IAVCEI 2013 Scientific Assembly - July 20 - 24, Kagoshima, Japan
Forecasting Volcanic Activity - Reading and translating the messages of nature for society

1W_4F-P11

Date/Time: July 21 Poster

Numerical Simulation of Transport and Sedimentation of Volcanic Ash for the Eruptionsat Mt. Shinmoe-dake during 26-27 January 2011
Akihiro Hashimoto1 , Toshiki Shimbori1 , Keiichi Fukui2 , Akimichi Takagi1
1

Meteorological Research Institute, Japan, 2 Kakioka Magnetic Observatory, Japan
E-mail: ahashimo@mri-jma.go.jp

The tephra transport and sedimentation associated with the eruptions at Mt. Shinmoe-dake during 26 to 27
January 2011 are investigated with Japan Meteorological Agency Non-Hydrostatic Model (JMA-NHM) in which themixing ratio and number concentration of tephra particles are prognosed to represent the behavior of tephra in
the atmosphere. In the model, one-dimensional eruption column model is applied in order to represent injectionof tephra particles into the atmosphere. The release of tephra is expressed by giving the production rates of total
mass and number of tephra particles in the grids that compose the column. The production rate is a function ofthe column height, the level of the release point, and the size of released particle, following Suzuki (1983) andShimbori et al. (2010). In actual eruption events, the eruption clouds were detected by the Tanegashima andFukuoka radars of JMA as well as the high-sensitivity camera that is installed about 7.5 km away to the south of Mt.
Shinmoe-dake and monitored at Kagoshima Local Meteorological Observatory. Based on the results of radar andcamera observations (Shimbori et al., 2013), the temporal change of column height is given during the simulation.
Comparison of the model result with ground survey on tephra deposit shows that the model well represents themajor axis of tephra deposit and the difference in the grain size on both sides of the axis due to the shearedhorizontal wind and a variety of the fall velocity of tephra particles (Hashimoto et al., 2012). On the other hand, thesimulated ash cloud goes too far compared with the satellite observation after transported hundreds kilo meters
away from the volcano. This means that the long-transported fine particles are released at higher altitude in themodel than in the actual atmosphere, since the horizontal wind generally gets stronger in higher altitude. It isindicated that the eruption column model applied in the simulation needs modification with respect to the release
rate of tephra particles as a function of the level of the release point and the size of released particle. The current
performance and the issues for improvement of the model will be discussed.

Hashimoto, A., T. Shimbori and K. Fukui, 2012: Tephra fall simulation for the eruptions at Mt. Shinmoe-dake during
26-27 January 2011 with JMANHM. SOLA, 8, 37-40.
Shimbori, T., Y. Aikawa, K. Fukui, A. Hashimoto, N. Seino, and H. Yamasato, 2010: Quantitative tephra fall
prediction with the JMA mesoscale tracer transport model for volcanic ash: A case study of the eruption at Asama
volcano in 2009. Pap. Met. Geophys., 61, 13-29.
Shimbori, T., T. Sakurai, M. Tahara and K. Fukui, 2013: Observation of eruption clouds with weather radars andmeteorological satellites: A case study of the eruptions at Shinmoe-dake volcano in 2011. Submitted to Q. J.
Seismol.
Suzuki, T., 1983: A theoretical model for dispersion of tephra. Arc Volcanism: Physics and Tectonics. TERRAPUB,
85-113.

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