The Effect and Implications of Increased Stratospheric Aerosols from Small Injections and Background Increases

Stratospheric aerosols affect global climate by influencing the radiative budget and chemistry of the lower stratosphere. Presently the stratospheric aerosol levels are in a background state. This provides the opportunity for studies of stratospheric injections by small volcanic eruptions and boreal forest fires. Recent observations of stratospheric aerosols by the Arctic Lidar Technology (ARCLITE) system Sondrestrom, Greenland suggest volcanic and boreal emissions may significantly perturb stratospheric aerosols in the Arctic. Longterm observations made by lidars in Boulder, Colorado and at the Mauna Loa Observatory show positive trends in the global background of stratospheric aerosols. Profiles derived from the ARCLITE observations include depolarization, backscatter and temperature which allow for a characterization of the stratospheric layer on a regular basis. A thin stratospheric aerosol layer was identified during the month of July 2009 using the Arctic Lidar Technology (ARCLITE) System operated at Sondrestrom. Observations after the eruption of the Sarychev Peak volcano in the Russian Kuril Islands on June 12, 2009 provide a time series of measurements showing the evolution of the aerosol layer over the month after a typical small injection within the global context of the profiles provided by the global GMD network. From the optical qualities observed, the exact nature of the aerosols and their role in the radiative budget and stratospheric chemistry are elucidated. These types of observations are unique to ground-based lidar systems like ARCLITE due to the optically thin qualities of the layer which prevent detection in the visible band by nadir-looking satellites. The long term effect of this injection of sulfur dioxide into the stratosphere may influence the formation of polar stratospheric clouds during the coming winter.