Extended observations of volcanic SO₂ and sulfate aerosol in the stratosphere

Abstract. Sulfate aerosol produced after injection of sulfur dioxide (SO₂) into the stratosphere by volcanic eruptions can trigger climate change. We present new satellite data from the Ozone Monitoring Instrument (OMI) and Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) missions that reveal the composition, structure and longevity of a stratospheric SO₂ cloud and derived sulfate layer following a modest eruption (0.2 Tg total SO₂) of Soufriere Hills volcano, Montserrat on 20 May 2006. The SO₂ cloud alone was tracked for over 3 weeks and a distance of over 20 000 km; unprecedented for an eruption of this size. Derived sulfate aerosol at an altitude of ~20 km had circled the globe by 22 June and remained visible in CALIPSO data until at least 6 July. These synergistic NASA A-Train observations permit a new appreciation of the potential effects of frequent, small-to-moderate volcanic eruptions on stratospheric composition and climate.