An Advanced System to Monitor the 3D Structure of Diffuse Volcanic Ash Clouds
Résumé
Major disruptions of the aviation system from recent volcanic eruptions have intensified discussions and increased the international consensus to improve volcanic ash warnings. Central to making progress is to better discern low volcanic ash loadings, and to describe the ash cloud structure more accurately in 3-dimensional space, and time. Here, we study dispersed volcanic ash observed by the CALIPSO space-based lidar near 20,000-40,000ft (~6-13 km) over Australia and New Zealand in June 2011, 3 weeks after the Puyehue-Cordon Caulle eruption, which disrupted air traffic in much of the Southern Hemisphere. The volcanic ash layers are shown to exhibit color ratios (1064/532 nm) near 0.5, significantly lower than unity which is observed with ice. We use those optical properties to develop an ash detection algorithm. We then demonstrate a "trajectory-mapping" technique, wherein ash cloud observations are ingested into a Lagrangian model, to construct ash dispersion maps and cross-sections. Comparisons of the model results with independent observations suggest that the model successfully reproduces the 3D structure of volcanic ash clouds. This technique has a potential operational application to provide important additional information to worldwide Volcanic Ash Advisory Centers.
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