Realmuto, V.J., Eldering, A., (2004). A Multisensor Approach to the Remote Sensing of Volcanic Emissions. Eos Trans. AGU, 85(47), Fall Meet. Suppl. 2004, Abstract # V32A-03
NASA's series of Earth Observing System satellites present remote sensing volcanologists with a potent suite of instruments for the study of volcanic emissions. In this presentation we focus on applications of data acquired with the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER), Atmospheric Infrared Sounder (AIRS), Moderate-Resolution Imaging Spectrometer (MODIS), and Multiangle Imaging SpectroRadiometer (MISR). The volcanic emission products of interest are sulfur dioxide, silicate ash, and sulfate aerosols. The ASTER, MODIS, AIRS, and MISR data are applied to studies of the sulfur dioxide, ash, and aerosol emissions associated with recent eruptions of Mount Etna. The measurements provided by these instruments are complimentary. ASTER collects visible and near-infrared (VNIR), short-wave infrared (SWIR), and thermal infrared (TIR) radiance measurements at (nadir) spatial resolutions of 15, 30, and 90 m, respectively. MODIS collects radiance measurements in 32 spectral channels between the VNIR and TIR. The majority of these measurements are acquired at a (nadir) spatial resolution of 1 km. There are MODIS instruments on two EOS platforms, providing daily coverage of the Earth at non-Tropical latitudes. AIRS collects radiance measurements in over 2300 spectral channels between the SWIR and TIR, with a (nadir) spatial resolution of approximately 17 km. MISR acquires multispectral VNIR radiance measurements at nine distinct viewing angles through the simultaneous use of nine nadir, fore, and aft-viewing cameras. The spatial resolution of the nadir scene and the red channels of the off-nadir scenes is 275 m. The remaining off-nadir scenes have a spatial resolution of 1100 m. The high spatial resolution of ASTER data allows us to detect volcanic emissions at low concentrations, making ASTER the primary instrument for monitoring passive emissions of sulfur dioxide. The comprehensive spectral, spatial, and temporal coverage provided by MODIS make these data the most versatile for the study of volcanic sulfur dioxide, ash, and aerosol emissions. The high spectral resolution of AIRS data permits unambiguous identification of sulfur dioxide, ash, and aerosol and facilitates the estimation of the quantities of these materials. In addition, AIRS data are used to map the 3D distributions of atmospheric temperature and water vapor. MISR data are used to derive estimates of aerosol optical depth, cloud-top altitude, wind direction, and wind speed. Volcanic plumes and clouds exhibit apparent displacement, known as parallax or disparity, in the off-nadir views relative to the nadir view. These disparities are a function of the altitude of these features as well as wind-induced motion during the seven-minute period required to obtain a suite of fore- and aft-viewing scenes over a given point on the Earth's surface.
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