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 SO 2 . 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.