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Numerical models of volcanic eruption plumes: inter-comparison and sensitivity
Journal of Volcanology and Geothermal Research 326 (2016) 1
Contents lists available at ScienceDirect
Journal of Volcanology and Geothermal Research journal homepage: www.elsevier.com/locate/jvolgeores
Preface
Numerical models of volcanic eruption plumes: inter-comparison and sensitivity The accurate description of the dynamics of convective plumes developed during explosive volcanic eruptions represents one of the most crucial and intriguing challenges in volcanology. Eruptive plume dynamics are significantly affected by complex interactions with the surrounding atmosphere, in the case of both strong eruption columns, rising vertically above the tropopause, and weak volcanic plumes, developing within the troposphere and often following bended trajectories. The understanding of eruptive plume dynamics is pivotal for estimating mass flow rates of volcanic sources, a crucial aspect for tephra dispersion models used to assess aviation safety and tephra fallout hazard. For these reasons, several eruption column models have been developed in the past decades, including the more recent sophisticated computational fluid dynamic models. This volume presents results of the eruption column model intercomparison study promoted by the International Association of Volcanology and Chemistry of Earth’s Interior (IAVCEI) Commission on Tephra Hazard Modelling. The study compared empirical parameterizations (0D), aimed to estimate mass flow rates from column heights, and simulations of onedimensional (1D) and three-dimensional (3D) numerical models in a set of inter-comparison exercises to evaluate model capabilities and highlight aspects requiring improvement and future research. The exercises were designed as tests in which a set of common input parameters was given for two reference eruptions, representing a strong and a weak eruption column, under different meteorological conditions. In particular, the study involved nine 1D models based on different extensions of the Buoyant Plume Theory (Morton et al., 1956) to the volcanic context, and four 3D models describing the transient dynamics of volcanic plumes. Moreover, a series of sensitivity studies aimed to quantify the effects of the typical uncertainties on input parameters were also carried out. The Special Issue presenting the results of this collaborative twoyear long effort consists of 11 articles. The first article describes the setting of the inter-comparison study and summarizes the main outcomes, highlighting strengths and shortcomings of the state-of-the-art models used by the scientific community to describe eruptive plumes. The inter-comparison and sensitivity studies clearly revealed some robust features and some limitations of the existing models. In particular, one of the unexpected outcomes of the study is that weak and strong plumes, regardless of wind conditions, are governed by different physics related to air entrainment processes, not always well captured by current parameterizations, highlighting the need of further research. Furthermore, 3D model results evidenced the inappropriateness of the Buoyant Plume Theory in capturing the dynamics of strong plumes. The second article presents the results of a detailed inter-comparison study of 3D models and addresses important aspects that need to be considered in order to compare outputs of these models with those of simpler 1D models. The inter-comparison study highlights the different capabilities of 3D models and identifies key features of weak and strong plumes,
http://dx.doi.org/10.1016/j.jvolgeores.2016.04.017 0377-0273/© 2016 Elsevier B.V. All rights reserved.
including the roles of jet stability, air entrainment efficiency, and particle non-equilibrium, which deserve future field, laboratory, and numerical studies. The next six contributions (articles 3 to 8) present results of sensitivity and parametric studies aimed at quantifying the effects of typical uncertainties on model inputs and different processes and parameterizations, using different statistical approaches. The last three contributions (articles 9 to 11) discuss the outcomes of 3D numerical simulations, focussing on different aspects, such as the analysis of the conditions of breakdown of self-similarity in eruption columns, the effects of kinetic and thermal non-equilibrium processes in ash-laden plumes, and the role of kinematic decoupling and turbulent entrainment in both weak and strong eruptive columns. As Guest Editors, we would like to thank the authors involved in the Special Issue and all reviewers, who provided thorough, supportive, and constructive reviews. We acknowledge the collaborative spirit behind the work carried out for this inter-comparison study that makes this Special Issue a groundbreaking example of collective research, which has allowed fundamental advances for the volcanological community and beyond. Finally, we dedicate this Special Issue to our dear young colleague, Dr. Solène Pouget, who sadly passed away while working on this study. Her contributions to fundamental physical volcanology were motivated by a deep love of humanity. Reference Morton, B.R., Taylor, G.I., Turner, J.S., 1956. Turbulent gravitational convection from maintained and instantaneous source. Philos. Trans. R. Soc. Lond. A 234, 1–23.
Antonio Costa Guess Editor Istituto Nazionale di Geofisica e Vulcanologia, Bologna, Italy and Earthquake and Research Institute, The University of Tokyo, Japan Corresponding author. E-mail address: [email protected]. Yujiro Suzuki Guest Editor Earthquake Research Institute, The University of Tokyo, Japan Arnau Folch IAVCEI Commission on Tephra Hazard Modelling Barcelona Supercomputing Center, Barcelona, Spain Raffaello Cioni IAVCEI Commission on Tephra Hazard Modelling Department of Earth Sciences, University of Florence, Italy
Contents lists available at ScienceDirect
Journal of Volcanology and Geothermal Research journal homepage: www.elsevier.com/locate/jvolgeores
Preface
Numerical models of volcanic eruption plumes: inter-comparison and sensitivity The accurate description of the dynamics of convective plumes developed during explosive volcanic eruptions represents one of the most crucial and intriguing challenges in volcanology. Eruptive plume dynamics are significantly affected by complex interactions with the surrounding atmosphere, in the case of both strong eruption columns, rising vertically above the tropopause, and weak volcanic plumes, developing within the troposphere and often following bended trajectories. The understanding of eruptive plume dynamics is pivotal for estimating mass flow rates of volcanic sources, a crucial aspect for tephra dispersion models used to assess aviation safety and tephra fallout hazard. For these reasons, several eruption column models have been developed in the past decades, including the more recent sophisticated computational fluid dynamic models. This volume presents results of the eruption column model intercomparison study promoted by the International Association of Volcanology and Chemistry of Earth’s Interior (IAVCEI) Commission on Tephra Hazard Modelling. The study compared empirical parameterizations (0D), aimed to estimate mass flow rates from column heights, and simulations of onedimensional (1D) and three-dimensional (3D) numerical models in a set of inter-comparison exercises to evaluate model capabilities and highlight aspects requiring improvement and future research. The exercises were designed as tests in which a set of common input parameters was given for two reference eruptions, representing a strong and a weak eruption column, under different meteorological conditions. In particular, the study involved nine 1D models based on different extensions of the Buoyant Plume Theory (Morton et al., 1956) to the volcanic context, and four 3D models describing the transient dynamics of volcanic plumes. Moreover, a series of sensitivity studies aimed to quantify the effects of the typical uncertainties on input parameters were also carried out. The Special Issue presenting the results of this collaborative twoyear long effort consists of 11 articles. The first article describes the setting of the inter-comparison study and summarizes the main outcomes, highlighting strengths and shortcomings of the state-of-the-art models used by the scientific community to describe eruptive plumes. The inter-comparison and sensitivity studies clearly revealed some robust features and some limitations of the existing models. In particular, one of the unexpected outcomes of the study is that weak and strong plumes, regardless of wind conditions, are governed by different physics related to air entrainment processes, not always well captured by current parameterizations, highlighting the need of further research. Furthermore, 3D model results evidenced the inappropriateness of the Buoyant Plume Theory in capturing the dynamics of strong plumes. The second article presents the results of a detailed inter-comparison study of 3D models and addresses important aspects that need to be considered in order to compare outputs of these models with those of simpler 1D models. The inter-comparison study highlights the different capabilities of 3D models and identifies key features of weak and strong plumes,
http://dx.doi.org/10.1016/j.jvolgeores.2016.04.017 0377-0273/© 2016 Elsevier B.V. All rights reserved.
including the roles of jet stability, air entrainment efficiency, and particle non-equilibrium, which deserve future field, laboratory, and numerical studies. The next six contributions (articles 3 to 8) present results of sensitivity and parametric studies aimed at quantifying the effects of typical uncertainties on model inputs and different processes and parameterizations, using different statistical approaches. The last three contributions (articles 9 to 11) discuss the outcomes of 3D numerical simulations, focussing on different aspects, such as the analysis of the conditions of breakdown of self-similarity in eruption columns, the effects of kinetic and thermal non-equilibrium processes in ash-laden plumes, and the role of kinematic decoupling and turbulent entrainment in both weak and strong eruptive columns. As Guest Editors, we would like to thank the authors involved in the Special Issue and all reviewers, who provided thorough, supportive, and constructive reviews. We acknowledge the collaborative spirit behind the work carried out for this inter-comparison study that makes this Special Issue a groundbreaking example of collective research, which has allowed fundamental advances for the volcanological community and beyond. Finally, we dedicate this Special Issue to our dear young colleague, Dr. Solène Pouget, who sadly passed away while working on this study. Her contributions to fundamental physical volcanology were motivated by a deep love of humanity. Reference Morton, B.R., Taylor, G.I., Turner, J.S., 1956. Turbulent gravitational convection from maintained and instantaneous source. Philos. Trans. R. Soc. Lond. A 234, 1–23.
Antonio Costa Guess Editor Istituto Nazionale di Geofisica e Vulcanologia, Bologna, Italy and Earthquake and Research Institute, The University of Tokyo, Japan Corresponding author. E-mail address: [email protected]. Yujiro Suzuki Guest Editor Earthquake Research Institute, The University of Tokyo, Japan Arnau Folch IAVCEI Commission on Tephra Hazard Modelling Barcelona Supercomputing Center, Barcelona, Spain Raffaello Cioni IAVCEI Commission on Tephra Hazard Modelling Department of Earth Sciences, University of Florence, Italy