Volcanic SO2 Flux Estimates Inferred from Satellite Observations: Sensitivity to Assumptions about Atmospheric Transport and Instrument Sensitivity

Abstract:

Atmospheric sulphur dioxide (SO2) is a good tracer for the emission and atmospheric dispersion of volcanic material. We use the GEOS-Chem atmospheric chemistry transport model to interpret the observed variability of SO2 column data collected by the Ozone Monitoring Instrument (OMI) aboard the NASA Aura satellite during the May 2010 eruption of Eyjafjallajökull. We sample the model at the time and location of each observed OMI scene, and convolve the vertical profiles with a scene-specific OMI averaging kernel, which describes the vertical sensitivity of the column data to changes in SO2. To describe the time-dependent injection of volcanic material from the eruption of Eyjafjallajökull we use weather radar observations from nearby Keflavík International Airport. We assume a uniform distribution of SO2 between the top of the volcano and the maximum injection height measured by the radar. We report the magnitude and uncertainty of volcanic SO2 flux estimates inferred from OMI data using a maximum a posteriori approach, taking into account uncertainties associated with the a priori fluxes, the measurements, and the atmospheric transport model. We also present the sensitivity of our results to assumptions about the injection height and the horizontal grid resolution of the atmospheric transport model. Finally, we quantify the impact of the OMI SO2 observations on describing transport of volcanic material into European air space.