EVOLUTION OF THE PINATUBO VOLCANIC AEROSOL COLUMN ABOVE PASADENA, CALIFORNIA OBSERVED WITH A MIDINFRARED BACKSCATTER LIDAR

The evolution of the volcanic debris plume originating from the June 1 991 eruption of Mt. Pinatubo has been monitored since its genesis usin g a ground-based backscatter lidar facility sited at the Jet Propulsio n Laboratory (JPL). Both absolute and relative pre- and post-Pinatubo backscatter observations are in accord with Mie scattering projections based on measured aerosol particle size distributions reported in the literature. The post-Pinatubo column-integrated backscatter coefficie nt peaked approximately 400 days after the eruption, and the observed upper boundary of the aerosol column subsided at a rate of approximate ly 200 m mon-1.