2-dimensional Mapping of Sulfur Dioxide and Bromine Oxide at the Sakurajima Volcano with a Ground Based Scanning Imaging Spectrograph System

Abstract

A scanning imaging spectrograph system was used in this study to retrieve readings of the 2-D distribution of <TEX>$SO_2$</TEX> and BrO around the crater of the Sakurajima volcano in Japan. The measurement was carried out during the daytime on November 2, 2005. Measurements were made at the surface of the site, located 5 km from the Sakurajima crater. One hundred horizontal scans were performed. Each column scanned by the system consists of 64 vertical pixels in order to retrieve the spatial distributions of BrO and <TEX>$SO_2$</TEX> in the plume in terms of slant column densities (SCDs). Measured spectra were analyzed to identify and quantify <TEX>$SO_2$</TEX> and BrO in the volcanic plume utilizing the plume's specific absorption features in the ultra violet region. Two-dimensional BrO and <TEX>$SO_2$</TEX> distributions in SCD were retrieved horizontally covering the upwind, crater and downwind areas, and vertically, including the plume in the center of the scanned image. Both horizontal and vertical dispersions of <TEX>$SO_2$</TEX> SCD from the crater were successfully measured to be from <TEX>$10^{17}$</TEX> to <TEX>$4.5{\times}10^{18}$</TEX> molecules <TEX>$cm^{-2}$</TEX>. However, BrO was measured below <TEX>$10^{15}$</TEX> molecules <TEX>$cm^{-2}$</TEX>, which is considered its background level.