Tracking Explosive Eruptions with Volcanic Lightning
Abstract
Over the past ~5 years, several well-documented eruptions have produced powerful electrical storms in which lightning rates match or exceed those from regular convection. Volcanic lightning provides valuable information about ash-related hazards, including the timing, location, and duration of ash emissions. Lightning also illuminates the spatial footprint of charge carriers (ash and ice) in the atmosphere. But our ability to detect and interpret electrical activity has important limitations. For example, some eruptions take time to generate globally-detectable lightning—more than 20-30 min after eruption onset. And others fail to become electrified at all. In this study, we examine the conditions under which recent, well-characterized eruptions have become lightning-rich, and speculate on the charging mechanisms involved. We present a conceptual model for electrification across the observed range of eruption intensities. Small, short-lived eruptions with plumes <3 km high (e.g., Sakurajima Volcano in Japan) undergo silicate charging due to colliding, fracturing particles. They produce low rates of globally-detectable lightning, if at all. On the other end of the spectrum are powerful lightning generators—sustained eruptions with plumes >15-20 km high, which maintain vigorous updrafts through regions of the plume with coexisting liquid water and ice. These processes are expected to promote collisional charging of ice, similar to conventional storms. Examples include the 2014 eruption of Kelud in Indonesia and the 2016 eruption of Calbuco in Chile. Between the two end-members are intermediate eruptions with plume heights of ~10 km (e.g., Bogoslof, Alaska in 2016-2017). Even the 3-4 km high Bogoslof eruption plumes were electrically quiet until they rose into freezing levels of the atmosphere (colder than -20oC). How might we adapt existing lightning-detection technology to improve early warning for this wide range of eruption styles? New strategies are emerging to augment and fine-tune the current framework of global sensors to provide more targeted coverage of active volcanoes. Ultimately, we seek to understand how the evolving, and sometimes overlapping, charge regimes of an eruption plume shape the full spectrum of volcanic thunderstorms.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A21K2824V
- Keywords:
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- 3311 Clouds and aerosols;
- ATMOSPHERIC PROCESSES;
- 3314 Convective processes;
- ATMOSPHERIC PROCESSES;
- 4313 Extreme events;
- NATURAL HAZARDS;
- 8409 Atmospheric effects;
- VOLCANOLOGY