and geographic locations. A considerable fraction of the atmospheric particles is formed by such nucleation processes. The newly formed particles may grow by condensation to sizes where they are large enough to act as cloud condensation nuclei and therefore may affect cloud properties. The fundamental processes of aerosol nucleation are described and typical atmospheric observations are discussed. Two recent studies are introduced that potentially change our current understanding of atmospheric nucleation substantially.
Non-forest ecosystems, dominated by shrubs, grasses and herbaceous plants, provide ecosystem services including carbon sequestration and forage for grazing, and are highly sensitive to climatic changes. Yet these ecosystems are poorly represented in remotely sensed biomass products and are undersampled by in situ monitoring. Current global change threats emphasize the need for new tools to capture biomass change in non-forest ecosystems at appropriate scales. Here we developed and deployed a new protocol for photogrammetric height using unoccupied aerial vehicle (UAV) images to test its capability for delivering standardized measurements of biomass across a globally distributed field experiment. We assessed whether canopy height inferred from UAV photogrammetry allows the prediction of aboveground biomass (AGB) across low-stature plant species by conducting 38 photogrammetric surveys over 741 harvested plots to sample 50 species. We found mean canopy height was strongly predictive of AGB across species, with a median adjusted R2 of 0.87 (ranging from 0.46 to 0.99) and median prediction error from leave-one-out cross-validation of 3.9%. Biomass per-unit-of-height was similar within but different among, plant functional types. We found that photogrammetric reconstructions of canopy height were sensitive to wind speed but not sun elevation during surveys. We demonstrated that our photogrammetric approach produced generalizable measurements across growth forms and environmental settings and yielded accuracies as good as those obtained from in situ approaches. We demonstrate that using a standardized approach for UAV photogrammetry can deliver accurate AGB estimates across a wide range of dynamic and heterogeneous ecosystems. Many academic and land management institutions have the technical capacity to deploy these approaches over extents of 1–10 ha−1. Photogrammetric approaches could provide much-needed information required to calibrate and validate the vegetation models and satellite-derived biomass products that are essential to understand vulnerable and understudied non-forested ecosystems around the globe.
We combine structural analysis of fractures with 22 U–Pb dates measured in fracture-filling carbonate cements from bed-parallel fibrous calcite veins (beef), conjugated veins and faults within the Vaca Muerta Formation along the Andean fold and thrust belt in the Neuquén Basin. The measured ages constrain accurately the relationships between overpressures caused by hydrocarbon generation and Andean compression as mechanisms for natural fracturing and vein formation. Two generations of fibres have been identified in beef. The first one, consists of dark fibres from the inner zones, which are perpendicular to bedding and contain abundant cone-in-cone structures and hydrocarbon inclusions. U–Pb dating of these fibres yielded Early to Late Cretaceous ages from 116.7 ± 17.7 to 78.8 ± 10.2 Ma. The second generation of fibres corresponds to the outer zones and consists of white fibres oblique to bedding, indicating growth during layer-parallel shortening. Bed-perpendicular veins cutting beef yielded Late Cretaceous-late Palaeocene dates from 72.8 ± 22.4 to 60.9 ± 10.4 Ma. Eocene ages from 52.0 ± 2.9 to 42.2 ± 18.9 Ma were measured in bed-parallel slip surfaces and reverse and strike-slip faults, whereas Miocene dates from 13.9 ± 2.6 to 6.2 ± 1.1 Ma were measured in E-W calcite veins. U–Pb dating of veins, structural analysis of fractures and subsidence curves, indicate that beef inner zones formed in the oil window during burial of the Neuquén basin, and that tectonic stresses could enhance their formation. Beef outer zones and bed-perpendicular veins formed during E-W Late Cretaceous-late Palaeocene layer-parallel shortening. Contrarily, late Palaeocene-late Eocene bed-parallel slip surfaces and faults and Miocene E-W veins formed during NE-SW and E-W syn-to post-folding deformation, respectively. In both cases, syn-to post-folding compression occurred synchronously with forelandward migration of magmatic activity attributed to flat subduction of the Pacific slab beneath the Andes.
A new, two-channel instrument for simultaneous NO3 and N2O5 monitoring was used to make the first comprehensive set of nocturnal NOx measurements (NO, NO2, NO3 and N2O5) at the Taunus Observatory, a rural mountain site (Kleiner Feldberg) in South-western Germany. In May 2008, NO3 and N2O5 mixing ratios were well above the instrumental detection limit (a few ppt) on all nights of the campaign and were characterised by large variability resulting from inhomogeneously distributed sinks. The concentrations of NO3, N2O5 and NO2 were consistent with the equilibrium constant, K2, defining the rates of formation and thermal dissociation of N2O5. A steady-state lifetime analysis showed that nocturnal NOx losses were generally dominated by reaction of NO3 with volatile organic compounds in this forested region, with N2O5 uptake to aerosols of secondary importance. Analysis of a limited dataset obtained at high relative humidity indicated that the loss of N2O5 by reaction with water vapour is less efficient (> factor 3) than derived using laboratory kinetic data. The fraction of NOx present as NO3 and N2O5 reached ≈20% on some nights, with night-time losses of NOx competing with daytime losses.
A new, two-channel instrument for simultaneous NO3 and N2O5 monitoring was used to make the first comprehensive set of nocturnal NOx measurements (NO, NO2, NO3 and N2O5) at the Taunus Observatory, a rural mountain site (Kleiner Feldberg) in South-western Germany. In May 2008, NO3 and N2O5 mixing ratios were well above the instrumental detection limit (a few ppt) on all nights of the campaign and were characterised by large variability. The concentrations of NO3, N2O5 and NO2 were consistent with the equilibrium constant, K2, defining the rates of formation and thermal dissociation of N2O5. A steady-state lifetime analysis is consistent with the loss of nocturnal NOx being dominated by the reaction of NO3 with volatile organic compounds in this forested region, with N2O5 uptake to aerosols of secondary importance. Analysis of a limited dataset obtained at high relative humidity indicated that the loss of N2O5 by reaction with water vapour is less efficient (>factor 3) than derived using laboratory kinetic data. The fraction of NOx present as NO3 and N2O5 reached ~20% on some nights, with night-time losses of NOx competing with daytime losses.
Global warming, changes in the hydrological cycle and enhanced marine primary productivity all have been invoked to have contributed to the occurrence of widespread ocean anoxia during the Cenomanian-Turonian Oceanic Anoxic Event (OAE2; ~ 94 Ma), but disentangling these factors on a regional scale has remained problematic. We generated palynological and organic geochemical records that allow the separation of these forcing factors in a core spanning the OAE2 from Wunstorf, Lower Saxony Basin (LSB; North Gemany), which exhibits cyclic black shale–marl alternations related to the orbital precession cycle.
Despite the widely varying depositional conditions complicating the interpretation of the obtained records, TEX86H indicates that sea-surface temperature (SST) evolution in the LSB during OAE2 resembles that of previously studied sites throughout the proto-North Atlantic. Cooling during the so-called Plenus Cold Event interrupted black shale deposition during the early stages of OAE2. However, TEX86 does not vary significantly across marl–black shale alternations, suggesting that temperature variations did not force the formation of the cyclic black shale horizons. Relative (i.e., with respect to marine palynomorphs) and absolute abundances of pollen and spores are elevated during phases of black shale deposition, indicative of enhanced precipitation and run-off. High abundances of cysts from inferred heterotrophic and euryhaline dinoflagellates supports high run-off, which likely introduced additional nutrients to the epicontinental shelf resulting in elevated marine primary productivity.
We conclude that orbitally-forced enhanced precipitation and run-off, in tandem with elevated marine primary productivity, were critical in cyclic black shale formation on the northwest European epicontinental shelf and potentially for other OAE2 sections in the proto-Atlantic and Western Interior Seaway at similar latitudes as well.