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Evaluating the importance of ash aggregation representation: insights from a three-dimensional plume model.

Jack Campbell 1, Michael Herzog1, Ben Devenish2,3, Clive Oppenheimer1

  • Affiliations: 1Department of Geography, University of Cambridge, Cambridge, UK; 2Met Office, Exeter, UK; 3Department of Civil and Environmental Engineering, Imperial College, London, UK

  • Presentation type: Poster

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

  • Poster Board Number: 83

  • Programme No: 3.12.9

  • Theme 3 > Session 12

Abstract

While many field studies document ash aggregate presence in fallout regions, and the role of aggregation in stripping fine ash from eruption clouds is widely acknowledged, numerical plume models often neglect or oversimplify ash aggregation processes. This inadequate representation leads to considerable uncertainties and errors in the eruption source parameters used to initialise operational ash dispersal models, compromising precision and limiting forecast performance to levels below those required to ensure safe and efficient flight operations during explosive volcanic eruptions.  Using the plume model ATHAM to simulate the eruption of Mount Redoubt, Alaska (2009), this study will evaluate the importance of adequately representing ash aggregation in volcanic plume models towards achieving more robust plume evolution and eruption source parameter constraints. The study will explore and test aggregation schemes of varying sophistication to highlight the necessity of developing a theoretical understanding of ash aggregation processes in numerical models with more comprehensive and explicit considerations of plume dynamics and microphysical processes. We will demonstrate the feedbacks between ash aggregation and plume development and quantify the significance of ash aggregation for long range transport.