Simulating the Transport and Dispersal of Volcanic Ash Clouds With Initial Conditions Created by a 3D Plume Model

Abstract

Volcanic ash transport and dispersion (VATD) models simulate atmospheric transport of ash from a volcanic source represented by parameterized concentration of ash with height. Most VATD models represent the volcanic plume source as a simple line with a parameterized ash emission rate as a function of height, constrained only by a total mass eruption rate (MER) for a given total rise height. However, the actual vertical ash distribution in volcanic plumes varies from case to case, having complex dependencies on eruption source parameters, such as grain size, speed at the vent, vent size, buoyancy flux, and atmospheric conditions. We present here for the first time the use of a three-dimensional (3D) plume model based on conservation laws to represent the ash cloud source without any prior assumption or simplification regarding plume geometry. By eliminating assumed behavior associated with a parameterized plume geometry, the predictive skill of VATD simulations is improved. We use our recently developed volcanic plume model based on a 3D smoothed-particle hydrodynamic Lagrangian method and couple the output to a standard Lagrangian VATD model. We apply the coupled model to the Pinatubo eruption in 1991 to illustrate the effectiveness of the approach. Our investigation reveals that initial particle distribution in the vertical direction, including within the umbrella cloud, has more impact on the long-range transport of ash clouds than does the horizontal distribution. Comparison with satellite data indicates that the 3D model-based distribution of ash particles through the depth of the volcanic umbrella cloud, which is much lower than the observed maximum plume height, produces improved long-range VATD simulations. We thus show that initial conditions have a significant impact on VATD, and it is possible to obtain a better estimate of initial conditions for VATD simulations with deterministic, 3D forward modeling of the volcanic plume. Such modeling may therefore provide a path to better forecasts lessening the need for user intervention, or attempts to observe details of an eruption that are beyond the resolution of any potential satellite or ground-based technique, or a posteriori creating a history of ash emission height via inversion.

Particle Sedimentation in Numerical Modelling: A Case Study from the Puyehue-Cordón Caulle 2011 Eruption with the PLUME-MoM/HYSPLIT Models

“…This is Laboratory of Excellence ClerVolc contribution number 538. This research was also partially financed by the French government IDEX-ISITE initiative 16-IDEX-0001 (CAP [20][21][22][23][24][25]. Acknowledgments: Nourddine Azzaoui is acknowledged for assistance in running the simulations through the cluster of Laboratoire de mathématiques Blaise Pascal, Universitè Clermont Auvergne.…”

“…The same models are also widely used in the production of tephra fallout probabilistic hazard maps. Regarding the source conditions (i.e., the spatio-temporal release of particles/mass from the eruption column to the volcanic cloud), they could range from simple geometric distributions to 1D integral models [2] and 3D models [24], while complex multicomponent and multiphase flow models are still too expensive from a computational point of view [20]. Meteorological data (typically wind field, air density/temperature, and, in some cases, humidity, pressure, boundary layer altitude, turbulence, and precipitation) are necessary to simulate the transport of tephra cloud.…”

Retrieval of refractive indices of ten volcanic ash samples in the infrared, visible and ultraviolet spectral region

“…By absorbing terrestrial radiation and scattering the solar radiation, volcanic ashes also have a significant influence on the Earth's radiation balance (Laakso et al, 2016;Zhu et al, 2020) The properties of ash clouds such as plume height, concentration and particle size distribution are studied by ground-based and satellite remote sensing techniques. The prediction of ash cloud trajectories has required the development of transport and dispersion models of in-situ volcanic ash that can calculate the trajectory of an ash cloud at the scale of a continent or the hemisphere (Cao, Bursik, Yang, & Patra, 2021;Harvey et al, 2018;Heffter & Stunder, 1993;Peterson et al, 2015). Volcanological parameters such as plume height, eruptive rate, duration of eruption, ash distribution with altitude and particle size distribution are essential in real time during an event to constrain these models, often with limited observations (de Michele et al, 2019;Stohl et al, 2011).…”