Particle Aging and Aerosol--Radiation Interaction Affect Volcanic Plume Dispersion: Evidence from Raikoke Eruption 2019.

A correct and reliable forecast of volcanic plume dispersion is vital for aviation safety. This can only be achieved by representing all responsible physical and chemical processes (sources, sinks, and interactions) in the forecast models. The representation of the sources has been enhanced over the last decade, while the sinks and interactions have received less attention. In particular, aerosol dynamic processes and aerosol-radiation interaction are neglected so far. Here we address this gap by further developing the ICON-ART (ICOsahedral Nonhydrostatic - Aerosols and Reactive Trace gases) global modelling system to account for these processes. We use this extended model for the simulation of volcanic aerosol dispersion after the Raikoke eruption in June 2019. Additionally, we validate the simulation results with measurements from AHI (Advanced Himawari Imager), CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization), and OMPS-LP (Ozone Mapping and Profiling Suite - Limb Profiler). Our results show that around 50 % of very fine volcanic ash mass (particles with diameter d < 30 µm) is removed due to particle growth and aging. Furthermore, the maximum volcanic cloud top height rises more than 6 km over the course of 4 days after the eruption due to aerosol-radiation interaction. This is the first direct evidence that shows how cumulative effects of aerosol dynamics and aerosol-radiation interaction lead to a more precise forecast of very fine ash lifetime in volcanic clouds. [ABSTRACT FROM AUTHOR]