Effect of volcanic emissions on clouds during the 2008 and 2018 Kilauea degassing events

Abstract. Aerosol emissions from volcanic eruptions in otherwise clean environments are regarded as natural experiments where the aerosol effects on clouds and climate can be partitioned from other effects like meteorology and anthropogenic emissions. In this work, we combined satellite retrievals, reanalysis products, and atmospheric modeling to analyze the mechanism of aerosol-cloud interactions during two degassing events at the Kilauea Volcano in 2008 and 2018. The eruptive nature of the 2008 and 2018 degassing events was distinct from long-term volcanic activity for Kilauea. For both events, we performed a comprehensive investigation on the effects of aerosol emissions on macro and microphysical cloud processes for both liquid and ice clouds. This is the first time such an analysis has been reported for the 2018 event. Similarities between both events suggested that aerosol-cloud interactions related to the cloud albedo modification were likely decoupled from local meteorology. In both events the ingestion of aerosols within convective parcels enhanced the detrainment of condensate in the upper troposphere resulting in deeper clouds than in pristine conditions. Accounting for ice nucleation on ash particles led to enhanced ice crystal concentrations at cirrus levels and a slight decrease in ice water content, improving the correlation of the model results with the satellite retrievals. Overall, aerosol loading, plume characteristics, and meteorology contributed to observed and simulated changes in clouds during the Kilauea degassing events.