Trajectory modeling of Kasatochi eruption plume compared with OMI SO2 observations

Three major explosive eruptions occurred at Kasatochi volcano (52.18ºN, 175.51ºW) in the afternoon of August 7. These eruptions injected SO2 and ash directly into Arctic lower stratosphere between 35,000 and 45,000 feet. Ozone Monitoring Instrument (OMI) overpass data on August 8 has shown peak SO2 columns over 200DU and absorption aerosol index larger than 5 due to volcanic ash. Initial OMI estimate of total SO2 mass is on the order of 1Tg, which characterizes Kasatochi eruption as largest since Pinatubo and Cerro Hudson eruptions in 1991. Although the plume dispersed, the dispersal structure was quite filamentary and plume filaments were evident in the OMI data over three weeks later. OMI SO2 data on August 8 and subsequent days were used to initialize Goddard trajectory model to forecast of the SO2 plume dispersion during the three weeks. The trajectory model used the latest GEOS-5 assimilation. The model predicted locations of the plume are compared with daily OMI SO2 measurements and used to make forecast corrections for subsequent days. The dispersal of the plume is reasonably represented in the trajectory calculation with the largest dispersion occurring below 12 km. Using plume dispersal information we estimate a lifetime for SO2 in the lower stratosphere.