An Advanced System to Monitor the 3D Structure of Diffuse Volcanic Ash Clouds

AbstractMajor disruptions of the aviation system from recent volcaniceruptions have intensified discussions about and increased the international consensus toward improving volcanic ashwarnings. Central to making progress is to better discern low volcanic ashloadings and to describe the ashcloud structure more accurately in three-dimensional spaceand time. Here, dispersed volcanic ashobserved by the Cloud–Aerosol Lidar and Infrared PathfinderSatellite Observations (CALIPSO) space-based lidar near 20 000–40 000 ft [~(6–13) km] over Australia and New Zealand during June 2011 is studied. This ashevent took place 3 weeks after the Puyehue-Cordon Caulle eruption, which disrupted air traffic in much of the Southern Hemisphere. The volcanic ashlayers are shown to exhibit color ratios (1064/532 nm) near 0.5, significantly lower than unity, as is observed with ice. Those optical properties are used to develop an ashdetection algorithm. A “trajectory mapping” technique is then demonstrated wherein ashclo...