Observations of a Volcanic Plume from the Eruption of Soufriere Hills, Montserrat, on May 20 CALIPSO Total Attenuated Backscatter 532 nm 7 June 2006 Volcanic plume Aura/OMI Column SO2 8 June 2006 CALIPSO Orbit Track 7 June 2006 The Soufriere volcano on Montserrat experienced a major eruption on May 20, 2006. The plume was estimated to reach 17 km, probably entering the lower stratosphere. The SO2 column has been tracked by the Aura/OMI instrument for several weeks. On 6 and 8 June, OMI observed the SO2 plume over Indonesia. On June 7, during it’s first day of lidar operations, CALIPSO observed a thin scattering layer at an altitude of about 20 km. Because of the altitude and the correlation with the location of the SO2 plume this appears to be the aerosol component of the plume from Soufriere. The layer appears to be non-depolarizing so it appears to be primarily composed of sulfuric acid droplets, rather than ash particles. Volcanic plumes such as this can be hazardous to air traffic if they cross air traffic lanes at the altitude where commercial aircraft fly. This example illustrates the ability of CALIPSO to detect and track these volcanic plumes. Also visible are thin tropical cirrus clouds (greenish-blue, 12-15 km), the tops of tropical storm systems (red and green, 5-10 km) and aerosols in the planetary boundary layer (green, lowest few kilometers). The ability of CALIPSO to observe where aerosols occur, and their altitude, around the globe improves our abilities to assess and forecast air quality. The lidar image here is calibrated Level 1 data: total attenuated backscatter at 532 nm. There was a range bias at the time this data was acquired, so the ocean surface appears to be at an altitude of –500 m.