Reconstruction of eruption column model based on the 3D numerical simulation of volcanic plume for 2011 Shinmoe-dake eruption

Abstract:

The result of volcanic ash transport simulation strongly depends on an eruption column model, that gives a profile of discharging rate of ash particles, for a predictability of dispersion of ash particles. Simple eruption column models, such as proposed by Suzuki (1983), have been adopted in volcanic ash transport simulations for its simplicity and convenience. However, such a model sometimes brings erroneous results especially when an environmental wind field considerably affects the behavior of eruption column. The distortion of eruption column and enhancement of turbulent mixing due to wind shear should be taken into account in an eruption column model for the improvement of its applicability.

The authors have conducted the three-dimensional simulation of volcanic plume for the 2011 Shinmoe-dake eruption, assuming the vertically-sheared wind field actually observed in the event, and have taken statistics of the locations and mobile vectors of the ash particles getting out of the simulated volcanic plume to establish the profile of discharging rate. The resulted profile is distinctly different from that based on a usual eruption column model. The new profile is characterized by the relatively large discharge of micron-sized ash particles from the middle level of the plume, comparing to the usual one. The authors plan to validate the new model in the simulation of long-range transport of volcanic ash, based on satellite observation data. This work will be a basis for a future improvement of the volcanic ash fall forecast by Japan Meteorological Agency, which is established with the Suzuki’s model. The characteristics and validity of new model will be discussed in the presentation.

Acknowledgement

This study was supported by the Earthquake Research Institute cooperative research program.

References

Suzuki, T., 1983: A theoretical model for dispersion of tephra. Arc Volcanism: Physics and Tectonics. TERRAPUB, 95-113.