Wind-driven dispersal of volcanic ash plumes and its control on the thermal structure of the plume-top

Woods, Andrew W.; Holasek, Rick E.; Self, Stephen

doi:10.1007/s004450050094

Cited by 10 publications

(16 citation statements)

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“…However, WM1 does not reproduce the common observation of a linear increase of wind velocity in the troposphere and a sublinear decrease in the stratosphere [e.g., Carey and Sigurdsson , 1982; Holasek and Self , 1995; Woods et al , 1995; Bonadonna et al , 2002a]. WM2 consists of a linear decrease of wind velocity up to 20 km a.s.l.…”

Section: New Modelingmentioning

confidence: 84%

“…Previous models and observations [e.g., Carey and Sigurdsson , 1982; Brazier et al , 1983; Woods et al , 1995; Carey and Sparks , 1986; Schumacher , 1994; Veitch and Woods , 2001; Rose et al , 2001; Bonadonna et al , 2002a] have already shown that wind advection and particle aggregation significantly affect tephra fallout deposition. However, our broad parameter study provides a comparison of relative effects of several parameters that characterize particle deposition.…”

Section: Discussionmentioning

confidence: 99%

“…The understanding of sedimentation from volcanic plumes has significantly progressed in the last two decades and models have been developed and show good agreement with field data [ Suzuki , 1983; Carey and Sparks , 1986; Armienti et al , 1988; Bursik et al , 1992a, 1992b; Sparks et al , 1992; Woods et al , 1995; Bonadonna et al , 1998; Koyaguchi and Ohno , 2001]. The study of tephra fallout deposition provides important insights into eruptive‐column dynamics.…”

Section: Introduction and Previous Workmentioning

confidence: 99%

“…The numerical models developed during the last two decades to describe particle sedimentation from volcanic plumes have followed different approaches, mainly focusing on: (1) turbulent dispersion of particles during fallout [e.g., Suzuki , 1983; Armienti et al , 1988; Glaze and Self , 1991]; (2) particle deposition in a wind field [e.g., Carey and Sigurdsson , 1982; Carey and Sparks , 1986; Woods et al , 1995; Bonadonna et al , 2002a]; (3) large eddy sedimentation from plume margins combined with gravity‐driven intrusion of the volcanic current at the neutral buoyancy level [e.g., Bursik et al , 1992a, 1992b; Sparks et al , 1992; Ernst et al , 1996; Bonadonna et al , 1998; Koyaguchi and Ohno , 2001]. The first two approaches give good agreement with observed tephra‐fallout accumulation (e.g., Mount St. Helens, 1980), but fail to give an adequate description of the current spreading in the atmosphere.…”

Section: Introduction and Previous Workmentioning

confidence: 99%

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Sedimentation from strong volcanic plumes

2003

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[1] We develop descriptions of the key processes influencing tephra dispersal from strong volcanic plumes. These are characterized by the development of a subvertical eruption column in the atmosphere that forms a spreading current at a level of neutral buoyancy. We describe the propagation of the spreading current due to both gravity and wind advection using scaling arguments and a simplified geometry to model particle sedimentation in a windy as well as a wind-free environment. New parameterizations are used to describe the wind field below the spreading current, particle aggregation, and particle density variations. We conducted a broad study to investigate the effects of these processes and made comparisons with field observations. The greatest variations resulted from wind advection below the spreading current, which shifts the plumecorner mass accumulation and the position of transitions in fallout regimes downwind. Particle aggregation strongly depends on the initial grain-size distribution and significantly affects deposit thinning, depending on the aggregate size and density, and on the relative amount of aggregating particles. Small aggregates can reproduce secondary maxima of mass accumulation when sedimenting in a wind field. Variation of particle density also affects the resulting thinning trend. The model provides acceptable reproduction of observations of the propagation of the spreading current (tested with the Plinian phase of the 18 May 1980 eruption of Mount St. Helens) and of observed thinning of tephra fallout deposits (tested with deposits from Mount St.

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Section: New Modelingmentioning

confidence: 84%

Section: Discussionmentioning

confidence: 99%

Section: Introduction and Previous Workmentioning

confidence: 99%

Section: Introduction and Previous Workmentioning

confidence: 99%

See 2 more Smart Citations

Sedimentation from strong volcanic plumes

2003

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“…The second column, formed just 20 min before the image was acquired, was reported to have reached a slightly lower altitude (Smithsonian Institution 1993a) but possessed a colder cloud top temperature of -80 7C. We presume that this discrepancy is due to the effects of undercool-ing on the second plume (Woods et al 1995). The earlier plume is likely to have equilibrated to the ambient air temperature and may also have had time to retreat to its neutral buoyancy height by the time this image was recorded (Woods and Kienle 1994).…”

Section: Resultsmentioning

confidence: 99%

Thermal monitoring of Lascar Volcano, Chile, using infrared data from the along-track scanning radiometer: a 1992-1995 time series

Wooster

Rothery

1997

Bulletin of Volcanology

107

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Particle sedimentation and diffusive convection in volcanic ash‐clouds

Carazzo

Jellinek

2013

JGR Solid Earth

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[1] Understanding the longevity of volcanic ash-clouds generated by powerful explosive eruptions is a long standing problem for assessing volcanic hazards and the nature and time scale of volcanic forcings on climate change. It is well known that the lateral spreading and longevity of these clouds is influenced by stratospheric winds, particle settling and turbulent diffusion. Observations of the recent 2010 Eyjafjallajökull and 2011 Grimsvötn umbrella clouds, as well as the structure of atmospheric aerosol clouds from the 1991 Mt Pinatubo event, suggest that an additional key process governing the cloud dynamics is the production of internal layering. Here, we use analog experiments on turbulent particle-laden umbrella clouds to show that this layering occurs where natural convection driven by particle sedimentation and the differential diffusion of primarily heat and fine particles give rise to a large scale instability. Where umbrella clouds are particularly enriched in fine ash, this "particle diffusive convection" strongly influences the cloud longevity. More generally, cloud residence time will depend on fluxes due to both individual settling and diffusive convection. We develop a new sedimentation model that includes both sedimentation processes, and which is found to capture real-time measurements of the rate of change of particle concentration in the 1982 El Chichon, 1991 Mt Pinatubo and 1992 Mt Spurr ash-clouds. A key result is that these combined sedimentation processes enhance the fallout of fine particles relative to expectations from individual settling suggesting that particle aggregation is not the only mechanism required to explain volcanic umbrella longevity.

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Wind-driven dispersal of volcanic ash plumes and its control on the thermal structure of the plume-top

Cited by 10 publications

References 0 publications

Sedimentation from strong volcanic plumes

Sedimentation from strong volcanic plumes

Thermal monitoring of Lascar Volcano, Chile, using infrared data from the along-track scanning radiometer: a 1992-1995 time series

Particle sedimentation and diffusive convection in volcanic ash‐clouds

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