Abstract
The active volcano Oyama on Miyake Island has been emitting a huge amount of volcanic gases since the first eruption in July 2000. High concentrations of SO2 gas originating from Oyama have frequently appeared over a wide area of Honshu, Japan. This paper describes real-time prediction of SO2 dispersion covering the Tokai and Kanto Districts, and verification by comparing SO2 data observed from October to November 2000. The atmospheric dispersion of SO2 was calculated by using a combination of software systems that combines a regional atmospheric dynamic model and a particle random walk model.
It was proved that the real-time prediction system is adequately precise. The importance of including the effect of wet deposition for more accurate calculation was also shown. The release amounts estimated from the comparison between the calculated results and the monitored data were 20, 000-50, 000 tons/day, which is consistent with results measured from Miyake Island. The transport of SO2 to the Tokai District mainly occured under synoptic meteorological conditions, during which traveling anticyclones move their centers in the eastern region of the Kanto District with troughs approaching from the west. The frequent appearance of high concentrations of SO2 in the Tokai District from late October to early November 2000 would have been promoted by low pressure or the seasonal rain front in the southwestern region, since pressure off the Pacific was unusually high at that time.
