Submicron volcanic ash detected in sulfate aerosol mixtures observed by the Atmospheric Chemistry Experiment satellite

Abstract. Mixtures of volcanic ash and stratospheric sulfate aerosol (SSA) have been observed by the Atmospheric Chemistry Experiment (ACE), a remote sensing satellite mission in operation since 2004. The migration of the volcanic plumes from the Puyehue-Cordón Caulle eruption in June of 2011 and the Calbuco eruption of April 2015 aligned well with ACE’s sampling pattern, providing extended sampling of volcanic aerosol from these two eruptions. Weak volcanic ash spectral signatures are observed in the presence of SSA in the Southern Hemisphere up to 165 days following the Calbuco eruption and 125 days following the Puyehue-Cordón Caulle eruption. ACE residual spectra of ash-sulfate mixtures were simultaneously modelled to retrieve the line-of-sight column densities and the median particle radii for both ash and SSA. Pure volcanic ash from the Puyehue-Cordón Caulle eruption was modelled with a bimodal lognormal distribution.