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Barcelona Supercomputing Center, Barcelona, Spain
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- PublicationRestrictedAn automatic procedure to forecast tephra fallout(2008)
; ; ; ; ;Folch, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Cavazzoni, C.; Consorzio Interuniversitario CINECA, Bologna, Italy ;Costa, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Macedonio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; ; Tephra fallout constitutes a serious threat to communities around active volcanoes. Reliable short-term 13 forecasts represent a valuable aid for scientists and civil authorities to mitigate the effects of fallout on the 14 surrounding areas during an episode of crisis. We present a platform-independent automatic procedure with Q1 15 the aim to daily forecast transport and deposition of volcanic particles. The procedure builds on a series of 16 programs and interfaces that automate the data flow and the execution and subsequent postprocess of fallout 17 models. Firstly, the procedure downloads regional meteorological forecasts for the area and time interval of 18 interest, filters and converts data from its native format, and runs the CALMET diagnostic model to obtain the 19 wind field and other micro-meteorological variables on a finer local-scale 3-D grid defined by the user. 20 Secondly, it assesses the distribution of mass along the eruptive column, commonly by means of the radial 21 averaged buoyant plume equations depending on the prognostic wind field and on the conditions at the vent 22 (granulometry, mass flow rate, etc). All these data serve as input for the fallout models. The initial version of 23 the procedure includes only two Eulerian models, HAZMAP and FALL3D, the latter available as serial and 24 parallel implementations. However, the procedure is designed to incorporate easily other models in a near 25 future with minor modifications on the model source code. The last step is to postprocess the outcomes of 26 models to obtain maps written in standard file formats. These maps contain plots of relevant quantities such 27 as predicted ground load, expected deposit thickness and, for the case of or 3-D models, concentration on air 28 or flight safety concentration thresholds243 33 - PublicationOpen AccessVIGIL: A Python tool for automatized probabilistic VolcanIc Gas dIspersion modeLling(2022)
; ; ; ; ; ; ; ; ; ;; ; ; ;; ; ; Probabilistic volcanic hazard assessment is a standard methodology based on running a deterministic hazard quantification tool multiple times to explore the full range of uncertainty in the input parameters and boundary conditions, in order to probabilistically quantify the variability of outputs accounting for such uncertainties. Nowadays, different volcanic hazards are quantified by means of this approach. Among these, volcanic gas emission is particularly relevant given the threat posed to human health if concentrations and exposure times exceed certain thresholds. There are different types of gas emissions but two main scenarios can be recognized: hot buoyant gas emissions from fumaroles and the ground and dense gas emissions feeding density currents that can occur, e.g., in limnic eruptions. Simulation tools are available to model the evolution of critical gas concentrations over an area of interest. Moreover, in order to perform probabilistic hazard assessments of volcanic gases, simulations should account for the natural variability associated to aspects such as seasonal and daily wind conditions, localized or diffuse source locations, and gas fluxes. Here we present VIGIL (automatized probabilistic VolcanIc Gas dIspersion modeLling), a new Python tool designed for managing the entire simulation workflow involved in single and probabilistic applications of gas dispersion modelling. VIGIL is able to manage the whole process from meteorological data processing, needed to run gas dispersion in both the dilute and dense gas flow scenarios, to the post processing of models’ outputs. Two application examples are presented to show some of the modelling capabilities offered by VIGIL.466 15 - PublicationRestrictedA model for wet aggregation of ash particles in volcanic plumes and clouds: 1. Theoretical formulation(2010)
; ; ; ;Costa, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Folch, A.; Barcelona Supercomputing Center, Barcelona, Spain ;Macedonio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; We develop a model to describe ash aggregates in a volcanic plume. The model is based on a solution of the classical Smoluchowski equation, obtained by introducing a similarity variable and a fractal relationship for the number of primary particles in an aggregate. The considered collision frequency function accounts for different mechanisms of aggregation, such as Brownian motion, ambient fluid shear, and differential sedimentation. Although model formulation is general, here only sticking efficiency related to the presence of water is considered. However, the different binding effect of liquid water and ice is discerned. The proposed approach represents a first compromise between the full description of the aggregation process and the need to decrease the computational time necessary for solving the full Smoluchowski equation. We also perform a parametric study on the main model parameters and estimate coagulation kernels and timescales of the aggregation process under simplified conditions of interest in volcanology. Further analyses and applications to real eruptions are presented in the companion paper by Folch et al.289 28 - PublicationOpen Access3D volcanic aerosol dispersal: a comparison between misr data and numerical simulations(2010-05-21)
; ; ; ; ;Scollo, S.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Folch, A.; Barcelona Supercomputing Center, Barcelona, Spain. ;Coltelli, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Catania, Catania, Italia ;Realmuto, V. J.; Jet Propulsion Laboratory, California Institute of Technology.; ; ; The three dimensional reconstruction of volcanic plumes is a central goal to enhance our understanding on dispersal processes. In this paper, we use data from the Multi-angle Imaging SpectroRadiometer (MISR) on board NASA’s Terra spacecraft combined with a stereo matching retrieval procedure. We show the potential of MISR in capturing important features of volcanic plumes like column height, optical depth, type and shape of the finest particles of two highly explosive eruptions occurring on Mt. Etna in 2001 and 2002. This work tests how tephra dispersal models reconstruct the 3D shape of volcanic clouds. We compare MISR data with FALL3D, an Eulerian model for the transport and deposition of volcanic ash and aerosols coupled with the Weather Research and Forecasting (WRF) mesoscale meteorological model. Agreement between simulations and MISR data is good regarding both events, although it could be improved by increasing the accuracy of the meteorological data, a better constraint on volcanological input parameters like the height of the eruptive column and improving our understanding of processes such as aggregation phenomena and volcanic cloud microphysics.341 632 - PublicationOpen AccessAnak Krakatau triggers volcanic freezer in the upper troposphere(2020-02-27)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; Volcanic activity occurring in tropical moist atmospheres can promote deep convection and trigger volcanic thunderstorms. These phenomena, however, are rarely observed to last continuously for more than a day and so insights into the dynamics, microphysics and electrification processes are limited. Here we present a multidisciplinary study on an extreme case, where volcanically-triggered deep convection lasted for six days. We show that this unprecedented event was caused and sustained by phreatomagmatic activity at Anak Krakatau volcano, Indonesia during 22-28 December 2018. Our modelling suggests an ice mass flow rate of ~5 × 106 kg/s for the initial explosive eruption associated with a flank collapse. Following the flank collapse, a deep convective cloud column formed over the volcano and acted as a 'volcanic freezer' containing ~3 × 109 kg of ice on average with maxima reaching ~1010 kg. Our satellite analyses reveal that the convective anvil cloud, reaching 16-18 km above sea level, was ice-rich and ash-poor. Cloud-top temperatures hovered around -80 °C and ice particles produced in the anvil were notably small (effective radii ~20 µm). Our analyses indicate that vigorous updrafts (>50 m/s) and prodigious ice production explain the impressive number of lightning flashes (~100,000) recorded near the volcano from 22 to 28 December 2018. Our results, together with the unique dataset we have compiled, show that lightning flash rates were strongly correlated (R = 0.77) with satellite-derived plume heights for this event.320 29 - PublicationOpen AccessLong-term hazard assessment of explosive eruptions at Jan Mayen (Norway) and implications for air traffic in the North Atlantic(2022)
; ; ; ; ; ; ; ; ;; ;; ; ;; Volcanic eruptions are among the most jeopardizing natural events due to their potential impacts on life, assets, and the environment. In particular, atmospheric dispersal of volcanic tephra and aerosols during explosive eruptions poses a serious threat to life and has significant consequences for infrastructures and global aviation safety. The volcanic island of Jan Mayen, located in the North Atlantic under trans-continental air traffic routes, is considered the northernmost active volcanic area in the world with at least five eruptive periods recorded during the last 200 years. However, quantitative hazard assessments on the possible consequences for the air traffic of a future ash-forming eruption at Jan Mayen are nonexistent. This study presents the first comprehensive long-term volcanic hazard assessment for the volcanic island of Jan Mayen in terms of ash dispersal and concentration at different flight levels. In order to delve into the characterization and modeling of that potential impact, a probabilistic approach based on merging a large number of numerical simulations is adopted, varying the volcano's eruption source parameters (ESPs) and meteorological scenario. Each ESP value is randomly sampled following a continuous probability density function (PDF) based on the Jan Mayen geological record. Over 20 years of meteorological data is considered in order to explore the natural variability associated with weather conditions and is used to run thousands of simulations of the ash dispersal model FALL3D on a 2 km resolution grid. The simulated scenarios are combined to produce probability maps of airborne ash concentration, arrival time, and persistence of unfavorable conditions at flight levels 50 and 250 (FL050 and FL250). The resulting maps can serve as an aid during the development of civil protection strategies, to decision-makers and aviation stakeholders, in assessing and preventing the potential impact of a future ash-rich eruption at Jan Mayen.406 12 - PublicationOpen AccessTemporal evolution of flow conditions in sustained magmatic explosive eruptions(2005)
; ; ; ; ;Macedonio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Neri, A.; Istituto Nazionale di Geofisica e Vulcanologia, Centro per la Modellistica Fisica e Pericolosita` dei Processi Vulcanici ;Marti, J.; Istitut de Ciences de le Terra Jaume Almera, CSIC, Barcelona, Spain ;Folch, A.; Istitut de Ciences de le Terra Jaume Almera, CSIC, Barcelona, Spain; ; ; The temporal evolution of fundamental flow conditions in the magma chamber plus conduit system–such as pressure, velocity, mass flow-rate, erupted mass, etc.–during sustained magmatic explosive eruptions was investigated. To this aim, simplified one-dimensional and isothermal models of magma chamber emptying and conduit flow were developed and coupled together. The chamber model assumed an homogeneous composition of magma and a vertical profile of water content. The chamber could have a cylindrical, elliptical or spherical rigid geometry. Inside the chamber, magma was assumed to be in hydrostatic equilibrium both before and during the eruption. Since the time-scale of pressure variations at the conduit inlet–of the order of hours–is much longer than the travel time of magma in the conduit–of the order of a few minutes–the flow in the conduit was assumed as at steady-state. The one dimensional mass and momentum balance equations were solved along a circular conduit with constant diameter assuming choked-flow conditions at the exit. Bubble nucleation was considered when the homogeneous flow pressure dropped below the nucleation pressure given the total water content and the solubility law. Above the nucleation level, bubbles and liquid magma were considered in mechanical equilibrium. The same equilibrium assumption was made above the fragmentation level between gas and pyroclasts. Due to the hydrostatic hypothesis, the integration of the density distribution in the chamber allowed to obtain the total mass in the chamber as a function of pressure at the chamber top and, through the conduit model, as a function of time. Simulation results pertaining to rhyolitic and basaltic magmas defined at the Volcanic Eruption Mechanism Modeling Workshops (Durham, NH, 2002; Nice, France, 2003) are presented. Important flow variables, such as pressure, density, velocity, shear stress in the chamber and conduit, are discussed as a function of time and magma chamber and conduit properties. Results indicate that vent variables react in different ways to the pressure variation of the chamber. Pressure, density and mass flow-rate show relative variations of the same order of magnitude as the conduit inlet pressure, whereas velocity is more constant in time. Sill-like chambers produce also significantly longer and more voluminous eruptions than dike-like chambers. Water content stratification in the chamber and the increase of chamber depth significantly reduce the eruption duration and volume. Maximum erupted mass fractions of about 0.2 are computed for small water-saturated and shallow chambers.289 92 - PublicationOpen AccessFALL3D: A Computational Model for Trans-port and Deposition of Volcanic Ash(2009)
; ; ; ;Folch, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Costa, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Macedonio, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia; ; FALL3D is a 3-D time-dependent Eulerian model for the transport and deposition of 8 volcanic ash. The model solves the advection-diffusion-sedimentation (ADS) equa- 9 tion on a structured terrain-following grid using a second-order Finite Differences 10 (FD) explicit scheme. Different parameterizations for the eddy diffusivity tensor 11 and for the particle terminal settling velocities can be used. The code, written 12 in FORTRAN 90, is available in both serial and parallel versions for Windows and 13 Unix/Linux/Mac X Operating Systems (OS). A series of pre- and post-process util- 14 ity programs and OS-dependent scripts to launch them are also included in the 15 FALL3D distribution package. Although the model has been designed to forecast 16 volcanic ash concentration in the atmosphere and ash loading at ground, it can also 17 be used to model the transport of any kind of airborne solid particles. The model 18 inputs are meteorological data, topography, grain-size distribution, shape and den- 19 sity of particles, and mass rate of particle injected into the atmosphere. Optionally, 20 FALL3D can be coupled with the output of the meteorological processor CALMET, a 21 diagnostic model which generates 3-D time-dependent zero-divergence wind fields 22 from mesoscale forecasts incorporating local terrain effects. The FALL3D model can 23 be a tool for short-term ash deposition forecasting and for volcanic fallout hazard 24 assessment. As an example, an application to the 22 July 1998 Etna eruption is also 25 presented.215 100 - PublicationRestrictedTWODEE-2: A shallow layer model for dense gas dispersion on complex topography(2009)
; ; ; ;Folch, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Costa, A.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione OV, Napoli, Italia ;Hankin, R. K. S.; National Oceanography Centre, Southampton SO14 3ZH, UK; ; TWODEE-2 is a FORTRAN 90 code based on previous code (TWODEE). It is designed to solve the shallow water equations for fluid depth, depth-averaged horizontal velocities and depth-averaged fluid density. The shallow layer approach used by TWODEE-2 is a compromise between the complexity of CFD models and the simpler integral models. It can be used for forecasting gas dispersion near the ground and/or for hazard assessment over complex terrains. The inputs to the model are topography, terrain roughness, wind measurements from meteorological stations and gas flow rate from the ground sources. Optionally the model can be coupled with the output of a meteorological processor which generates a zero-divergence wind field incorporating terrain effects. Model outputs are gas concentration, depth-averaged velocity, averaged cloud thickness and dose. The model can be a useful tool for gas hazard assessment by evaluating where and when lethal concentrations for humans and animals can be reached.199 32