Sedimentation and growth of volcanic aerosols within the Hunga plume

Abstract

The Hunga eruption was an unprecedented event which influenced stratospheric aerosols. This study analyzes the unique dynamics of aerosol plumes using balloon measurements from the Brazil Volcano campaign in Bauru (22.36° S, 49.03 °W) and the Stratospheric Aerosol and Gas Experiment III/ISS along with theoretical calculations. They revealed consistent trends in particle sedimentation and spreading. Temporal analysis showed that smaller particles (<225 nm) experienced slower sedimentation rates, with a larger influence by the Brewer-Dobson circulation. Larger particles (>400 nm) exhibited faster sedimentation, descending approximately 3 km by the end of 2022. The descent of the plume into the Upper Troposphere and Lower Stratosphere (UTLS) by February-March 2023 is accompanied by an increase of effective radius from 400 nm to 450 nm due to hygroscopic growth from moist convection. These unique observations suggest that Hunga could have impacted cirrus cloud formation by re-entering the UTLS.