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-shape d plume formed above the volcano that later drifted to the east, dropp ing ash on the underlying terrain. The plume was recorded on two satel lite images. The images show the plume as being circular 20 minutes af ter the eruption, and widely dispersed 4 hours later. Digital analyses of the images reveal variations in the morphology and spectral respon se of the top of the plume. The morphology is attributed to relief fea tures which are related to the ascending motion of the plume. The spec tral responses are attributed to variations in the physical characteri stics of the plume and to slope-aspect-solar illumination factors. By comparing the two sequential images, the trajectory, velocity and disp ersion of the plume were investigated. The height of the plume and the air mass that transported it were determined by comparing pilot repor ts, radiosonde observations, and plume temperature measurements from s atellite images. Results from these analyses will provide a better und erstanding of what satellite sensors detect and aid development of tec hniques to track and assess plumes during an eruption.