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| Titel |
On the relationship between eruption intensity and volcanic plume height: insights from three-dimensional numerical simulations |
| VerfasserIn |
Yujiro Suzuki, Antonio Costa, Takehiro Koyaguchi |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250127999
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| Publikation (Nr.) |
 EGU/EGU2016-7939.pdf |
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| Zusammenfassung |
| Height of plumes generated during explosive volcanic eruptions are commonly used to
estimate the associated eruption intensity (i.e., mass eruption rate; MER). In order to quantify
the relationship between plume height and MER, we performed a parametric study
using a three-dimensional (3D) numerical model of volcanic plumes for different
MERs. We estimated the maximum height of plume, the neutral buoyancy level
where the cloud density is equal to the atmospheric density, and the height with the
maximum radial injection of the erupted material from the simulation results. We also
analyzed the simulation results by comparing with the plume heights predicted
by a one-dimensional model based on the Buoyant Plume Theory (Morton et al.,
1956).
The simulation results indicate that the flow pattern in the lower region of the plume
systematically changes with MER. For MERs < 4×107 kg s−1, the flow in the lower region
has a jet-like structure (the jet-like regime). For MERs > 108 kg s−1, the flow shows a
fountain-like structure (the fountain-like regime). The flow pattern of plumes with 4×107 kg
s−1 < MERs < 108 kg s−1 shows transitional features between the two flow regimes. Within
each of the two flow regimes, the plume height increases as the MER increases, whereas
plume heights remain almost constant or even decrease as MER increases in the transitional
regime; as a results, the jet-like and fountain-like regimes show distinct relationships of
plume height and MER.
Our analyses of the simulation results indicate that the different relationships of plume height
and MER between the two regimes reflect the change in the efficiency of air entrainment; the
entrainment efficiency in the jet-like regime is substantially lower than that in the
fountain-like regime. It is suggested that, the different flow regimes depending on MER
should be taken into account for a correct estimation of eruption intensity from the observed
plume heights. |
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