A MULTIFREQUENCY LABORATORY INVESTIGATION OF ATTENUATION AND SCATTERING FROM VOLCANIC ASH CLOUDS

Interest in remote monitoring of volcanic activity has increased in th e last several years partly as a result of several powerful eruptions and partly as a result of satellite-borne spectrometers with thermal I R bands with which to monitor the physical makeup and effects of the v olcanic inputs to the atmosphere. In this paper, we consider the first wide-bandwidth laboratory experiments intended to improve our underst anding of the spectral response of volcanic ash important for remote s ensing of volcano eruption ejecta, making comparisons between data fro m the laboratory of ash suspensions and Mie theory for scattering and attenuation from spheres, Described are the experimental configuration , the sample preparation techniques and the results obtained, The resu lts indicate a general sphere-like behavior of the ash, however the le vels indicate effective radii that lie at the extremes of the actual p article size ranges. The data presented here are unique in their multi spectral character as well as their control over ash particle size dis tributions, They should be useful in the process of selecting appropri ate remote sensing datasets and for improving models for retrieving es timates of particle size distribution, concentration, total mass of as h ejected, cloud drift, and fall-out rate from that data, They should also be useful for designing and assessing performance of ash hazard s ensors for flying aircraft.