<title>Analysis of thermal infrared multispectral images for the detection of sulfur dioxide in volcanic plumes: a case study from Mount Etna, Sicily</title>

Abstract

The sulfur dioxide molecule shows absorption features in UV, thermal IR and microwave regions. These three portions of the electromagnetic spectrum can be investigated with remote sensing systems. The first non-imaging remote sensing instrument used to make quantitative measures of SO2 in volcanic plumes was the COSPEC. The resultant measurements have allowed volcanologist to recognise that a rapid increase in the sulfur dioxide flux from a volcano can signal an impeding eruption. This technique although producing good results can require a considerable logistical planning and in some cases personal risk. Spaceborne imaging sensors have been used to detect stratospheric sulfur dioxide plumes during volcanic eruptions. Nevertheless the atmospheric effects and coarse spatial resolution (between 5 and 50 Km) of the acquired images prevent the detection of tropospheric volcanic plumes formed by the continuous degassing from summit craters. In this study an analysis of image data acquired from NASA's Airborne Thermal Infrared Multispectral Scanner (TIMS) to estimate sulfur dioxide content of a tropospheric volcanic plume is presented. The estimation procedure is based on LOWTRAN 7 radiative transfer code, which is used to model the radiance perceived by TIMS when it looks at ground through a volcanic plume. The described technique was developed on the TIMS data acquired over Mt. Etna, Sicily on July 29, 1986.