Computed tomography reconstruction of SO₂ concentration distribution in the volcanic plume of Miyakejima, Japan, by airborne traverse technique using three UV spectrometers

We present here a new method for measuring the SO 2 concentration distribution in a volcanic plume cross‐section, by using the airborne traverse technique with three UV spectrometers and calculating a computed tomography (CT) reconstruction. Our observation requires only one traverse, and is as easy as conventional measurements of SO 2 flux. The plume is traverse scanned using three UV spectrometers aligned at three different zenith angles, and a CT technique initially designed for air pollutant monitoring was improved by using ‘Akaike's Bayesian Information Criterion' (ABIC). We applied this method to a volcanic plume at 10 km downwind from the caldera of Miyakejima volcano in Aug. 2004. The results of the application show that the profile of the plumes significantly changed in only a matter of a few minutes. Due to the flexibility and ease of the observation procedure, this method is widely applicable to various fields and shows promise in volcanic gas monitoring.