Comment on “Particle aggregation in volcanic eruption columns” by Graham Veitch and Andrew W. Woods

Textor, C.; Ernst, Gérald

doi:10.1029/2002jb002291

Cited by 10 publications

(20 citation statements)

References 48 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…As collision and sticking efficiency is decoupled and the relative speed of particles is enhanced by turbulence, the collision rate is high in the eruption column. Veitch and Woods (2001) According to Textor and Ernst (2004) the plume model considered by Veitch and Woods (2001) provides an overly-simplistic description of the aggregation process as it does not consider microphysical processes crucial for the aggregation of ash in the presence of water. Textor et al (2006a, b) presented a more sophisticated model of wet aggregation using ATHAM (Active Tracer High-resolution Atmospheric Model, Graf et al 1999;Herzog et al 2003;Oberhuber et al 1998) which accounts for the formation of liquid and solid hydrometeors and the effect on the plume dynamics from the latent heat generated by water phases changes.…”

Section: Empirical and Numerical Studies On Aggregationmentioning

confidence: 99%

A review of volcanic ash aggregation

Brown

Bonadonna

Durant

2012

Physics and Chemistry of the Earth, Parts A/B/C

223

298

View full text Add to dashboard Cite

. (2012) 'A review of volcanic ash aggregation.', Physics and chemistry of the earth, parts A/B/C., 45-46 . pp. 65-78. Further information on publisher's website:http://dx.doi.org/10.1016/j.pce. 2011.11.001 Publisher's copyright statement:Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-pro t purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. AbstractMost volcanic ash particles with diameters < 63 µm settle from eruption clouds as particle aggregates that cumulatively have larger sizes, lower densities, and higher terminal fall velocities than individual constituent particles. Particle aggregation reduces the atmospheric residence time of fine ash, which results in a proportional increase in fine ash fallout within 10s km to 100s km from the volcano and a reduction in airborne fine ash mass concentrations 1000s km from the volcano. Aggregate characteristics vary with distance from the volcano: proximal aggregates are typically larger (up to cm size) with concentric structures, while distal aggregates are typically smaller (sub-millimetre size). Particles comprising ash aggregates are bound through hydro-bonds (liquid and ice water) and electrostatic forces, and the rate of particle aggregation correlates with cloud liquid water availability. Eruption source parameters (including initial particle size distribution, erupted mass, eruption column height, cloud water content and temperature) and the eruption plume temperature lapse rate, coupled with the environmental parameters, determines the type and spatiotemporal distribution of aggregates. Field studies, lab experiments and modelling investigations have already provided important insights on the process of particle aggregation. However, new integrated observations that combine remote sensing studies of 2 ash clouds with field measurement and sampling, and lab experiments are required to fill current gaps in knowledge surrounding the theory of ash aggregate formation. Abstract word count: 222

show abstract

Section: Empirical and Numerical Studies On Aggregationmentioning

confidence: 99%

A review of volcanic ash aggregation

Brown

Bonadonna

Durant

2012

Physics and Chemistry of the Earth, Parts A/B/C

223

298

View full text Add to dashboard Cite

show abstract

“…The settling velocity of nonspherical particles is also allowed to vary as a function of height above the ground due to major variations in air density and viscosity with altitude [ Wilson , 1972]. In contrast, particle aggregation processes are not described by the present model, although they can play a major role in some conditions [ Textor and Ernst , 2004; Veitch and Woods , 2004].…”

Section: The Vol‐calpuff Codementioning

confidence: 99%

The VOL‐CALPUFF model for atmospheric ash dispersal: 1. Approach and physical formulation

2008

View full text Add to dashboard Cite

[1] We present a new modeling tool, named VOL-CALPUFF, that is able to simulate the transient and three-dimensional transport and deposition of volcanic ash under the action of realistic meteorological and volcanological conditions throughout eruption duration. The new model derives from the CALPUFF System, a software program widely used in environmental applications of pollutant dispersion, that describes the dispersal process in both the proximal and distal regions and also in the presence of complex orography. The main novel feature of the model is its capability of coupling a Eulerian description of plume rise with a Lagrangian representation of ash dispersal described as a series of diffusing packets of particles or puffs. The model is also able to describe the multiparticle nature of the mixture as well as the tilting effects of the plume due to wind action. The dispersal dynamics and ash deposition are described by using refined orography-corrected meteorological data with a spatial resolution up to 1 km or less and a temporal step of 1 h. The modeling approach also keeps the execution time to a few minutes on common PCs, thus making VOL-CALPUFF a possible tool for the production of ash dispersal forecasts for hazard assessment. Besides the model formulation, this paper presents the type of outcomes produced by VOL-CALPUFF, shows the effect of main model parameters on results, and also anticipates the fundamental control of atmospheric conditions on the ash dispersal processes. In the companion paper, Barsotti and Neri present a first thorough application of VOL-CALPUFF to the simulation of a weak plume at Mount Etna (Italy) with the specific aim of comparing model predictions with independent observations.

show abstract

“…Our approach of isolating and exploring particular processes, by using a much simplified model, can help to identify some of the complex physical interactions and also provides a framework in which more realistic, but necessarily more complex, models may be understood. This approach has been a feature of much of the recent progress in volcanology [e.g., Sparks et al, 1997].[3] Much of the comment by Textor and Ernst involves detailed criticism of the simplifying assumptions, yet although they state that the simplifications lead to erroneous results (e.g., the neglect of the freezing process), they do not present any estimates of the magnitude of the errors. The first comment pertains to the use of a steady state eruption column model and neglect of electrostatic charges.[4] As stated at the start of VW, the purpose of is to explore the possible role of atmospheric water in producing aggregates, essentially through condensation of this water as it rises in the plume; evidence of moisture contributing to the aggregation process in volcanic plumes has been furnished by, for example, Schumacher and Schminke [1995] and numerous references therein; also, earlier calculations of Woods [1993] indicated that for modest eruption rates the mass flux of water vapor which may be entrained into an eruption column from the lower few kilometers of the atmosphere may be comparable to the mass flux of solid material in the eruption column.…”

mentioning

confidence: 99%

“…VW do not argue or even imply that electrostatic effects are negligible; rather, they state at the start of the work that it is a theoretical study which attempts to explore wet aggregation as a process in its own right, as one building block toward a more comprehensive model; it would clearly be interesting to develop a model of electrostatically induced aggregation and then combine it with aspects of the VW model.[5] VW are concerned with Plinian eruptions and not phreatomagmatic eruptions. As shown by Woods [1993] and described by Sparks et al [1997], the entrainment of atmospheric water vapor can, in smaller eruptions, lead to eruption columns with a much larger water mass flux than is present in the mixture erupting from the volcanic vent; indeed, the water mass flux may be comparable to or even exceed the solid mass flux. Textor and Ernst describe such columns as dry Plinian eruptions, but this does not always mean that there is a shortage of water in the eruption column.…”

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation