Reactive transport modeling as a tool for the integrated interpretation of laboratory and field studies in environmental geochemistry

The interaction between moving water and stationary rock within the Earth's crust and on its surface is typically controlled by a series of coupled processes occurring in porous media at various spatio-temporal scales. An example is chemical weathering, which takes place within a thin layer at the Earth’s surface called the Critical Zone and eventually leads to the formation of soils on the time-scale of hundreds to thousands of years. Chemical weathering is kinetically limited and its rate depends on the transport of CO2 and O2 through the Critical Zone. It is also strongly affected by physical weathering processes controlling the grain size distribution within the Critical Zone and thus the available mineral surface area where chemical reactions can take place. In addition, variations in biological activity that produce CO2 may change chemical weathering rates. The complex feedbacks and interrelationships within such coupled systems cannot be understood by traditional geochemical approaches that combine field observations, laboratory analyses and theoretical treatments of the individual uncoupled processes. Therefore, the quantitative interpretation of field studies requires a numerical simulation tool that is able to capture the coupled behavior of subsurface systems and to upscale experimental findings. The main requirements for such a tool are to (i) simulate the relevant geochemical and biogeochemical processes in a mechanistic way and (ii) simultaneously couple these processes to flow and transport rates. Over the past 30 years, the field of reactive transport modeling (RTM) has mastered these requirements and thus has become an essential method for the entire Earth Sciences. This Habilitationsschrift describes the contributions by the Author to advancing the field of reactive transport modeling, thereby demonstrating how RTM enables an integrated interpretation of laboratory and/or field studies. In addition, this Habilitationsschrift emphasizes how RTM contributes to solving environmental challenges, such as those identified by the United Nations’ Sustainable Development Goals 6 (Clean Water and Sanitation), 7 (Affordable and Clean Energy), and 13 (Climate Action). Chapter 1 introduces groundwater contamination, geothermal energy, and silicate weathering as important topics in environmental geochemistry and describes the role of coupled processes in the corresponding systems. Moreover, the Chapter introduces the general concept of reactive transport modeling and illustrates its ability to numerically capture the coupling between non-isothermal geochemical and biogeochemical processes, as well as fluid flow and transport rates. Chapter 2 provides a detailed summary of the key accomplishments by the Author to advancing RTM. These include (i) the integration of stable isotopes in RTM simulations that address challenges relevant to environmental geochemistry, and (ii) the use of reactive transport models as an exploration tool for geothermal systems. These contributions resulted, among others, in the publication of nine peer-reviewed publications, which are presented in Chapters 3–5 and form the core of this Habilitationsschrift. Chapter 3 presents three selected RTM applications where Cr or U isotopes are integrated in reactive transport model simulations to understand Cr- and U-contaminated groundwaters. In the first two studies, small-scale laboratory experiments are numerically simulated using a novel approach for obtaining a high spatial resolution of the simulated systems. The model results and their comparison to measured Cr and U isotope ratios provide fundamental insights into the processes controlling the magnitude of Cr and U isotope fractionation occurring in porous media. Obtaining a predictive understanding of such isotopic fractionation is crucial, because it opens the way to quantify the most important processes limiting the mobility of Cr and U in the subsurface. The third application presents a benchmarking exercise, which allowed testing and improvement of the approaches for numerically simulating stable Cr isotope fractionation in geochemical processes. Altogether, the RTM applications presented in Chapter 3 contribute to a more informed assessment and management of groundwater bodies contaminated by Cr and U. Chapter 4 presents three applications where RTM is used as an exploration tool for geothermal systems. The first one involves 2D simulations carried out for the Dixie Valley geothermal system located in the western USA. The model output is then applied via a geochemical method called solute geothermometry, which is used to estimate the maximum temperature of deep geothermal systems. Eventually, the combined approach demonstrates which particular solute geothermometry method works best for various scenarios of rock–water interactions and thus contributes to an improved estimation of deep reservoir temperatures. Obtaining reliable temperatures is important because the reservoir temperature is a major limit on the energy that can be exploited from the deep subsurface. In the other two applications, RTM simulations are performed to quantitatively assess the geothermal potential of two geothermal systems in the Swiss Alps. All simulations are carried out in 3D and are constrained and calibrated by multiple field observations, such as chemical and isotopic compositions of thermal and cold springs, as well as temperature measurements along tunnels. The model results suggest that mountain belts such as the Swiss Alps are more promising targets for geothermal power production than previously thought, and they identify the favorable geological settings for such systems, which leads to useful implications for exploration. Chapter 5 presents a sequence of three RTM applications, which for the first time integrate Li isotopes in the simulations. The motivation for numerically simulating the fate of Li isotopes is that their ratios serve as proxies to track and quantify the rates of silicate weathering, which in turn constitutes a major natural sink for atmospheric CO2. The first study describes a new numerical approach to integrate Li isotopes in RTM simulations. In the first and second applications, the developed approach is used to simulate the fate of Li and its isotopes in granitic and basaltic rainwater catchments, respectively. Subsequently, the model results are compared to Li data from major worldwide rivers and from a series of small streams draining the Columbia River Basalt area in the western USA. This model-based, integrated interpretation of measured Li isotope ratios permits identification of the processes governing Li isotope ratios in groundwater, riverwater and even seawater. Moreover, the results imply that seawater Li isotope ratios may be closely related to the amount of CO2 globally consumed by continental silicate weathering. In the third application, the numerical approach to simulate the fate of Li isotopes is expanded to account for the limited amount of Li that precipitates in secondary minerals. The updated approach is used to unravel a complex set of Li data collected from groundwater samples discharging into the Gotthard railway base tunnel in the Swiss Alps. This study reveals that the behavior of Li isotopes in environmental samples is more complicated than hitherto realized. Overall, the applications presented in Chapter 5 contribute to assessing the use of Li isotopes as a proxy for silicate weathering and may help to better quantify this important natural sink for CO2. Chapter 6 summarizes the main implications of this Habilitationsschrift regarding the use of RTM in environmental geochemistry and how it contributes to meeting the listed Sustainable Development Goals. In particular, this final chapter concludes that the inclusion of stable isotopes into RTM simulations provides fundamental new insights into the processes controlling stable isotope ratios in environmental samples. This underscores how RTM serves as a powerful tool for the integrated interpretation of multiple datasets obtained from field and laboratory studies. Moreover, the Chapter discusses how RTM simulations are limited by the availability of thermodynamic and kinetic data, and by the need for detailed geochemical, biogeochemical, hydrological, and geophysical site-characterizations in order to calibrate such simulations. Finally, the Chapter contains a brief outlook emphasizing the numerous opportunities for new code development and for laboratory as well as field studies to constrain and calibrate future RTM applications. These activities will enable even more powerful RTM simulations to meet the environmental challenges of the future

Quantifying the glacial meltwater contribution to mountainous streams using stable water isotopes: What are the opportunities and limitations?

This study aims to determine the opportunities and limitations of using stable water isotopes to quantify the glacial meltwater contribution to mountainous streams. For this purpose, three partially glaciated catchments in the Swiss Alps were selected as the study area. In the three catchments, stable isotope analysis (δ18O and δ2H) was conducted of the streams and the end-members that contribute to the stream discharge (glacial meltwater, rain, snow). The investigations revealed that the contribution of glacial meltwater to mountainous streams can be quantified using stable water isotopes if three criteria are met: (A) The snow meltwater contribution to mountainous streams must be negligible due to its highly variable stable isotope signature; (B) the groundwater input needs to be either insignificant during this snow-free period or the groundwater residence time must be short such that groundwater contribution does not delay the end-member signal arriving in the streams; and (C) the isotope signal of the glacial melt end-member needs to be distinct from the other end-members. One of the three investigated catchments fulfilled these criteria in August and September, and the glacial meltwater contribution to the mountainous streams could be estimated based on stable water isotopes. During this time period, the glacial meltwater contribution to the stream discharge corresponded to up to 85% ± 2% and to 28.7% ± 10% of the total annual discharge, respectively. This high glacial meltwater contribution demonstrates that the mountainous stream discharges in August and September will probably strongly decrease in the future due to global warming-induced deglaciation. Overall, this study demonstrates that many hydrogeological conditions need to be met so that stable water isotopes can be used to quantify the glacial meltwater contribution to mountainous streams. This highlights the challenges when using stable water isotopes for hydrograph separation and serves as a guide for future stable water isotope studies in mountainous regions

Chronic kidney disease as cardiovascular risk factor in routine clinical practice:a position statement by the Council of the European Renal Association

The European Society of Cardiology 2021 guideline on cardiovascular (CV) disease (CVD) prevention in clinical practice has major implications for both CV risk screening and kidney health of interest to primary care physicians, cardiologists, nephrologists, and other professionals involved in CVD prevention. The proposed CVD prevention strategies require as first step the categorization of individuals into those with established atherosclerotic CVD, diabetes, familiar hypercholesterolaemia, or chronic kidney disease (CKD), i.e. conditions that are already associated with a moderate to very-high CVD risk. This places CKD, defined as decreased kidney function or increased albuminuria as a starting step for CVD risk assessment. Thus, for adequate CVD risk assessment, patients with diabetes, familiar hypercholesterolaemia, or CKD should be identified by an initial laboratory assessment that requires not only serum to assess glucose, cholesterol, and creatinine to estimate the glomerular filtration rate, but also urine to assess albuminuria. The addition of albuminuria as an entry-level step in CVD risk assessment should change clinical practice as it differs from the current healthcare situation in which albuminuria is only assessed in persons already considered to be at high risk of CVD. A diagnosis of moderate of severe CKD requires a specific set of interventions to prevent CVD. Further research should address the optimal method for CV risk assessment that includes CKD assessment in the general population, i.e. whether this should remain opportunistic screening or whether systematic screening.</p

Permeability and Groundwater Flow Dynamics in Deep‐Reaching Orogenic Faults Estimated From Regional‐Scale Hydraulic Simulations

Numerical modeling is used to understand the regional scale flow dynamics of the fault-hosted orogenic geothermal system at the Grimsel Mountain Pass in the Swiss Alps. The model is calibrated against observations from thermal springs discharging in a tunnel some 250 m underneath Grimsel Pass to derive estimates for the bulk permeability of the fault. Simulations confirm that without the fault as a hydraulic conductor the thermal springs would not exist. Regional topography alone drives meteoric water in a single pass through the fault plane where it penetrates to depths exceeding 10 km and acquires temperatures in excess of 250°C. Thermal constraints from the thermal springs at Grimsel Pass suggest bulk fault permeabilities in the range of 2e−15 m2–4.8e−15 m2. Reported residence times of >30,000 and 7 years for the deep geothermal and shallow groundwater components in the thermal spring water, respectively, suggest fault permeabilities of around 2.5e−15 m2. We show that the long residence time of the deep geothermal water is likely a consequence of low recharge rates during the last glaciation event in the Swiss Alps, which started some 30,000 years ago. Deep groundwater discharging at Grimsel Pass today thus infiltrated the Grimsel fault prior to the last glaciation event. The range of permeabilities estimated from observational constraints is fully consistent with a subcritical single-pass flow system in the fault plane

Rosiglitazone Affects Nitric Oxide Synthases and Improves Renal Outcome in a Rat Model of Severe Ischemia/Reperfusion Injury

Background. Nitric oxide (NO)-signal transduction plays an important role in renal ischemia/reperfusion (I/R) injury. NO produced by endothelial NO-synthase (eNOS) has protective functions whereas NO from inducible NO-synthase (iNOS) induces impairment. Rosiglitazone (RGZ), a peroxisome proliferator-activated receptor (PPAR)-γ agonist exerted beneficial effects after renal I/R injury, so we investigated whether this might be causally linked with NOS imbalance. Methods. RGZ (5 mg/kg) was administered i.p. to SD-rats (f) subjected to bilateral renal ischemia (60 min). Following 24 h of reperfusion, inulin- and PAH-clearance as well as PAH-net secretion were determined. Morphological alterations were graded by histopathological scoring. Plasma NOx-production was measured. eNOS and iNOS expression was analyzed by qPCR. Cleaved caspase 3 (CC3) was determined as an apoptosis indicator and ED1 as a marker of macrophage infiltration in renal tissue. Results. RGZ improves renal function after renal I/R injury (PAH-/inulin-clearance, PAH-net secretion) and reduces histomorphological injury. Additionally, RGZ reduces NOx plasma levels, ED-1 positive cell infiltration and CC3 expression. iNOS-mRNA is reduced whereas eNOS-mRNA is increased by RGZ. Conclusion. RGZ has protective properties after severe renal I/R injury. Alterations of the NO pathway regarding eNOS and iNOS could be an explanation of the underlying mechanism of RGZ protection in renal I/R injury

Causes of abundant calcite scaling in geothermal wells in the Bavarian Molasse Basin, Southern Germany

The carbonate-dominated Malm aquifer in the Bavarian Molasse Basin in Southern Germany is being widely exploited and explored for geothermal energy. Despite favorable reservoir conditions, the use of geothermal wells for heat and power production is highly challenging. The main difficulty, especially in boreholes >3000 m deep with temperatures >120 °C, is that substantial amounts of calcite scales are hindering the proper operation of the pumps within the wells and of the heat exchangers at the surface. To elucidate the causes of scaling we present an extensive geochemical dataset from the geothermal plant in Kirchstockach. Based on chemical analyses of wellhead water samples, chemical and mineralogical analyses of scales collected along the uppermost 800 m of the production well, and chemical analyses of gas inclusions trapped in calcite-scale crystals, four processes are evaluated that could promote calcite scaling. These are (i) decompression of the produced fluid between the reservoir and the wellhead, (ii) corrosion of the casing that drives pH increase and subsequent calcite solubility decrease, (iii) gas influx from the geothermal reservoir and subsequent stripping of CO2 from the aqueous fluid, and (iv) boiling within the geothermal well. The effectiveness of the four scenarios was assessed by performing geochemical speciation calculations using the codes TOUGHREACT and CHILLER, which explicitly simulate boiling of aqueous fluids (CHILLER) and take into account the pressure dependence of calcite solubility (TOUGHREACT). The results show that process i causes notable calcite supersaturation but cannot act as the sole driver for scaling, whereas ii and iii are negligible in the present case. In contrast, process iv is consistent with all the available observations. That is, scaling is controlled by the exsolution of CO2 upon boiling at the markedly sub-hydrostatic pressure of 4–6 bar within the production well. This process is confirmed by the visible presence of gas inclusions in the calcite scales above the downhole pump, where the production fluid should nominally have been in the homogeneous liquid state. Whereas minor calcite scaling may have been triggered by fluid decompression within the production well, we conclude that the abundant scaling along the pump casing is due to cavitation induced by operating the pump at high production rates

20th century minimum and maximum temperature variations analysed on a regional scale in Switzerland: statistical analyses of observational data

The major aim of this study is to describe in a detailed manner the 20th century minimum and maximum temperature variations in Switzerland and to assess whether the magnitude of the secular warming and its interannual to interdecadal fluctuations show common seasonal patterns in different climatological regions. In a first step different climatological regions could successfully be established for all four seasons applying a statistical clustering method (Cluster Analysis) to the minimum and maximum temperature time series of a maximum number of climatological stations situated in different parts of the country. A Principal Component Analysis is preceding the actual clustering method which allows to compare the climatological station time series based on minimum and maximum temperature variations as well as on specific station related characteristics. Each of the resulting clusters aggregates a number of climatological stations, which follow a similar temporal development in the temperature data and own comparable station related characteristics. These clusters can therefore be considered as representative of a certain climatological region, which however is not necessarily geographically uniform. The clustering is carried out separately for two different climatological parameters in all four seasons, namely minimum and maximum temperatures in winter, spring, summer and autumn. The resulting clustering patterns reflect a strong dependency upon these climatological parameters as well as upon the seasons. Typical seasonal night-time and day-time temperature distributions over complex terrain have a determining influence on the emerging clustering patterns, which are similar in winter and autumn and in spring and summer. The classic fog and stratus areas combined with the particular cold air drainage over complex terrain have a determining influence on the clustering pattern in winter and autumn and thus the clusters are mainly specified through altitudinal stages. In spring and summer the clustering patterns are still related to the altitude they show however an additional dependency on specific geographical areas. Out of each of the eight clustering patterns three main regions emerged which could be related to the three most contrasting climatic areas in Switzerland and identified as "low altitudes, north", "high altitudes", and "low altitudes, south". The description of the following analyses is restricted to these three regions. The quantitative analyses of the minimum and maximum temperature trends and fluctuations over the 20th century are carried out on regional mean time series computed for each cluster. A new and very detailed description for the seasonal minimum and maximum temperature variations during the 20th century in Switzerland results. Secular warming trends are detected for both, minimum and maximum temperatures. The magnitudes differ mostly between the seasons. The minimum temperatures show generally higher trend estimates than the maximum temperatures with a more pronounced secular warming in winter and autumn. Analysing the temperatures on a decadal scale an abrupt warming is detected during the 1990s, which is especially emphasised for winter minimum temperatures in the region "high altitudes". A further warm period during the 20th century occurred from 1940 to 1950. In contrast to the warming at the end of the century this mid-century warming is most evident in maximum temperatures during spring and summer in the regions "low altitudes, north" and "high altitudes". The long- term decadal trend shows that minimum and maximum temperatures in all regions and seasons except for autumn are persistently increasing since 1980. The autumn temperatures play a special role since their secular warming trend is principally related to rather cold temperatures in the beginning of the century and a mild period during the 1980s, which, however, is not extended into the 1990s. These observations lead to the conclusion that a change in the seasonal warming pattern occurred during the last few decades. Analyses of minimum and maximum temperature extremes are supporting the conclusions formulated above. The warming trends as well as the mild phases, which are observed in minimum and maximum temperatures, can generally be related to a warming in both tails of the distribution (warm and cold). The described results can be linked to the 20th century evolution of large and small scale synoptic systems. The North Atlantic Oscillation exerts a high influence on winter weather types in Switzerland. The increasingly positive North Atlantic Oscillation Index during the last two decades most probably generated a changed frequency pattern of the alpine weather types in winter. In the 1990s this is expressed with a higher frequency of warm winter weather types (convective high-pressure and western advective) on the expenses of a major cold type (eastern advective). The frequency analysis of the alpine weather types for the other seasons does not yield as obvious results as for winter. It was found however, that the main warm periods occurring in different seasons during the century (mid-century summer warming; autumn mild phase in the 1980s) can principally be related to an elevated number of convective high-pressure weather types which usually generate milder temperatures. In an additional chapter the climatological regionalisation method, previously used with temperature data is applied to wind gust data. The analyses show that the gust factor between maximum and mean daily wind speeds over complex terrain follow a lognormal distribution. This knowledge in combination with the climatological regionalisation serves to estimate wind gust speed probabilities over the complex terrain of Switzerland according to three types of synoptic weather situations.Das Hauptziel dieser Studie ist eine möglichst detaillierte Beschreibung der Variationen der Minimum- und Maximumtemperaturen während des 20. Jahrhunderts, wobei es von Interesse ist abzuklären, ob der Umfang der Jahrhunderterwärmung sowie die annuellen und dekadalen Schwankungen in verschiedenen Regionen der Schweiz übereinstimmende saisonale Muster aufweisen. In einem ersten Schritt wurde eine möglichst hohe Anzahl von Minimum- und Maximumtemperaturzeitreihen der Landesklimastationen mit einer statistischen Gruppierungsmethode (Clusterananlyse) erfolgreich nach Jahreszeit geordnet. Vor der eigentlichen Gruppierungsmethode wird eine Hauptkomponentenanylse durchgeführt, die es erlaubt, einen Vergleich der Klimastationen anhand der Variationen in Minimum- und Maximumtemperaturen sowie spezifischen stationsbezogenen Eigenschaften vorzunehmen. In jeder dieser so erhaltenen Gruppen werden Klimastationen vereint, welche ähnliche zeitliche Temperaturvariationen aufweisen und deren stationsbezogenen Eigenschaften vergleichbar sind. Somit können diese Gruppen als jeweilige Vertreter einer bestimmten Klimaregion, deren Gebiet jedoch nicht unbedingt geographisch zusammenhängt, angenommen werden. Die Clusteranalyse wird jeweils auf Minimum- und Maximumtemperatur in den vier verschiedenen Jahreszeiten Winter, Frühling, Sommer und Herbst angewendet. Die daraus resultierenden verschiedenen Gruppierungsmuster widerspiegeln eine starke Abhängigkeit von den Klimaparametern und den Jahreszeiten. Die saisontypische Nachtund Tagestemperaturverteilung über komplexem Terrain übt einen bestimmenden Einfluss aus auf die sich bildenden Gruppierungsmuster, welche im Winter und im Herbst sowie im Frühling und im Sommer am ähnlichsten sind. Während den kühlen Jahreszeiten wird die Gruppierung der Klimastationen von den typischen herbstlichen und winterlichen Nebel- und Stratusgebieten wie auch vom Absinkverhalten der Kaltluft über komplexem Terrain am stärksten beeinflusst. Das Gruppierungsmuster ist daher eng verbunden mit der Höhe über Meer, auf welcher sich eine Klimastation befindet. Während den warmen Jahreszeiten ist die Verbindung zur Höhe immer noch zu finden, die Zugehörigkeit zu einer geographischen Region ist jedoch genauso massgebend. Drei bestimmte Klimaregionen, welche mit den drei gegensätzlichsten Klimazonen in der Schweiz in Verbindung gebracht werden können, treten innerhalb der acht erhaltenen Gruppierungsmuster regelmässig auf. Die drei Regionen werden dementsprechend benannt als: "tiefere Lagen, Nord", "hohe Lagen" und "tiefere Lagen, Süd". Die Beschreibung der Analysen beschränkt sich im weiteren Verlauf der Arbeit auf diese drei Regionen. Die weiteren quantitativen Analysen, welche der Erfassung des Trends in den Minimumund Maximumtemperaturen und deren Schwankungen während des 20. Jahrhunderts dienen, basieren auf mittleren regionalen Zeitreihen, die für jede einzelne Gruppe berechnet werden. Daraus geht eine neue und sehr detaillierte Beschreibung der saisonalen Minimum- und Maximumtemperaturvariationen während des 20. Jahrhunderts hervor. Die Minimum- sowie die Maximumtemperaturen unterliegen einer allgemeinen Erwärmung, welche sich in ihrem Ausmass zwischen den verschiedenen Jahreszeiten am meisten unterscheidet. Die Minimumtemperaturen weisen eine grundsätzlich grössere Erwärmung als die Maximumtemperaturen auf, was sich am stärksten im Winter und im Herbst äussert. Eine dekadal skalierte Untersuchung der Temperaturen lässt darauf schliessen, dass die 90er Jahre einer abrupten Erwärmung unterlagen, welche in den winterlichen Minimumtemperaturen in der Region "hohe Lagen" besonders nachdrücklich ist. Zwischen 1945 und 1950 ist eine weitere Warmphase zu finden, welche im Gegensatz zur Warmphase in den 90er Jahren vor allem in den Maximumtemperaturen des Frühlings und des Sommers in den Regionen "tiefere Lagen, Nord" und "hohe Lagen" ermittelt werden kann. Der dekadal skalierte Langzeittrend weist für alle Regionen und Jahreszeiten, ausser dem Herbst, von 1980 an kontinuierlich ansteigende Temperaturen auf. Die Herbsttemperaturen nehmen eine etwas spezielle Rolle ein, da sie nicht von einer Erwärmung in den 90er Jahren geprägt werden. Die starke Erwärmung, die ihnen über das Jahrhundert hinweg eigen, ist kann vor allem auf kalte Werte am Anfang des Jahrhunderts und eine milde Phase während den 80er Jahren zurückgeführt werden. Diese Beobachtungen lassen auf einen Wandel des jahreszeitlichen Erwärmungsmusters über die letzten Dekaden hinweg schliessen. Die bisher beschriebenen Resultate können auf den Ergebnissen aus der Analyse der Minimum- und Maximumtemperaturextreme abgestützt werden. Die gefundenen Erwärmungstrends sowie die verschiedenen Warmphasen stehen in enger Verbindung mit einer Erwärmung der Extremwerte in beiden Enden (extrem warm und extrem kalt) der Minimum- und Maximumtemperaturverteilung. Die Ergebnisse können in einen direkten Zusammenhang mit der Entwicklung diverser klein- und grossräumiger synoptischer Systeme im 20. Jahrhundert gebracht werden. Die Nordatlantische Oszillation übt einen grossen Einfluss auf die Wetterlagen in der Schweiz während des Winters aus. Mit grosser Wahrscheinlichkeit ist der über die letzten zwei Jahrzehnte hinweg zunehmend positive Nordatlantische Oszillationsindex bezeichnend für einen Wandel im Frequenzenmuster der winterlichen Wetterlagen. Es steht fest, dass während der 90er Jahre ein vermehrtes Auftreten von sogenannten "warmen" winterlichen Wetterlagen, wie konvektive Hochdrucklagen und advektive Westlagen, einhergeht mit einem markanten Rückgang der sogenannten "kalten" winterlichen Wetterlagen wie sie die advektiven Ostlagen darstellen. Die Frequenzanalyse der Wetterlagen in den anderen Jahreszeiten ergibt keine so klaren Resultate. Die grossen Warmphasen während des Jahrhunderts (Sommer Mitte Jahrhundert, Herbst in den 80er Jahren) können jedoch in Verbindung gebracht werden mit einem erhöhten Auftreten von konvektiven Hochdrucklagen, welche für mildere Temperaturen bedeutend sind. In einem zusätzlichen Kapitel wird die klimatologische Regionalisierungsmethode wie sie im vorhergehenden Teil an Temperaturdaten angewendet worden ist an Windgeschwindigkeitsdaten getestet. In der Analyse wird aufgezeigt, dass über komplexem Terrain, der Faktor zwischen den täglichen maximalen und mittleren Windgeschwindigkeiten eine lognormale Verteilung annimmt. In Verbindung mit einer klimatologischen Regionalisierung, welche für drei Arten von synoptischen Wetterlagen vorgenommen wird, dient diese Erkenntnis dazu, die Wahrscheinlichkeit der Windböengeschwindigkeit über dem komplexen Terrain der Schweiz abzuschätzen

A European pattern climatology 1766-2000

Using monthly independently reconstructed gridded European fields for the 500hPa geopotential height, temperature, and precipitation covering the last 235years we investigate the temporal and spatial evolution of these key climate variables and assess the leading combined patterns of climate variability. Seasonal European temperatures show a positive trend mainly over the last 40years with absolute highest values since 1766. Precipitation indicates no clear trend. Spatial correlation technique reveals that winter, spring, and autumn covariability between European temperature and precipitation is mainly influenced by advective processes, whereas during summer convection plays the dominant role. Empirical Orthogonal Function analysis is applied to the combined fields of pressure, temperature, and precipitation. The dominant patterns of climate variability for winter, spring, and autumn resemble the North Atlantic Oscillation and show a distinct positive trend during the past 40years for winter and spring. A positive trend is also detected for summer pattern 2, which reflects an increased influence of the Azores High towards central Europe and the Mediterranean coinciding with warm and dry conditions. The question to which extent these recent trends in European climate patterns can be explained by internal variability or are a result of radiative forcing is answered using cross wavelets on an annual basis. Natural radiative forcing (solar and volcanic) has no imprint on annual European climate patterns. Connections to CO2 forcing are only detected at the margins of the wavelets where edge effects are apparent and hence one has to be cautious in a further interpretatio

Understanding competing risks: a simulation point of view

<p>Abstract</p> <p>Background</p> <p>Competing risks methodology allows for an event-specific analysis of the single components of composite time-to-event endpoints. A key feature of competing risks is that there are as many hazards as there are competing risks. This is not always well accounted for in the applied literature.</p> <p>Methods</p> <p>We advocate a simulation point of view for understanding competing risks. The hazards are envisaged as momentary event forces. They jointly determine the event time. Their relative magnitude determines the event type. 'Empirical simulations' using data from a recent study on cardiovascular events in diabetes patients illustrate subsequent interpretation. The method avoids concerns on identifiability and plausibility known from the latent failure time approach.</p> <p>Results</p> <p>The 'empirical simulations' served as a proof of concept. Additionally manipulating baseline hazards and treatment effects illustrated both scenarios that require greater care for interpretation and how the simulation point of view aids the interpretation. The simulation algorithm applied to real data also provides for a general tool for study planning.</p> <p>Conclusions</p> <p>There are as many hazards as there are competing risks. All of them should be analysed. This includes estimation of baseline hazards. Study planning must equally account for these aspects.</p

Effect of Glacial/Interglacial Recharge Conditions on Flow of Meteoric Water Through Deep Orogenic Faults: Insights Into the Geothermal System at Grimsel Pass, Switzerland

Many meteoric-recharged, fault-hosted geothermal systems in amagmatic orogenic belts have been active through the Pleistocene glacial/interglacial climate fluctuations. The effects of climate-induced recharge variations on fluid flow patterns and residence times of the thermal waters are complex and may influence how the geothermal and mineralization potential of the systems are evaluated. We report systematic thermal-hydraulic simulations designed to reveal the effects of recharge variations, using a model patterned on the orogenic geothermal system at Grimsel Pass in the Swiss Alps. Previous studies have shown that fault-bounded circulation of meteoric water is driven to depths of ∼10 km by the high alpine topography. Simulations suggest that the current single-pass flow is typical of interglacial periods, during which (a) meteoric recharge into the fault is high (above tens of centimeters per year), (b) conditions are at or somewhat below the critical Rayleigh number, and (c) hydraulic connectivity along the fault plane is extensive (an extent of at least 10 km into increasingly higher terrain is required to explain the 10 km penetration depth). The subcritical condition constrains the bulk fault permeability to <1e-14 m2. In contrast, the limited recharge during the numerous Pleistocene glaciation events likely induced a layered flow system, with single-pass flow confined to shallow depths while non-Rayleigh convection occurred deeper in the fault. The same layering can be observed at low aspect ratios (length/depth) of the fault plane, when the available recharge area limits flux through the fault