Monitoring the 3D structure of diffuse volcanic ash clouds

Recent volcanic eruptions have triggered important air-traffic disruptions, which led to intense discussions in the international volcanic ash research community on how to improve the warning system. Recommendations from the International Volcanic Ash Task Group called for improving the detection of ash cloud layering as well as the long-term presence of diffuse volcanic ash. In this context, the CALIPSO satellite, which includes lidar and infrared imager technologies, presents interesting capabilities to monitor the 3D structure of volcanic ash clouds. We present here a case study on the long-term dispersion of volcanic ash in the Upper Troposphere and Lower Stratosphere after the Puyehue-Cordon Caulle eruption in Chile on 5 June 2011, which disrupted air traffic for more than 3 weeks in most of the southern hemisphere. The study provides particular insight on how ash might have been better predicted had space-based lidar been used in operational dispersion models . The ash cloud was detected using the optical parameters derived from the CALIPSO lidar and then introduced into a Lagrangrian model to reconstruct the 3D structure of volcanic ash. This new approach has a potential application to provide valuable information to the Volcanic Ash Advisory Center.