Lidar and SAGE II observations of Shishaldin volcano aerosols and lower stratospheric transport.

During May 1999, data collected with two of University of L'Aquila lidar sy stems, Italy show an increase in the stratospheric aerosol content at altit udes between 15 and 18 km. Our initial hypothesis is that these aerosols or iginated from the Shishaldin (Alaska) volcanic eruption of 19 April 1999. S AGE IT observations, taken between Julian day 100 and 180, at latitudes abo ve 40 degreesN, show several sightings that are good candidates for volcani c aerosols. A trajectory analysis shows that a few SAGE II. measurements ar e in space and time compatible with the Shishaldin eruption, and the aeroso l enhancements observed by L'Aquila lidars have been also sampled by SAGE I I, later and in different locations.