Lidar measurements of forest fire smoke and stratospheric aerosol

Lidar measurements of atmospheric aerosols were conducted during two airborne campaigns; Montana in 2007 and the Arctic in 2009. The principle goal of this was to establish whether pyro-convection is a source of stratospheric aerosol. Layers of material were observed downwind of forest fires in the 11 km to 15 km height range during August 2009. The analysis consists of isentropic back trajectory calculations from the Hybrid Single Particle Lagrangian Integrated Trajectory (HYSPLIT) model which traces the path of stratospheric aerosol layers over forest fires. Satellite imagery was used to determine the altitude of convection in the vicinity of the fires. The depolarization ratio in the lidar backscatter signal was determined in smoke within the troposphere and also within the stratospheric aerosol layers. The smoke had a depolarization ratio of 5.41% ± 0.04% while the stratospheric aerosol layers had depolarization ratios ranging from 0.20% ± 0.01% to 1.80% ± 0.03%. It was concluded that the stratospheric aerosol layers did not originate from fires. As a result, the evidence favours the eruption of Sarychev volcano in mid-June of 2009 as the likely source of stratospheric aerosols observed in Northern Canada.