Skip to content

Towards real-time quantification of tephra fallout deposits using optical disdrometers

Valentin Freret-Lorgeril 1,2, Simon Thivet3, Simona Scollo4, Costanza Bonadonna3, Allan Fries3, Jonathan Lemus3, Thierry Latchimy2, Frédéric Peyrin2

  • Affiliations: 1Université Clermont Auvergne, CNRS, IRD, OPGC, Laboratoire Magmas et Volcans, F-63000 Clermont-Ferrand, France; 2Université Clermont-Auvergne, CNRS, UAR 833, OPGC, F-63177 Aubière, France; 3Department of Earth Sciences, University of Geneva, 13, Rue des Maraichers, CH-1205 Geneva, Switzerland; 4Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo, Sezione di Catania, Catania, Italy

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 113

  • Programme No: 3.15.18

  • Theme 3 > Session 15

Abstract

Explosive eruptions generate tephra plumes that may impact human populations, infrastructures and air traffic at various time- and space-scales. The forecast of the impact zones in the atmosphere and on the ground of these plumes relies on the quantification of the eruption source parameters (e.g., mass eruption rate; MER, plume height and Total Grainsize Distribution; TGSD). While multi-sensor strategies are used to determine MERs and plume heights, real-time estimates of the TGSD are rare and difficult to obtain. A solution to the lack of such data is the use of optical disdrometers which provide numbers, sizes and settling velocities of detected tephra. We tested the Laser Precipitation Monitor at Sakurajima (Japan) in 2019 and 2023, during the 2021 Tajogaite eruption (La Palma Island, Spain) and more recently at Etna in July 2024. Over a size range of 2.5ϕ down to -1ϕ, a linear trend is found between Mdϕ values of grainsize distributions derived from collected samples and disdrometer data. Moreover, an exponential relationship is found between disdrometer- and sample-derived accumulation rates with an excellent R² of 0.95. These excellent correlations strengthen the capacity of optical disdrometers to provide real-time data for very different eruptive conditions (from low to high intensity explosive activity). Based on these results, we are now creating the first European disdrometer network dedicated to tephra fallout monitoring at Etna which will aim at quantifying in real time tephra fallout deposits (i.e., grainsize and sedimentation rate) and studying the temporal relations between the plume dynamics and tephra deposition.