Dispersion and optical properties of the Kasatochi volcanic plume based on the CALIPSO space-borne lidar

Volcanic eruptions represent an important threat for aviation primary due to the abrasive properties of ash particles, which can damaged aircraft engines, and from the presence of sulfate aerosols which can corrode and damage aircraft windows or eventually penetrate the cabin. During the first week following the August 2008 Kasatochi eruption, a volcano located in the Aleutian Island (USA), several unexpected ash/sulfate encounters by commercial aircrafts were reported. We examine this event using our new CALIPSO-based Lagragian system to follow the dispersion of this plume between Alaska and Europe. The backscatter, depolarization and color ratio (1064/532nm) measured by CALIPSO are used to infer the optical properties and identify the plume throughout its dispersion in the upper troposphere and lower stratosphere between 10 and 18 km. We find the ratio between ash and sulfate backscatter to be around 10-20% in agreement with aircraft observations. The CALIPSO lidar curtains are used to initialize a Lagrangian transport model to produce continuous 3D maps of ash and sulfate backscatter at different levels. The volcanic plume is shown to cross North America, the Atlantic, and Europe during the first 10 days after the eruption between 20000-40000ft. At that time, the plume retained a significant ash content, but below the threshold detection limit of geostationary satellites using the split window technique. We will discuss here how the retrieval of ash using this technique can be affected by other compounds within a volcanic plume.