Abstract
A very fine mesh dispersion model was developed for volcanic gas over Miyake Island. The model consisted of a meteorological prediction part and a dispersion part. The multi-nesting method was used for the meteorological prediction part to express the field, depending on synoptic weather pattern in this study. The grid size of the innermost model was 100 m. The days when the observed SO2 concentration was comparatively high were chosen for the verification of the model. Four cases of 24-hour numerical simulations were conducted. We try to reproduce the SO2 concentration in each situation. Following results were derived. The effect of the advection was dominant as compared with other physics, so the volcanic gas moved leeward. Even the slight change of the wind direction largely varied the concentration. The volcanic gas spread widely, in case of weak wind at night, because of the mountain breeze. Although there were some cases of time-lags of the peaks, and some degrees of overestimation, or underestimation, each situation was almost well reproduced.
