Rapid Ash Removal in the 2022 Hunga Volcano Plume: The Role of Aerosol Microphysical Processes

The record-breaking January 2022 Hunga eruption raised questions regarding the large amount of water vapor (150 Tg) reaching the stratosphere and the surprisingly less amount of ash detected. The emission of such large amount of water vapor in numerical models poses its own challenges and limitations. From ground-based estimates of emitted ash, the emitted fine ash is estimated to be around 17-34 Tg, however, only up to 1-2 Tg was present in the atmosphere which indicates an extremely fast removal of ash. This study investigates the role of various aerosol dynamical processes and hence, the accelerated removal of ash particles. This is done through emission of ash, water vapor, SO2 and NaCl in the ICOsahedral Nonhydrostatic model with Aerosols and Reactive Tracers (ICON-ART). Three possible pathways of faster growth and consequently, removal of particles, are explored in this study. These include (1) ash particle growth due to coagulation with sea salt and further growth by water owing to the highly hygroscopic nature of sea salt, (2) fast wet aggregation of particles during the plume rise, and (3) activation of particles to large hydrometeors.  The results emphasize the importance of including sea salts emission along with ash and SO2 in modelling studies and the subsequent effects on aerosol dynamical processes.