Influence of the 2008 Kasatochi Volcanic Eruption on Sulfurous and Carbonaceous Aerosol Constituents in the Lower Stratosphere

Influences on stratospheric aerosol during the first four

months following the eruption of Kasatochi volcano (Alaska)

were studied using observations at 10700 ± 600 m altitude

from the CARIBIC platform. Collected aerosol samples

were analyzed for elemental constituents. Particle number

concentrations were recorded in three size intervals

together with ozone mixing ratios and slant column

densities of SO2. The eruption increased particulate sulfur

concentrations by a factor of up to 10 compared to periods

before the eruption (1999–2002 and 2005–August 2008).

Three to four months later, the concentration was still

elevated by a factor of 3 in the lowermost stratosphere at

northern midlatitudes. Besides sulfur, the Kasatochi

aerosol contained a significant carbonaceous component

and ash that declined in time after the eruption. The carbon to-

sulfur mass concentration ratio of the volcanic aerosol

was 2.6 seven days after the eruption and reached 1.2 after

3 – 4 months.