Lidar observations of volcanic aerosols in the troposphere and stratosphere

A lidar was used to measure aerosol profiles above Halifax, Nova Scotia (44.64° N, 63.59° W) during Summer-Fall 2008. 650 hours of data were collected between 30 July-4 December using improved high and low altitude measurement capabilities.The 7-8 August 2008 Kasatochi eruption (52.17° N, 175.51° W) injected aerosols high into the atmosphere, which were detected by the lidar within one week and observed for four months. A Lagrangian transport model was used to verify the aerosol origin, and a global chemical transport model was used to assess ground level impacts, indicating a small influence at the surface. The stratospheric aerosols descended with the tropopause, which determined the plume base likely causing an addition of aerosols to the upper troposphere. Stratospheric aerosol optical depths remained constant despite extensive horizontal and vertical dispersion. The measurements have implications for air quality and climate indirect effects.