Observation of sulphate aerosols and SO2 from volcanic eruptions using data from the Atmospheric Chemistry Experiment (ACE)

Infrared spectra measured by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) on board of the SCISAT satellite were used to analyse the temporal and spatial evolution of volcanic aerosols from the Kasatochi (August 2008), Sarychev (June 2009) and Grimsvötn (May 2011) eruptions. Evidence of the Kasatochi and Sarychev eruptions has first be seen one month after the eruptions, while the Grimsvötn plume has been detected with a maximum age of 3 days, from enhanced SO2 concentrations and atmospheric extinction. Evidence for differences within these plumes have been obtained, showing the evolution of H2 SO4 from no sulphate aerosol signature in fresh volcanic plumes to clear signatures in aged volcanic plumes. The atmosphere had returned to pre-eruption conditions, between seven and eight months after the eruptions of Kasatochi and Sarychev. The first SO2 and sulphate aerosol retrievals determined using the infrared solar occultation spectra recorded with ACE-FTS are presented here. The size distribution parameters, aerosol volume slant column and composition of the sulphate aerosol were obtained using a least-squares algorithm, employing a continuum spectrum between 800 − 4200 cm−1 . The maximum volume slant column of the aerosol was found to be 500 μm3 cm−3 km (for Kasatochi) and 850 μm3 cm−3 km (for Sarychev), which results in an approximate aerosol loading of 1.8 μm3 cm−3 and 3 μm3 cm−3, respectively. One month after the eruptions the effective radius (Reff ) is below 0.2 μm (Kasatochi) and 0.1 − 0.3 μm (Sarychev).