@article{71c87e9eeaaa40a8b942ec575be91ee7,
title = "A low-rank update for relaxed Schur complement preconditioners in fluid flow problems",
abstract = "The simulation of fluid dynamic problems often involves solving large-scale saddle-point systems. Their numerical solution with iterative solvers requires efficient preconditioners. Low-rank updates can adapt standard preconditioners to accelerate their convergence. We consider a multiplicative low-rank correction for pressure Schur complement preconditioners that is based on a (randomized) low-rank approximation of the error between the identity and the preconditioned Schur complement. We further introduce a relaxation parameter that scales the initial preconditioner. This parameter can improve the initial preconditioner as well as the update scheme. We provide an error analysis for the described update method. Numerical results for the linearized Navier–Stokes equations in a model for atmospheric dynamics on two different geometries illustrate the action of the update scheme. We numerically analyze various parameters of the low-rank update with respect to their influence on convergence and computational time.",
keywords = "Low-rank update, Preconditioner, Saddle-point system, Schur complement",
author = "Beddig, {Rebekka S.} and J{\"o}rn Behrens and Sabine Le Borne",
year = "2023",
month = may,
day = "10",
doi = "10.1007/s11075-023-01548-3",
language = "English",
volume = "94",
pages = "1597--1618",
journal = "Numer. Algorithms",
issn = "1017-1398",
publisher = "Springer Netherlands",
number = "4",
}
@article{ab0ca8c0d94f415abe9d7c51edde974f,
title = "A linear low effort stabilization method for the Euler equations using discontinuous Galerkin methods",
abstract = "We present a novel and simple yet intuitive approach to the stabilization problem for the numerically solved Euler equations with gravity source term relying on a low-order nodal Discontinuous Galerkin Method (DGM). Instead of assuming isothermal or polytropic solutions, we only take a hydrostatic balance as a given property of the flow and use the hydrostatic equation to calculate a hydrostatic pressure reconstruction that replaces the gravity source term. We compare two environments that both solve the Euler equations using the DGM: deal.II and StormFlash. We utilize StormFlash as it allows for the use of the novel stabilization method. Without stabilization, StormFlash does not yield results that resemble correct physical behavior while the results with stabilization for StormFlash, as well as deal.II model the fluid flow more accurately. Convergence rates for deal.II do not match the expected order while the convergence rates for StormFlash with the stabilization scheme (with the exceptions for the L (Formula presented.) errors for momentum) meet the expectation. The results from StormFlash with stabilization also fit reference solutions from the literature much better than those from deal.II. We conclude that this novel scheme is a low cost approach to stabilize the Euler equations while not limiting the flow in any way other than it being in hydrostatic balance.",
keywords = "general approach, discontinuous Galerkin method, stabilization, Euler equations",
author = "Michel B{\"a}nsch and J{\"o}rn Behrens and Stefan Vater",
year = "2023",
doi = "10.1002/fld.5243",
language = "English",
journal = "International Journal for Numerical Methods in Fluids",
issn = "0271-2091",
publisher = "John Wiley and Sons Ltd",
}
@article{ffd5cd847949432e8c825285afc00ce5,
title = "Towards the new Thematic Core Service Tsunami within the EPOS Research Infrastructure",
abstract = "Tsunamis constitute a significant hazard for European coastal populations, and the impact of tsunami events worldwide can extend well beyond the coastal regions directly affected. Understanding the complex mechanisms of tsunami generation, propagation, and inundation, as well as managing the tsunami risk, requires multidisciplinary research and infrastructures that cross national boundaries. Recent decades have seen both great advances in tsunami science and consolidation of the European tsunami research community. A recurring theme has been the need for a sustainable platform for coordinated tsunami community activities and a hub for tsunami services. Following about three years of preparation, in July 2021, the European tsunami community attained the status of Candidate Thematic Core Service (cTCS) within the European Plate Observing System (EPOS) Research Infrastructure. Within a transition period of three years, the Tsunami candidate TCS is anticipated to develop into a fully operational EPOS TCS. We here outline the path taken to reach this point, and the envisaged form of the future EPOS TCS Tsunami. Our cTCS is planned to be organised within four thematic pillars: (1) Support to Tsunami Service Providers, (2) Tsunami Data, (3) Numerical Models, and (4) Hazard and Risk Products. We outline how identified needs in tsunami science and tsunami risk mitigation will be addressed within this structure and how participation within EPOS will become an integration point for community development.",
keywords = "Tsunami, Infrastructures",
author = "Andrey Babeyko and Stefano Lorito and Francisco Hernandez and J{\"o}rn Lauterjung and Finn L{\o}vholt and Alexander Rudloff and Mathilde S{\o}rensen and Alexey Androsov and Inigo Aniel-Quiroga and Alberto Armigliato and Baptista, {Maria Ana} and Enrico Baglione and J{\"o}rn Behrens and Beatriz Brizuela and Sergio Bruni and Didem Cambaz and {Cantavella Nadal}, Juan and Fernando Carillho and Ian Chandler and Denis Chang-Seng and Marinos Charalampakis and Lorenzo Cugliari and Clea Denamiel and Doğan, {G{\"o}zde G{\"u}ney} and Gaetano Festa and David Fuhrman and Alice-Agnes Gabriel and Pauline Galea and Steven Gibbons and Mauricio Gonz{\'a}lez and Laura Graziani and Marc-Andr{\'e} Gutscher and Sven Harig and Helene Hebert and Constantin Ionescu and Fatemeh Jalayer and Nikos Kalligeris and Utku K{\^a}noğlu and Piero Lanucara and {Macias S{\'a}nchez}, Jorge and Shane Murphy and {\"O}cal Necmioğlu and Rachid Omira and Gerassimos Papadopoulos and Rapha{\"e}l Paris and Fabrizio Romano and Tiziana Rossetto and Jacopo Selva and Antonio Scala and Roberto Tonini and Konstantinos Trevlopoulos and Ioanna Triantafyllou and Roger Urgeles and Roberto Vallone and Ivica Vilibi{\'c} and Manuela Volpe and Ahmet Yalciner",
year = "2022",
month = apr,
day = "29",
doi = "10.4401/ag-8762",
language = "English",
volume = "65",
journal = "Annals of Geophysics",
issn = "1593-5213",
publisher = "Istituto Nazionale di Geofisica e Vulcanologia",
number = "2",
}
@article{9945020b2f94444dab6aacda3a21965f,
title = "Performance Assessment of the Cloud for Prototypical Instant Computing Approaches in Geoscientific Hazard Simulations",
abstract = "Computing forecasts of hazards, such as tsunamis, requires fast reaction times and high precision, which in turn demands for large computing facilities that are needed only in rare occasions. Cloud computing environments allow to configure largely scalable on-demand computing environments. In this study, we tested two of the major cloud computing environments for parallel scalability for relevant prototypical applications. These applications solve stationary and non-stationary partial differential equations by means of finite differences and finite elements. These test cases demonstrate the capacity of cloud computing environments to provide scalable computing power for typical tasks in geophysical applications. As a proof-of-concept example of an instant computing application for geohazards, we propose a workflow and prototypical implementation for tsunami forecasting in the cloud. We demonstrate that minimal on-site computing resources are necessary for such a forecasting environment. We conclude by outlining the additional steps necessary to implement an operational tsunami forecasting cloud service, considering availability and cost. Copyright {\textcopyright} 2022 Behrens, Schulz and Simon.",
keywords = "cloud computing, instant computing, natural hazard, parallel performance, tsunami",
author = "J. Behrens and Arne Schulz and K. Simon",
note = "Export Date: 20 April 2022 Correspondence Address: Behrens, J.; Department of Mathematics/CEN, Germany; email: joern.behrens@uni-hamburg.de Funding details: 603839 Funding details: Deutsche Forschungsgemeinschaft, DFG, 390683824 Funding details: Universit{\"a}t Hamburg, UH Funding text 1: Parts of this research were conducted in the framework of the ASTARTE project with funding from the European Unions Seventh Program for research, technological development and demonstration under grant agreement No. 603839. Additional funding was obtained by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany{\textquoteright}s Excellence Strategy—EXC 2037 {\textquoteright}CLICCS—Climate, Climatic Change, and Society{\textquoteright}—Project Number: 390683824, contribution to the Center for Earth System Research and Sustainability (CEN) of Universit{\"a}t Hamburg.",
year = "2022",
month = mar,
day = "9",
doi = "10.3389/feart.2022.762768",
language = "English",
volume = "10",
journal = "Frontiers in Earth Science",
issn = "2296-6463",
publisher = "Frontiers Media S. A.",
}
@article{3702b81cd85a406d8d51391df24debe9,
title = "Tsunami risk communication and management: Contemporary gaps and challenges",
abstract = "Very large tsunamis are associated with low probabilities of occurrence. In many parts of the world, these events have usually occurred in a distant time in the past. As a result, there is low risk perception and a lack of collective memories, making tsunami risk communication both challenging and complex. Furthermore, immense challenges lie ahead as population and risk exposure continue to increase in coastal areas. Through the last decades, tsunamis have caught coastal populations off-guard, providing evidence of lack of preparedness. Recent tsunamis, such as the Indian Ocean Tsunami in 2004, 2011 Tohoku and 2018 Palu, have shaped the way tsunami risk is perceived and acted upon. Based on lessons learned from a selection of past tsunami events, this paper aims to review the existing body of knowledge and the current challenges in tsunami risk communication, and to identify the gaps in the tsunami risk management methodologies. The important lessons provided by the past events call for strengthening community resilience and improvement in risk-informed actions and policy measures. This paper shows that research efforts related to tsunami risk communication remain fragmented. The analysis of tsunami risk together with a thorough understanding of risk communication gaps and challenges is indispensable towards developing and deploying comprehensive disaster risk reduction measures. Moving from a broad and interdisciplinary perspective, the paper suggests that probabilistic hazard and risk assessments could potentially contribute towards better science communication and improved planning and implementation of risk mitigation measures.",
keywords = "NEAM Region, Perception, Preparedness, Preventive measures, Tsunami risk, Uncertainties",
author = "Irina Rafliana and Fatemeh Jalayer and Andrea Cerase and Lorenzo Cugliari and Marco Baiguera and Dimitra Salmanidou and {\"O}cal Necmioğlu and Ayerbe, {Ignacio Aguirre} and Stefano Lorito and Stuart Fraser and Finn L{\o}vholt and Andrey Babeyko and Salgado-G{\'a}lvez, {Mario A.} and Jacopo Selva and {De Risi}, Raffaele and S{\o}rensen, {Mathilde B.} and J{\"o}rn Behrens and I{\~n}igo Aniel-Quiroga and {Del Zoppo}, Marta and Stefano Belliazzi and Pranantyo, {Ignatius Ryan} and Alessandro Amato and Ufuk Hancilar",
year = "2022",
month = feb,
day = "15",
doi = "10.1016/j.ijdrr.2021.102771",
language = "English",
volume = "70",
journal = "International Journal of Disaster Risk Reduction",
issn = "2212-4209",
publisher = "Elsevier Ltd",
}
@article{b805bf17001149db848d2b21de524395,
title = "Editorial: From Tsunami Science to Hazard and Risk Assessment: Methods and Models",
keywords = "early warning, hazard, numerical modelling, observations, probabilities, risk, tsunami",
author = "Stefano Lorito and J{\"o}rn Behrens and Finn L{\o}vholt and Tiziana Rossetto and Jacopo Selva",
year = "2021",
month = oct,
day = "8",
doi = "10.3389/feart.2021.764922",
language = "English",
volume = "9",
journal = "Frontiers in Earth Science",
issn = "2296-6463",
publisher = "Frontiers Media S. A.",
}
@article{725a4721ba754b13b543569b2ba773a3,
title = "Extending legacy climate models by adaptive mesh refinement for single-component tracer transport: a case study with ECHAM6-HAMMOZ (ECHAM6.3-HAM2.3-MOZ1.0)",
abstract = "The model error in climate models depends on mesh resolution, among other factors. While global refinement of the computational mesh is often not feasible computationally, adaptive mesh refinement (AMR) can be an option for spatially localized features. Creating a climate model with AMR has been prohibitive so far. We use AMR in one single-model component, namely the tracer transport scheme.Particularly, we integrate AMR into the tracer transport module of the atmospheric model ECHAM6 and test our implementation in several idealized scenarios and in a realistic application scenario (dust transport). To achieve this goal, we modify the flux-form semi-Lagrangian (FFSL) transport scheme in ECHAM6 such that we can use it on adaptive meshes while retaining all important properties (such as mass conservation) of the original FFSL implementation. Our proposed AMR scheme is dimensionally split and ensures that high-resolution information is always propagated on (locally) highly resolved meshes. We utilize a data structure that can accommodate an adaptive Gaussian grid.We demonstrate that our AMR scheme improves both accuracy and efficiency compared to the original FFSL scheme. More importantly, our approach improves the representation of transport processes in ECHAM6 for coarse-resolution simulations. Hence, this paper suggests that we can overcome the overhead of developing a fully adaptive Earth system model by integrating AMR into single components while leaving data structures of the dynamical core untouched. This enables studies to retain well-tested and complex legacy code of existing models while still improving the accuracy of specific components without sacrificing efficiency.",
author = "Yumeng Chen and Konrad Simon and J{\"o}rn Behrens",
year = "2021",
month = may,
day = "3",
doi = "10.5194/gmd-14-2289-2021",
language = "English",
volume = "14",
pages = "2289–2316",
journal = "Geoscientific Model Development",
issn = "1991-9603",
publisher = "Copernicus GmbH",
number = "5",
}
@article{b7112ba0dfbd4dcf9d7633ca7dccc48f,
title = "Probabilistic Tsunami Hazard and Risk Analysis: A Review of Research Gaps",
abstract = "Tsunamis are unpredictable and infrequent but potentially large impact natural disasters. To prepare, mitigate and prevent losses from tsunamis, probabilistic hazard and risk analysis methods have been developed and have proved useful. However, large gaps and uncertainties still exist and many steps in the assessment methods lack information, theoretical foundation, or commonly accepted methods. Moreover, applied methods have very different levels of maturity, from already advanced probabilistic tsunami hazard analysis for earthquake sources, to less mature probabilistic risk analysis. In this review we give an overview of the current state of probabilistic tsunami hazard and risk analysis. Identifying research gaps, we offer suggestions for future research directions. An extensive literature list allows for branching into diverse aspects of this scientific approach.",
keywords = "hazard, probabilistic method, research gap, risk, tsunami",
author = "J{\"o}rn Behrens and Finn L{\o}vholt and Fatemeh Jalayer and Stefano Lorito and Salgado-G{\'a}lvez, {Mario A.} and Mathilde S{\o}rensen and Stephane Abadie and Ignacio Aguirre-Ayerbe and I{\~n}igo Aniel-Quiroga and Andrey Babeyko and Marco Baiguera and Roberto Basili and Stefano Belliazzi and Anita Grezio and Kendra Johnson and Shane Murphy and Rapha{\"e}l Paris and Irina Rafliana and {De Risi}, Raffaele and Tiziana Rossetto and Jacopo Selva and Matteo Taroni and {Del Zoppo}, Marta and Alberto Armigliato and Vladim{\'i}r Bure{\v s} and Pavel Cech and Claudia Cecioni and Paul Christodoulides and Gareth Davies and Fr{\'e}d{\'e}ric Dias and Bayraktar, {Hafize Ba{\c s}ak} and Mauricio Gonz{\'a}lez and Maria Gritsevich and Serge Guillas and Harbitz, {Carl Bonnevie} and Utku K{\^a}noǧlu and Jorge Mac{\'i}as and Papadopoulos, {Gerassimos A.} and Jascha Polet and Fabrizio Romano and Amos Salamon and Antonio Scala and Mislav Stepinac and Tappin, {David R.} and Thio, {Hong Kie} and Roberto Tonini and Ioanna Triantafyllou and Thomas Ulrich and Elisa Varini and Manuela Volpe and Eduardo Vyhmeister",
year = "2021",
month = apr,
day = "29",
doi = "10.3389/feart.2021.628772",
language = "English",
volume = "9",
journal = "Frontiers in Earth Science",
issn = "2296-6463",
publisher = "Frontiers Media S. A.",
}
@article{2f68dab20c684d7185888355c8cccd60,
title = "Metrics for Performance Quantification of Adaptive Mesh Refinement",
abstract = "Non-uniform, dynamically adaptive meshes are a useful tool for reducing computational complexities for geophysical simulations that exhibit strongly localised features such as is the case for tsunami, hurricane or typhoon prediction. Using the example of a shallow water solver, this study explores a set of metrics as a tool to distinguish the performance of numerical methods using adaptively refined versus uniform meshes independent of computational architecture or implementation. These metrics allow us to quantify how a numerical simulation benefits from the use of adaptive mesh refinement. The type of meshes we are focusing on are adaptive triangular meshes that are non-uniform and structured. Refinement is controlled by physics-based indicators that capture relevant physical processes and determine the areas of mesh refinement and coarsening. The proposed performance metrics take into account a number of characteristics of numerical simulations such as numerical errors, spatial resolution, as well as computing time. Using a number of test cases we demonstrate that correlating different quantities offers insight into computational overhead, the distribution of numerical error across various mesh resolutions as well as the evolution of numerical error and run-time per degree of freedom.",
keywords = "Adaptive mesh refinement, Computational efficiency, Discontinuous Galerkin, Metrics, Shallow water equation",
author = "Nicole Beisiegel and Castro, {Crist{\'o}bal E.} and J{\"o}rn Behrens",
year = "2021",
month = apr,
doi = "10.1007/s10915-021-01423-0",
language = "English",
volume = "87",
journal = "Journal of Scientific Computing",
issn = "0885-7474",
publisher = "Springer New York",
number = "1",
}
@article{2911fda8d5e4482c95447fdc85e97132,
title = "Semi-Lagrangian Subgrid Reconstruction for Advection-Dominant Multiscale Problems with Rough Data",
abstract = "We introduce a new framework of numerical multiscale methods for advection-dominated problems motivated by climate sciences. Current numerical multiscale methods (MsFEM) work well on stationary elliptic problems but have difficulties when the model involves dominant lower order terms. Our idea to overcome the associated difficulties is a semi-Lagrangian based reconstruction of subgrid variability into a multiscale basis by solving many local inverse problems. Globally the method looks like a Eulerian method with multiscale stabilized basis. We show example runs in one and two dimensions and a comparison to standard methods to support our ideas and discuss possible extensions to other types of Galerkin methods, higher dimensions and nonlinear problems.",
keywords = "Advection–, Inverse problems, Multiscale finite elements, Multiscale simulation, Semi-Lagrangian, diffusion",
author = "Konrad Simon and J{\"o}rn Behrens",
year = "2021",
month = mar,
day = "28",
doi = "10.1007/s10915-021-01451-w",
language = "English",
volume = "87",
journal = "Journal of Scientific Computing",
issn = "0885-7474",
publisher = "Springer New York",
number = "2",
}