Sulfur dioxide (SO2) absorbs ultraviolet (UV) radiation, and airborne spectrometers can measure its spatial distribution using backscattered solar light. A new algorithm was developed to estimate the SO2 vertical column amount. This algorithm is based on the Differential Optical Absorption Spectroscopy (DOAS) technique and the radiative transfer calculation. Aircraft-borne measurements using a ultraviolet spectrometer, the Airborne-OPUS, were performed above Miyake-jima (34°N, 139.5°E) in January 2002. The amount of SO2 estimated by the Airborne-OPUS was validated using SO2 mixing ratios measured simultaneously by an onboard air-sampling sensor during the spiral-down flight above and inside volcanic plumes. The results suggested that the above algorithm is capable of quantifying the column amount of volcanic SO2.
