Aerosol-cloud interactions derived from the 2014 Holuhraun volcanic eruption

Aerosol effective radiative forcing (ERF) has persisted as the most uncertain aspect of anthropogenic forcing over the industrial period, limiting our ability to constrain estimates of climate sensitivity and the accuracy of climate projections. Aerosol-cloud interactions are the most uncertain component of aerosol ERF. The 2014 Holuhraun volcanic eruption acted as large source of sulfur dioxide, providing a natural experiment for testing aerosol-cloud interaction hypotheses at a climatically relevant scale. Our study builds on previous aerosol-cloud interaction analyses of the eruption. We evaluate the observed aerosol perturbation to cloud properties inside the volcanic plume in the weeks following the eruption. As expected, on most days, we find an in-plume shift to increased cloud droplet concentration and decreased effective radius. The sign and magnitude of an in-plume shift in liquid water path varies in the weeks following the eruption. We probe this variation in the observed in-plume cloud perturbations to elucidate the aerosol-cloud interaction mechanisms following the Holuhraun eruption.