Das Projekt "Predictability of local Weather - C4: Coupling of planetary-scale Rossby wave trains to local extremes in heat waves over Europe" wird vom Umweltbundesamt gefördert und von Johannes Gutenberg-Universität Mainz, Institut für Physik der Atmosphäre durchgeführt. This project aims at improving the basic understanding of heat waves over Europe. Such heat waves have a significant impact on society as well as on natural ecosystems. They can be expected to become more severe in future decades owing to the projected global warming. The strength and duration of a heat wave is hard to predict with state-of-the-art weather forecast systems, presumably because of the interaction between multiple scales and processes involved. This project focuses on the downscale coupling between the planetary-scale flow in the upper troposphere and synoptic and mesoscale processes which eventually lead to local hot weather over a prolonged period. It is hypothesized that upper-tropospheric quasi-stationary Rossby wave packets play an important role, but that a true heat wave requires further processes acting on smaller scales. An important goal is to find out which of these scales and processes limit the predictability of heat waves. The statistics of past heat waves will be investigated and characterized using reanalysis data. Based on this work, individual cases of heat waves will be selected and studied in detail. Tools will be developed and applied in order to study the upper tropospheric waveguide and associated wave trains with significant ridging over a localized area for an extended period. The main idea here is to focus on regional wave packets rather than global-scale waves; correspondingly, this project goes beyond the traditional Fourier analysis and uses wavelet analysis instead. In addition, the upper tropospheric Rossby waveguide will be analyzed using established ideas from linear wave theory, but generalizing these ideas to zonally non-uniform references states. This will allow one to evaluate a previously suggested 'quasi-resonance hypothesis' in a more focused and, arguably, more relevant framework. This set of diagnostic tools will be complemented by another set of tools that will quantify the relevant smaller-scale processes like warm air advection, subsidence, irradiation and cloudiness/rainfall as well as soil moisture. One particular focus will be on the evolution of the heat that builds up in the deep boundary layer during several diurnal cycles. Here, we will distinguish between periods with and without synoptic-scale warm air advection. Related to the strength of the boundary layer inversion and to the moisture distribution, the role of cloudiness and shallow thunderstorm lows in augmenting/reducing the heat will be studied. This will be done in case studies using atmospheric reanalyses, surface and upper-air data as well as assessments of radiation budget terms from satellites. This project will also investigate the predictability of heat waves based on ensembles from atmospheric reforecast data sets; this activity will be started during phase 1, but it will become more dominant during later phases, when the diagnostic methods developed during phase 1 have reached a mature stage.
Das Projekt "Interactions and complex structures in the dynamics of changing climate: impact of tipping elements in presence and past (Causal Networks)" wird vom Umweltbundesamt gefördert und von Potsdam-Institut für Klimafolgenforschung e.V. durchgeführt. Investigation of past and present climate dynamics and impact of climate tipping elements by means of a spatio-temporal analysis of climate data using complex networks. DFG-Project in cooperation with the Academy of Sciences of the Czech Republic, Prag. Investigation of past and present climate dynamics and impact of climate tipping elements by means of a spatio-temporal analysis of climate data using complex networks. The study of the stability of the climate system and the impacts of the changes it undergoes requires both data analysis and modelling approaches. Recent findings of particularly sensitive sub-systems in the climate system (tipping elements), have risen concerns that common climate models still underestimate climate change. Focusing on the data analysis part, this project aims to investigate the role and connectivity of tipping elements with respect to global and regional climate and environmental change, using ideas from complex network theory for a spatio-temporal, multi-variate analysis of climate data. This approach will be critically reviewed and tested. For this purpose, new methods for inferring coupling directions and indirect couplings will be developed and implemented. Tipping elements will be studied by their spatio-temporal interactions; this will help to understand the stability or multi-stability of the global climate network due to changes of tipping elements and the crossing of tipping points. This study is complemented by comparing modern spatio-temporal climate interactions with past changes of climate during the Holocene, including the development of an appropriate approach to compare sparsely distributed data (palaeo-data) with complex network data (recent climate interaction network). The project will, therefore, significantly contribute to the climate change studies (better understanding tipping elements) and the methodological development (new approaches for spatio-temporal analysis), which could eventually also be used to improve climate models.
Das Projekt "Competence platform on energy crop and Agroforestry systems for arid and semi-arid ecosystems - Africa (COMPETE)" wird vom Umweltbundesamt gefördert und von WIP, Wirtschaft und Infrastruktur GmbH & Co Planungs-KG durchgeführt.
Das Projekt "Formation of brine channels in sea ice" wird vom Umweltbundesamt gefördert und von Fachhochschule Münster, Fachbereich Physikalische Technik durchgeführt. Within this interdisciplinary project the formation of brine channels in sea ice will be explored. The microscopic properties of sea ice, especially the permeability plays an important role for the energy exchange between ocean and atmosphere and is determined by the brine channel volume. The brine channel structure will be measured by computer tomography and image analysis. We intend to describe the channel structure by two phenomenological models, a morphogenesis approach of Alan Turing in connection with the phase transition theory of Ginzburg and Landau, and the phase field method with respect to the Cahn-Hilliard equation. We solve these nonlinear evolution equations in two and three dimensions and compare the size and texture of the brine channels with the measurements. In addition to the phenomenological equations we support our studies with molecular dynamics simulations and the density functional theory in order to obtain deeper insights at the molecular scale. Comparative first-principles studies will then enhance the trust in the extracted parameters and will lead to classical density functional for the two phases. We will discuss the phase transitions in terms of a phenomenological theory based on microscopic parameters and try to extract the underlying mechanism for the formation of water-ice boundaries. Specifically, we want to explore three theoretical questions: (i) How are ice-water melting fronts moving, (ii) How are brine channels formed and (iii) How do surface properties influence the structure formation of brine channels. The project is based on the experiences of three fields, the theoretical biological physics, chemical physics and the many-body theory. The final aim of the project is to provide input parameters for global climate models.
Das Projekt "Subproject: 4D Modelling of Seismic Signatures of Fluid Flow in Crystalline Rocks" wird vom Umweltbundesamt gefördert und von Karlsruher Institut für Technologie (KIT), Geophysikalisches Institut durchgeführt. The main objective of this research is to optimize data acquisition of future seismological time-lapse experiments around the site of the Kontinentale Tiefbohrung (KTB) in Germany by predictive numerical modelling. Second objective is to understand how fluid pressure variations manifest themselves in the recorded elastic wavefields given a specific asquisition geometry. These objectives will be achieved by 6 essential steps: (1) Establishment of a three-dimensional elastic model with a professional software tool (GOCAD) on a scale of 10 x 10 km that incorporates the major reflectors found in previous investigations (SE1 and SE2). (2) Development of a realistic model of the SE1 reflector with variable lateral heterogeneities. The model must be consistent with logging results and previous measurements and consists of an elastic background model and a porosity and permeability model of the SE1 reflector. (3) Development of a two-dimensional elastic model of the area between pilot and main hole. (4) Utilization of Gassmann 'theory (low-frequency surface seismic) and Biot's theory (high-frequency cross-hole seismic) to estabilish the influence of pore pressure variations on elastic parameters. (5) Simulation of three-dimensional low-frequency wave propagation from surface sources for variable fluid pressure evolving in the SE1 reflector due to fluid injection. (6) Simulation of two-dimensional higt-frequency wave propagation for a cross-hole experiment.
Das Projekt "Durchführung einer Stoffstromanalyse auf der Basis des TOC-Vorgehensmodells (DISOLAR II)" wird vom Umweltbundesamt gefördert und von Hochschule für Technik und Wirtschaft Berlin (HTW Berlin) durchgeführt. Fortführung des DISOLAR-Projektes. Verfeinerung der Stoffstromanalyse der Wäscher und Erweiterung der Betrachtung der Stoffströme des Stickstoffkreislaufes mit der Software Umberto. Identifizierung des Schwachpunktes mittels des TOC-Ansatzes (Theory of Constraints).
Das Projekt "Modeling mass transfer processes for multi-phase flow in porous media including fluid-fluid interfacial areas" wird vom Umweltbundesamt gefördert und von Universität Stuttgart, Institut für Wasser- und Umweltsystemmodellierung durchgeführt. Multi-phase flow and transport processes in porous media play an essential role in many environmental, biological, and industrial systems. These processes are especially complex when the phase composition changes, i.e. when mass transfer between phases takes place. It is well known that fluid-fluid interfaces play a central role in mass transfer among various phases. Nevertheless, currently, these interfaces are absent in mass transport theories. Also, almost all macro-scale numerical models completely ignore interfacial areas and either assume thermodynamic equilibrium between the phases or they use empirical functions for their estimation. However, new theories of two-phase flow in porous media have been developed in the last decades which explicitly account for the fluid-fluid interfaces, both without and with interphase mass transfer. The aim of this project is to first compare a two-phase model with interphase mass transfer, accounting for the role of interfacial area, to experimental data. Next, it is planned to extend the new theories to three-phase flow and non-isothermal situations. The new balance equations and constitutive relationships will be implemented into a numerical simulator and applied to an example of carbon dioxide storage in a deep geological formation. When storing carbon dioxide, processes occurring locally within the regions of supercritical carbon dioxide are much more complex and much more dependent on finescale processes than in the large remaining part of the domain of interest. Therefore, a multi-scale-multi-physics approach is envisaged for the solution of this problem.
Das Projekt "Quantification of shear-induced convection and bottom-boundary mixing in natural waters" wird vom Umweltbundesamt gefördert und von Rheinland-Pfälzische Technische Universität Kaiserslautern-Landau, Institut für Umweltwissenschaften durchgeführt. It has been pointed out by numerous authors that estimates of the vertical mixing obtained by microstructure profiling techniques in lakes and the ocean can, in general, not explain the total mixing suggested by the global budgets of matter and heat. Searching for additional mixing mechanisms, boundary mixing has been identified as a key process. In this study, a boundary mixing process driven by a gravitationally unstable bottom boundary layer (BBL) is investigated. Such unstable BBLs in stably stratified basins are the result of strong up-slope currents, typically caused by internal seiching in lakes or by long internal-inertial waves in the coastal ocean. Due to the fact that in a turbulent BBL, the up-slope speed increases with increasing distance from the sediment, heavy (i.e. cold or salty) water in the BBL may be advected above lighter (i.e. warmer or fresher) water, leading to convective mixing. Inversely, down-slope currents lead to a suppression of mixing. We plan to investigate this process with an interdisciplinary approach: our primary study site will be Lake Constance, where the BBL dynamics and turbulence will be studied in detail for a limnological set-up. Our oceanographic study site will be the Baltic Sea, where a similar mixing process takes place. A numerical turbulence model will be used to analyze this process at the measuring sites, study the basin-wide effect, and construct a general theory.
Das Projekt "Investigation of past and present climate dynamics and its stability by means of a spatio-temporal analysis of climate data using complex networks" wird vom Umweltbundesamt gefördert und von Potsdam-Institut für Klimafolgenforschung e.V. durchgeführt. The study of the stability of the climate system and the impacts of the changes it undergoes requires both data analysis and modelling approaches. Recent findings of particularly sensitive sub-systems in the climate system (tipping elements), have risen concerns that common climate models still underestimate climate change. Focusing on the data analysis part, this project aims to investigate the role and connectivity of tipping elements with respect to global and regional climate and environmental change, using ideas from complex network theory for a spatio-temporal, multi-variate analysis of climate data. This approach will be critically reviewed and tested. For this purpose, new methods for inferring indirect couplings, extreme events, spatial predominant directions, and boundary effects will be developed and implemented as well as applied to the monsoon regions in South America and Asia. This includes a novel anisotropy measure which is able to quantify directions along which extreme events synchronize locally. Spatio-temporal interactions between and within these specific tipping elements will investigated in order to understand the stability or multi-stability of the considered monsoon regions due to environmental changes or crossing of tipping points. The project will, therefore, significantly contribute to the climate change studies (better understanding tipping elements) and the methodological development (new approaches for spatio-temporal analysis), which could eventually also be used to improve climate models.
Das Projekt "Co-estimation of the Earth main magnetic field and the ionospheric variation field" wird vom Umweltbundesamt gefördert und von Universität Potsdam, Institut für Mathematik durchgeführt. The aim of this project is to co-estimate models of the core and ionosphere magnetic fields, with the longer-term view of building a 'comprehensive' model of the Earths magnetic field. In this first step we would like to take advantage of the progresses made in the understanding of the ionosphere by global M-I-T modelling to better separate the core and ionospheric signals in satellite data. The magnetic signal generated in the ionosphere is particularly difficult to handle because satellite data provide only information on a very narrow local time window at a time. To get around this difficulty, we would like to apply a technique derived from assimilation methods and that has been already successfully applied in outer-core flow studies. The technique relies on a theoretical model of the ionosphere such as the Upper Atmosphere Model (UAM), where statistics on the deviations from a simple background model are estimated. The derived statistics provided in a covariance matrix format can then be use directly in the magnetic data inversion process to obtain the expected core and ionospheric models. We plan to apply the technique on the German CHAMP satellite data selected for magnetically quiet times. As an output we should obtain a model of the ionospheric magnetic variation field tailored for the selected data and a core-lithosphere field model where possible leakage from ionospheric signals are avoided or at least reduced. The technique can in theory be easily extended to handle the large-scale field generated in the magnetosphere.
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