Key points are not available for this paper at this time.
Hemispherical dispersion of the SO 2 cloud from the August 2008 Kasatochi eruption is analyzed using satellite data from the Ozone Monitoring Instrument (OMI) and the Goddard Trajectory Model (GTM). The operational OMI retrievals underestimate the total SO 2 mass by 20–30% on 8–11 August, as compared with more accurate offline Extended Iterative Spectral Fit (EISF) retrievals, but the error decreases with time due to plume dispersion and a drop in peak SO 2 column densities. The GTM runs were initialized with and compared to the operational OMI SO 2 data during early plume dispersion to constrain SO 2 plume heights and eruption times. The most probable SO 2 heights during initial dispersion are estimated to be 10–12 km, in agreement with direct height retrievals using EISF algorithm and IR measurements. Using these height constraints a forward GTM run was initialized on 11 August to compare with the month‐long Kasatochi SO 2 cloud dispersion patterns. Predicted volcanic cloud locations generally agree with OMI observations, although some discrepancies were observed. Operational OMI SO 2 burdens were refined using GTM‐predicted mass‐weighted probability density height distributions. The total refined SO 2 mass was integrated over the Northern Hemisphere to place empirical constraints on the SO 2 chemical decay rate. The resulting lower limit of the Kasatochi SO 2 e‐folding time is ∼8–9 days. Extrapolation of the exponential decay back in time yields an initial erupted SO 2 mass of ∼2.2 Tg on 8 August, twice as much as the measured mass on that day.
Krotkov et al. (Wed,) studied this question.