Remote-sensing of Volcanic Sulfur Dioxide by the Aircraft-borne Sensor "Airborne-OPUS"

Algorithm Developments and its Validation Experiment

Abstract

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.