Three-dimensional transport simulations of the dispersal of volcanic aerosol from Mount Pinatubo

Three-dimensional Eulerian and Lagrangian transport simulations are used to investigate aspects of the initial dispersal of the volcanic aerosol plume from the 1991 eruption of Mount Pinatubo. A global finite-difference model that simulates the large-scale dynamics of the earth's stratosphere is combined with an Eulerian spectral transport model and a Lagrangian trajectory model. The simulated transport of the volcanic plume is compared with observations of the volcanic plume made from the SAGE II satellite instrument. Dynamical quantities, diagnosed from the simulated wind- and temperature-fields, provide insight into the evolution of the volcanic plume. Lagrangian trajectories help assess the performance of the Eulerian transport model and highlight small-scale structure that is masked by the finite resolution of the Eulerian model. Exponential material-stretching rates, symptomatic of efficient mixing, are found when air is peeled off the volcanic plume into southern mid-latitudes. On-line simulations show that radiative heating of the cloud has a major impact on its transport. Details of the local and far-field dynamical responses to the heating are discussed.