SATELLITE ANALYSES OF MOVEMENT AND CHARACTERISTICS OF THE REDOUBT VOLCANO PLUME, JANUARY 8, 1990

On January 8, 1990 Redoubt Volcano in Alaska erupted. A mushroom-shaped plume formed above the volcano that later drifted to the east, dropping ash on the underlying terrain. The plume was recorded on two satellite images. The images show the plume as being circular 20 minutes after the eruption, and widely dispersed 4 hours later. Digital analyses of the images reveal variations in the morphology and spectral response of the top of the plume. The morphology is attributed to relief features which are related to the ascending motion of the plume. The spectral responses are attributed to variations in the physical characteristics of the plume and to slope-aspect-solar illumination factors. By comparing the two sequential images, the trajectory, velocity and dispersion of the plume were investigated. The height of the plume and the air mass that transported it were determined by comparing pilot reports, radiosonde observations, and plume temperature measurements from satellite images. Results from these analyses will provide a better understanding of what satellite sensors detect and aid development of techniques to track and assess plumes during an eruption.