Dr. Leah Courtland has been awarded an NSF Earth Science Postdoctoral Fellowship to carry out a research and education plan at Georgia Institute of Technology. This study will use a combination of laboratory experiments and numerical modeling to better constrain the rate of tephra (volcanic ash) aggregation in the uppermost regions of volcanic plumes. Laboratory experiments will utilize an ice nucleation chamber to parameterize the rate of tephra aggregation under a variety of relative humidities and applied electric field strengths. The main goal is to improve our understanding of the response of tephra in the atmosphere to the relative humidity conditions prevalent in volcanic plumes and the presence of an electric field within these plumes. The result of experiments will be a parameterization of the expected change in particle size distribution for varying plume conditions (humidity, temperature, electrical field). If successful, this will allow tephra dispersion models to use near-real- time meteorological data to better forecast particle residence time in the atmosphere. Research results will help to constrain tephra hazard models used in crisis response scenarios. Improvement in these models should ultimately lead to increased aviation safety and more effective hazard mitigation strategies for far-field tephra impacts on the ground.
Tephra fallout is the most far reaching hazard of volcanic eruptions, capable of causing roof collapse, polluting water supplies, damaging critical facilities, and threatening the health of people and livestock. The 2010 eruption of Eyjafjallajökull in Iceland spewed ash into the atmosphere for days, effectively shutting down most of European air space, affecting hundreds of thousands of travelers, and costing the aviation industry billions of dollars. The global nature and high economic consequence of this event expose an urgent need for accurate forecasts of the distribution of tephra in the atmosphere and on the ground. While the study of the transport and sedimentation of volcanic ash over the last forty years has greatly increased our understanding of these processes and enabled the development of numerical models to simulate tephra dispersion, the injection of large volumes of fine (<63 um) ash into the atmosphere is not yet captured in a meaningful way by the current generation of tephra models. The discrepancy between model calculations and the true distribution of tephra reflects the failure of the majority of models to account for natural processes that rapidly remove the fine ash fraction of volcanic ejecta from the atmosphere as constituent pieces of larger aggregates. To facilitate understanding of ash aggregation while fostering model literacy and quantitative skills building among university students, a series of educational modules will be designed and implemented via the Vhub.org web platform. VHub.org is an online resource for volcano modeling and education. The numerical parameterization of ash aggregation to result from this work will ultimately be installed on Vhub.org as well, in order facilitate use of the model by the larger scientific community.
