Sulphur mass balance and radiative forcing estimation for a moderate volcanic eruption using new sulphate aerosols retrievals based on IASI observations

Abstract. We developed a new retrieval algorithm based on the Infrared Atmospheric Sounding Interferometer (IASI) observations, called AEROIASI-Sulphates, to measure vertically-resolved sulphate aerosols (SA) extinction and mass concentration profiles, with limited theoretical uncertainties (typically ~25 % total uncertainty for SA mass column estimations). The algorithm, based on a self-adapting Tikhonov-Phillips regularization method, is applied to a medium-sized-intensity eruption of Mount Etna volcano (18 March 2012). Comparisons with simultaneous and independent SO₂ plume observations and simulations show that AEROIASI-Sulphates correctly identifies the volcanic plume morphology both horizontally and vertically. This method provided, for the first time, crucial information pieces to describe the gaseous-to-particulate volcanic sulphur mass balance (60 % of the injected sulphur mass is converted to particulate matter, after ~24 hours) and to estimate the regional shortwave direct radiative forcing (a regional forcing of −0.8 W/m² is exerted in the eastern Mediterranean) for moderate volcanic eruptions.