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

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doi: 10.1007/s004450050094
Authors:Woods, A. W.; Holasek, R. E.; Self, S.
Author Affiliations:Primary:
University of Cambridge, Cambridge, United Kingdom
Volume Title:Bulletin of Volcanology
Source:for the [Bulletin of Volcanology, 57(5), p.283-292. Publisher: Springer International] International Association of Volcanology and Chemistry of the Earth's Interior (IAVCEI), Heidelberg, International. ISSN: 0258-8900
Publication Date:1995
Note:In English. 19 refs.; sects., 1 table, geol. sketch maps
Summary:The dispersal of an ash plume as it propagates downwind with the ash settling under gravity is examined. It is shown that wind shear, the initial plume height, and the plume grain size distribution, play an important role in the dispersal of the ash, particularly in determining the evolution of the upper surface and the leading edge of the ash cloud. Once the ash has thermally equilibrated with the atmosphere, the T of the plume's upper surface is directly related to its altitude. As a result the model can be used to interpret satellite images of the T of the upper surface of ash plumes. These calculations are compared with new analyses of satellite data from the 18 May 1980 eruptions of Mt St Helens. In accord with the data, the model is able to predict the rate at which the Mt St Helens ash plume propagated downwind through a combination of wind shear and gravitational settling of different size particles. The model also explains the observed thermal structure of the upper surface of the ash plume, in which the T initially decreases, but then increases with downwind distance as the ash falls through the tropopause. [R.E.S.]
Subjects:Case studies; Current directions; Eruptions; Grain size; Remote sensing; Satellite methods; Temperature; Velocity; Volcanic ash; Volcanoes; Wind transport; Winds; Cascade Range; Mount Saint Helens; Skamania County Washington; United States; Washington
Coordinates:N461200 N461200 W1221100 W1221100
Abstract Numbers:96M/3681
Record ID:1999010636
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom, Reference includes data from Geoline, Bundesanstalt fur Geowissenschaften und Rohstoffe
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