Analysis for eruptive product using remote sensing data

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Since the volcanic eruption in the year 2000, continuous monitoring of sulfur dioxide(SO_2) gas has been conducted in Miyakejima, a volcano island around 180 km south of Tokyo. Since the sampling measurements are carried out at 14 observation posts, all located along the seashore road, it is difficult to monitor exact pollution levels inside the areas where high concentration of SO_2 often takes place. In this paper we report on our differential optical absorption spectroscopy(DOAS) measurements carried out inside the highly-polluted, restricted areas in Miyakejima in December 2009 and September 2010.The DOAS method enables the monitoring of SO_2 concentration averaged over a light path of several hundred meters with high temporal resolution of around 5 min. The comparison of DOAS data and ground sampling posts nearby the light path has exhibited similar temporal behavior, indicating that highly concentrated SO_2 gas is in fact distributed in a range of several hundred meters. The combinatory measurements with two DOAS paths perpendicular to each other have revealed that the distribution of volcanic gas near the ground level is determined by both geographical features and wind fields.