Earth Planets Space, Vol. 65 (No. 6), pp. 581-589, 2013
Yujiro J. Suzuki and Takehiro Koyaguchi
Earthquake Research Institute, University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-0032, Japan
(Received October 31, 2012; Revised March 15, 2013; Accepted March 16, 2013; Online published July 8, 2013)
We present simulations of the development of volcanic plumes during the 2011 eruptions of the Kirishima-Shinmoe-dake volcano, Japan, using a new three-dimensional (3D) numerical model that calculates eruption cloud dynamics and the wind-borne transport of volcanic ash. This model quantitatively reproduces the relationship between the eruption conditions (e.g., magma discharge rate) and field observations, such as plume height and ash fall area. The simulation results indicate that the efficiency of turbulent mixing between ejected material and ambient air was substantially enhanced by strong winds during the 2011 Shinmoe-dake eruptions, which caused a significant decrease in the maximum height of the plumes compared with those that develop in still environment. Our 3D simulations also suggest that the existing 1D plume model tends to overestimate the effect of wind on turbulent mixing efficiency, and hence, to underestimate plume height in a strong wind field for a given magma discharge rate.
Key words: Volcanic plume, eruption column, numerical simulation, turbulent mixing.